Brown sugar as a carbon source can make agricultural organic waste compost enter the secondary thermophilic stage and promote compost decomposition

Brown sugar as a carbon source can make agricultural organic waste compost enter the secondary thermophilic stage and promote compost decomposition | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Brown sugar as a carbon source can make agricultural organic waste compost enter the secondary thermophilic stage and promote compost decomposition Peng Xu, Xue Li, Shiwen Zhao, Luolin Shu, Guanzhi Zhang, Yongjun Wu, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3205436/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The utilization of microbial agents can enhance the composting process of agricultural organic waste and enhance the quality of compost products. However, several challenges persist in the composting of such waste, including the limited degradation capacity of the introduced microbial agents and the short duration of the high-temperature phase during composting. To enhance the composting efficiency of agro-organic waste, this study investigated the impact of inoculating tomato straw compost with two microbial agents: ZZ, a complex microbial agent, and EM, a commercial microbial agent. Additionally, 10% brown sugar was added as a carbon source to the compost after the initial high-temperature phase, aiming to assess its effect on the composting process. The findings revealed that compared to the control (CK) group, the ZZ and EM treatments extended the first high-temperature phase by 2 and 1 day, respectively. Furthermore, with the addition of 10% brown sugar, the ZZ and EM treatments remained in the second high-temperature phase for 8 and 7 days, respectively, while the CK treatment had already entered the cooling stage by then. Notably, the inoculation of microbial agents and the addition of brown sugar substantially augmented the activity of lignocellulose-related hydrolases, thereby promoting the degradation of lignocellulose in the ZZ and EM treatment groups. This was confirmed by FTIR analysis, which demonstrated that the addition of microbial agents facilitated the degradation of specific substances, leading to reduced absorbance in the corresponding spectra. XRD analysis further indicated a notable reduction in cellulose crystallinity for both the ZZ (8.00%) and EM (7.73%) treatments. Hence, the incorporation of microbial agents and brown sugar in tomato straw compost effectively enhances the composting process and improves the quality of compost products. Earth and environmental sciences/Environmental sciences/Environmental impact Earth and environmental sciences/Environmental sciences/Environmental chemistry/Pollution remediation Microbial agents Brown sugar carbon source Lignocellulose Cellulose crystallinity Compost product quality Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 0 Introduction The burgeoning global population and improved living standards have sparked a rising need for food production, exerting immense pressure on agricultural activities 1 , 2 . It is estimated that agricultural production worldwide generates a staggering 140 billion tonnes of lignocellulose-related organic waste annually 3 . Notably, this organic waste holds potential as a reusable resource 4 . However, when incorrectly disposed of in substantial quantities, it leads to a wastage of resources and becomes a significant environmental pollutant, affecting both surface and groundwater through contamination and contributing to the emission of substantial amounts of greenhouse gases, among other consequences 5 . Consequently, the proper and safe management of organic agricultural waste emerges as a critical global challenge 6 . The recycling of organic agricultural waste plays a pivotal role in fostering sustainable agricultural development. When agricultural organic waste is directly reintroduced to the land without proper treatment, it poses significant environmental risks. These risks include water pollution resulting from leachate released by agricultural organic waste, soil pollution caused by toxic elements, air pollution stemming from volatile gas emissions, and potential threats to human health due to residual pathogens 7 . To mitigate these concerns, composting agricultural organic waste proves effective as it reduces toxicity and yields a valuable biofertilizer/soil conditioner that enhances agricultural productivity 8 . Numerous studies have consistently demonstrated that aerobic composting transforms agricultural organic waste into stable humus, diminishes its toxicity, stimulates plant growth, and boosts yields 9 – 11 . By incorporating compost products into the soil, nutrient levels are enriched, soil structure and water retention capacity are improved, and the proliferation of soil pathogens is curtailed, thereby fostering crop growth and maximizing yield potential 12 . The beneficial impact of composted agricultural production primarily hinges on the compost's maturity and stability, the biological activity of the microbial community, and the ability of soil organic matter (OM) to support microbial growth 12 . Furthermore, certain microorganisms present in compost products can create an unfavorable environment for soil pathogens, thereby enhancing soil nutrition, promoting plant health, and positively influencing plant growth 13 . However, agricultural organic waste poses challenges due to its high cellulose and lignin content, which hinder degradation and result in prolonged composting cycles and subpar compost quality. The naturally occurring microorganisms in agricultural waste are often insufficient in number and degradation capacity to effectively process the substantial volumes of agricultural waste 14 . Therefore, the addition of microbial agents is commonly employed to facilitate composting 15 . Inoculating compost with microbial agents not only enhances composting efficiency but also offers advantages such as affordability 16 , 17 , minimal secondary contamination, and ease of handling 18 . Xi et al. observed that the inoculation of compost with microbial agents extended the high-temperature phase and promoted humification of the compost 19 . Yang et al. introduced Trametes hirsuta S13 and Pleurotus ostreatus S18 to tobacco straw, resulting in an increased lignin degradation from 23.7–41.1% 20 . Chu et al. developed a composite strain comprising Phanerochaete chrysosporium , Trametes versicolor , and Pleurotus ostreatus , which exhibited respective lignin, cellulose, and hemicellulose degradation rates of 43.36%, 31.29%, and 48.36% 21 . Wan et al. conducted composting with the addition of microbial agents and observed a significant acceleration in the degradation of organic waste 22 . Decades of research have focused on the utilization of microbial agents for degrading agricultural organic waste. However, when applying these microbial agents, several challenges arise, including inadequate compost temperatures, short duration of high-temperature maintenance, insufficient compost maturity, and substandard compost quality. These issues often result from the introduced microbial agents' poor adaptation to the composting environment or even antagonistic interactions with native microorganisms present in the pile. Such interactions can hinder the degradation of agricultural organic waste and compromise the quality of the final compost product. To address the problem of low microbial activity in the compost pile at lower temperatures, the addition of protein, glucose, and urea during the composting process provides essential nutrients for microorganisms. This supplementation stimulates the decomposition rate of agricultural organic waste by microorganisms, yielding a notable "bursting" effect that improves the overall composting efficiency 23 . In this study, five microbial strains isolated from agricultural organic waste piles in the pre-laboratory setting were combined to create the microbial agent ZZ. ZZ was then inoculated into the compost containing agricultural organic waste, with the addition of 10% brown sugar towards the end of the high-temperature phase of the pile. The objectives of this study were to evaluate: (I) the degradation capacity of the microbial agent ZZ for composting agricultural organic waste; (II) the impact of introducing 10% brown sugar at the end of the initial high-temperature phase, reinitiating the high-temperature phase of the pile; and (III) the effects of both microbial agent inoculation and brown sugar addition on the quality of the resulting compost product. 1 Materials and Methods 1.1 Compost design and sampling The composting material was sourced from tomato straw in local facility greenhouses in Shaanxi, China. The straw was collected, sun-dried, and subsequently crushed to approximately 2–5 cm using a straw grinder (Table 1 ). For each experimental group, 15 kg (dry weight) of tomato straw was placed in a 60L compost fermentation bucket, and the moisture content of the compost material was adjusted to 60–70% using distilled water. The experimental groups consisted of ZZ inoculated with 10% ZZ microbial agent, which included Aspergillus niger , Falsochrobactrum ovis , Paenibacillus xylanilyticus , Bacillus subtilis subsp , and Paenibacillus amylolyticus . These microorganisms were isolated from agricultural organic waste in a previous phase of our laboratory research. Additionally, the EM experimental group was inoculated with 10% EM microbial agent (purchased from Hangzhou Goyo Ecological Environment Technology Co., Ltd, China), primarily containing Bacillus subtilis, Lactobacillus acidophilus, Saccharomyces cerevisiae, and purified water. The control group (CK) was inoculated with 10% distilled water. Sampling was performed on days 0, 3, 8, 14, 18, 22, 26, 32, 38, 44, 52, 58, and 65 of the composting process, utilizing the five-point sampling method. The collected compost samples were divided into two parts: one part was used for analyzing physicochemical properties, nutrient elements, and lignocellulose changes, while the other portion was stored at -20℃ for enzyme activity determination. Table 1 Physicochemical properties of tomato straw compost feedstock Raw materials TOC (g/kg) TN (g/kg) C/N pH EC(ms/cm) Moisture content Tomato straws 317.11 19.58 16.19 6.64 4.30 25% 1.2 Physico-chemical analysis of compost The temperature variations within the compost fermentation drum and its surrounding environment were diligently monitored using a digital temperature sensor from Shenzhen Shenghua Xuan Technology Co., Ltd, Shenzhen, China. Fresh solid samples were mixed with deionized water at a 1:10 ratio (volume) to obtain an aqueous extract. The extract was acquired after one hour of oscillatory maceration at 220 r-min^-1 and was used for analyzing pH, electrical conductivity (EC), and the germination index (GI). pH measurements were taken using a pH meter (pHS-3C, Lei Magnetic, Shanghai, China), while EC was determined using a conductivity meter (ST3100M, Ohaus, China) 24 . For GI determination, 5 ml of the extracted water was placed in a Petri dish with filter paper. Then, 20 seeds were uniformly arranged in the dish and placed in an incubator at (25 ± 1) °C for 48 hours. The germination and root length of seeds were measured for each sample, with three parallel groups taken into account. The GI was calculated as follows: GI (%) = (mean number of germinated seeds in the treatment