Biochar from guinea pig manure as soil amendment: agronomic potential and cost analysis for sustainable agricultural circularity

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This study evaluated the physicochemical characteristics, toxicity, and neutralizing capacity of biochar produced by open pyrolysis in Huancayo, Junín, Peru. Fresh manure was also characterized before pyrolysis, and its median lethal dose was determined. Results showed that uncompacted manure had a volume of 2,883.99 cm³ (0.293 kg/cm³), and compacted manure 2,205.41 cm³ (0.380 kg/cm³). The resulting biochar had high contents of nitrogen, phosphorus, potassium, ash (34.6%), and fixed carbon (37.9%), along with an alkaline pH (9.07), high cation exchange capacity (48.8 meq/100g), and elevated organic matter (62%), indicating its potential to improve acidic soils. Moisture content (34.8%) and the presence of microelements (Mg, Cu, Ca, Zn) also suggest agronomic benefits. Economically, producing one ton of biochar from guinea pig manure costs approximately 231.23 soles, while its market value is 3,515.31 soles per ton, reflecting significant added value. Overall, guinea pig manure-derived biochar presents a promising alternative to plant-based biochars due to its superior nutrient profile. Nonetheless, crop-specific safety evaluations are essential prior to its agricultural use to ensure both effectiveness and safety. Earth and environmental sciences/Environmental sciences Physical sciences/Materials science Biochar physicochemical properties manure guinea pig soil circularity Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction Soil degradation and contamination lead to excessive soil depletion 1 and represent a deterioration of soil quality, structure, fertility, and functionality. When agricultural activities are not managed in a sustainable and circular manner, they can lead to alarming rates of soil erosion. Peru is not exempt to this reality, with its intensive agricultural production and increased use of fertilizers, especially in the high Andean areas 31 . That is why it is necessary to adopt green alternatives that restore the soil in a sustainable manner. Conventional agriculture has driven to losses in the top-soil layer and deterioration of its properties, limiting crop yields. For example, soil acidity is a constraining factor in potato production in the high Andean region of Peru, leading to try new applications associated with other plant coverings to reduce soil erosion 71 . However, the relationship between soil and plant nutritional status involves the availability of soil nutrients, especially in temperate climates 74 and the safety of food available to consumers 46 . One way to overcome soil acidity involves alternatives such as the temporal-spatial diversification in crop rotations that improve the conversion of atmospheric CO 2 into plant biomass 46 or organic agriculture. This one does not use synthetic fertilizers and chemical pesticides, but uses farm manure, sand, compost and green manure 85 ; or the adoption of integrated nutrient management practices, which restore the integration of organic fertilizer and residue retention, further improving soil aggregates and microbiota, generating lower bulk density, greater porosity and greater water retention capacity 61 . On the other hand, liming can raise the acid pH of the soil due to a rapid reaction rate 86 but the use of biochar, in addition to increasing the pH of the soil, can improve its fertility as it is a slow but sustained desorption process. In addition, liming can alter the microbial balance, while biochar improves the microbial habitat and enhances cation exchange. The approach of applying biochar can be promising and sustainable if it is based on the use of waste, especially agroforestry, agricultural, and domestic waste. One of the most promising is the recovery of organic waste, such as animal manure, traditionally considered a waste with high polluting potential when it is not managed properly. The benefits of using livestock manure as an important component of livestock farming and support for agricultural sustainability and part of the circular economy, have been studied. Without proper management, it can have environmental implications, but proper application may require the use of technologies that increase their added value as a rich source of nutrients essential for crop growth, taking care to avoid excessive application of original sterol in the soil 71 . However, cattle are only one of the groups of animals domesticated for agricultural production. Recently, special attention has been given to a very charming species, guinea pigs (Cavia porcellus). These are ancestral animals from South America that have served as food and objects of veneration in South American countries since pre-colonial times and is a crucial source of protein, cholesterol-free and an economic driver in vulnerable, marginalized and remote communities in the region 21 . In developing countries, interest in guinea pig (C. porcellus) farming has grown significantly, as these animals offer a source of high-quality protein for human consumption 73 . In addition, guinea pigs are prolific species that grow quickly, reproduce efficiently on a varied diet, and adapt to diverse climatic conditions 43 . However, the storage of excrement in sheds poses an environmental and health challenge, creating unsanitary conditions for the animals and their caretakers 33 . Although guinea pig manure is easy collected and can be deposited in centralized areas, it is estimated that between 2 and 3 kg are produced per 100 kg of live weight per day, given that between 60% and 80% of the food consumed is eliminated as manure 57 . Given this scenario, the circular economy approach proposes to take advantage of these by-products instead of discarding them, opening the possibility of transforming them into high value-added inputs 43 . Although most studies have explored alternatives such as composting, vermicomposting or the production of biol and biogas, the conversion of guinea pig manure into biochar represents a promising and still under-researched strategy 58 , 51 , 13 . Biochar is obtained by controlled heating of organic matter under oxygen-limited conditions, generating a highly porous and chemically stable material 45 . In agricultural applications, its use has been shown to improve water retention, increase cation exchange capacity, stabilize soil pH, and provide a favorable habitat for beneficial microorganisms 3 , 60 . To produce biochar in this study, a Kon-Tiki reactor is used, an innovation originally developed in Switzerland, which uses an inverted conical design to facilitate natural air circulation and achieve progressive and efficient combustion at controlled temperatures between 500 and 700°C 17 . This method not only optimizes the conversion of biomass into biochar but also minimizes the emission of polluting gases 16 . Among the critical variables that affect the properties of biochar are temperature and residence time during pyrolysis 89 . Temperatures above 600°C favor greater carbonization and the development of a porous structure with a high surface area, while prolonged times (> 60 minutes) enhance the formation of fixed carbon and stable aromatic structures, although they may decrease the presence of beneficial functional groups for nutrient adsorption 65 . In addition, biochar acts as a liming agent in acidic soils thanks to the presence of basic cations (Ca²⁺, Mg²⁺, K⁺) and its microporous structure, which facilitates the adsorption of protons and the gradual release of bases, thus improving soil quality 49 . However, overuse of biochar can alter micronutrients’ availability and affect soil microbial activity 34 , 82 . Recent studies have shown that doses above 5% (w/w) can cause side effects, such as nutrient immobilization, especially in alkaline soils 25 . In this context, corn (Zea mays) has established itself as an effective bioindicator for assessing biochar toxicity, as its early response to changes in pH and the presence of heavy metals results in root growth inhibition and biomass reduction 77 , 90 . Currently, the characteristics of biochar obtained from guinea pig manure through open pyrolysis are unknown, likewise its liming capacity in acidic soils and its potential toxicity in sensitive crops. It is important to analyze the dynamics of the value chain in guinea pig production and marketing in order to propose a model for the valorization of this waste as an input for biochar production in the context of circularity and agricultural sustainability. The present study aims to characterize the properties of guinea pig manure biochar, evaluate its potential toxicity and determine its liming capacity in acidic soils and its use as a model of circularity and agricultural sustainability. The hypothesis is that the transformation of guinea pig manure into biochar through pyrolysis significantly improves its physicochemical properties compared to fresh manure, increasing its stability, nutrient fact and ability to improve acidic soils. Therefore, it is expected that guinea pig manure biochar will establish itself as a profitable and efficient alternative for use as an agricultural amendment, whenever be applied in optimal doses that maximize its benefits without causing adverse effects. Material and Methods Location of the experiment The experiment took place at the Santa Ana Agricultural Experiment Station, located in the province of Huancayo at 3,290 m.a.s.l, with coordinates 12°00' 37.4"S 75°13'19.8" W. The climate in the area is temperate and cold, with low humidity. The prevailing weather is cold and rainy, with dry autumns and winters; meanwhile, temperatures fluctuate between 20°C during the day and below 0°C at night. Collection and physical and chemical characterization of guinea pig manure Guinea pig manure was obtained from the Santa Ana Agricultural Experiment Station in Junín, Peru. This manure was then dried at room temperature and under the sun for seven days. It was then sieved with a 12 mm mesh as contaminants, such as crops or feed residues, were removed. These feed residues were part of the guinea pig diet. Subsequently, 1 kg of the collected samples were used after being sieved, they were sent to the Chemical Analysis Services laboratory at the Agricultural University of La Molina (UNALM) for characterization and analysis. The guide for the characterization of municipal solid waste (Ministerial Resolution No. 457-2018-MINAM) was used as the proposed solid waste characterization procedure (Ministry of the Environment, 2018). To this end, from 1 kg of the collected sample, the guinea pig manure and plant debris accompanying the sample were segregated. The weight was recorded separately. A plastic cylinder-type container was filled to the top with guinea pig manure, then dropped from a 5 cm height (three repetitions) and the free height was recorded to evaluate the volume and density of the waste (Density = Weight/Volume). Biochar production from guinea pigs excrement The open or rapid pyrolysis method was used to produce biochar using guinea pig excrement. To this aims a metal tank was used to construct the pyrolytic oven, which served as a reactor, yielding 20 kg of biochar from guinea pig manure. This method is also known as an open-top pyrolytic reactor. Special care was taken to obtain biochar and not ash or semi-charcoal. The temperature variation, which depends on the calorific value of the material, was estimated to be between 400°C and 700°C. At the end of the homogeneous formation of the charcoal, enough water was added to cool and stop the heat reaction. The collected charcoal was stored in a polypropylene bag, under a cool and dry conditions place. Afterward, it was ground to produce particles approximately 3 mm thick, ready for application. The fresh guinea pig manure had an approximate volume of 2,883.989 cm³ in the uncompacted state and 2,205.41 cm³ in the compacted state. The average density recorded was 0.293 kg/cm³ in the uncompacted state and 0.380 kg/cm³ in the compacted state Analysis of FTIR to determine biochar’s functional groups respect to its raw material. The dry, ground precursor material (guinea pig manure), as well as the dry guinea pig biochar, were manually analyzed using Fourier Transform Infrared Spectroscopy (FT-IR). This technique is based on the absorption of radiation at certain frequencies, and it allowed us to reach the conclusions about the functional groups on the surface of the biochar. 200 scans were taken across a range of 4000–600 nm to characterize the chemical structure of the sample. Using a Thermo Fisher Scientific-Nicolet iS10 equipment (USA) in the Laboratory of the Faculty of Sciences – Chemistry at the National Agrarian University La Molina. Spectra of radiation in this range were recorded for each sample; potassium bromide was used as a blank; and then absorption spectra were obtained from the radiation spectra. Biochar cost calculation from guinea pig manure The economic cost of producing one kilogram of biochar (USD kg⁻¹) was calculated by taking into account the following factors:- 130% of the market price of guinea pig manure (USD kg⁻¹); the conversion ratio of the quantity of biochar produced per kilogram of manure; labour costs (USD day⁻¹); the number of days required to produce one megagram (Mg) of biochar (day Mg⁻¹); the energy costs for the pyrolysis process, based on the price of wood (USD kg⁻¹) and the transformation ratio of the quantity of wood used to produce one megagram of biochar. Biochar assay of the average tolerance limit on corn seed germination tests (Zea mays) The median lethal dose (LD₅₀) of guinea pig manure biochar was measured using the methodology proposed by Duó et al. (2010) adjusted to our case. A DCA was designed with 11 treatments and three replicates. Each treatment was a mixture of river sand and biochar in increasing biochar volume proportions (0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100%). After leaving the pyrolytic reactor, the biochar was ground and passed through a 2 mm sieve before being mixed. The experimental unit was defined as a set of six cells arranged in rows in a seedling tray, containing a mixture of river sand and biochar in the proportions determined by each treatment. These units were arranged in three seedling trays, each containing 72 cells (six rows by 12 columns), with dimensions of 2.5 cm × 3.3 cm × 4.5 cm and a volume of 37 cm³. The 11 treatments were randomized within each tray. A mark was placed to identify each treatment and its repetition. One INIA 619 corn seed was then sown in each cell at a depth of 1 cm. For a period of eight days, the number of seeds that had germinated in each experimental unit was recorded daily. The germination percentage for each day was calculated using the following formula: % Germination = ( \(\:\frac{\#\:germinated\:seeds}{6}\) ) (Ec. 1) Acidity neutralizing capacity and salinization effect of guinea pig manure The ability to neutralize acidity (pH) and the effect of salinization (EC) were evaluated according to the methodology proposed by 32 , with adaptations, using two tests: one in a laboratory and the other in pots. The first laboratory test was designed using a DCA with six treatments and five replicates. Each treatment consisted of a mixture of soil and biochar at proportions of 0%, 3%, 4%, 5%, 6% and 7% by weight. To calculate the neutralizing capacity of guinea pig manure biochar on soil, agricultural soil from the high Andes mountains at 4,000 m.a.s.l. in the Junín province of Peru was used. This soil had an average pH of 6.33, which is considered slightly acidic. The biochar used had an average pH of 9.8, which is alkaline. The experiment began with a 20 g soil sample being weighed in a test tube. Biochar was then added to the soil in different quantities (see Table 1 ). The mixture was then stirred, and 40 mL of distilled water was added. After shaking and mixing, the mixture was left to settle before the electrode was inserted and the pH was recorded 75 . This process was repeated five times for each percentage and/or dose of biochar (Table 1 ). Table 1 Biochar doses used in the neutralization test Traitments Biochar doses (%) Biochar weight (gr) Soil weight (gr) T1 0 0.0 20 T2 3 0.6 20 T3 4 0.8 20 T4 5 1.0 20 T5 6 1.2 20 T6 7 1.4 20 For the second test to assess the neutralizing capacity of guinea pig biochar, soil was collected from agricultural land in Pachacamac, Lima. This soil was supplied by a testing laboratory accredited by the INACAL-DA accreditation body (registration number LE-200) and had a pH of 5.296 and an aluminum content of 9.954. This soil was mixed with biochar obtained from guinea pig manure in capsule form. One kilogram of the acidic soil was placed in plastic bags, with guinea pig biochar added at 0% (0 kg), 10% (0.09 kg) and 20% (0.27 kg) to allow individual mixing within each bag. The bags were then placed in 5 x 5 cm pots with a volume of 90 ml and labelled T1 (0%), T2 (10%) and T3 (20%) for a period of 10 days. The pH and EC parameters were measured for each treatment before watering on day 0, and again after 10 days of watering to check for any changes in the pH and EC data. Samples were taken from each treatment at the end of the 10-day period. The mixture of acidic soil and guinea pig manure biochar was added to a laboratory flask until the volume of soil solution in the graduated flask reached 90 ml, and the pH and EC parameters were measured in the same way. As part of the methodology for determining the neutralizing capacity, 90 ml samples of the wet mixture were taken from each treatment. These samples were placed in paper bags, which were then placed in an oven to begin the drying process for each treatment, lasting one day. The treatments were divided into graduated flasks and each treatment consisted of three repetitions with 30 ml of the solid mixture. Distilled water was added to each flask, which was then placed in a shaker for 10 minutes before being left to rest. After