group × mean root length of seeds in the treatment group) / (mean number of germinated seeds in CK × mean root length of seeds in CK) ×100% 25 . Changes in the dry capacity (DC), water-holding porosity (WHP), ventilation porosity (VEP), and total porosity (TTP) of compost materials were determined following the method of Yin et al 26 , 27 . Initially, the air-dried samples were placed in a 200 cm^3-ring knife (M0) and weighed (M1). Next, the ring knife was submerged in distilled water for 24 hours (M2) and then removed from the water. Subsequently, the ring knife was sealed with permeable gauze after removing the lid. The saturated compost in the ring knife was inverted on a screen until water stopped dripping from the bottom, a process that took about 4 hours. Once the dripping ceased, the ring knife was weighed and recorded as M3. Finally, the ring knife was dried at 65℃ until a constant weight was achieved (M4). The calculation of the physical properties is as follows: DC (g/cm 3 ) = (M4 - M0) / 200 TTP (%) = (M2 - M4) / 200 VEP (%) = (M2 - M3) / 200 WHP (%) = TTP - VEP These aforementioned physical properties are commonly used to evaluate composting efficiency and compost maturity. NH 4 + -N was quantified using the colorimetric method, while NO 3 - -N was determined using the spectrophotometric method 28 . Active P(AP) was assessed using 0.5 M NaHCO 3 . Available K(AK) extraction was carried out with NH4OAc, and its quantification was performed through the flame photometric method 29 . HA and FA contents were determined using the oxidative volumetric method with potassium dichromate 30 . OM content was determined through dry combustion at 550℃ for 6 hours 31 . Cellulose, hemicellulose, and lignin contents were assessed following the method outlined by Sajid et al 32 . Cellulase activity was determined using a previously described method 33 . Lignin peroxidase activity was measured with quinuclidinol, and the change in absorbance at 310 nm was recorded within 3 minutes of the reaction 34 . Xylanase activity was determined using beech wood xylan as a substrate. The mixture was incubated at 50℃ for 10 minutes, and the xylan content was measured at 540 nm using the DNS method. Urease activity (UR) was evaluated based on the method established by Zhou et al 35 . Similarly, sucrase activity was determined according to the method outlined by Ma et al 36 . 1.3 Observations on structural characterisation of degraded materials 1.3.1 Scanning electron microscope (SEM) observation of rice straw before and after degradation Prior to and following degradation, a small sample was collected, then washed with distilled water to eliminate surface impurities. The samples were left to dry naturally at room temperature and subsequently sieved. Subsequently, the sample stage was coated with double-sided conductive tape. With the aid of tweezers, a small amount of the sample was taken and placed onto the tape. The sample stage, containing the sample, was then inserted into the sample chamber of the K570 ion sputtering instrument. To avoid the charge effect, gold was sputtered onto the samples under vacuum conditions. Once the samples were uniformly coated with a conductive film, they were subjected to observation and analysis using a SEM. The observation was performed at a probe current of 50 PA, a filament current of 2.7 A, and an accelerating voltage of 20 kV 37 . 1.3.2 Fourier Transform Ioncyclotron Resonance (FTIR) analysis of rice straw before and after degradation A small quantity of the sample was collected both before and after degradation. The samples were then washed with distilled water to remove any surface impurities, left to naturally dry at room temperature, and subsequently sieved. In an onyx mortar, potassium bromide (KBr) was added at a ratio of 1:100, thoroughly ground until it transformed into a powdered form, and dried using infrared light. A small portion of this mixture was utilized to create thin tablets on a tablet press, which were then placed into a sample holder. As a reference, pure potassium bromide powder served as the blank sample, and the background spectrum was captured at room temperature for each measurement, with the background automatically subtracted from the sample. Analysis of the samples was conducted using a FTIR, with a scanning wavelength range spanning 400–4000 cm − 1 and 32 scans performed on each sample. The spectral resolution achieved was better than 0.09 cm − 1 38 . 1.3.3 X-ray diffraction (XRD) observations of rice straw before and after degradation A small amount of samples, both before and after degradation, was collected and then subjected to washing with distilled water to eliminate surface impurities. Following this, the samples were naturally dried at room temperature and-assed through a 60-mesh sieve. Crystallinity analysis was performed using an X-ray diffractometer. The samples were positioned in a sample holder, and Cu-Kα radiation served as the radiation source, operating at 40 kV and 40 mA. The scanning conditions (2θ) ranged from 5° to 40°, with a scanning speed of 2°/min and a step size of 0.01 39 . The cellulose crystallinity of the rice straw was assessed both before and after degradation. To calculate the sample crystallinity (CrI), Siegel's method was applied to all the samples. Crystallinity calculation formula: The CrI% represents the crystallinity index, where I002 corresponds to the peak intensity at 2θ = 22°, signifying the diffraction intensity of the crystalline region. On the other hand, Iam denotes the peak intensity at 2θ = 18°, representing the peak diffraction intensity of the amorphous region. 1.3.4 representations The use of plants in this study was in accordance with international, national and/or institutional guidelines. 1.4 Statistical analysis The experiment was analysed by ANOVA using SPSS. Statistical analyses were performed using SPSS 16.0 statistical software (Chicago, USA). One-way analysis of variance (one-way ANOVA) was used to determine if there was significance between the treatments. The significance level was set at 0.05 (p < 0.05). 2 Results and Discussion 2.1 Variation in physicochemical properties between treatments 2.1.1 Temperature Temperature serves as a crucial indicator for assessing composting efficiency and the stability of the final compost product 40 (Fig. 1 a). The fluctuations in temperature during composting reflect the degradation of OM and changes in microbial diversity within agricultural organic waste 41 . In the initial stages of composting, the heap's abundance of water-soluble nutrients enhances the metabolic decomposition capacity of microorganisms, leading to a rapid rise in heap temperature to a high-temperature phase, as verified in the study by Şevik et al 42 . Both ZZ (6th day) and CK (6th day) were the first to enter the high-temperature stage (> 55°C), followed by EM (8th day). The longer the high-temperature phase persisted, the more advantageous it was in reducing compost toxicity. All treatments conformed to the requirements of ZZ (7th day), EM (6th day), and CK (5th day) to maintain the high-temperature stage 43 . Subsequently, as the heap's soluble nutrients diminished and the composting materials became more recalcitrant, the heap temperature gradually declined 44 . On the 20th day of composting, 10% brown sugar was added to the ZZ and EM treatments. This resulted in a remarkable temperature surge in the heap, commencing on day 22, with temperatures reaching 59.5°C (ZZ) and 63.5°C (EM), maintaining the high-temperature phase for 8 days (ZZ) and 7 days (EM). By day 36 of composting, the temperature trends closely resembled those of the CK treatment. The addition of ZZ and EM microbial agents prolonged the high-temperature stage of composting, while the incorporation of brown sugar provided a renewed carbon source for the microorganisms within the compost. Consequently, the microorganisms regained their activity, leading the compost back into the high-temperature stage. This can be attributed to the fact that during the early stages of composting, an abundance of carbon sources is available to foster the activity of relevant degrading microorganisms. However, as composting progresses, the accessible carbon source for microorganisms gradually declines, inhibiting their activity. When 10% brown sugar was introduced on the 22nd day, the microorganisms were once again provided with an available carbon source, reviving their activity and raising the heap's temperature once more. 2.1.2 GI The GI serves as a common measure to evaluate the maturity and phytotoxicity of the final compost product 45 . Initially, all treatments maintained a low GI level (< 50%). ZS and EM displayed a decreasing trend in GI from day 0 to 8, whereas this trend appeared later in the CK treatment, specifically on day 14 (Fig. 1 b). As composting progressed, the GI of all treatments gradually increased, surpassing 80% on day 32 for ZS (83.20%) and EM (87.62%), and on day 38 for CK (84.34%), respectively, meeting the criteria for compost decomposition 46 . These findings closely aligned with the experimental results of Li et al 47 . The early-stage decrease in GI can be attributed to the degradation of OM in the compost pile, producing carboxylic acids, polyphenols, and other intermediate products that can be phytotoxic 34 . On the other hand, the subsequent rise in GI values was due to the gradual degradation of phytotoxic substances like organic acids and tannins present in the raw materials 48 . However, the final GI values did not exhibit significant differences, likely due to the low sensitivity of GI values to the bacteriophage's effect, and the resistance of the raw materials to degradation weakened the bacteriophage's impact on GI. 2.1.3 pH During the composting process, the pH of the heap exhibited variations, initially rising, then stabilizing for approximately 30 days, and finally, gradually declining. The pH increase at the start of composting may be attributed to the depletion of organic acids resulting from the physiological and biochemical activities of microorganisms, along with the release of ammonia compounds due to nitrogen mineralization processes 49 . On the 14th day of composting, the pH surpassed 9.0 in ZZ (9.26), EM (9.22), and CK (9.47) (Fig. 1 c). As composting advanced, the pH of the compost decreased due to the progressive nitrification within the heap, the emission of NH3 and CO 2 , and the degradation of OM, leading to the formation of acids 50 . The decline in pH commenced on day 44, and eventually, ZZ, EM, and CK all met the compost decay criteria (pH < 9) 51 . 2.1.4 EC EC in compost primarily indicates the salt concentration within the compost product, serving as an indicator of compost maturity and its potential impact on plant growth 52 . Initially, the EC values of the ZZ (4.24 ms/cm), EM (4.31 ms/cm), and CK (4.30 ms/cm) treatments remained at low levels during the early stages of composting (Fig. 1 d). However, as composting progressed, the EC values increased due to heap coagulation and the mineralization of OM, leading to the production of soluble salts 50 . By day 44, the EC values of the treatments ceased to increase, indicating the transition of the heap into the humification stage. The decline in EC values can be attributed to the release of soluble salt ions involved in the humification process 53 , as well as the leaching of soluble salt ions. Additionally, denitrification may contribute to the decrease in EC values 54 . Eventually, the treatments maintained EC values of approximately 5.5 ms/cm. 2.2 Changes in physical properties of the pile The physical properties of compost significantly influence moisture retention, gas environment, and heat transfer rate during seedling root growth 55 . Conversely, the substrate's moisture retention affects nutrient supply to plants. DC, WHP, VEP, and TTP are established methods for assessing compost properties 56 . Bulk density of the compost product plays a crucial role in root immobilization, while VEP and WHP have a pronounced impact on the water-vapor environment 57 . Additionally, TTP reflects the compost's physical structure during and at the end of the composting process, providing valuable insights into pore structure, permeability, and water retention 58 . The volume reduction of the compost pile during composting is not solely attributable to a loss of mass; it is primarily due to the decomposition of the pile, resulting in smaller particles 42 . Consequently, the DC of the pile gradually increased as composting progressed (Fig. 2 a). At the initial stage of composting, ZZ (0.13 g/cm 3 ), EM (0.15 g/cm 3 ), and CK (0.13 g/cm 3 ) exhibited low DC, which gradually rose over time. By the end of composting, the DC of ZZ (0.38 g/cm 3 ), EM (0.35 g/cm 3 ), and CK (0.34 g/cm 3 ) treatments approached the suitable criterion (0.4 g/cm3) for use as a substrate in soilless culture 56 . Interestingly, on the 18th day of composting, a temporary decrease in DC was observed, possibly due to microbial degradation of organic carbon in the heap, leading to CO 2 production and a transient reduction in DC 59 . The TTP of the treatments exhibited a gradual increase throughout composting, promoting microbial activity and facilitating the composting process 60 (Fig. 2 d). WHP (Fig. 2 b) and VEP (Fig. 2 c) displayed opposite trends during the initial 0–3 days of composting. WHP sharply increased, while VEP sharply decreased. 2.3 Nutrient changes during composting 2.3.1 NH 4 + -N和NO 3 - -N The NH4+-N levels during the composting process exhibited an initial increase followed by a gradual decrease until compost maturity (see Fig. 3 a). At the outset of composting, the NH 4 + -N content was relatively low in the ZZ (1.05 g/kg), EM (0.92 g/kg), and CK (1.10 g/kg) treatments. As composting progressed, the NH 4 + -N content continuously increased, peaking on the 14th day for ZZ (5.34 g/kg), EM (5.42 g/kg), and CK (4.34 g/kg), after which it steadily declined. By the end of composting, the NH 4 + -N content in each treatment reached its lowest values in ZZ (0.68 g/kg), EM (0.54 g/kg), and CK (0.29 g/kg). The initial increase in NH 4 + -N content resulted from the release of ammonium due to the degradation of nitrogenous OM 49 and weak nitrification when the pile temperature was higher during the early stages of composting 61 . The subsequent decrease was influenced by nitrification (NH4 + + 2O2→NO3-+H2O + 2H+), the humification process, and NH3 volatilization (NH4+→NH3↑+H+) 62 . The trend of NH 4 + -N changes throughout the composting process was generally consistent across all treatments, although it appeared more pronounced in ZZ and EM, likely due to the addition of microbial agents. The NO 3 − -N content in the compost was notably influenced by the compost temperature, leading to a gradual increase in its concentration. Initially, ZZ (0.47 g/kg), EM (0.47 g/kg), and CK (0.51 g/kg) exhibited low levels of NO 3 − -N content during the early stages of composting. However, as composting progressed, the NO 3 − -N content steadily increased, reaching its peak value at the end of composting for ZZ (1.79 g/kg), EM (1.87 g/kg), and CK (1.49 g/kg) (refer to Fig. 3 b). The rise in NO 3 − -N content was primarily attributed to the conversion of NH 4 + -N to NO 3 − -N through nitrification 62 . During the initial 0–14 days of composting, the NO 3 − -N content exhibited fluctuations, likely due to the heightened activity of nitrifying bacteria in response to lower heap temperatures. Conversely, when the heap temperature exceeded 40°C after day 8, the activity of nitrifying bacteria was inhibited, leading to a decline in NO 3 − -N content 63 . Subsequently, as the heap temperature decreased, the activity of nitrifying bacteria resumed, leading to a subsequent increase in NO 3 − -N content 64 . Upon entering the high-temperature phase again, the NO 3 − -N content remained relatively stable during days 38–52. 2.3.2 Active P Aerobic composting facilitates the conversion of phosphorus within the OM of compost into a more easily absorbable form known as AP. This AP is readily utilized by plants. The release of AP is associated with the reaction of organic acid compounds with organophosphorus, as well as the decomposition of biodegradable OM 65 . During the initial stage of composting, the content of AP in the ZZ (1.19 g/kg), EM (1.14 g/kg), and CK (1.15 g/kg) treatments remained consistently low across all samples. However, as composting progressed (Fig. 3 c), the content of AP increased in all treatments. Notably, the content of AP demonstrated the most rapid increase during the initial stage of composting. After the 22nd day of composting, the content of AP tended to stabilize gradually, reaching its maximum value at the end of composting for ZZ (1.63 g/kg), EM (1.61 g/kg), and CK (1.55 g/kg). This observation aligns with Yang et al.'s study, which similarly reported a rapid increase in AP during the initial composting stage, followed by a stabilizing trend 66 . 2.3.3 Available K The potassium content in compost plays a crucial role in enhancing soil fertility and promoting crop growth 67 . Notably, the content of AK exhibits an increase when composting with ZZ, EM, and CK treatments. The most significant change in AK content occurs between days 14 and 22 of composting. Subsequently, the content of AK in the compost undergoes a gradual increase until the end of the composting period. At the conclusion of composting, the AK content in all treatments, ZZ (49.88 g/kg), EM (45.18 g/kg), and CK (43.41 g/kg), reaches its maximum value (Fig. 3 d). This rise in AK content is attributed to the decomposition process of OM facilitated by microorganisms, which produce various acidic substances. These acidic substances, in turn, promote the formation of AK. 2.4 Substance transformation during composting 2.4.1 Fulvic acid and humic acid Humic acid and fulvic acid comprised the primary components of humus in the composted products 22 . Throughout the composting process (Fig. 4 a), the content of humic acid increased gradually, while that of fulvic acid decreased gradually (Fig. 4 b). This observation aligns with the findings of Xu et al 68 . Initially, the variation in humic acid content was not significant among ZZ (18.12 g/kg), EM (17.80 g/kg), and CK (18.01 g/kg) at the beginning of the composting period. However, humic acid was predominantly produced during the later rotting stage of composting, corroborating the conclusions of Zhang et al. As composting progressed, the differences in humic acid content among the treatments gradually increased until the end of the composting period, with ZZ (25.61 g/kg) showing a significantly higher content compared to EM (22.02 g/kg) and CK (21.64 g/kg). The relatively slow rise in humic acid content during the pre-composting period can be attributed to the requirement of numerous small molecules for humic acid formation. The slow degradation of lignin and cellulose leads to a scarcity of these small molecules, leading to their condensation into smaller molecular masses of fulvic acid, thereby impeding a substantial increase in humic acid content 69 . Fulvic acid plays a vital role in maintaining microbial populations and controlling pile temperature during the early stages of composting 70 , eventually transforming into humic acid as composting progresses 68 . In the initial composting stage of ZZ (64.17 g/kg), EM (66.14 g/kg), and CK (68.66 g/kg), the content of fulvic acid remained relatively high. However, as composting advanced, the fulvic acid content decreased gradually in each treatment. This decline in fulvic acid content in the composting treatments can be attributed to its depletion through microbial activity, leading to a sharp decrease. The diminishing presence of fulvic acid suggests a reduction in readily available organic carbon in the compost, thereby increasing compost stability. This trend was observed similarly by Wu et al. 53 , who concluded that the decrease in fulvic acid was partly due to its small molecular weight, making it easily consumable by microorganisms, and partly because fulvic acid acts as a precursor to humic acid, which offers greater structural stability. As composting proceeded, the changes in fulvic acid content became less pronounced. This smoothing-out effect was mainly due to a reduction in microbial activity within the compost. Eventually, ZZ (14.55 g/kg), EM (18.42 g/kg), and CK (22.77 g/kg) maintained low levels of fulvic acid content. 2.4.2 OM OM experiences a gradual reduction throughout the composting process (Fig. 4 c). This decline directly correlates with the decomposition rate of agricultural organic waste 71 , and it primarily results from the degradation of OM by relevant microorganisms present in the compost pile 50 . Initial composting levels showed ZZ (527.24 g/kg), EM (547.91 g/kg), and CK (531.75 g/kg), whereas, at the end of composting, the levels were ZZ (355.16 g/kg), EM (390.96 g/kg), and CK (398.05 g/kg). The degradation of OM mainly occurred within the first 22 days of composting. Analyzing the trend of OM content reveals that the rate of decline during the pre-composting period exceeds that of the later stages. This can be attributed to the high concentration of readily absorbable substances in the heap during the initial phase 72 , which stimulates microbial activity and promotes OM degradation. 2.4.3 Lignocellulosic changes during composting 2.4.3.1 Cellulose and hemicellulose Tomato straw compost exhibits significant amounts of cellulose and hemicellulose, leading to a reduced rate of microbial decomposition due to their hydrophobic nature 73 . Initially, ZZ (39.90%/9.33%), EM (37.92%/9.72%), and CK (37.4%/9.86%) displayed higher relative contents of cellulose and hemicellulose at the onset of composting. These relative contents gradually declined as composting progressed, reaching their lowest values by the end of the process (see Fig. 4 d and e). The graphs illustrate a rapid decrease in the relative content of cellulose, particularly for hemicellulose, during the early stages of composting. However, the changes in relative content for both components gradually slowed down during the compost maturation stage, indicating that the degradation of cellulose and hemicellulose predominantly occurs during the thermophilic and high-temperature phases of composting 37 . This decrease in relative content at the initial stages of composting may be attributed to their higher biodegradability compared to lignin, which consequently becomes the preferred carbon source for microbial activity 74 . 