this time, the samples were placed on filter paper suspended over a beaker. Finally, the liquid was collected from the filter paper and left to rest for a further 15 minutes. Radish seeds were used for this parameter and evaluated over an eight-day period. Method and data analysis The data obtained were tabulated using data collection forms from Excel spreadsheets. A descriptive statistical analysis was performed for presentation in tables and figures showing the average values. Toxicity was evaluated using PROBIT analysis. The results obtained in the evaluations of the variables studied were analyzed using the Shapiro-Wilk test for normality by Shapiro and Wilk (1965) and the test for homogeneity of variances (Bartlett, 1937) (p < 0.05). They were then subjected to an analysis of variance (ANOVA). For the comparison of means, the Tukey test at 0.05% was used. Results and Discussion Productive chain of guinea pig in Peru The guinea pig is considered part of Peru's natural heritage. In 2018, there were more than 800,000 small-scale producers dedicated to raising guinea pigs (Cavia porcellus), mainly in the regions of Cajamarca, Cusco, Ancash, Apurímac, Junín, Lima, La Libertad, Ayacucho, Arequipa, and Lambayeque. This represented 57.1% of agricultural producers according to the breeding of minor livestock species and reached 60% in 2023 (Fig. 1 ) as the main breeding activity after chickens (76.4%) 38 . Production amounted to between 17.96 and 18.6 x10⁶ units in 2018, involving 824,994 agricultural units nationwide 38 . From 2019 onwards, guinea pig farming has steadily increased, reaching a maximum of 23.6 million in 2019. However, the pandemic and other atypical economic factors negatively impacted the industry in 2020. Nevertheless, the guinea pig population recovered notably in 2021, with production reaching 25.8 million. Information on guinea pig production in Peru comes from various official sources, primarily the National Institute of Statistics and Informatics (INEI) and the Ministry of Agricultural Development and Irrigation (MIDAGRI). The state pays special attention to the evolution of guinea pig farming in the country, with responsibility lying on MIDAGRI and its various state agencies. The National Agricultural Survey (ENA) is conducted periodically by the INEI, which provides annual data on agricultural production in Peru and contains relevant information on guinea pig farming. An analysis of the guinea pig production chain (Fig. 2 ) begins with the supply of inputs . Peru has been researching the genetic improvement of the species and has developed improved guinea pig breeds called 'Perú, Andina, Inti and Kuri', created by the National Institute of Agrarian Innovation (INIA). These breeds have been transferred to over 15,000 breeders, generating a 20% increase in family breeding and a profit margin of up to 51%, as well as a marginal benefit index of 1.19 54 . In this context, it has generated an increase of food dotation with forages such as alfalfa, ryegrass, commercial concentrated, likewise agro-industrial derivates. The growth has posed an infrastructure increasing of breeders and the need to dynamic and carry an efficient management of manure included veterinarian service to supply vaccines y sanitarian control. This need points to innovation in the supply chain to improve organizational performance 43 , especially for microenterprises and entrepreneurial family groups. Regarding primary production , there are three types of production: a) that managed by family units for their own subsistence, which represents the largest percentage of producers but the lowest percentage of productivity; b) semi-intensive production, which is carried out by medium-scale producers for commercial sale; and c) intensive production at the business level, intended to supply the local or regional market and for export. This reached 8. 5 MT of guinea pig meat, alone, between January and September 2022 4 . Guinea pigs have an average reproduction or gestation period of 68 days, with an average rearing period of 19 days and a fattening average of 1000 g in 2.5 months (INIA, nd). Processing includes slaughtering, which involves killing, eviscerating, skinning, and washing, as well as primary processing. In this case, when it comes to families, they take the fresh meat to the market for sale. On medium scale production, meat is frozen and on a larger scale, it is vacuum-packed. Local markets play a role in the marketing stage, this one is characterized for involving local markets in fairs, the sale of food dishes in restaurants, and exports. The trading is still limited and held by 4 companies and intermediaries addressed, through small channels, to the US and Europe. Thus, sales are conducted directly by the producer-consumer or intermediaries, with a slight participation of producer associations 53 . The consumption of guinea pig in Peru dates back thousands of years. It was traditionally eaten by the Andean population and has increased nationwide due to its high nutritional value, through government consumer education campaigns regarding its richness in iron, omega-3, and protein. Valorization of guinea pig manure as a by-product in the guinea pig chain in a new agricultural application product: Biochar. Table 2 shows the amount of guinea pig manure estimated obtained as a by-product, likewise the yielding after being transformed into biochar by pyrolysis and under conditions controlled of 500 o C. Table 2 Production of guinea pig manure and annual yielding Year Population of guinea pig (millions) Production of manure kg/year* Yield in biochar k/year** 2015 16.05 406.07 121.8 2016 20.91 529.02 158.7 2017 21.1 533.83 160.1 2018 17.96 454.39 136.3 2019 23.6 597.08 179.1 2020 11.9 301.07 90.3 2021 25.8 652.74 195.8 * 25.3 kg per guinea pig until release to market ** yield: 30% In general, the values show an upward trend between manure production and its potential conversion into biochar, closely related to the increase in guinea pig production reported in recent years, despite the decline observed in 2020 due to the COVID-19 pandemic. The increase is a response to government support for the guinea pig production chain in the country, particularly in the Andean regions of the central and southern highlands, where production units have experienced a parallel increase in the number of units or heads and in the volume of organic by-products such as manure. The application of pyrolysis techniques includes the use of artisanal or medium-tech reactors that can transform manure, previously considered waste, into a raw material or precursor material and enter the valued inputs plan to produce biochar , a product with multiple agronomic and environmental benefits. The average conversion yield from dry manure to biochar is 30%, with slight variations attributable to manure moisture content, pyrolysis temperature and process operating conditions. This advance in the circular economy confirms that the approach to integrating valorization technologies such as pyrolysis contributes significantly to closing the nutrient cycle and improving the sustainability of the guinea pig chain. This represents an opportunity for the economic diversification of production units by taking advantage of a by-product with commercial potential such as an agricultural amendment, biofilter, or carbon sink. Below is a literature review reporting on the physicochemical properties of biochar that make it an amendment that improves soil quality for agriculture (Table 3 ). Table 3 Physicochemical properties of biochar produced from animal manure Biochar source Temperature (oC) pH N (%) CIC (cmol/kg) Reference Cow manure 300 8.62 2.72 185.89 Zhang et al. (2021) [96] 400 9.86 2.09 169.07 500 10.75 1.76 156.91 600 10.79 1.72 156.52 700 10.83 1.54 147.52 Cow manure 300 8.48 2.55 Qin et al. (2019) [63] 400 9.86 nd nd 500 10.75 nd nd 600 10.79 nd nd 700 10.83 nd nd sheep 500 nd 2.89 nd Huang, Chen & Zhang (2018) [35] rabbit 500 nd 2.57 nd Pig 500 nd 2.23 nd rabbit 300 8.6 2.1 146 Cárdenas-Aguiar et al. (2022) [12] rabbit 600 10.8 0.8 127 rabbit 550 6.98 2.98 23.1 Medyńska-Juraszek et al. (2022) [50] Table 3 confirms the variability of biochar properties depending on the type of manure, although the pyrolysis temperatures applied (300–500°C) are decisive for the concentration or reduction of more volatile materials in the manure used as precursor material. In general, it is observed that the pH increases with temperature, reaching more alkaline values above pH (9) in the case of cow and pig manure. It is important to highlight the presence of a higher concentration of ashes rich in carbonates and alkaline oxides 96 , allowing biochar to be used as an acid soil improver. It is also observed that the nitrogen content (N%) is higher in rabbit and pig biochar when it is produced at temperatures below 400°C. At higher temperatures, there will be a loss of volatile nitrogen compounds 28 . The cation exchange capacity (CEC) varies significantly, as sheep and rabbit biochar show higher values at medium temperatures (350–400°C), indicating better nutrient retention in agricultural soils due to the conservation of oxygenated functional groups. This shows that CEC is maximized at lower temperatures < 450°C but decreases at higher temperatures due to the removal of oxygenated functional groups that favor cation retention 28 . The different biochars evaluated have specific applications depending on their origin and neutralizing capacity, highlighting their potential as amendments to correct acidity and improve fertility in degraded soils. Table 4 shows relevant information from various authors on the application and efficiency of biochar as a corrective agent or soil improver for acidic soils. Table 4 Applications and neutralizing capacity of biochar produced from various types of waste Biochar source Suggested application and neutralizing capacity Reference Biochar from waste trees at 550℃ for 5 h. Increase of soil pH, decrease in exchangeable acidity, due to the increase in exchangeable and water-soluble basic cations, because biochar is rich in carbonates and other alkaline substances. Chen et al. (2023) [15] Plat debris and cow manure pH increasing in one unit Geng et al. (2022) [28] Increasing of soil pH (+ 1), organic matter (120.8%) and CEC (16.2%) and soil K availability were improved. Zhang et al. (2022) [95] Commercial Products Biochar has a positive effect on reducing soil acidity (it raises the initial pH by one unit: 5.56), MOS, releases available Ca2 + and Mg2 + and improves soil fertility. Dang, Ngoc & Hung (2022) [18] Rice straw Biochar improves heterotrophic nitrification (pH 4.0–7.4) and promotes nitrogen retention in soil at pH 4.5–6.4. It improves nitrogen use efficiency. Qian et al. (2023) [62] Organic wastes Application of 1.5% biochar to the soil, pH value (0.26–0.47 units) increases. Guo et al. (2022) [30] Biochar of abeto Douglas Biochar provides alkalinity and buffering capacity, has greater solubility in water and provides greater availability of bases and pH and its buffering capacity depends on cation exchange sites Arwenyo et al. (2023) [6] Physicochemical characteristics of biochar from guinea pig manure The results show that the values ​​for hydrogen potential were 9.07, showing a high pH suitable for use in acidic soils (Table 5 ), acting as an acidity compensator and with potential for the environmental remediation of acidic waters. The data obtained in this work are related to the studies of 84 . In works related to the biochar production at different temperatures, they report pH values ​​between 8.92 and 11.14, as indicated by 27 , who used the slow pyrolysis technique in vine cultivation at the end of its production cycle, reporting a pH of 10.5. Other authors’ work such as 80 , on biochars in the Peruvian Amazon, produced by slow pyrolysis in a furnace, obtained pH between 7.14 and 10.74. 57 in the study of biochar production at temperatures from 350 to 600°C had a pH that ranged from 7.97 to 10.35. Meanwhile, a pH of 9.07 suggests its potential use for the adjustment of acidic soils. Its high cation exchange capacity (48.8 meq/100g) and high fixed carbon content (37.9%) turn it into a material with high stability and nutrient retention, like that reported by 80 in biochar obtained from poultry manure. However, concentrations of heavy metals such as Cr (7.09 mg/kg) and Cd (1.05 mg/kg) were detected, suggesting the need to evaluate its safety before its application in sensitive crops 10 . For the EC, a high value of 17.28 mS/m is observed, directly related to the salt content in the rhytidome, as indicated by Nunes et al. (2021), which would reflect the results of the guinea pigs' feeding. Compared to studies carried out by 27 , 9 , 83 , biochar, by fast and open pyrolysis, of manure achieved the highest levels, with 1% of nitrogen. The authors mentioned found that by fast and open pyrolysis of plant tissues they obtained percentages(N) ranging from 0.31–0.84%, being this aspect the one that contributes to the development of microbial life and soil recovery. The phosphorus content present in the biochar obtained from guinea pig manure reports 4.0%, which is high if we compare it with studies where different pyrolysis processes were carried out applied to eucalyptus biomass, where they report levels of 0.50% except for biochar by slow pyrolysis of branches. This high level of phosphorus could affect eutrophic processes in an aqueous medium, which confirms that biochar obtained from plant tissues and/or animal manure sources depends greatly on it, as indicated by 27 , 9 . The characterization of the biochar obtained at the laboratory shows levels of microelements available to plants in the openly pyrolyzed matter, being consistent with 2 , 11 .This also show evidence that biochar obtained from biomass and animal manure improve soil conditions. The results of the analysis, in Table 5 , indicate a notable increase in some compounds such as Mn, Mg, Cu, Ca, Zn, Na, and electrical conductivity, closely correlated variables, which increase during rapid pyrolysis of guinea pig manure. Several of these characteristics are replicated to a lesser extent during slow pyrolysis and these levels are closely associated with changes in pH. This confirms that biochar obtained from animal manure exhibits higher nutrient levels than those obtained from plant biomass, and depends on the type of pyrolysis used, as indicated by 9 , 11 . The levels of essential microelements (Mg, Cu, Ca, Zn) coincide with the optimal ranges established by international biochar quality standards (IBI, 2023). However, the presence of heavy metals such as Cr (7.09 mg/kg) and Cd (1.05 mg/kg), although below the maximum permissible limits, require continuous monitoring in long-term applications. Zhang et al. (2024) suggest that these elements can be stabilized in the biochar matrix by complexation and precipitation processes, reducing their bioavailability. Table 5 Physicochemical characteristics of guinea pig manure pH - EC dS/m CIC meq/100g OM % N % P % K % Ca % Mg % Na % Fe mg/Kg Cu mg/Kg Zn mg/Kg Mn mg/Kg Pb mg/Kg Cd mg/Kg Cr mg/Kg 9.17 17.28 48.8 62 1 4 3 5 1.7 1.3 4530 72 435 840 15.68 1.05 7.09 EC: Electric conductivity; CIC: cation interchange capacity OM: organic matter; N: Nitrogen; P: phosphorus; K: Potassium; Ca: Calcium; Mg: Magnesium; Na: Sodium; Fe: iron; Cu: Copper; Zn: Zinc; Mn: Manganese; Pb: P; Lead Cd: Cadmium; mS/m: Milisiemens per metro; meq/100g: Miliequivalent per 100 gramos; mg/kg: Miligrams per kilogram Proximal composition of guinea pig manure biochar The values ​​shown in Table 6 for ash were 34.6%. This condition will allow greater availability of nutrients when using biochar as an amendment; however, the high levels of ash could indicate a possible alteration of the physical part of the biochar obtained, but confirms that the biochar obtained can clearly be used as a product with an alkalizing effect, being an alternative for environmental remediation (Silva et al., 2024; Nunes et al., 2021). The amount of carbon obtained was 37.9%, confirming biochar’s capacity to save part of the carbon and preserve it in its molecular form ( 37 , 22 ). Related studies, when characterizing 60 types of biomasses converted into biochar, show carbon values ​​​​from 26.61 to 53.26% according to the plant tissue used. The values ​​obtained in this study are consistent with values ​​reported by 84 . Table 6 Proximal composition of guinea pig manure Humidity % Volatil material %MS Ashes %MS Carbon fix %MS 34.8 65.4 34.6 37.9 %MS: Dry materia percentage FTIR -functional groups analysis in manure and biochar Figure 3 shows functional groups in raw material (guinea pig manure) and biochar. Figure 3 of the blue spectrum shows that the surface area of ​​the manure contained C-H bonds with peaks in the region 850 to 897 cm − 1 , associated with vibrations of aromatic rings, oxygen-rich groups and aromatic structures. These C-H bonds in the aromatic chains increased in the biochar at the 873 cm − 1 peak similarly to those described by 35 in sheep manure, rabbit feces and pig manure biochar, all, prepared by controlled thermal pyrolysis at 500°C. On the other hand, near this region the manure presented a large valley at 986 cm − 1 still related to vibrations of alkene groups (unsaturated) or C-H heterocyclic rings; while the valley originating at 1033 cm − 1 would be related to stretching of C-O bonds in the form of ethers or similar, since the region from 1100 to 1300 cm − 1 is characterized by the presence of C-O ether bonds. However, in biochar the functional groups of the original raw material were notably destroyed or reduced during pyrolysis at 500°C (red spectrum), removing heteroatoms to form a more pronounced valley at 1000 cm − 1 corresponding to aromatic structures of greater polarity (Guo et al., 2021). This situation was observed in the range of 897 to 1645 cm⁻¹. Furthermore, the 1033 cm⁻¹ peak showed a possible P–O stretching also recorded by 74 for a biochar made from animal manure, which also coincided