2.4.3.2 Lignin Lignin exhibits a highly irregular three-dimensional structure, rendering it one of the most challenging aromatic compounds for microorganisms to degrade 34 . Its degradation, as opposed to cellulose and hemicellulose, predominantly transpires during the rotting phase of composting (see Fig. 4 f) 37 . During the initial stage of composting, the easier degradation of cellulose and hemicellulose results in an observed tendency towards an increase in the relative content of lignin. The maximum relative content of lignin was achieved on day 38 in ZZ (16.30%), EM (16.01%), and CK (15.12%), after which its content gradually decreased. Moreover, the degradation of lignin within the compost pile is primarily associated with the compost maturation stage, likely attributed to the lower cellulose and hemicellulose content in the compost and the loss of nitrogen, which further facilitates lignin degradation 75 . 2.4 Enzyme activities associated with the composting process 2.4.1 Cellulase activity Cellulase activity plays a crucial role in the composting process of agricultural organic waste by facilitating the hydrolysis of cellulose into D-glucose 76 . Consequently, the level of cellulose during composting is closely associated with compost quality. Initially, cellulase activity remained low in ZZ (0.34 U/g), EM (0.31 U/g), and CK (0.39 U/g) at the onset of composting. However, as composting progressed (Fig. 5 a), cellulase activity increased. This upsurge can be attributed to the proliferation of cellulase-producing microorganisms during the initial stages of composting, leading to an augmentation in cellulase activity. Nonetheless, as composting continued, the heap's nutrient reserves were progressively depleted, resulting in reduced activity of these microorganisms and a subsequent decline in cellulase activity. During the decomposition phase of composting, a decline in the pile's temperature and the accumulation of nutrients during the high-temperature phase rejuvenated some cellulase-secreting microorganisms, causing their activity to resurge. This resurgence resulted in a subsequent increase in cellulase activity in the compost pile on day 38. Thus, understanding the dynamics of cellulase activity during the composting process is crucial for optimizing compost quality. 2.4.3 Xylanase activity Xylanase serves as the primary enzyme responsible for hemicellulose degradation in the compost heap, facilitating the breakdown of xylan into xylose and oligosaccharides 34 . At the outset of the composting period, all treatments, namely ZZ (12.06 U/g), EM (12.15 U/g), and CK (12.44 U/g), exhibited the highest xylanase activity. However, as composting progressed (Fig. 5 b), xylanase activity gradually decreased, consistent with findings by Zhu et al 34 . The decline in xylanase activity in the compost can be attributed to the increasing temperature of the heap, which inhibits the activity of microorganisms responsible for xylanase secretion. Notably, on day 8, all treatments experienced a sharp reduction in enzyme activity, with the CK treatment (1.27 U/g) reaching the lowest value. This substantial decline in enzyme activity warrants further investigation to comprehend its implications for the overall composting process. 2.4.2 Lignin peroxidase activity At the commencement of the composting period, all treatments, including ZZ (5.32 U/g), EM (5.24 U/g), and CK (5.11 U/g), exhibited higher lignin peroxidase activity. However, as composting progressed, the enzyme activity gradually declined and maintained a relatively stable level until the conclusion of the composting process (Fig. 5 c). Notably, during the initial 0–26 days, lignin peroxidase activity sharply decreased across all treatments, indicating that Lignin peroxidase activity was predominantly produced by thermophilic microorganisms during composting 34 . In contrast, only the ZZ treatment (1.64 U/g) displayed a slight increase in lignin peroxidase activity during the later stages of composting, while EM (1.10 U/g) and CK (0.71 U/g) treatments remained nearly constant. This phenomenon can be attributed to two possible reasons. Firstly, the decreasing temperature of the compost heap during the later stages of composting might suppress the activity of the involved microorganisms. Secondly, as the compost heap matured, the available nutrients for microorganisms became scarce, posing challenges for their reactivation. Understanding the dynamics of lignin peroxidase activity during composting sheds light on the role of thermophilic microorganisms and the influence of environmental factors on enzyme behavior throughout the composting process. Further investigations can deepen our comprehension of these phenomena and their implications for composting efficiency and nutrient cycling. 2.4.4 Urease enzyme activity Urease plays a pivotal role in the composting process by catalyzing the hydrolysis of urea into ammonium and CO2 77 . Throughout composting, urease activity exhibited a consistent decreasing trend until the late stage of composting (Fig. 5 d), aligning with findings by Zhu et al 34 . Initially, the enzyme activities of ZZ (2021.95 U/g), EM (1856.25 U/g), and CK (1705.47 U/g) were maintained at high levels. However, as composting progressed, especially during the high-temperature stage, urease activities experienced a drastic decline. This decline can be attributed to the inhibitory effect of the high-temperature environment on urease activity. As composting advanced, urease activity remained low during the later stages. Two primary reasons may explain this phenomenon. Firstly, the decreasing water-soluble nitrogen and organic value content in the compost pile hinder the availability of substrates necessary for urease activity. Secondly, the ongoing decomposition processes may result in a reduced abundance of the substrates required for urease activity. Understanding the dynamics of urease activity during composting provides valuable insights into nitrogen transformation processes, which are essential for optimizing composting strategies and enhancing nutrient management in agricultural practices. Further research is warranted to delve deeper into these mechanisms and their implications for composting efficiency. 2.4.5 Sucrase activity Sucrase plays a significant role in compost by hydrolyzing glucose from sucrose analogues, thereby providing a carbon source for microorganisms. The sucrase activity of each treatment initially increased during the composting period, peaking on day 26 in ZZ (61.30 U/g) and EM (71.61 U/g) treatments, with CK (28.33 U/g) showing a different trend (Fig. 5 e). The higher sucrase activity in both ZZ and EM treatments at the beginning of composting may be attributed to the inoculation of microbial agents, which led to an increase in sucrase-secreting microorganisms in the compost. Subsequently, the decrease in sucrase activity in both ZZ and EM treatments could be attributed to the reduction of nutrients available for microbial utilization within the compost pile, along with the inhibitory effect of high temperatures on the associated microbes. During the putrefaction phase of composting, as the pile's temperature decreases and nutrients increase, the involved microorganisms become active again, leading to a resurgence in sucrase secretion. Understanding the dynamics of sucrase activity during composting provides valuable insights into carbon cycling and microbial activity. Further investigations into the factors influencing sucrase-secreting microorganisms can enhance composting efficiency and promote nutrient recycling in composting processes. 2.5 Changes in straw structure before and after composting 2.5.1 FTIR Composting treatment induces discernible modifications in the lignocellulosic structure of the composted material, evident through distinct absorbance patterns in the FTIR spectra. The FTIR spectrograms before and after composting treatment exhibited minimal changes in overall shape but variations in absorption peak intensities (Fig. 6 a). Notably, at 340 cm − 1 , the hydroxyl (-OH) stretching vibration peak showed a decrease in absorption intensity after treatment, indicating partial lignin removal 78 , 79 . Similarly, the peak near 2926 cm − 1 , representing the methyl (-OCH3) group's C-H vibrational band within cellulose, experienced further reduction post-composting, signifying the composting process's capacity to cleave the carbon chain of lignocellulose 80 . Moreover, the absorption peak near 1641 cm − 1 , associated with the carbon-carbon double bond (C = C), exhibited a decrease, indicating depolymerization of lignin and partial benzene ring degradation 81 . We observed weak C-H and aromatic backbone bonds at 1420 cm − 1 and 1100 cm − 1 , suggesting enhanced biodegradation of lignin and hemicellulose during composting 82 . Additionally, the peak at 1046 cm − 1 , representing the ether bond (C-O-C), and the aromatic C-H bond deformation from lignin, together with the C-O-C glycosidic bond from hemicellulose and cellulose, demonstrated alterations, further affirming the composting-induced changes in lignocellulose composition 83 . The peak around 895 cm − 1 weakened during composting, indicating partial microbial utilization of sugars and glycocycle cleavage. These findings shed light on the structural changes in lignocellulose during composting and offer valuable insights into the degradation processes and potential applications in waste management and organic recycling. 2.5.2 XRD The formation of a crystal structure in the cellulose region of tomato straw compost poses a significant obstacle to the invasion of hydrolysis enzymes and water molecules 84 . This phenomenon accounts for the challenges encountered during lignocellulose degradation in tomato straw compost. However, composting has proven effective in reducing cellulose crystallinity to varying degrees. Comparing the crystallinity index of all treatments to that of 0CK (28.36%), reductions of 6.96% (65CK), 8% (65EM), and 7.73% (65ZZ) were observed, respectively (Fig. 6 b). The XRD peaks' positions remained relatively stable across all treatments after composting, with only slight changes in the intensity of the diffraction peaks. Notably, the smaller reduction in cellulose crystallinity observed in 65CK compared to 65EM and 65ZZ could be attributed to the presence of microbial agents in 65EM and 65ZZ, which facilitated the degradation of lignocellulose. These results emphasize the role of composting in mitigating cellulose crystallinity and its implications for improving lignocellulose breakdown in tomato straw compost. 3. Conclusion The study demonstrated that isolating compost from tomato stage piles of compost maturation yielded effective bacteria strains that facilitated compost maturation. Additionally, the research established that lowering the pile temperature and subsequently reintroducing an exogenous carbon source, glucose, could further promote compost maturation. Introducing microbial agents to the compost heap significantly extended the high-temperature phase while reducing the presence of insect pests. The combination of microbial agents and brown sugar in the heap enhanced nutrient content and facilitated straw waste degradation. Furthermore, treatments involving ZZ and EM, combined with brown sugar addition, exhibited superior lignocellulose degradation capacity. Fourier Infrared Transform and XRD analyses were conducted to investigate the structural changes in straw during tomato straw composting. These analyses provided further evidence that adding microbial agents and brown sugar promoted the degradation of relevant substances in the compost and reduced cellulose crystallinity. This study supports scenarios where short high-temperature phases and low composting environment temperatures hinder compost decomposition. However, the high cost associated with brown sugar addition can be mitigated by substituting it with glucose-rich waste materials like sugarcane waste after the initial high-temperature composting phase. Declarations Data Availability ： All data generated or analysed during this study are included in this published article. Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐ The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Acknowledgements: We thank Ⅰ Shaanxi Province Technology Innovation Guidance Special Project (2021QFY08-02); Ⅱ Tibetan plateau facility vegetable key technology innovation and integration (XZ202202YD0002C); Ⅲ Construction of a demonstration base for the introduction and standardization of famous varieties of vegetables, melons and fruits (QYXTZX-AL2023-07) fund for support. Author contributions: Conceptualization, P. Xu and X. Li; Methodology, P. Xu; Validation, P. Xu; Formal analysis, S. W. Zhao and L. L. Shu. ; investigation, G. Z. Zhang; resources, Z. C. Yang and Y. j. Wu; writing-original draft preparation, P. 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University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Guanzhi","middleName":"","lastName":"Zhang","suffix":""},{"id":222957735,"identity":"68683d3f-c616-4812-bd5a-3ed8ae6b0445","order_by":5,"name":"Yongjun Wu","email":"","orcid":"","institution":"North West Agriculture and Forestry University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yongjun","middleName":"","lastName":"Wu","suffix":""},{"id":222957736,"identity":"6b118948-bbb8-4ff5-b222-6d3ee4702213","order_by":6,"name":"Zhenchao Yang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA8ElEQVRIie2RPWrDQBBGRwysmiXb2ogk5AYjFowL4bNICLZS4SMsCFz5APYt9gijLHFlSJvChSHgNgppUqiI3Btt0qXYV33FPOYPIBL5j6Dq/UDFg0jb7txTsQorKeQs10Yreajz3drUYUWBZtk/V/tds8jGkNiQQR5KnhFXjkutC2KE1L+4KWXeAjPRSTvm6r2h0x1IY94m58LEckmXe9dZrxu6IMzkYlIRiNc2PnE+2WTLMdiQolBAZ8k/7TcoMviNMm8leKDrkQXmWzK1CO1Cr0f8gmF85ePH5/l7KFYq9YdJ5cZ2fyuPRCKRyC1+ADpzTwWvxh8jAAAAAElFTkSuQmCC","orcid":"","institution":"North West Agriculture and Forestry University","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Zhenchao","middleName":"","lastName":"Yang","suffix":""}],"badges":[],"createdAt":"2023-07-26 08:14:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3205436/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3205436/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":41086863,"identity":"55bfb421-0353-46e1-bd0a-d6c4c5d6f359","added_by":"auto","created_at":"2023-08-04 17:07:11","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":100192,"visible":true,"origin":"","legend":"\u003cp\u003eVariation in physicochemical properties between treatments during composting. a-d represent the variation in temperature, GI, pH and EC during the composting process, respectively.\u003c/p\u003e","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-3205436/v1/f80fa4195e5d1bc8b08c7e71.png"},{"id":41086864,"identity":"d60f2e32-82a7-4cce-9336-4e04df116f26","added_by":"auto","created_at":"2023-08-04 17:07:11","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":81040,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eChanges in physical properties of compost piles during the composting process. a-d represent the changes in dry capacity, water-holding porosity, ventilation porosity and total porosity of compost piles during the composting process, respectively.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Onlinefloatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-3205436/v1/239f57e8bd10be2cc7052389.png"},{"id":41086866,"identity":"f03cb502-a2c2-4cac-9d0f-1612a8af444f","added_by":"auto","created_at":"2023-08-04 17:07:11","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":73429,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eNutrient changes between treatments during composting. a-d represent the changes in NH4+-N, NO3-N, AP and AK during composting, respectively.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Onlinefloatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-3205436/v1/8eaafa5dcf7a04c2829099b0.png"},{"id":41086865,"identity":"fcfa4292-339a-45fd-89f9-f3088bde42db","added_by":"auto","created_at":"2023-08-04 17:07:11","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":829123,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003erepresents the changes associated with the heap during the composting process. a-c represent the changes in humic acid, fulvic acid, and organic matter, respectively. d-f represent the changes in the relative content of cellulose, hemicellulose and lignin, respectively.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-3205436/v1/ee43052164b5e28192bd2e84.png"},{"id":41086867,"identity":"b63a754a-f238-4938-a6fb-1b57f3d4270c","added_by":"auto","created_at":"2023-08-04 17:07:12","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":93770,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eChanges in enzyme activities associated with the composting process. a-d represent the changes in cellulase activity, xylanase activity, lignin peroxidase activity, urease activity, and sucrase activity during composting, respectively.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Onlinefloatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-3205436/v1/d59da9bdc39a967159c55336.png"},{"id":41088095,"identity":"452a528e-286c-4472-acd8-e5402f91aa77","added_by":"auto","created_at":"2023-08-04 17:15:12","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":71742,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eChanges in microstructure as well as cellulose crystallinity of straw before and after composting. a-b represent Fourier infrared transformation and XRD of straw during composting, respectively.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"Onlinefloatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-3205436/v1/8fbd4381f1b036ca73055d42.png"},{"id":42217572,"identity":"a4ec8aa7-0b1a-40d6-9753-beec0d6584f9","added_by":"auto","created_at":"2023-08-28 06:37:36","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2110495,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3205436/v1/38965b0a-feb8-4b4f-8aec-f939c2038fd2.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Brown sugar as a carbon source can make agricultural organic waste compost enter the secondary thermophilic stage and promote compost decomposition","fulltext":[{"header":"0 Introduction","content":"\u003cp\u003eThe burgeoning global population and improved living standards have sparked a rising need for food production, exerting immense pressure on agricultural activities\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. It is estimated that agricultural production worldwide generates a staggering 140\u0026nbsp;billion tonnes of lignocellulose-related organic waste annually\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. Notably, this organic waste holds potential as a reusable resource\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. However, when incorrectly disposed of in substantial quantities, it leads to a wastage of resources and becomes a significant environmental pollutant, affecting both surface and groundwater through contamination and contributing to the emission of substantial amounts of greenhouse gases, among other consequences\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. Consequently, the proper and safe management of organic agricultural waste emerges as a critical global challenge\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe recycling of organic agricultural waste plays a pivotal role in fostering sustainable agricultural development. When agricultural organic waste is directly reintroduced to the land without proper treatment, it poses significant environmental risks. These risks include water pollution resulting from leachate released by agricultural organic waste, soil pollution caused by toxic elements, air pollution stemming from volatile gas emissions, and potential threats to human health due to residual pathogens\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. To mitigate these concerns, composting agricultural organic waste proves effective as it reduces toxicity and yields a valuable biofertilizer/soil conditioner that enhances agricultural productivity\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. Numerous studies have consistently demonstrated that aerobic composting transforms agricultural organic waste into stable humus, diminishes its toxicity, stimulates plant growth, and boosts yields\u003csup\u003e\u003cspan additionalcitationids=\"CR10\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. By incorporating compost products into the soil, nutrient levels are enriched, soil structure and water retention capacity are improved, and the proliferation of soil pathogens is curtailed, thereby fostering crop growth and maximizing yield potential\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. The beneficial impact of composted agricultural production primarily hinges on the compost's maturity and stability, the biological activity of the microbial community, and the ability of soil organic matter (OM) to support microbial growth\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. Furthermore, certain microorganisms present in compost products can create an unfavorable environment for soil pathogens, thereby enhancing soil nutrition, promoting plant health, and positively influencing plant growth\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eHowever, agricultural organic waste poses challenges due to its high cellulose and lignin content, which hinder degradation and result in prolonged composting cycles and subpar compost quality. The naturally occurring microorganisms in agricultural waste are often insufficient in number and degradation capacity to effectively process the substantial volumes of agricultural waste\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. Therefore, the addition of microbial agents is commonly employed to facilitate composting\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. Inoculating compost with microbial agents not only enhances composting efficiency but also offers advantages such as affordability\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e, minimal secondary contamination, and ease of handling\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. Xi et al. observed that the inoculation of compost with microbial agents extended the high-temperature phase and promoted humification of the compost\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e. Yang et al. introduced \u003cem\u003eTrametes hirsuta S13\u003c/em\u003e and \u003cem\u003ePleurotus ostreatus S18\u003c/em\u003e to tobacco straw, resulting in an increased lignin degradation from 23.7\u0026ndash;41.1%\u003csup\u003e20\u003c/sup\u003e. Chu et al. developed a composite strain comprising \u003cem\u003ePhanerochaete chrysosporium\u003c/em\u003e, \u003cem\u003eTrametes versicolor\u003c/em\u003e, and \u003cem\u003ePleurotus ostreatus\u003c/em\u003e, which exhibited respective lignin, cellulose, and hemicellulose degradation rates of 43.36%, 31.29%, and 48.36%\u003csup\u003e21\u003c/sup\u003e. Wan et al. conducted composting with the addition of microbial agents and observed a significant acceleration