with the rich presence of P minerals as occurred in this research. It is important to mention that in the 1645 cm − 1 region, stretching of C = O bonds normally occurs in carbonyl groups of carboxylic acids, amides or ketones present in proteins and other organic components 93 . Likewise, unlike manure that presented C-H bonds (alcohols, ethers, carboxylic acids and esters) in the 1488–1700 cm − 1 region, pyrolysis at 500 o C caused the decomposition of the groups, causing a decrease in the C-H and C-O bands with the appearance of more stable structures, such as C = C. Furthermore, the 3630 cm⁻¹ region, characteristic of -OH groups and normally associated with the stretching vibration of non-alcoholic hydroxyl (-OH) groups, also decreased with temperature. In manure, near 3278 cm⁻¹, phenolic-OH stretching of hydroxyl groups was observed, while in biochar, a decrease in the signal was observed, attributable to a loss of the -OH group. This could be due to the O-H vibrations of carboxylic acid, phenol, and alcohols (cellulose/lignin); while the vibrations at 2920 cm⁻¹ correspond to the symmetric or asymmetric C-H stretching of methyl groups 20 , 59 . Tolerance limit assay of guinea pig manure biochar on corn seedlings Toxicity was based on the evaluation of plant mortality associated to the established biochar dose. The physical, chemical, and structural properties of biochar caused relatively high levels of mortality and survival in corn seedlings. The biochar properties obtained from guinea pig manure tend toward alkalinity (Table 5 ), but at high doses, seedling mortality increases, which is not favorable for seed germination. The results related to radicle sprouting, embryonic gemmule growth of seeds and seedling development are shown in Fig. 4 , which shows that the highest germination percentages were achieved with a median lethal dose (LD 50 ) of 40%, 40 units of biochar over 100 units of soil, quantified by the volume reached in the beaker by biochar or soil and mixed in a rate 40 solid biochar /100 solid soil, measured solid-solid. These results are consistent with those reported by 5 , when conducting a systematic review of the physicochemical properties of biochar. Biochar applied at a dose of 40% (as described before) showed no lethal effects on corn germination, but higher doses caused a 30% decrease in seedling emergence. These results are consistent with those of 5 who reported adverse effects on cereal germination at high doses of alkaline biochar. Toxicity analysis revealed an LD 50 of 40%, significantly higher than the 2–5% range typically recommended for agricultural applications 47 . This unusually high tolerance could be attributed to (1) the effective stabilization of potentially toxic compounds during pyrolysis, (2) the high buffering capacity of the material that prevents abrupt changes in substrate pH, and (3) the presence of biostimulant compounds that counteract negative effects. However, considering the precautionary principle and the results of long-term studies 66 , it is recommended to limit the application to a maximum of 30% for agricultural use. Neutralizing capacity of biochar The results in Fig. 5 show that the greatest pH increases occurred in acidic and neutral soil, as mentioned by 93 , where most biochar have neutral to basic pH and corroborating the results of this study, where an increase in soil pH was recorded after biochar application, when the initial pH was low 27 . For soils with alkaline pH, this may be undesirable, as mentioned by other authors, for greater sustained liming effects in acidic pH soils, regular applications would be needed 66 . Biochar increased the pH of acidic soils from 6.37 to 7.15 at a 7% dose, confirming its liming effect 93 . Its application in soils with neutral or alkaline pH may not be advisable, as it could lead to imbalances in nutrient availability. The progressive increase in pH observed in acidic soils treated with different doses of biochar demonstrates its effectiveness as a liming amendment. The 7% dose produced the greatest increase in pH, consistent with the results of 88 , who reported maximum neutralization efficiency between 5–8% application. The mechanism of action involves (1) initial release of carbonates and basic oxides, (2) formation of organo-mineral complexes that increase the buffering capacity of the soil and (3) stimulation of microbial activity that favors alkalization. The results reveal a positive and significant interaction of biochar dose on pH increase (p < 0.05). The use of biochar at a percentage of 7% showed the highest pH increase (Table 7 ) in reference to the treatment without biochar doses; 10 mention that biochar is an effective soil amendment since it reduces acidity due to its liming potential. 80 evaluated the dynamic changes in soil pH in relation to the biochar dose, concluding that the addition of the amendment in the soil increased the pH at a rate of 10 t/ha combined with 40 kg of N, also pointing out that a higher dose of biochar in the absence of N fertilizer generates a greater increase in soil pH. Biochar derived from organic waste generates a source of carbon input to the soil and multifunctional values 10 ​​, the alkaline level of biochar will depend on the type of precursor material and the processing conditions. Table 7 Comparative table of pH in relation to biochar application rates. Characteristic Porcentaje of biochar 0% 3% 4% 5% 6% 7% pH 0 (0) a 0.547 (0.025) b 0.587 (0.006) b 0.550 (0.026) b 0.643 (0.074) bc 0.777 (0.072) c Figure 6 , shows that treatments 3%, 4%, 5%, 6% y 7% increased significantly pH from 6.37 to 6.92, 6.92, 6.96, 7.01 and 7.15, respectively. ANOVA analysis shows significant differences in soil pH between treatments (p < 0.05), like studies of 79 who found pH increases between 0.38 to 0.67, with values of pH from 5.66 to 6.13, 6.33, 6.04 and 6.14 with biochar, produced from cereal husks which had a pH of 8.8. These results are confirmed by other authors about the neutralizing effect of biochar in soils 40 , 41 . 19 indicate that biochar from organic waste could be used as a substitute for lime materials to increase soil pH. The pH of biochar is directly influenced by the type of feedstock, temperature and time of production (Liu & Zhang, 2012). Biochar can be alkaline in nature and can neutralize released protons, thereby reducing soil acidity to 10 , 69 . This is because soil acidification is due to an increase in protons (H + ) releasing from the transformation reactions of compounds containing carbon (C), nitrogen (N) and sulfur (S) 10 . Finally, 52 points out that soil pH and EC are related to biochar (pyrolysis temperature of 600°C) due to a higher concentration of K + ions and a lower CEC. This is due to the increase in exchangeable and soluble K + and the decrease in soil buffering capacity due to the high rate of biochar application. Table 8 represents the cost analysis of guinea pig manure, for this purpose the data reported by other authors and production values ​​from the Santa Ana experimental station (INIA-Junín, Peru) were used along the production of this species. The most important values ​​to use were the cost of feed and the amount of manure produced by the guinea pig for 24 hours; the price of feed considered was the use of forage, balanced feed or other inputs depending on the type of breeding and/or production. Then, in Yamada et al. (2019)’s research, they consider that the feeding expense with balanced feed and forage was S/. 1.61 until the sale of the guinea pig also called achieved guinea pig. Then considering the amount of manure produced per guinea pig, which is 230 grams, the price of guinea pig manure per ton was calculated at S/. 83; Likewise, in the study by 14 , higher feeding expenses were reported with S/. 7.97 using balanced feed and forage until the guinea pig is sold, thus reaching a cost of S/. 409.5 per ton of guinea pig manure. Finally, at the Santa Ana experimental station where the guinea pig is fed with green forage, the cost of feeding reaches an average of S/. 4.5 until the sale and calculating the price of the ton of guinea pig manure it reached S/. 231.2. In Table 7 , a price increase of 30% was considered to the real cost of the kilogram of guinea pig manure, because in the future it can be wholesale considering taxes or other. Table 8 Comparison of guinea pig manure production in different locations. Production cost of guinea pig manure (Yamada A et al., 2019) (Cayetano Robles, 2019) EEA Santa Ana- INIA Description Unit Quantity Quantity Quantity Time from feeding to market release Days 110.00 110.00 110.00 Cost from feeding to market release (kg de carne) S/. 1.61 7.97 4.50 Amount of manure (kg/Guinea pig) * Day 0.23 0.23 0.23 Total manure produced per guinea pig until market release kg 25.3 25.3 25.3 Production cost of waste per kg S/. 0.06 0.32 0.18 Calculated sale price (30% additional) per kg S/. 0.08 0.41 0.23 Calculated price per ton of manure S/. 82.73 409.53 231.23 * source: (Leonardo & Adrian, 2015) Meanwhile, Table 9 presents the cost analysis for producing biochar from guinea pig manure. It was found that the cost of fresh manure is very important in this process. That is, the lower the cost, the greater the economic benefits are obtained from the sale of guinea pig manure biochar. Regarding biochar production costs, based on research and data from the experimental station, values ​​of S/. 662.7 were found according to 91 , S/. 989.5 were found according to 14 , and S/. 811.2 were found according to the experimental station data. These costs were for the use of fresh manure per ton until biochar was obtained. Following this, a 30% increase in the cost per kilogram of biochar price was considered, reaching a price of S/. 2.87, S/. 4.29 and S/. 3.5 per kilogram of biochar. Finally, the price per ton of biochar was calculated obtaining costs of S/. 287, S/1.82 and S/. 4287.94 with the values ​​of 91 , 14 . In the experimental station the cost per ton would be S/. 3515.3 for biochar. Considering the American currency, it is estimated that the cost per ton of guinea pig manure biochar would be $ 774.1 and $ 1155 with the type of feeding developed in the animals in the studies by 91 , 14 and for the station the cost is 947.5 dollars, but the costs vary depending on the type of material with which the biochar is made, as shown by the study by 68 . This last one made biochar with the derivative of Miscanthus (a perennial herb), estimated at 513.1 Canadian dollars per ton. In this study, various components such as the collection, harvesting and transportation of Miscanthus, crushing to reduce the material to chips and transportation costs within the process. In addition, it covers the cost of pyrolysis, which transforms Miscanthus into biochar, bio-oil and non-condensable gas, as well as the necessary inputs such as diesel to start the pyrolysis. A profit margin of 20% is also considered on the costs of each stage of the process. Also, it is mentioned that the production cost of biochar depends on the system used. The BSI (Biochar Solutions Incorporated) costs USD 745,000 and the ACB (Air Curtain Burner) USD 601,168. Costs include equipment, logistics, labor, maintenance, inputs (fuels, electricity) and palletization. The total cost and minimum selling price are USD 1,674-1,909 for the BSI, and USD 528-1,051 for the ACB (Bergman et al., 2022). Finally, the biochar production cost includes fixed costs (equipment, vehicles, storage) of USD 754.68/ton and variable costs (fuel, labor) of USD 717.76/ton, adding up to a total of USD 1,542.16/ton. The cost varies between USD 448.78 and USD 1,846.96/ton, depending on uncertain factors 55 . Although economic analysis was not a primary objective of the study, the calculated production costs (3,515.31 soles/ton) are competitive considering the high added value of the product. 87 reported similar costs for semi-industrial production systems, suggesting the economic viability of the process. Table 9 Comparison of the cost of producing biochar from guinea pig manure in different locations. Producing cost of biochar from guinea pig manure (Yamada A et al., 2019) (Cayetano Robles, 2019) EEA Santa Ana- INIA Description Unit Quantity Quantity Quantity Cost of one ton of fresh guinea pig manure S/. 82.73 409.53 231.23 Operator - Screening, drying, collection, and packaging (1 ton) Unidad 500.00 500.00 500.00 Energy (Pyrolytic oven) (1 ton) S/. 80.00 80.00 80.00 Total, production cost 662.73 989.53 811.23 Biochar obtained (30%) kg 300.00 300.00 300.00 Cost of guinea pig manure biochar per kg S/. 2.21 3.30 2.70 Estimated sale price (30% additional) per kg of biochar S/. 2.87 4.29 3.52 Sale price of total biochar production 861.55 1286.38 1054.59 Cost of wood charcoal per kg S/. 6.00 6.00 6.00 Cost of wood charcoal 300 kg kg 1800.00 1800.00 1800.00 Difference between guinea pig manure biochar and wood charcoal per kg S/. 3.13 1.71 2.48 Difference between guinea pig manure biochar and wood charcoal per 300 kg S/. 938.45 513.62 745.41 Cost per 1 ton of biochar S/. 2871.82 4287.94 3515.31 Guinea pig manure: a circle solution before acidic soils . Despite the negative impact of the COVID-19 pandemic, Peru has made efforts to increase guinea pig meat production. The genetic improvement of the species by INEI has made inroads into the local market in the five regions with the largest populations, such as Cajamarca (18.9%), Cusco (13.6%), Ancash (12.9%), Apurímac (7.9%), and Junín (7.6%) (Midagri, 2023). Its entry into the international market, considering that slaughtered guinea pigs can cost between $ 30 and $ 80 (Midagri, 2023), means that Peruvian export companies need to improve their supply chain management and waste utilization. However, this initiative must reach the most disadvantaged communities and small entrepreneurs, considering that in 2024, Peruvian guinea pig meat grew by 183%. More comprehensive and inclusive agricultural policies must be implemented. In this context, it is important to identify the actors involved in the supply chain and those who are leading the way toward sustainable use: individual producers and associations/cooperatives, input suppliers (seeds, fodder, medicines), agricultural and veterinary technicians, food processors, marketers, intermediaries and retailers, restaurants and catering companies, public institutions (INIA, SENASA, regional governments), and universities and research centers. Figure 7 shows a comprehensive circularity based on the role of each actor. The inclusion of the thermochemical conversion of waste into biochar in a practical way to produce biochar as a soil quality improver, especially for acidic soils, contributes to environmental sustainability 81 . This leads to improved crop quality by generating greater efficiency in the use of agricultural waste, including guinea pig manure, which in turn promotes a reduction in GHG emissions. In this way, small-scale pyrolysis pilot modules are favorable near areas of guinea pig production, especially in the high Andean areas of the mountains and part of the high jungle. Greater integration is also needed between knowledge management actors, research centers, universities and NGOs to expand training for guinea pig producers and agricultural technicians in the production and use of biochar. INEI is leading this process and needs to expand its coverage through collaborative work with universities and civil society. It is important to introduce the circular economy, approach into agricultural and nutritional management systems 68 . This also involves the development of technical protocols for the application of biochar in various crop soils that are particularly sensitive to acidity. Peru is characterized by significant production of potatoes, coffee, and citrus fruits. Depending on the type of soil, the optimal dose must be established and to do so, it is necessary to expand the range of research that improves productivity and food security through soil conservation. Incentives for rural development policies, including subsidies or public-private partnerships, will be necessary for the implementation of manure valorization technologies with potential application to other types of livestock farming that are developing with higher production in the country. However, it is crucial to integrate this proposal through a portfolio of national strategies for sustainable agriculture and climate change mitigation, which will enable the fulfillment of commitments to reduce GHG emissions and adapt to climate change. The development of biochar systems is a challenge that takes many years due to its complexity and while initial funding and international experience are crucial at the outset, education, awareness and consistent practice are key to maintaining sustainability 26 . Conclusion The economy based on the guinea pig production value chain is promising given its growing productivity, which is increasing local, regional and international consumption. The generation of waste such as guinea pig manure represents a potential for generating a circular and sustainable economy. The use of guinea pig manure as a precursor material for the production of biochar is a strategic opportunity whose practice not only allows for the valorization of an underutilized agricultural waste, but also represents an ecological alternative that significantly improves soil quality, carbon sequestration and the sustainability of agricultural systems, primarily in high Andean areas where guinea pig farming is traditional and widespread and even in coastal soils. Biochar becomes an amendment that, in appropriate doses, is convenient and non-toxic. In this research, it was demonstrated that guinea pig manure biochar has an LD50 of 40%. However, within the probability of finding plants with no signs of toxicity, doses ranging from 0–30% mixed with the substrate. Regarding nutrient content, manure biochar stood out for its high content of Mn, Mg, Cu, Ca, Zn, and Na. It also contained considerable amounts of Pb, Cd, and Cr. It also has a high amount of fixed carbon (37.9%). Guinea pig manure biochar has a salt concentration that gives it a significant CEC (48.8 meq/100g) and an EC of (17.28 dS/m), making it suitable for agriculture. The neutralizing capacity of guinea pig manure biochar was found to be manifested in an increase in soil alkalinity as the dose is increased. This effect is more pronounced at low doses compared to higher ones. Therefore, the application of biochar is more effective in improving alkaline in soil with an acidic tendency than in soils with an alkaline tendency. However, for its implementation, it is essential to develop sustainable value chains based on agricultural waste, through economic incentives, training programs and support schemes for applied research. Peru presents a unique opportunity to lead rural circularity models by taking advantage of local resources such as guinea pig manure, but this requires multisectoral coordination that integrates innovation, inclusive policies and community participation to overcome existing barriers and turn this waste into a model for other types of agricultural/agroforestry waste. Declarations Conflicts of Interest : The authors declare no conflicts of interest Funding: This investigation was funded by the INIA project “Mejoramiento de los servicios de investigación y transferencia tecnológica en el manejo y recuperación de suelos agrícolas degradados y aguas para riego en la pequeña y mediana agricultura en los departamentos de Lima, Áncash, San Martín, Cajamarca, Lambayeque, Junín, Ayacucho, Arequipa, Puno y Ucayali” CUI 2487112. Author Contribution Conceptualization, R.S.; methodology, LD. and S.H.; validation, C.P.C.; formal analysis, R.S., R.C. 