in the degradation of organic waste\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eDecades of research have focused on the utilization of microbial agents for degrading agricultural organic waste. However, when applying these microbial agents, several challenges arise, including inadequate compost temperatures, short duration of high-temperature maintenance, insufficient compost maturity, and substandard compost quality. These issues often result from the introduced microbial agents' poor adaptation to the composting environment or even antagonistic interactions with native microorganisms present in the pile. Such interactions can hinder the degradation of agricultural organic waste and compromise the quality of the final compost product. To address the problem of low microbial activity in the compost pile at lower temperatures, the addition of protein, glucose, and urea during the composting process provides essential nutrients for microorganisms. This supplementation stimulates the decomposition rate of agricultural organic waste by microorganisms, yielding a notable \"bursting\" effect that improves the overall composting efficiency\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. In this study, five microbial strains isolated from agricultural organic waste piles in the pre-laboratory setting were combined to create the microbial agent ZZ. ZZ was then inoculated into the compost containing agricultural organic waste, with the addition of 10% brown sugar towards the end of the high-temperature phase of the pile. The objectives of this study were to evaluate: (I) the degradation capacity of the microbial agent ZZ for composting agricultural organic waste; (II) the impact of introducing 10% brown sugar at the end of the initial high-temperature phase, reinitiating the high-temperature phase of the pile; and (III) the effects of both microbial agent inoculation and brown sugar addition on the quality of the resulting compost product.\u003c/p\u003e"},{"header":"1 Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e1.1 Compost design and sampling\u003c/h2\u003e\n \u003cp\u003eThe composting material was sourced from tomato straw in local facility greenhouses in Shaanxi, China. The straw was collected, sun-dried, and subsequently crushed to approximately 2\u0026ndash;5 cm using a straw grinder (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). For each experimental group, 15 kg (dry weight) of tomato straw was placed in a 60L compost fermentation bucket, and the moisture content of the compost material was adjusted to 60\u0026ndash;70% using distilled water. The experimental groups consisted of ZZ inoculated with 10% ZZ microbial agent, which included \u003cem\u003eAspergillus niger\u003c/em\u003e, \u003cem\u003eFalsochrobactrum ovis\u003c/em\u003e, \u003cem\u003ePaenibacillus xylanilyticus\u003c/em\u003e, \u003cem\u003eBacillus subtilis subsp\u003c/em\u003e, and \u003cem\u003ePaenibacillus amylolyticus\u003c/em\u003e. These microorganisms were isolated from agricultural organic waste in a previous phase of our laboratory research. Additionally, the EM experimental group was inoculated with 10% EM microbial agent (purchased from Hangzhou Goyo Ecological Environment Technology Co., Ltd, China), primarily containing Bacillus subtilis, Lactobacillus acidophilus, Saccharomyces cerevisiae, and purified water. The control group (CK) was inoculated with 10% distilled water. Sampling was performed on days 0, 3, 8, 14, 18, 22, 26, 32, 38, 44, 52, 58, and 65 of the composting process, utilizing the five-point sampling method. The collected compost samples were divided into two parts: one part was used for analyzing physicochemical properties, nutrient elements, and lignocellulose changes, while the other portion was stored at -20℃ for enzyme activity determination.\u003c/p\u003e\n \u003cp\u003e\u003c/p\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003ePhysicochemical properties of tomato straw compost feedstock\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRaw materials\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTOC (g/kg)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTN (g/kg)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eC/N\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003epH\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eEC(ms/cm)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMoisture content\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTomato straws\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e317.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e19.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16.19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e25%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e1.2 Physico-chemical analysis of compost\u003c/h2\u003e\n \u003cp\u003eThe temperature variations within the compost fermentation drum and its surrounding environment were diligently monitored using a digital temperature sensor from Shenzhen Shenghua Xuan Technology Co., Ltd, Shenzhen, China. Fresh solid samples were mixed with deionized water at a 1:10 ratio (volume) to obtain an aqueous extract. The extract was acquired after one hour of oscillatory maceration at 220 r-min^-1 and was used for analyzing pH, electrical conductivity (EC), and the germination index (GI). pH measurements were taken using a pH meter (pHS-3C, Lei Magnetic, Shanghai, China), while EC was determined using a conductivity meter (ST3100M, Ohaus, China) \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. For GI determination, 5 ml of the extracted water was placed in a Petri dish with filter paper. Then, 20 seeds were uniformly arranged in the dish and placed in an incubator at (25\u0026thinsp;\u0026plusmn;\u0026thinsp;1) \u0026deg;C for 48 hours. The germination and root length of seeds were measured for each sample, with three parallel groups taken into account. The GI was calculated as follows: GI (%) = (mean number of germinated seeds in the treatment group \u0026times; mean root length of seeds in the treatment group) / (mean number of germinated seeds in CK \u0026times; mean root length of seeds in CK) \u0026times;100%\u003csup\u003e25\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eChanges in the dry capacity (DC), water-holding porosity (WHP), ventilation porosity (VEP), and total porosity (TTP) of compost materials were determined following the method of Yin et al\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e26\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. Initially, the air-dried samples were placed in a 200 cm^3-ring knife (M0) and weighed (M1). Next, the ring knife was submerged in distilled water for 24 hours (M2) and then removed from the water. Subsequently, the ring knife was sealed with permeable gauze after removing the lid. The saturated compost in the ring knife was inverted on a screen until water stopped dripping from the bottom, a process that took about 4 hours. Once the dripping ceased, the ring knife was weighed and recorded as M3. Finally, the ring knife was dried at 65℃ until a constant weight was achieved (M4).\u003c/p\u003e\n \u003cp\u003eThe calculation of the physical properties is as follows:\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eDC (g/cm\u003csup\u003e3\u003c/sup\u003e) = (M4 - M0) / 200\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eTTP (%) = (M2 - M4) / 200\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eVEP (%) = (M2 - M3) / 200\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eWHP (%) = TTP - VEP\u003c/strong\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\n \u003cdiv id=\"Sec7\" class=\"Section4\"\u003e\n \u003cp\u003eThese aforementioned physical properties are commonly used to evaluate composting efficiency and compost maturity.\u003c/p\u003e\n \u003cp\u003eNH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e-N was quantified using the colorimetric method, while NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e-N was determined using the spectrophotometric method\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. Active P(AP) was assessed using 0.5 M NaHCO\u003csub\u003e3\u003c/sub\u003e. Available K(AK) extraction was carried out with NH4OAc, and its quantification was performed through the flame photometric method\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. HA and FA contents were determined using the oxidative volumetric method with potassium dichromate\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. OM content was determined through dry combustion at 550℃ for 6 hours\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. Cellulose, hemicellulose, and lignin contents were assessed following the method outlined by Sajid et al\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eCellulase activity was determined using a previously described method\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. Lignin peroxidase activity was measured with quinuclidinol, and the change in absorbance at 310 nm was recorded within 3 minutes of the reaction\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. Xylanase activity was determined using beech wood xylan as a substrate. The mixture was incubated at 50℃ for 10 minutes, and the xylan content was measured at 540 nm using the DNS method. Urease activity (UR) was evaluated based on the method established by Zhou et al\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. Similarly, sucrase activity was determined according to the method outlined by Ma et al\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e1.3 Observations on structural characterisation of degraded materials\u003c/h2\u003e\n \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\n \u003ch2\u003e1.3.1 Scanning electron microscope (SEM) observation of rice straw before and after degradation\u003c/h2\u003e\n \u003cp\u003ePrior to and following degradation, a small sample was collected, then washed with distilled water to eliminate surface impurities. The samples were left to dry naturally at room temperature and subsequently sieved. Subsequently, the sample stage was coated with double-sided conductive tape. With the aid of tweezers, a small amount of the sample was taken and placed onto the tape. The sample stage, containing the sample, was then inserted into the sample chamber of the K570 ion sputtering instrument. To avoid the charge effect, gold was sputtered onto the samples under vacuum conditions. Once the samples were uniformly coated with a conductive film, they were subjected to observation and analysis using a SEM. The observation was performed at a probe current of 50 PA, a filament current of 2.7 A, and an accelerating voltage of 20 kV\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e1.3.2 Fourier Transform Ioncyclotron Resonance (FTIR) analysis of rice straw before and after degradation\u003c/h2\u003e\n \u003cp\u003eA small quantity of the sample was collected both before and after degradation. The samples were then washed with distilled water to remove any surface impurities, left to naturally dry at room temperature, and subsequently sieved. In an onyx mortar, potassium bromide (KBr) was added at a ratio of 1:100, thoroughly ground until it transformed into a powdered form, and dried using infrared light. A small portion of this mixture was utilized to create thin tablets on a tablet press, which were then placed into a sample holder. As a reference, pure potassium bromide powder served as the blank sample, and the background spectrum was captured at room temperature for each measurement, with the background automatically subtracted from the sample. Analysis of the samples was conducted using a FTIR, with a scanning wavelength range spanning 400\u0026ndash;4000 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 32 scans performed on each sample. The spectral resolution achieved was better than 0.09 cm\u003csup\u003e\u0026minus;\u0026thinsp;1 \u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003e1.3.3 X-ray diffraction (XRD) observations of rice straw before and after degradation\u003c/h2\u003e\n \u003cp\u003eA small amount of samples, both before and after degradation, was collected and then subjected to washing with distilled water to eliminate surface impurities. Following this, the samples were naturally dried at room temperature and-assed through a 60-mesh sieve. Crystallinity analysis was performed using an X-ray diffractometer. The samples were positioned in a sample holder, and Cu-K\u0026alpha; radiation served as the radiation source, operating at 40 kV and 40 mA. The scanning conditions (2\u0026theta;) ranged from 5\u0026deg; to 40\u0026deg;, with a scanning speed of 2\u0026deg;/min and a step size of 0.01\u003csup\u003e39\u003c/sup\u003e. The cellulose crystallinity of the rice straw was assessed both before and after degradation. To calculate the sample crystallinity (CrI), Siegel\u0026apos;s method was applied to all the samples.