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Yang, Y. et al. Spectroscopic characteristics of dissolved organic matter during pig manure composting with bean dregs and biochar amendments. Microchem. J. 158 , 105226 (2020). Zanutel, M., Garré, S., Sanglier, P. & Bielders, C. Biochar modifies soil physical properties mostly through changes in soil structure rather than through its internal porosity. Vadose Zone J. , 23 (1). (2024). Zhang, K., Liu, Y., Sun, H. & Yang, J. Metal stabilization mechanisms in animal manure-derived biochars: A molecular-level investigation. Chemosphere 336 , 139241 (2024). Zhang, M. et al. Four-year biochar study: Positive response of acidic soil microenvironment and citrus growth to biochar under potassium deficiency conditions. Sci. Total Environ. 813 , 152515 (2022). Zhang, P., Zhang, X., Yuan, X., Xie, R. & Han, L. Characteristics, adsorption behaviors, Cu (II) adsorption mechanisms by cow manure biochar derived at various pyrolysis temperatures. Bioresour. Technol. 331 , 1250131 (2021). 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b) biochar from guinea pig manure.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6857389/v1/e6c17aa4d7f7dd846d64870a.png"},{"id":85000151,"identity":"07190dfd-3de2-4463-963f-b8c5dbd5f22c","added_by":"auto","created_at":"2025-06-19 17:25:43","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":106562,"visible":true,"origin":"","legend":"\u003cp\u003eCorn seedling mortality\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6857389/v1/1045a7a32846643b62f61be0.png"},{"id":85001223,"identity":"3d5b8eec-833a-46bb-8c6d-f029ccbfb670","added_by":"auto","created_at":"2025-06-19 17:49:43","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":57394,"visible":true,"origin":"","legend":"\u003cp\u003eMeasure of pH and electric conductivity to biochar doses: 0%, 10% y 20%\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6857389/v1/89558cebdad92fafe196b9f4.png"},{"id":85001717,"identity":"b9530085-dd91-4288-9ff4-71a97962c500","added_by":"auto","created_at":"2025-06-19 17:57:43","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":44814,"visible":true,"origin":"","legend":"\u003cp\u003eSoil pH evaluated to different biochar doses.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6857389/v1/6afd0a7b27e9f72f0614af3f.png"},{"id":85000162,"identity":"f62ed84f-43b3-457b-a0dd-66513537114f","added_by":"auto","created_at":"2025-06-19 17:25:43","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":766098,"visible":true,"origin":"","legend":"\u003cp\u003eRelevant factors in the development of the circular economy in the transformation of guinea pig manure into biochar for the restoration of acidic soils.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6857389/v1/f0c8962f4ec6edf2ffef0f0d.png"},{"id":89110199,"identity":"58b05721-0524-471a-aee2-fb16dfc34a4a","added_by":"auto","created_at":"2025-08-14 18:53:36","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2887305,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6857389/v1/c8e34dfd-a956-4b58-b9ea-42a9970a7bde.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Biochar from guinea pig manure as soil amendment: agronomic potential and cost analysis for sustainable agricultural circularity","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSoil degradation and contamination lead to excessive soil depletion\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e and represent a deterioration of soil quality, structure, fertility, and functionality. When agricultural activities are not managed in a sustainable and circular manner, they can lead to alarming rates of soil erosion. Peru is not exempt to this reality, with its intensive agricultural production and increased use of fertilizers, especially in the high Andean areas\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. That is why it is necessary to adopt green alternatives that restore the soil in a sustainable manner.\u003c/p\u003e \u003cp\u003eConventional agriculture has driven to losses in the top-soil layer and deterioration of its properties, limiting crop yields. For example, soil acidity is a constraining factor in potato production in the high Andean region of Peru, leading to try new applications associated with other plant coverings to reduce soil erosion\u003csup\u003e\u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e71\u003c/span\u003e\u003c/sup\u003e. However, the relationship between soil and plant nutritional status involves the availability of soil nutrients, especially in temperate climates\u003csup\u003e\u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e\u003c/sup\u003e and the safety of food available to consumers\u003csup\u003e\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eOne way to overcome soil acidity involves alternatives such as the temporal-spatial diversification in crop rotations that improve the conversion of atmospheric CO\u003csub\u003e2\u003c/sub\u003e into plant biomass\u003csup\u003e\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e or organic agriculture. This one does not use synthetic fertilizers and chemical pesticides, but uses farm manure, sand, compost and green manure\u003csup\u003e\u003cspan citationid=\"CR85\" class=\"CitationRef\"\u003e85\u003c/span\u003e\u003c/sup\u003e; or the adoption of integrated nutrient management practices, which restore the integration of organic fertilizer and residue retention, further improving soil aggregates and microbiota, generating lower bulk density, greater porosity and greater water retention capacity\u003csup\u003e\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eOn the other hand, liming can raise the acid pH of the soil due to a rapid reaction rate\u003csup\u003e\u003cspan citationid=\"CR86\" class=\"CitationRef\"\u003e86\u003c/span\u003e\u003c/sup\u003e but the use of biochar, in addition to increasing the pH of the soil, can improve its fertility as it is a slow but sustained desorption process. In addition, liming can alter the microbial balance, while biochar improves the microbial habitat and enhances cation exchange. The approach of applying biochar can be promising and sustainable if it is based on the use of waste, especially agroforestry, agricultural, and domestic waste.\u003c/p\u003e \u003cp\u003eOne of the most promising is the recovery of organic waste, such as animal manure, traditionally considered a waste with high polluting potential when it is not managed properly. The benefits of using livestock manure as an important component of livestock farming and support for agricultural sustainability and part of the circular economy, have been studied. Without proper management, it can have environmental implications, but proper application may require the use of technologies that increase their added value as a rich source of nutrients essential for crop growth, taking care to avoid excessive application of original sterol in the soil\u003csup\u003e\u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e71\u003c/span\u003e\u003c/sup\u003e. However, cattle are only one of the groups of animals domesticated for agricultural production.\u003c/p\u003e \u003cp\u003eRecently, special attention has been given to a very charming species, guinea pigs (Cavia porcellus). These are ancestral animals from South America that have served as food and objects of veneration in South American countries since pre-colonial times and is a crucial source of protein, cholesterol-free and an economic driver in vulnerable, marginalized and remote communities in the region\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIn developing countries, interest in guinea pig (C. porcellus) farming has grown significantly, as these animals offer a source of high-quality protein for human consumption\u003csup\u003e\u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e73\u003c/span\u003e\u003c/sup\u003e. In addition, guinea pigs are prolific species that grow quickly, reproduce efficiently on a varied diet, and adapt to diverse climatic conditions\u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e. However, the storage of excrement in sheds poses an environmental and health challenge, creating unsanitary conditions for the animals and their caretakers\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAlthough guinea pig manure is easy collected and can be deposited in centralized areas, it is estimated that between 2 and 3 kg are produced per 100 kg of live weight per day, given that between 60% and 80% of the food consumed is eliminated as manure\u003csup\u003e\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e\u003c/sup\u003e. Given this scenario, the circular economy approach proposes to take advantage of these by-products instead of discarding them, opening the possibility of transforming them into high value-added inputs\u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e. Although most studies have explored alternatives such as composting, vermicomposting or the production of biol and biogas, the conversion of guinea pig manure into biochar represents a promising and still under-researched strategy\u003csup\u003e\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e, \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eBiochar is obtained by controlled heating of organic matter under oxygen-limited conditions, generating a highly porous and chemically stable material\u003csup\u003e\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e. In agricultural applications, its use has been shown to improve water retention, increase cation exchange capacity, stabilize soil pH, and provide a favorable habitat for beneficial microorganisms\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eTo produce biochar in this study, a Kon-Tiki reactor is used, an innovation originally developed in Switzerland, which uses an inverted conical design to facilitate natural air circulation and achieve progressive and efficient combustion at controlled temperatures between 500 and 700\u0026deg;C\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. This method not only optimizes the conversion of biomass into biochar but also minimizes the emission of polluting gases\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. Among the critical variables that affect the properties of biochar are temperature and residence time during pyrolysis\u003csup\u003e\u003cspan citationid=\"CR89\" class=\"CitationRef\"\u003e89\u003c/span\u003e\u003c/sup\u003e. Temperatures above 600\u0026deg;C favor greater carbonization and the development of a porous structure with a high surface area, while prolonged times (\u0026gt;\u0026thinsp;60 minutes) enhance the formation of fixed carbon and stable aromatic structures, although they may decrease the presence of beneficial functional groups for nutrient adsorption\u003csup\u003e\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIn addition, biochar acts as a liming agent in acidic soils thanks to the presence of basic cations (Ca\u0026sup2;⁺, Mg\u0026sup2;⁺, K⁺) and its microporous structure, which facilitates the adsorption of protons and the gradual release of bases, thus improving soil quality\u003csup\u003e\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e. However, overuse of biochar can alter micronutrients\u0026rsquo; availability and affect soil microbial activity\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR82\" class=\"CitationRef\"\u003e82\u003c/span\u003e\u003c/sup\u003e. Recent studies have shown that doses above 5% (w/w) can cause side effects, such as nutrient immobilization, especially in alkaline soils\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. In this context, corn (Zea mays) has established itself as an effective bioindicator for assessing biochar toxicity, as its early response to changes in pH and the presence of heavy metals results in root growth inhibition and biomass reduction\u003csup\u003e\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e77\u003c/span\u003e, \u003cspan citationid=\"CR90\" class=\"CitationRef\"\u003e90\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eCurrently, the characteristics of biochar obtained from guinea pig manure through open pyrolysis are unknown, likewise its liming capacity in acidic soils and its potential toxicity in sensitive crops. It is important to analyze the dynamics of the value chain in guinea pig production and marketing in order to propose a model for the valorization of this waste as an input for biochar production in the context of circularity and agricultural sustainability. The present study aims to characterize the properties of guinea pig manure biochar, evaluate its potential toxicity and determine its liming capacity in acidic soils and its use as a model of circularity and agricultural sustainability. The hypothesis is that the transformation of guinea pig manure into biochar through pyrolysis significantly improves its physicochemical properties compared to fresh manure, increasing its stability, nutrient fact and ability to improve acidic soils. Therefore, it is expected that guinea pig manure biochar will establish itself as a profitable and efficient alternative for use as an agricultural amendment, whenever be applied in optimal doses that maximize its benefits without causing adverse effects.\u003c/p\u003e"},{"header":"Material and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eLocation of the experiment\u003c/h2\u003e \u003cp\u003eThe experiment took place at the Santa Ana Agricultural Experiment Station, located in the province of Huancayo at 3,290 m.a.s.l, with coordinates 12\u0026deg;00' 37.4\"S 75\u0026deg;13'19.8\" W. The climate in the area is temperate and cold, with low humidity. The prevailing weather is cold and rainy, with dry autumns and winters; meanwhile, temperatures fluctuate between 20\u0026deg;C during the day and below 0\u0026deg;C at night.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eCollection and physical and chemical characterization of guinea pig manure\u003c/h3\u003e\n\u003cp\u003eGuinea pig manure was obtained from the Santa Ana Agricultural Experiment Station in Jun\u0026iacute;n, Peru. This manure was then dried at room temperature and under the sun for seven days. It was then sieved with a 12 mm mesh as contaminants, such as crops or feed residues, were removed. These feed residues were part of the guinea pig diet. Subsequently, 1 kg of the collected samples were used after being sieved, they were sent to the Chemical Analysis Services laboratory at the Agricultural University of La Molina (UNALM) for characterization and analysis. The guide for the characterization of municipal solid waste (Ministerial Resolution No. 457-2018-MINAM) was used as the proposed solid waste characterization procedure (Ministry of the Environment, 2018). To this end, from 1 kg of the collected sample, the guinea pig manure and plant debris accompanying the sample were segregated. The weight was recorded separately. A plastic cylinder-type container was filled to the top with guinea pig manure, then dropped from a 5 cm height (three repetitions) and the free height was recorded to evaluate the volume and density of the waste (Density\u0026thinsp;=\u0026thinsp;Weight/Volume).\u003c/p\u003e\n\u003ch3\u003eBiochar production from guinea pigs excrement\u003c/h3\u003e\n\u003cp\u003eThe open or rapid pyrolysis method was used to produce biochar using guinea pig excrement. To this aims a metal tank was used to construct the pyrolytic oven, which served as a reactor, yielding 20 kg of biochar from guinea pig manure. This method is also known as an open-top pyrolytic reactor. Special care was taken to obtain biochar and not ash or semi-charcoal. The temperature variation, which depends on the calorific value of the material, was estimated to be between 400\u0026deg;C and 700\u0026deg;C. At the end of the homogeneous formation of the charcoal, enough water was added to cool and stop the heat reaction. The collected charcoal was stored in a polypropylene bag, under a cool and dry conditions place. Afterward, it was ground to produce particles approximately 3 mm thick, ready for application. The fresh guinea pig manure had an approximate volume of 2,883.989 cm\u0026sup3; in the uncompacted state and 2,205.41 cm\u0026sup3; in the compacted state. The average density recorded was 0.293 kg/cm\u0026sup3; in the uncompacted state and 0.380 kg/cm\u0026sup3; in the compacted state\u003c/p\u003e \u003cp\u003e \u003cb\u003eAnalysis of FTIR to determine biochar\u0026rsquo;s functional groups respect to its raw material.\u003c/b\u003e \u003c/p\u003e \u003cp\u003eThe dry, ground precursor material (guinea pig manure), as well as the dry guinea pig biochar, were manually analyzed using Fourier Transform Infrared Spectroscopy (FT-IR). This technique is based on the absorption of radiation at certain frequencies, and it allowed us to reach the conclusions about the functional groups on the surface of the biochar. 200 scans were taken across a range of 4000\u0026ndash;600 nm to characterize the chemical structure of the sample. Using a Thermo Fisher Scientific-Nicolet iS10 equipment (USA) in the Laboratory of the Faculty of Sciences \u0026ndash; Chemistry at the National Agrarian University La Molina. Spectra of radiation in this range were recorded for each sample; potassium bromide was used as a blank; and then absorption spectra were obtained from the radiation spectra.\u003c/p\u003e\n\u003ch3\u003eBiochar cost calculation from guinea pig manure\u003c/h3\u003e\n\u003cp\u003eThe economic cost of producing one kilogram of biochar (USD kg⁻\u0026sup1;) was calculated by taking into account the following factors:- 130% of the market price of guinea pig manure (USD kg⁻\u0026sup1;); the conversion ratio of the quantity of biochar produced per kilogram of manure; labour costs (USD day⁻\u0026sup1;); the number of days required to produce one megagram (Mg) of biochar (day Mg⁻\u0026sup1;); the energy costs for the pyrolysis process, based on the price of wood (USD kg⁻\u0026sup1;) and the transformation ratio of the quantity of wood used to produce one megagram of biochar.\u003c/p\u003e\n\u003ch3\u003eBiochar assay of the average tolerance limit on corn seed germination tests (Zea mays)\u003c/h3\u003e\n\u003cp\u003eThe median lethal dose (LD₅₀) of guinea pig manure biochar was measured using the methodology proposed by Du\u0026oacute; et al. (2010) adjusted to our case. A DCA was designed with 11 treatments and three replicates. Each treatment was a mixture of river sand and biochar in increasing biochar volume proportions (0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100%). After leaving the pyrolytic reactor, the biochar was ground and passed through a 2 mm sieve before being mixed. The experimental unit was defined as a set of six cells arranged in rows in a seedling tray, containing a mixture of river sand and biochar in the proportions determined by each treatment. These units were arranged in three seedling trays, each containing 72 cells (six rows by 12 columns), with dimensions of 2.5 cm \u0026times; 3.3 cm \u0026times; 4.5 cm and a volume of 37 cm\u0026sup3;. The 11 treatments were randomized within each tray. A mark was placed to identify each treatment and its repetition. One INIA 619 corn seed was then sown in each cell at a depth of 1 cm. For a period of eight days, the number of seeds that had germinated in each experimental unit was recorded daily. The germination percentage for each day was calculated using the following formula:\u003c/p\u003e \u003cp\u003e% Germination = (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\frac{\\#\\:germinated\\:seeds}{6}\\)\u003c/span\u003e\u003c/span\u003e) (Ec. 1)\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eAcidity neutralizing capacity and salinization effect of guinea pig manure\u003c/h2\u003e \u003cp\u003eThe ability to neutralize acidity (pH) and the effect of salinization (EC) were evaluated according to the methodology proposed by\u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e, with adaptations, using two tests: one in a laboratory and the other in pots.\u003c/p\u003e \u003cp\u003eThe first laboratory test was designed using a DCA with six treatments and five replicates. Each treatment consisted of a mixture of soil and biochar at proportions of 0%, 3%, 4%, 5%, 6% and 7% by weight. To calculate the neutralizing capacity of guinea pig manure biochar on soil, agricultural soil from the high Andes mountains at 4,000 m.a.s.l. in the Jun\u0026iacute;n province of Peru was used. This soil had an average pH of 6.33, which is considered slightly acidic. The biochar used had an average pH of 9.8, which is alkaline. The experiment began with a 20 g soil sample being weighed in a test tube. Biochar was then added to the soil in different quantities (see Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The mixture was then stirred, and 40 mL of distilled water was added. After shaking and mixing, the mixture was left to settle before the electrode was inserted and the pH was recorded\u003csup\u003e\u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e75\u003c/span\u003e\u003c/sup\u003e. This process was repeated five times for each percentage and/or dose of biochar (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eBiochar doses used in the neutralization test\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTraitments\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBiochar doses (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBiochar weight (gr)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSoil weight (gr)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eT1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eT2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eT3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eT4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eT5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eT6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eFor the second test to assess the neutralizing capacity of guinea pig biochar, soil was collected from agricultural land in Pachacamac, Lima. This soil was supplied by a testing laboratory accredited by the INACAL-DA accreditation body (registration number LE-200) and had a pH of 5.296 and an aluminum content of 9.954. This soil was mixed with biochar obtained from guinea pig manure in capsule form. One kilogram of the acidic soil was placed in plastic bags, with guinea pig biochar added at 0% (0 kg), 10% (0.09 kg) and 20% (0.27 kg) to allow individual mixing within each bag. The bags were then placed in 5 x 5 cm pots with a volume of 90 ml and labelled T1 (0%), T2 (10%) and T3 (20%) for a period of 10 days. The pH and EC parameters were measured for each treatment before watering on day 0, and again after 10 days of watering to check for any changes in the pH and EC data. Samples were taken from each treatment at the end of the 10-day period. The mixture of acidic soil and guinea pig manure biochar was added to a laboratory flask until the volume of soil solution in the graduated flask reached 90 ml, and the pH and EC parameters were measured in the same way. As part of the methodology for determining the neutralizing capacity, 90 ml samples of the wet mixture were taken from each treatment. These samples were placed in paper bags, which were then placed in an oven to begin the drying process for each treatment, lasting one day. The treatments were divided into graduated flasks and each treatment consisted of three repetitions with 30 ml of the solid mixture. Distilled water was added to each flask, which was then placed in a shaker for 10 minutes before being left to rest. After this time, the samples were placed on filter paper suspended over a beaker. Finally, the liquid was collected from the filter paper and left to rest for a further 15 minutes. Radish seeds were used for this parameter and evaluated over an eight-day period.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eMethod and data analysis\u003c/h3\u003e\n\u003cp\u003eThe data obtained were tabulated using data collection forms from Excel spreadsheets. A descriptive statistical analysis was performed for presentation in tables and figures showing the average values. Toxicity was evaluated using PROBIT analysis. The results obtained in the evaluations of the variables studied were analyzed using the Shapiro-Wilk test for normality by Shapiro and Wilk (1965) and the test for homogeneity of variances (Bartlett, 1937) (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). They were then subjected to an analysis of variance (ANOVA). For the comparison of means, the Tukey test at 0.05% was used.\u003c/p\u003e"},{"header":"Results and Discussion","content":"\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eProductive chain of guinea pig in Peru\u003c/h2\u003e \u003cp\u003eThe guinea pig is considered part of Peru's natural heritage. In 2018, there were more than 800,000 small-scale producers dedicated to raising guinea pigs (Cavia porcellus), mainly in the regions of Cajamarca, Cusco, Ancash, Apur\u0026iacute;mac, Jun\u0026iacute;n, Lima, La Libertad, Ayacucho, Arequipa, and Lambayeque. This represented 57.1% of agricultural producers according to the breeding of minor livestock species and reached 60% in 2023 (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) as the main breeding activity after chickens (76.4%)\u003csup\u003e38\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eProduction amounted to between 17.96 and 18.6 x10⁶ units in 2018, involving 824,994 agricultural units nationwide\u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e. From 2019 onwards, guinea pig farming has steadily increased, reaching a maximum of 23.6\u0026nbsp;million in 2019. However, the pandemic and other atypical economic factors negatively impacted the industry in 2020. Nevertheless, the guinea pig population recovered notably in 2021, with production reaching 25.8\u0026nbsp;million. Information on guinea pig production in Peru comes from various official sources, primarily the National Institute of Statistics and Informatics (INEI) and the Ministry of Agricultural Development and Irrigation (MIDAGRI).\u003c/p\u003e \u003cp\u003eThe state pays special attention to the evolution of guinea pig farming in the country, with responsibility lying on MIDAGRI and its various state agencies. The National Agricultural Survey (ENA) is conducted periodically by the INEI, which provides annual data on agricultural production in Peru and contains relevant information on guinea pig farming.\u003c/p\u003e \u003cp\u003eAn analysis of the guinea pig production chain (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e) begins with the \u003cb\u003esupply of inputs\u003c/b\u003e. Peru has been researching the genetic improvement of the species and has developed improved guinea pig breeds called 'Per\u0026uacute;, Andina, Inti and Kuri', created by the National Institute of Agrarian Innovation (INIA). These breeds have been transferred to over 15,000 breeders, generating a 20% increase in family breeding and a profit margin of up to 51%, as well as a marginal benefit index of 1.19\u003csup\u003e54\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn this context, it has generated an increase of food dotation with forages such as alfalfa, ryegrass, commercial concentrated, likewise agro-industrial derivates. The growth has posed an infrastructure increasing of breeders and the need to dynamic and carry an efficient management of manure included veterinarian service to supply vaccines y sanitarian control. This need points to innovation in the supply chain to improve organizational performance\u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e, especially for microenterprises and entrepreneurial family groups.\u003c/p\u003e \u003cp\u003eRegarding \u003cb\u003eprimary production\u003c/b\u003e, there are three types of production: a) that managed by family units for their own subsistence, which represents the largest percentage of producers but the lowest percentage of productivity; b) semi-intensive production, which is carried out by medium-scale producers for commercial sale; and c) intensive production at the business level, intended to supply the local or regional market and for export. This reached 8. 5 MT of guinea pig meat, alone, between January and September 2022\u003csup\u003e4\u003c/sup\u003e. Guinea pigs have an average reproduction or gestation period of 68 days, with an average rearing period of 19 days and a fattening average of 1000 g in 2.5 months (INIA, nd). \u003cb\u003eProcessing\u003c/b\u003e includes slaughtering, which involves killing, eviscerating, skinning, and washing, as well as primary processing. In this case, when it comes to families, they take the fresh meat to the market for sale. On medium scale production, meat is frozen and on a larger scale, it is vacuum-packed.\u003c/p\u003e \u003cp\u003eLocal markets play a role in the \u003cb\u003emarketing\u003c/b\u003e stage, this one is \u003cb\u003echaracterized\u003c/b\u003e for involving local markets in fairs, the sale of food dishes in restaurants, and exports. The trading is still limited and held by 4 companies and intermediaries addressed, through small channels, to the US and Europe. Thus, sales are conducted directly by the producer-consumer or intermediaries, with a slight participation of producer associations\u003csup\u003e\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe consumption of guinea pig in Peru dates back thousands of years. It was traditionally eaten by the Andean population and has increased nationwide due to its high nutritional value, through government consumer education campaigns regarding its richness in iron, omega-3, and protein.\u003c/p\u003e \u003cp\u003e \u003cb\u003eValorization of guinea pig manure as a by-product in the guinea pig chain in a new agricultural application product: Biochar.\u003c/b\u003e \u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e shows the amount of guinea pig manure estimated obtained as a by-product, likewise the yielding after being transformed into biochar by pyrolysis and under conditions controlled of 500 \u003csup\u003eo\u003c/sup\u003eC.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eProduction of guinea pig manure and annual yielding\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eYear\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePopulation of guinea pig (millions)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eProduction of manure kg/year*\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eYield in biochar k/year**\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2015\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e16.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e406.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e121.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e20.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e529.02\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e158.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2017\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e21.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e533.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e160.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2018\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e17.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e454.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e136.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2019\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e23.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e597.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e179.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2020\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e11.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e301.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e90.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e25.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e652.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e195.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003e* 25.3 kg per guinea pig until release to market\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003e** yield: 30%\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eIn general, the values show an upward \u003cb\u003etrend between\u003c/b\u003e manure production and its potential conversion into biochar, closely related to the increase in guinea pig production reported in recent years, despite the decline observed in 2020 due to the COVID-19 pandemic. The increase is a response to government support for the guinea pig production chain in the country, particularly in the Andean regions of the central and southern highlands, where production units have experienced a parallel increase in the number of units or heads and in the volume of organic by-products such as manure. The application of pyrolysis techniques includes the use of artisanal or medium-tech reactors that can transform manure, previously considered waste, into a raw material or precursor material and enter the valued inputs plan to produce \u003cb\u003ebiochar\u003c/b\u003e, a product with multiple agronomic and environmental benefits.\u003c/p\u003e \u003cp\u003eThe average conversion yield from dry manure to biochar is 30%, with slight variations attributable to manure moisture content, pyrolysis temperature and process operating conditions. This advance in the circular economy confirms that the approach to integrating valorization technologies such as pyrolysis contributes significantly to closing the nutrient cycle and improving the sustainability of the guinea pig chain. This represents an opportunity for the economic diversification of production units by taking advantage of a by-product with commercial potential such as an agricultural amendment, biofilter, or carbon sink. Below is a literature review reporting on the physicochemical properties of biochar that make it an amendment that improves soil quality for agriculture (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePhysicochemical properties of biochar produced from animal manure\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBiochar source\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTemperature (oC)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eN (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCIC (cmol/kg)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCow manure\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e185.89\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eZhang et al. (2021) [96]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e169.07\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.76\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e156.91\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e600\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.79\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e156.