\u003c/p\u003e\n \u003cp\u003eCrystallinity calculation formula:\u003c/p\u003e\n \u003cp\u003e\u003cimg src=\"https://myfiles.space/user_files/58895_8739fc6c57c1c19a/58895_custom_files/img1691144086.png\" width=\"369\" height=\"89\"\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003eThe CrI% represents the crystallinity index, where I002 corresponds to the peak intensity at 2\u0026theta;\u0026thinsp;=\u0026thinsp;22\u0026deg;, signifying the diffraction intensity of the crystalline region. On the other hand, Iam denotes the peak intensity at 2\u0026theta;\u0026thinsp;=\u0026thinsp;18\u0026deg;, representing the peak diffraction intensity of the amorphous region.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003e1.3.4 representations\u003c/h2\u003e\n \u003cp\u003eThe use of plants in this study was in accordance with international, national and/or institutional guidelines.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003e1.4 Statistical analysis\u003c/h2\u003e\n \u003cp\u003eThe experiment was analysed by ANOVA using SPSS. Statistical analyses were performed using SPSS 16.0 statistical software (Chicago, USA). One-way analysis of variance (one-way ANOVA) was used to determine if there was significance between the treatments. The significance level was set at 0.05 (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"2 Results and Discussion","content":"\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1 Variation in physicochemical properties between treatments\u003c/h2\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1.1 Temperature\u003c/h2\u003e\n \u003cp\u003eTemperature serves as a crucial indicator for assessing composting efficiency and the stability of the final compost product\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ea). The fluctuations in temperature during composting reflect the degradation of OM and changes in microbial diversity within agricultural organic waste\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. In the initial stages of composting, the heap\u0026apos;s abundance of water-soluble nutrients enhances the metabolic decomposition capacity of microorganisms, leading to a rapid rise in heap temperature to a high-temperature phase, as verified in the study by Şevik et al\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. Both ZZ (6th day) and CK (6th day) were the first to enter the high-temperature stage (\u0026gt;\u0026thinsp;55\u0026deg;C), followed by EM (8th day). The longer the high-temperature phase persisted, the more advantageous it was in reducing compost toxicity. All treatments conformed to the requirements of ZZ (7th day), EM (6th day), and CK (5th day) to maintain the high-temperature stage\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e. Subsequently, as the heap\u0026apos;s soluble nutrients diminished and the composting materials became more recalcitrant, the heap temperature gradually declined\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e. On the 20th day of composting, 10% brown sugar was added to the ZZ and EM treatments. This resulted in a remarkable temperature surge in the heap, commencing on day 22, with temperatures reaching 59.5\u0026deg;C (ZZ) and 63.5\u0026deg;C (EM), maintaining the high-temperature phase for 8 days (ZZ) and 7 days (EM). By day 36 of composting, the temperature trends closely resembled those of the CK treatment. The addition of ZZ and EM microbial agents prolonged the high-temperature stage of composting, while the incorporation of brown sugar provided a renewed carbon source for the microorganisms within the compost. Consequently, the microorganisms regained their activity, leading the compost back into the high-temperature stage. This can be attributed to the fact that during the early stages of composting, an abundance of carbon sources is available to foster the activity of relevant degrading microorganisms. However, as composting progresses, the accessible carbon source for microorganisms gradually declines, inhibiting their activity. When 10% brown sugar was introduced on the 22nd day, the microorganisms were once again provided with an available carbon source, reviving their activity and raising the heap\u0026apos;s temperature once more.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1.2 GI\u003c/h2\u003e\n \u003cp\u003eThe GI serves as a common measure to evaluate the maturity and phytotoxicity of the final compost product\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e. Initially, all treatments maintained a low GI level (\u0026lt;\u0026thinsp;50%). ZS and EM displayed a decreasing trend in GI from day 0 to 8, whereas this trend appeared later in the CK treatment, specifically on day 14 (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eb). As composting progressed, the GI of all treatments gradually increased, surpassing 80% on day 32 for ZS (83.20%) and EM (87.62%), and on day 38 for CK (84.34%), respectively, meeting the criteria for compost decomposition\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e. These findings closely aligned with the experimental results of Li et al\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e. The early-stage decrease in GI can be attributed to the degradation of OM in the compost pile, producing carboxylic acids, polyphenols, and other intermediate products that can be phytotoxic\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. On the other hand, the subsequent rise in GI values was due to the gradual degradation of phytotoxic substances like organic acids and tannins present in the raw materials\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e48\u003c/span\u003e\u003c/sup\u003e. However, the final GI values did not exhibit significant differences, likely due to the low sensitivity of GI values to the bacteriophage\u0026apos;s effect, and the resistance of the raw materials to degradation weakened the bacteriophage\u0026apos;s impact on GI.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1.3 pH\u003c/h2\u003e\n \u003cp\u003eDuring the composting process, the pH of the heap exhibited variations, initially rising, then stabilizing for approximately 30 days, and finally, gradually declining. The pH increase at the start of composting may be attributed to the depletion of organic acids resulting from the physiological and biochemical activities of microorganisms, along with the release of ammonia compounds due to nitrogen mineralization processes\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e. On the 14th day of composting, the pH surpassed 9.0 in ZZ (9.26), EM (9.22), and CK (9.47) (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ec). As composting advanced, the pH of the compost decreased due to the progressive nitrification within the heap, the emission of NH3 and CO\u003csub\u003e2\u003c/sub\u003e, and the degradation of OM, leading to the formation of acids\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e. The decline in pH commenced on day 44, and eventually, ZZ, EM, and CK all met the compost decay criteria (pH\u0026thinsp;\u0026lt;\u0026thinsp;9) \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e51\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec19\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1.4 EC\u003c/h2\u003e\n \u003cp\u003eEC in compost primarily indicates the salt concentration within the compost product, serving as an indicator of compost maturity and its potential impact on plant growth\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e52\u003c/span\u003e\u003c/sup\u003e. Initially, the EC values of the ZZ (4.24 ms/cm), EM (4.31 ms/cm), and CK (4.30 ms/cm) treatments remained at low levels during the early stages of composting (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ed). However, as composting progressed, the EC values increased due to heap coagulation and the mineralization of OM, leading to the production of soluble salts\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e. By day 44, the EC values of the treatments ceased to increase, indicating the transition of the heap into the humification stage. The decline in EC values can be attributed to the release of soluble salt ions involved in the humification process\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e53\u003c/span\u003e\u003c/sup\u003e, as well as the leaching of soluble salt ions. Additionally, denitrification may contribute to the decrease in EC values\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e54\u003c/span\u003e\u003c/sup\u003e. Eventually, the treatments maintained EC values of approximately 5.5 ms/cm.