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e700\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.54\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e147.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCow manure\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.48\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eQin et al. (2019) [63]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003end\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003end\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003end\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003end\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e600\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.79\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003end\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003end\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e700\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003end\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003end\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003esheep\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003end\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.89\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003end\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eHuang, Chen \u0026amp; Zhang (2018) [35]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003erabbit\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003end\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003end\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePig\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003end\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003end\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003erabbit\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e300\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e146\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eC\u0026aacute;rdenas-Aguiar et al. (2022) [12]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003erabbit\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e600\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e127\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003erabbit\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e550\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e23.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eMedyńska-Juraszek et al. (2022) [50]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e confirms the variability of biochar properties depending on the type of manure, although the pyrolysis temperatures applied (300\u0026ndash;500\u0026deg;C) are decisive for the concentration or reduction of more volatile materials in the manure used as precursor material. In general, it is observed that the pH increases with temperature, reaching more alkaline values above pH (9) in the case of cow and pig manure. It is important to highlight the presence of a higher concentration of ashes rich in carbonates and alkaline oxides\u003csup\u003e\u003cspan citationid=\"CR96\" class=\"CitationRef\"\u003e96\u003c/span\u003e\u003c/sup\u003e, allowing biochar to be used as an acid soil improver. It is also observed that the nitrogen content (N%) is higher in rabbit and pig biochar when it is produced at temperatures below 400\u0026deg;C. At higher temperatures, there will be a loss of volatile nitrogen compounds\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. The cation exchange capacity (CEC) varies significantly, as sheep and rabbit biochar show higher values at medium temperatures (350\u0026ndash;400\u0026deg;C), indicating better nutrient retention in agricultural soils due to the conservation of oxygenated functional groups. This shows that CEC is maximized at lower temperatures\u0026thinsp;\u0026lt;\u0026thinsp;450\u0026deg;C but decreases at higher temperatures due to the removal of oxygenated functional groups that favor cation retention\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe different biochars evaluated have specific applications depending on their origin and neutralizing capacity, highlighting their potential as amendments to correct acidity and improve fertility in degraded soils. Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e shows relevant information from various authors on the application and efficiency of biochar as a corrective agent or soil improver for acidic soils.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eApplications and neutralizing capacity of biochar produced from various types of waste\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBiochar source\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSuggested application and neutralizing capacity\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBiochar from waste trees at 550℃ for 5 h.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eIncrease of soil pH, decrease in exchangeable acidity, due to the increase in exchangeable and water-soluble basic cations, because biochar is rich in carbonates and other alkaline substances.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eChen et al. (2023) [15]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePlat debris and cow manure\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003epH increasing in one unit\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGeng et al. (2022) [28]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eIncreasing of soil pH (+\u0026thinsp;1), organic matter (120.8%) and CEC (16.2%) and soil K availability were improved.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eZhang et al. (2022) [95]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCommercial Products\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBiochar has a positive effect on reducing soil acidity (it raises the initial pH by one unit: 5.56), MOS, releases available Ca2\u003csup\u003e+\u003c/sup\u003e and Mg2\u003csup\u003e+\u003c/sup\u003e and improves soil fertility.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eDang, Ngoc \u0026amp; Hung (2022) [18]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRice straw\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBiochar improves heterotrophic nitrification (pH 4.0\u0026ndash;7.4) and promotes nitrogen retention in soil at pH 4.5\u0026ndash;6.4. It improves nitrogen use efficiency.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eQian et al. (2023) [62]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOrganic wastes\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eApplication of 1.5% biochar to the soil, pH value (0.26\u0026ndash;0.47 units) increases.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eGuo et al. (2022) [30]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBiochar of abeto Douglas\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBiochar provides alkalinity and buffering capacity, has greater solubility in water and provides greater availability of bases and pH and its buffering capacity depends on cation exchange sites\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eArwenyo et al. (2023) [6]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003ePhysicochemical characteristics of biochar from guinea pig manure\u003c/h2\u003e \u003cp\u003eThe results show that the values ​​for hydrogen potential were 9.07, showing a high pH suitable for use in acidic soils (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e), acting as an acidity compensator and with potential for the environmental remediation of acidic waters. The data obtained in this work are related to the studies of\u003csup\u003e\u003cspan citationid=\"CR84\" class=\"CitationRef\"\u003e84\u003c/span\u003e\u003c/sup\u003e. In works related to the biochar production at different temperatures, they report pH values ​​between 8.92 and 11.14, as indicated by\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e, who used the slow pyrolysis technique in vine cultivation at the end of its production cycle, reporting a pH of 10.5. Other authors\u0026rsquo; work such as \u003csup\u003e\u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e80\u003c/span\u003e\u003c/sup\u003e, on biochars in the Peruvian Amazon, produced by slow pyrolysis in a furnace, obtained pH between 7.14 and 10.74.\u003csup\u003e\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e\u003c/sup\u003ein the study of biochar production at temperatures from 350 to 600\u0026deg;C had a pH that ranged from 7.97 to 10.35. Meanwhile, a pH of 9.07 suggests its potential use for the adjustment of acidic soils. Its high cation exchange capacity (48.8 meq/100g) and high fixed carbon content (37.9%) turn it into a material with high stability and nutrient retention, like that reported by \u003csup\u003e\u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e80\u003c/span\u003e\u003c/sup\u003e in biochar obtained from poultry manure. However, concentrations of heavy metals such as Cr (7.09 mg/kg) and Cd (1.05 mg/kg) were detected, suggesting the need to evaluate its safety before its application in sensitive crops\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. For the EC, a high value of 17.28 mS/m is observed, directly related to the salt content in the rhytidome, as indicated by Nunes et al. (2021), which would reflect the results of the guinea pigs' feeding. Compared to studies carried out by \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR83\" class=\"CitationRef\"\u003e83\u003c/span\u003e\u003c/sup\u003e, biochar, by fast and open pyrolysis, of manure achieved the highest levels, with 1% of nitrogen. The authors mentioned found that by fast and open pyrolysis of plant tissues they obtained percentages(N) ranging from 0.31\u0026ndash;0.84%, being this aspect the one that contributes to the development of microbial life and soil recovery. The phosphorus content present in the biochar obtained from guinea pig manure reports 4.0%, which is high if we compare it with studies where different pyrolysis processes were carried out applied to eucalyptus biomass, where they report levels of 0.50% except for biochar by slow pyrolysis of branches. This high level of phosphorus could affect eutrophic processes in an aqueous medium, which confirms that biochar obtained from plant tissues and/or animal manure sources depends greatly on it, as indicated by \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. The characterization of the biochar obtained at the laboratory shows levels of microelements available to plants in the openly pyrolyzed matter, being consistent with \u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e .This also show evidence that biochar obtained from biomass and animal manure improve soil conditions.\u003c/p\u003e \u003cp\u003eThe results of the analysis, in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, indicate a notable increase in some compounds such as Mn, Mg, Cu, Ca, Zn, Na, and electrical conductivity, closely correlated variables, which increase during rapid pyrolysis of guinea pig manure. Several of these characteristics are replicated to a lesser extent during slow pyrolysis and these levels are closely associated with changes in pH. This confirms that biochar obtained from animal manure exhibits higher nutrient levels than those obtained from plant biomass, and depends on the type of pyrolysis used, as indicated by \u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. The levels of essential microelements (Mg, Cu, Ca, Zn) coincide with the optimal ranges established by international biochar quality standards (IBI, 2023). However, the presence of heavy metals such as Cr (7.09 mg/kg) and Cd (1.05 mg/kg), although below the maximum permissible limits, require continuous monitoring in long-term applications. Zhang et al. (2024) suggest that these elements can be stabilized in the biochar matrix by complexation and precipitation processes, reducing their bioavailability.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePhysicochemical characteristics of guinea pig manure\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"19\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c14\" colnum=\"14\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c15\" colnum=\"15\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c16\" colnum=\"16\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c17\" colnum=\"17\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c18\" colnum=\"18\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c19\" colnum=\"19\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH -\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEC dS/m\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCIC meq/100g\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eOM %\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eN %\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eP %\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eK %\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eCa %\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eMg %\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c12\"\u003e \u003cp\u003eNa %\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c13\"\u003e \u003cp\u003eFe mg/Kg\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c14\"\u003e \u003cp\u003eCu mg/Kg\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c15\"\u003e \u003cp\u003eZn mg/Kg\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c16\"\u003e \u003cp\u003eMn mg/Kg\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c17\"\u003e \u003cp\u003ePb mg/Kg\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c18\"\u003e \u003cp\u003eCd mg/Kg\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c19\"\u003e \u003cp\u003eCr mg/Kg\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e9.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e17.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e48.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e1.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e1.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c13\"\u003e \u003cp\u003e4530\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c14\"\u003e \u003cp\u003e72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c15\"\u003e \u003cp\u003e435\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c16\"\u003e \u003cp\u003e840\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c17\"\u003e \u003cp\u003e15.68\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c18\"\u003e \u003cp\u003e1.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c19\"\u003e \u003cp\u003e7.09\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"19\"\u003eEC: Electric conductivity; CIC: cation interchange capacity OM: organic matter; N: Nitrogen; P: phosphorus; K: Potassium; Ca: Calcium; Mg: Magnesium; Na: Sodium; Fe: iron; Cu: Copper; Zn: Zinc; Mn: Manganese; Pb: P; Lead Cd: Cadmium; mS/m: Milisiemens per metro; meq/100g: Miliequivalent per 100 gramos; mg/kg: Miligrams per kilogram\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eProximal composition of guinea pig manure biochar\u003c/h2\u003e \u003cp\u003eThe values ​​shown in Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e for ash were 34.6%. This condition will allow greater availability of nutrients when using biochar as an amendment; however, the high levels of ash could indicate a possible alteration of the physical part of the biochar obtained, but confirms that the biochar obtained can clearly be used as a product with an alkalizing effect, being an alternative for environmental remediation (Silva et al., 2024; Nunes et al., 2021). The amount of carbon obtained was 37.9%, confirming biochar\u0026rsquo;s capacity to save part of the carbon and preserve it in its molecular form (\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e). Related studies, when characterizing 60 types of biomasses converted into biochar, show carbon values ​​​​from 26.61 to 53.26% according to the plant tissue used. The values ​​obtained in this study are consistent with values ​​reported by \u003csup\u003e\u003cspan citationid=\"CR84\" class=\"CitationRef\"\u003e84\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eProximal composition of guinea pig manure\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eHumidity %\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eVolatil material %MS\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAshes %MS\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCarbon fix %MS\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"1\" nameend=\"c5\" namest=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e34.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e65.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e34.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e37.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003e%MS: Dry materia percentage\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eFTIR -functional groups analysis in manure and biochar\u003c/h2\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows functional groups in raw material (guinea pig manure) and biochar. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e of the blue spectrum shows that the surface area of ​​the manure contained C-H bonds with peaks in the region 850 to 897 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, associated with vibrations of aromatic rings, oxygen-rich groups and aromatic structures. These C-H bonds in the aromatic chains increased in the biochar at the 873 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e peak similarly to those described by \u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e in sheep manure, rabbit feces and pig manure biochar, all, prepared by controlled thermal pyrolysis at 500\u0026deg;C. On the other hand, near this region the manure presented a large valley at 986 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e still related to vibrations of alkene groups (unsaturated) or C-H heterocyclic rings; while the valley originating at 1033 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e would be related to stretching of C-O bonds in the form of ethers or similar, since the region from 1100 to 1300 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is characterized by the presence of C-O ether bonds. However, in biochar the functional groups of the original raw material were notably destroyed or reduced during pyrolysis at 500\u0026deg;C (red spectrum), removing heteroatoms to form a more pronounced valley at 1000 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponding to aromatic structures of greater polarity (Guo et al., 2021). This situation was observed in the range of 897 to 1645 cm⁻\u0026sup1;. Furthermore, the 1033 cm⁻\u0026sup1; peak showed a possible P\u0026ndash;O stretching also recorded by \u003csup\u003e\u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e\u003c/sup\u003e for a biochar made from animal manure, which also coincided with the rich presence of P minerals as occurred in this research. It is important to mention that in the 1645 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e region, stretching of C\u0026thinsp;=\u0026thinsp;O bonds normally occurs in carbonyl groups of carboxylic acids, amides or ketones present in proteins and other organic components \u003csup\u003e\u003cspan citationid=\"CR93\" class=\"CitationRef\"\u003e93\u003c/span\u003e\u003c/sup\u003e. Likewise, unlike manure that presented C-H bonds (alcohols, ethers, carboxylic acids and esters) in the 1488\u0026ndash;1700 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e region, pyrolysis at 500 \u003csup\u003eo\u003c/sup\u003eC caused the decomposition of the groups, causing a decrease in the C-H and C-O bands with the appearance of more stable structures, such as C\u0026thinsp;=\u0026thinsp;C. Furthermore, the 3630 cm⁻\u0026sup1; region, characteristic of -OH groups and normally associated with the stretching vibration of non-alcoholic hydroxyl (-OH) groups, also decreased with temperature. In manure, near 3278 cm⁻\u0026sup1;, phenolic-OH stretching of hydroxyl groups was observed, while in biochar, a decrease in the signal was observed, attributable to a loss of the -OH group. This could be due to the O-H vibrations of carboxylic acid, phenol, and alcohols (cellulose/lignin); while the vibrations at 2920 cm⁻\u0026sup1; correspond to the symmetric or asymmetric C-H stretching of methyl groups \u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eTolerance limit assay of guinea pig manure biochar on corn seedlings\u003c/h2\u003e \u003cp\u003eToxicity was based on the evaluation of plant mortality associated to the established biochar dose. The physical, chemical, and structural properties of biochar caused relatively high levels of mortality and survival in corn seedlings. The biochar properties obtained from guinea pig manure tend toward alkalinity (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e), but at high doses, seedling mortality increases, which is not favorable for seed germination. The results related to radicle sprouting, embryonic gemmule growth of seeds and seedling development are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, which shows that the highest germination percentages were achieved with a median lethal dose (LD\u003csub\u003e50\u003c/sub\u003e) of 40%, 40 units of biochar over 100 units of soil, quantified by the volume reached in the beaker by biochar or soil and mixed in a rate 40 solid biochar /100 solid soil, measured solid-solid. These results are consistent with those reported by \u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e, when conducting a systematic review of the physicochemical properties of biochar.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBiochar applied at a dose of 40% (as described before) showed no lethal effects on corn germination, but higher doses caused a 30% decrease in seedling emergence. These results are consistent with those of \u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e who reported adverse effects on cereal germination at high doses of alkaline biochar. Toxicity analysis revealed an LD\u003csub\u003e50\u003c/sub\u003e of 40%, significantly higher than the 2\u0026ndash;5% range typically recommended for agricultural applications \u003csup\u003e\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e. This unusually high tolerance could be attributed to (1) the effective stabilization of potentially toxic compounds during pyrolysis, (2) the high buffering capacity of the material that prevents abrupt changes in substrate pH, and (3) the presence of biostimulant compounds that counteract negative effects. However, considering the precautionary principle and the results of long-term studies \u003csup\u003e\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e\u003c/sup\u003e, it is recommended to limit the application to a maximum of 30% for agricultural use.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eNeutralizing capacity of biochar\u003c/h2\u003e \u003cp\u003eThe results in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e show that the greatest pH increases occurred in acidic and neutral soil, as mentioned by \u003csup\u003e\u003cspan citationid=\"CR93\" class=\"CitationRef\"\u003e93\u003c/span\u003e\u003c/sup\u003e, where most biochar have neutral to basic pH and corroborating the results of this study, where an increase in soil pH was recorded after biochar application, when the initial pH was low \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. For soils with alkaline pH, this may be undesirable, as mentioned by other authors, for greater sustained liming effects in acidic pH soils, regular applications would be needed \u003csup\u003e\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBiochar increased the pH of acidic soils from 6.37 to 7.15 at a 7% dose, confirming its liming effect \u003csup\u003e\u003cspan citationid=\"CR93\" class=\"CitationRef\"\u003e93\u003c/span\u003e\u003c/sup\u003e. Its application in soils with neutral or alkaline pH may not be advisable, as it could lead to imbalances in nutrient availability.\u003c/p\u003e \u003cp\u003eThe progressive increase in pH observed in acidic soils treated with different doses of biochar demonstrates its effectiveness as a liming amendment. The 7% dose produced the greatest increase in pH, consistent with the results of \u003csup\u003e\u003cspan citationid=\"CR88\" class=\"CitationRef\"\u003e88\u003c/span\u003e\u003c/sup\u003e, who reported maximum neutralization efficiency between 5\u0026ndash;8% application. The mechanism of action involves (1) initial release of carbonates and basic oxides, (2) formation of organo-mineral complexes that increase the buffering capacity of the soil and (3) stimulation of microbial activity that favors alkalization.\u003c/p\u003e \u003cp\u003eThe results reveal a positive and significant interaction of biochar dose on pH increase (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The use of biochar at a percentage of 7% showed the highest pH increase (Table\u0026nbsp;\u003cspan refid=\"Tab7\" class=\"InternalRef\"\u003e7\u003c/span\u003e) in reference to the treatment without biochar doses; \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e mention that biochar is an effective soil amendment since it reduces acidity due to its liming potential. \u003csup\u003e\u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e80\u003c/span\u003e\u003c/sup\u003e evaluated the dynamic changes in soil pH in relation to the biochar dose, concluding that the addition of the amendment in the soil increased the pH at a rate of 10 t/ha combined with 40 kg of N, also pointing out that a higher dose of biochar in the absence of N fertilizer generates a greater increase in soil pH. Biochar derived from organic waste generates a source of carbon input to the soil and multifunctional values\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e ​​, the alkaline level of biochar will depend on the type of precursor material and the processing conditions.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab7\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 7\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparative table of pH in relation to biochar application rates.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eCharacteristic\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"6\" nameend=\"c7\" namest=\"c2\"\u003e \u003cp\u003ePorcentaje of biochar\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e0%\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e3%\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003e4%\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003e5%\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003e6%\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003e7%\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003epH\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e(0) a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.547 (0.025) b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.587 (0.006) b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.550 (0.026) b\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.643 (0.074) bc\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.777 (0.072) c\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, shows that treatments 3%, 4%, 5%, 6% y 7% increased significantly pH from 6.37 to 6.92, 6.92, 6.96, 7.01 and 7.15, respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eANOVA analysis shows significant differences in soil pH between treatments (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), like studies of \u003csup\u003e\u003cspan citationid=\"CR79\" class=\"CitationRef\"\u003e79\u003c/span\u003e\u003c/sup\u003e who found pH increases between 0.38 to 0.67, with values of pH from 5.66 to 6.13, 6.33, 6.04 and 6.14 with biochar, produced from cereal husks which had a pH of 8.8. These results are confirmed by other authors about the neutralizing effect of biochar in soils\u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e, \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e indicate that biochar from organic waste could be used as a substitute for lime materials to increase soil pH. The pH of biochar is directly influenced by the type of feedstock, temperature and time of production (Liu \u0026amp; Zhang, 2012). Biochar can be alkaline in nature and can neutralize released protons, thereby reducing soil acidity to \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e69\u003c/span\u003e\u003c/sup\u003e. This is because soil acidification is due to an increase in protons (H\u003csup\u003e+\u003c/sup\u003e) releasing from the transformation reactions of compounds containing carbon (C), nitrogen (N) and sulfur (S)\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. Finally, \u003csup\u003e\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e\u003c/sup\u003e points out that soil pH and EC are related to biochar (pyrolysis temperature of 600\u0026deg;C) due to a higher concentration of K\u003csup\u003e+\u003c/sup\u003e ions and a lower CEC. This is due to the increase in exchangeable and soluble K\u003csup\u003e+\u003c/sup\u003e and the decrease in soil buffering capacity due to the high rate of biochar application.\u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab8\" class=\"InternalRef\"\u003e8\u003c/span\u003e represents the cost analysis of guinea pig manure, for this purpose the data reported by other authors and production values ​​from the Santa Ana experimental station (INIA-Jun\u0026iacute;n, Peru) were used along the production of this species. The most important values ​​to use were the cost of feed and the amount of manure produced by the guinea pig for 24 hours; the price of feed considered was the use of forage, balanced feed or other inputs depending on the type of breeding and/or production. Then, in Yamada et al. (2019)\u0026rsquo;s research, they consider that the feeding expense with balanced feed and forage was S/. 1.61 until the sale of the guinea pig also called achieved guinea pig. Then considering the amount of manure produced per guinea pig, which is 230 grams, the price of guinea pig manure per ton was calculated at S/. 83; Likewise, in the study by \u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e, higher feeding expenses were reported with S/. 7.97 using balanced feed and forage until the guinea pig is sold, thus reaching a cost of S/. 409.5 per ton of guinea pig manure. Finally, at the Santa Ana experimental station where the guinea pig is fed with green forage, the cost of feeding reaches an average of S/. 4.5 until the sale and calculating the price of the ton of guinea pig manure it reached S/. 231.2. In Table \u003cspan refid=\"Tab7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, a price increase of 30% was considered to the real cost of the kilogram of guinea pig manure, because in the future it can be wholesale considering taxes or other.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab8\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 8\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of guinea pig manure production in different locations.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eProduction cost of guinea pig manure\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e(Yamada A et\u0026nbsp;al., 2019)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e(Cayetano Robles, 2019)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eEEA Santa Ana- INIA\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDescription\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnit\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eQuantity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eQuantity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eQuantity\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTime from feeding to market release\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDays\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e110.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e110.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e110.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCost from feeding to market release (kg de carne)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS/.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.61\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAmount of manure (kg/Guinea pig) *\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDay\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.23\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal manure produced per guinea pig until market release\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ekg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e25.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e25.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e25.3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eProduction cost of waste per kg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS/.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.06\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.18\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCalculated sale price (30% additional) per kg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS/.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.41\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.23\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCalculated price per ton of manure\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS/.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e82.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e409.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e231.23\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"5\"\u003e* source: (Leonardo \u0026amp; Adrian, 2015)\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eMeanwhile, Table\u0026nbsp;\u003cspan refid=\"Tab9\" class=\"InternalRef\"\u003e9\u003c/span\u003e presents the cost analysis for producing biochar from guinea pig manure. It was found that the cost of fresh manure is very important in this process. That is, the lower the cost, the greater the economic benefits are obtained from the sale of guinea pig manure biochar.\u003c/p\u003e \u003cp\u003e Regarding biochar production costs, based on research and data from the experimental station, values ​​of S/. 662.7 were found according to \u003csup\u003e \u003cspan citationid=\"CR91\" class=\"CitationRef\"\u003e91\u003c/span\u003e \u003c/sup\u003e , S/. 989.5 were found according to \u003csup\u003e \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e \u003c/sup\u003e , and S/. 811.2 were found according to the experimental station data. These costs were for the use of fresh manure per ton until biochar was obtained. Following this, a 30% increase in the cost per kilogram of biochar price was considered, reaching a price of S/. 2.87, S/. 4.29 and S/. 3.5 per kilogram of biochar. Finally, the price per ton of biochar was calculated obtaining costs of S/. 287, S/1.82 and S/. 4287.94 with the values ​​of \u003csup\u003e \u003cspan citationid=\"CR91\" class=\"CitationRef\"\u003e91\u003c/span\u003e , \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e \u003c/sup\u003e . In the experimental station the cost per ton would be S/. 3515.3 for biochar. Considering the American currency, it is estimated that the cost per ton of guinea pig manure biochar would be \u003cspan\u003e$\u003c/span\u003e774.1 and \u003cspan\u003e$\u003c/span\u003e1155 with the type of feeding developed in the animals in the studies by \u003csup\u003e \u003cspan citationid=\"CR91\" class=\"CitationRef\"\u003e91\u003c/span\u003e , \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e \u003c/sup\u003e and for the station the cost is 947.5 dollars, but the costs vary depending on the type of material with which the biochar is made, as shown by the study by \u003csup\u003e \u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e68\u003c/span\u003e \u003c/sup\u003e . This last one made biochar with the derivative of Miscanthus (a perennial herb), estimated at 513.1 Canadian dollars per ton. In this study, various components such as the collection, harvesting and transportation of Miscanthus, crushing to reduce the material to chips and transportation costs within the process. In addition, it covers the cost of pyrolysis, which transforms Miscanthus into biochar, bio-oil and non-condensable gas, as well as the necessary inputs such as diesel to start the pyrolysis. A profit margin of 20% is also considered on the costs of each stage of the process. Also, it is mentioned that the production cost of biochar depends on the system used. The BSI (Biochar Solutions Incorporated) costs USD 745,000 and the ACB (Air Curtain Burner) USD 601,168. Costs include equipment, logistics, labor, maintenance, inputs (fuels, electricity) and palletization. The total cost and minimum selling price are USD 1,674-1,909 for the BSI, and USD 528-1,051 for the ACB (Bergman et al., 2022). Finally, the biochar production cost includes fixed costs (equipment, vehicles, storage) of USD 754.68/ton and variable costs (fuel, labor) of USD 717.76/ton, adding up to a total of USD 1,542.16/ton. The cost varies between USD 448.78 and USD 1,846.96/ton, depending on uncertain factors \u003csup\u003e \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e \u003c/sup\u003e . Although economic analysis was not a primary objective of the study, the calculated production costs (3,515.31 soles/ton) are competitive considering the high added value of the product. \u003csup\u003e \u003cspan citationid=\"CR87\" class=\"CitationRef\"\u003e87\u003c/span\u003e \u003c/sup\u003e reported similar costs for semi-industrial production systems, suggesting the economic viability of the process. \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab9\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 9\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of the cost of producing biochar from guinea pig manure in different locations.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003eProducing cost of biochar from guinea pig manure\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e(Yamada A et\u0026nbsp;al., 2019)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e(Cayetano Robles, 2019)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eEEA Santa Ana- INIA\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDescription\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnit\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eQuantity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eQuantity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eQuantity\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCost of one ton of fresh guinea pig manure\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS/.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e82.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e409.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e231.23\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOperator - Screening, drying, collection, and packaging (1 ton)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnidad\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e500.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e500.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e500.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEnergy (Pyrolytic oven) (1 ton)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS/.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e80.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e80.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e80.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTotal, production cost\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e662.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e989.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e811.23\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBiochar obtained (30%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ekg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e300.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e300.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e300.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCost of guinea pig manure biochar per kg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS/.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.70\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eEstimated sale price (30% additional) per kg of biochar\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS/.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2.87\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4.29\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.52\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSale price of total biochar production\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e861.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1286.38\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1054.59\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCost of wood charcoal per kg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS/.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCost of wood charcoal 300 kg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ekg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1800.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1800.00\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1800.00\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDifference between guinea pig manure biochar and wood charcoal per kg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS/.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.48\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDifference between guinea pig manure biochar and wood charcoal per 300 kg\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS/.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e938.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e513.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e745.41\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCost per 1 ton of biochar\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eS/.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2871.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4287.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3515.31\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cb\u003eGuinea pig manure: a circle solution before acidic soils\u003c/b\u003e.\u003c/p\u003e \u003cp\u003eDespite the negative impact of the COVID-19 pandemic, Peru has made efforts to increase guinea pig meat production. The genetic improvement of the species by INEI has made inroads into the local market in the five regions with the largest populations, such as Cajamarca (18.9%), Cusco (13.6%), Ancash (12.9%), Apur\u0026iacute;mac (7.9%), and Jun\u0026iacute;n (7.6%) (Midagri, 2023). Its entry into the international market, considering that slaughtered guinea pigs can cost between \u003cspan\u003e$\u003c/span\u003e30 and \u003cspan\u003e$\u003c/span\u003e80 (Midagri, 2023), means that Peruvian export companies need to improve their supply chain management and waste utilization. However, this initiative must reach the most disadvantaged communities and small entrepreneurs, considering that in 2024, Peruvian guinea pig meat grew by 183%. More comprehensive and inclusive agricultural policies must be implemented.\u003c/p\u003e \u003cp\u003eIn this context, it is important to identify the actors involved in the supply chain and those who are leading the way toward sustainable use: individual producers and associations/cooperatives, input suppliers (seeds, fodder, medicines), agricultural and veterinary technicians, food processors, marketers, intermediaries and retailers, restaurants and catering companies, public institutions (INIA, SENASA, regional governments), and universities and research centers. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e shows a comprehensive circularity based on the role of each actor. The inclusion of the thermochemical conversion of waste into biochar in a practical way to produce biochar as a soil quality improver, especially for acidic soils, contributes to environmental sustainability\u003csup\u003e\u003cspan citationid=\"CR81\" class=\"CitationRef\"\u003e81\u003c/span\u003e\u003c/sup\u003e. This leads to improved crop quality by generating greater efficiency in the use of agricultural waste, including guinea pig manure, which in turn promotes a reduction in GHG emissions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn this way, small-scale pyrolysis pilot modules are favorable near areas of guinea pig production, especially in the high Andean areas of the mountains and part of the high jungle. Greater integration is also needed between knowledge management actors, research centers, universities and NGOs to expand training for guinea pig producers and agricultural technicians in the production and use of biochar. INEI is leading this process and needs to expand its coverage through collaborative work with universities and civil society. It is important to introduce the circular economy, approach into agricultural and nutritional management systems\u003csup\u003e\u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e68\u003c/span\u003e\u003c/sup\u003e. This also involves the development of technical protocols for the application of biochar in various crop soils that are particularly sensitive to acidity. Peru is characterized by significant production of potatoes, coffee, and citrus fruits. Depending on the type of soil, the optimal dose must be established and to do so, it is necessary to expand the range of research that improves productivity and food security through soil conservation.\u003c/p\u003e \u003cp\u003eIncentives for rural development policies, including subsidies or public-private partnerships, will be necessary for the implementation of manure valorization technologies with potential application to other types of livestock farming that are developing with higher production in the country. However, it is crucial to integrate this proposal through a portfolio of national strategies for sustainable agriculture and climate change mitigation, which will enable the fulfillment of commitments to reduce GHG emissions and adapt to climate change. The development of biochar systems is a challenge that takes many years due to its complexity and while initial funding and international experience are crucial at the outset, education, awareness and consistent practice are key to maintaining sustainability\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe economy based on the guinea pig production value chain is promising given its growing productivity, which is increasing local, regional and international consumption. The generation of waste such as guinea pig manure represents a potential for generating a circular and sustainable economy. The use of guinea pig manure as a precursor material for the production of biochar is a strategic opportunity whose practice not only allows for the valorization of an underutilized agricultural waste, but also represents an ecological alternative that significantly improves soil quality, carbon sequestration and the sustainability of agricultural systems, primarily in high Andean areas where guinea pig farming is traditional and widespread and even in coastal soils.\u003c/p\u003e \u003cp\u003eBiochar becomes an amendment that, in appropriate doses, is convenient and non-toxic. In this research, it was demonstrated that guinea pig manure biochar has an LD50 of 40%. However, within the probability of finding plants with no signs of toxicity, doses ranging from 0\u0026ndash;30% mixed with the substrate. Regarding nutrient content, manure biochar stood out for its high content of Mn, Mg, Cu, Ca, Zn, and Na. It also contained considerable amounts of Pb, Cd, and Cr. It also has a high amount of fixed carbon (37.9%). Guinea pig manure biochar has a salt concentration that gives it a significant CEC (48.8 meq/100g) and an EC of (17.28 dS/m), making it suitable for agriculture. The neutralizing capacity of guinea pig manure biochar was found to be manifested in an increase in soil alkalinity as the dose is increased. This effect is more pronounced at low doses compared to higher ones. Therefore, the application of biochar is more effective in improving alkaline in soil with an acidic tendency than in soils with an alkaline tendency.\u003c/p\u003e \u003cp\u003eHowever, for its implementation, it is essential to develop sustainable value chains based on agricultural waste, through economic incentives, training programs and support schemes for applied research. Peru presents a unique opportunity to lead rural circularity models by taking advantage of local resources such as guinea pig manure, but this requires multisectoral coordination that integrates innovation, inclusive policies and community participation to overcome existing barriers and turn this waste into a model for other types of agricultural/agroforestry waste.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003e \u003cb\u003eConflicts of Interest\u003c/b\u003e:\u003c/h2\u003e \u003cp\u003eThe authors declare no conflicts of interest\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding:\u003c/h2\u003e \u003cp\u003eThis investigation was funded by the INIA project \u0026ldquo;Mejoramiento de los servicios de investigaci\u0026oacute;n y transferencia tecnol\u0026oacute;gica en el manejo y recuperaci\u0026oacute;n de suelos agr\u0026iacute;colas degradados y aguas para riego en la peque\u0026ntilde;a y mediana agricultura en los departamentos de Lima, \u0026Aacute;ncash, San Mart\u0026iacute;n, Cajamarca, Lambayeque, Jun\u0026iacute;n, Ayacucho, Arequipa, Puno y Ucayali\u0026rdquo; CUI 2487112.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eConceptualization, R.S.; methodology, LD. and S.H.; validation, C.P.C.; formal analysis, R.S., R.C. T. and R.P.G.; investigation, L.D., S.H., A.A., and A.C..; resources, R.S.; data curation, R.P..; writing\u0026mdash;original draft preparation, R.S, R.P.G, C.P.C.; writing\u0026mdash;review and editing, R.C.T. ; visualization, W.S.; supervision, R.S.; project administration, R.S.; funding acquisition, R.S.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eData is provided within the manuscript\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAbdelhak, M. Soil improvement in arid and semiarid regions for sustainable development. In Natural resources conservation and advances for sustainability (73\u0026ndash;90). Elsevier. (2022).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAbukari, A., Kaba, J. S., Dawoe, E. \u0026amp; Abunyewa, A. A. A comprehensive review of the effects of biochar on soil physicochemical properties and crop productivity. 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Technol.\u003c/em\u003e \u003cb\u003e331\u003c/b\u003e, 1250131 (2021).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Biochar, physicochemical properties, manure, guinea pig, soil, circularity","lastPublishedDoi":"10.21203/rs.3.rs-6857389/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6857389/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe valorization of guinea pig manure transforms a traditional input into a stable, high-value product like biochar. This study evaluated the physicochemical characteristics, toxicity, and neutralizing capacity of biochar produced by open pyrolysis in Huancayo, Jun\u0026iacute;n, Peru. Fresh manure was also characterized before pyrolysis, and its median lethal dose was determined. Results showed that uncompacted manure had a volume of 2,883.99 cm\u0026sup3; (0.293 kg/cm\u0026sup3;), and compacted manure 2,205.41 cm\u0026sup3; (0.380 kg/cm\u0026sup3;). The resulting biochar had high contents of nitrogen, phosphorus, potassium, ash (34.6%), and fixed carbon (37.9%), along with an alkaline pH (9.07), high cation exchange capacity (48.8 meq/100g), and elevated organic matter (62%), indicating its potential to improve acidic soils. Moisture content (34.8%) and the presence of microelements (Mg, Cu, Ca, Zn) also suggest agronomic benefits. Economically, producing one ton of biochar from guinea pig manure costs approximately 231.23 soles, while its market value is 3,515.31 soles per ton, reflecting significant added value. Overall, guinea pig manure-derived biochar presents a promising alternative to plant-based biochars due to its superior nutrient profile. Nonetheless, crop-specific safety evaluations are essential prior to its agricultural use to ensure both effectiveness and safety.\u003c/p\u003e","manuscriptTitle":"Biochar from guinea pig manure as soil amendment: agronomic potential and cost analysis for sustainable agricultural circularity","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-19 17:25:39","doi":"10.21203/rs.3.rs-6857389/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"766304c0-77eb-408f-9000-9aa8ebcc1255","owner":[],"postedDate":"June 19th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":50253750,"name":"Earth and environmental sciences/Environmental sciences"},{"id":50253751,"name":"Physical sciences/Materials science"}],"tags":[],"updatedAt":"2025-08-14T18:53:13+00:00","versionOfRecord":[],"versionCreatedAt":"2025-06-19 17:25:39","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6857389","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6857389","identity":"rs-6857389","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}