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec20\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2 Changes in physical properties of the pile\u003c/h2\u003e\n \u003cp\u003eThe physical properties of compost significantly influence moisture retention, gas environment, and heat transfer rate during seedling root growth\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e55\u003c/span\u003e\u003c/sup\u003e. Conversely, the substrate\u0026apos;s moisture retention affects nutrient supply to plants. DC, WHP, VEP, and TTP are established methods for assessing compost properties\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e56\u003c/span\u003e\u003c/sup\u003e. Bulk density of the compost product plays a crucial role in root immobilization, while VEP and WHP have a pronounced impact on the water-vapor environment\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e57\u003c/span\u003e\u003c/sup\u003e. Additionally, TTP reflects the compost\u0026apos;s physical structure during and at the end of the composting process, providing valuable insights into pore structure, permeability, and water retention\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e58\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eThe volume reduction of the compost pile during composting is not solely attributable to a loss of mass; it is primarily due to the decomposition of the pile, resulting in smaller particles\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. Consequently, the DC of the pile gradually increased as composting progressed (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ea). At the initial stage of composting, ZZ (0.13 g/cm\u003csup\u003e3\u003c/sup\u003e), EM (0.15 g/cm\u003csup\u003e3\u003c/sup\u003e), and CK (0.13 g/cm\u003csup\u003e3\u003c/sup\u003e) exhibited low DC, which gradually rose over time. By the end of composting, the DC of ZZ (0.38 g/cm\u003csup\u003e3\u003c/sup\u003e), EM (0.35 g/cm\u003csup\u003e3\u003c/sup\u003e), and CK (0.34 g/cm\u003csup\u003e3\u003c/sup\u003e) treatments approached the suitable criterion (0.4 g/cm3) for use as a substrate in soilless culture\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e56\u003c/span\u003e\u003c/sup\u003e. Interestingly, on the 18th day of composting, a temporary decrease in DC was observed, possibly due to microbial degradation of organic carbon in the heap, leading to CO\u003csub\u003e2\u003c/sub\u003e production and a transient reduction in DC\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e59\u003c/span\u003e\u003c/sup\u003e. The TTP of the treatments exhibited a gradual increase throughout composting, promoting microbial activity and facilitating the composting process\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e60\u003c/span\u003e\u003c/sup\u003e(Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ed). WHP (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eb) and VEP (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ec) displayed opposite trends during the initial 0\u0026ndash;3 days of composting. WHP sharply increased, while VEP sharply decreased.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec21\" class=\"Section2\"\u003e\n \u003ch2\u003e2.3 Nutrient changes during composting\u003c/h2\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec22\" class=\"Section2\"\u003e\n \u003ch2\u003e2.3.1 NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e-N和NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e-N\u003c/h2\u003e\n \u003cp\u003eThe NH4+-N levels during the composting process exhibited an initial increase followed by a gradual decrease until compost maturity (see Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ea). At the outset of composting, the NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e-N content was relatively low in the ZZ (1.05 g/kg), EM (0.92 g/kg), and CK (1.10 g/kg) treatments. As composting progressed, the NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e-N content continuously increased, peaking on the 14th day for ZZ (5.34 g/kg), EM (5.42 g/kg), and CK (4.34 g/kg), after which it steadily declined. By the end of composting, the NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e-N content in each treatment reached its lowest values in ZZ (0.68 g/kg), EM (0.54 g/kg), and CK (0.29 g/kg). The initial increase in NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e-N content resulted from the release of ammonium due to the degradation of nitrogenous OM\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e and weak nitrification when the pile temperature was higher during the early stages of composting\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e61\u003c/span\u003e\u003c/sup\u003e. The subsequent decrease was influenced by nitrification (NH4\u0026thinsp;+\u0026thinsp;+\u0026thinsp;2O2\u0026rarr;NO3-+H2O\u0026thinsp;+\u0026thinsp;2H+), the humification process, and NH3 volatilization (NH4+\u0026rarr;NH3\u0026uarr;+H+)\u003csup\u003e62\u003c/sup\u003e. The trend of NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e-N changes throughout the composting process was generally consistent across all treatments, although it appeared more pronounced in ZZ and EM, likely due to the addition of microbial agents.\u003c/p\u003e\n \u003cp\u003eThe NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e-N content in the compost was notably influenced by the compost temperature, leading to a gradual increase in its concentration. Initially, ZZ (0.47 g/kg), EM (0.47 g/kg), and CK (0.51 g/kg) exhibited low levels of NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e-N content during the early stages of composting. However, as composting progressed, the NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e-N content steadily increased, reaching its peak value at the end of composting for ZZ (1.79 g/kg), EM (1.87 g/kg), and CK (1.49 g/kg) (refer to Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eb). The rise in NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e-N content was primarily attributed to the conversion of NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e-N to NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e-N through nitrification\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e62\u003c/span\u003e\u003c/sup\u003e. During the initial 0\u0026ndash;14 days of composting, the NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e-N content exhibited fluctuations, likely due to the heightened activity of nitrifying bacteria in response to lower heap temperatures. Conversely, when the heap temperature exceeded 40\u0026deg;C after day 8, the activity of nitrifying bacteria was inhibited, leading to a decline in NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e-N content\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e63\u003c/span\u003e\u003c/sup\u003e. Subsequently, as the heap temperature decreased, the activity of nitrifying bacteria resumed, leading to a subsequent increase in NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e-N content\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e64\u003c/span\u003e\u003c/sup\u003e. Upon entering the high-temperature phase again, the NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e-N content remained relatively stable during days 38\u0026ndash;52.\u003c/p\u003e\n \u003cdiv id=\"Sec23\" class=\"Section3\"\u003e\n \u003ch2\u003e2.3.2 Active P\u003c/h2\u003e\n \u003cp\u003eAerobic composting facilitates the conversion of phosphorus within the OM of compost into a more easily absorbable form known as AP. This AP is readily utilized by plants. The release of AP is associated with the reaction of organic acid compounds with organophosphorus, as well as the decomposition of biodegradable OM\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e65\u003c/span\u003e\u003c/sup\u003e. During the initial stage of composting, the content of AP in the ZZ (1.19 g/kg), EM (1.14 g/kg), and CK (1.15 g/kg) treatments remained consistently low across all samples. However, as composting progressed (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ec), the content of AP increased in all treatments. Notably, the content of AP demonstrated the most rapid increase during the initial stage of composting. After the 22nd day of composting, the content of AP tended to stabilize gradually, reaching its maximum value at the end of composting for ZZ (1.63 g/kg), EM (1.61 g/kg), and CK (1.55 g/kg). This observation aligns with Yang et al.\u0026apos;s study, which similarly reported a rapid increase in AP during the initial composting stage, followed by a stabilizing trend\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e66\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec24\" class=\"Section2\"\u003e\n \u003ch2\u003e2.3.3 Available K\u003c/h2\u003e\n \u003cp\u003eThe potassium content in compost plays a crucial role in enhancing soil fertility and promoting crop growth\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e67\u003c/span\u003e\u003c/sup\u003e. Notably, the content of AK exhibits an increase when composting with ZZ, EM, and CK treatments. The most significant change in AK content occurs between days 14 and 22 of composting. Subsequently, the content of AK in the compost undergoes a gradual increase until the end of the composting period. At the conclusion of composting, the AK content in all treatments, ZZ (49.88 g/kg), EM (45.18 g/kg), and CK (43.41 g/kg), reaches its maximum value (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003ed). This rise in AK content is attributed to the decomposition process of OM facilitated by microorganisms, which produce various acidic substances. These acidic substances, in turn, promote the formation of AK.\u003c/p\u003e\n \u003cdiv id=\"Sec25\" class=\"Section3\"\u003e\n \u003ch2\u003e2.4 Substance transformation during composting\u003c/h2\u003e\n \u003ch2\u003e2.4.1 Fulvic acid and humic acid\u003c/h2\u003e\n \u003cp\u003eHumic acid and fulvic acid comprised the primary components of humus in the composted products\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. Throughout the composting process (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ea), the content of humic acid increased gradually, while that of fulvic acid decreased gradually (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eb). This observation aligns with the findings of Xu et al\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e68\u003c/span\u003e\u003c/sup\u003e. Initially, the variation in humic acid content was not significant among ZZ (18.12 g/kg), EM (17.80 g/kg), and CK (18.01 g/kg) at the beginning of the composting period. However, humic acid was predominantly produced during the later rotting stage of composting, corroborating the conclusions of Zhang et al. As composting progressed, the differences in humic acid content among the treatments gradually increased until the end of the composting period, with ZZ (25.61 g/kg) showing a significantly higher content compared to EM (22.02 g/kg) and CK (21.64 g/kg). The relatively slow rise in humic acid content during the pre-composting period can be attributed to the requirement of numerous small molecules for humic acid formation. The slow degradation of lignin and cellulose leads to a scarcity of these small molecules, leading to their condensation into smaller molecular masses of fulvic acid, thereby impeding a substantial increase in humic acid content\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e69\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eFulvic acid plays a vital role in maintaining microbial populations and controlling pile temperature during the early stages of composting\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e70\u003c/span\u003e\u003c/sup\u003e, eventually transforming into humic acid as composting progresses\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e68\u003c/span\u003e\u003c/sup\u003e. In the initial composting stage of ZZ (64.17 g/kg), EM (66.14 g/kg), and CK (68.66 g/kg), the content of fulvic acid remained relatively high. However, as composting advanced, the fulvic acid content decreased gradually in each treatment. This decline in fulvic acid content in the composting treatments can be attributed to its depletion through microbial activity, leading to a sharp decrease. The diminishing presence of fulvic acid suggests a reduction in readily available organic carbon in the compost, thereby increasing compost stability. This trend was observed similarly by Wu et al. \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e53\u003c/span\u003e\u003c/sup\u003e, who concluded that the decrease in fulvic acid was partly due to its small molecular weight, making it easily consumable by microorganisms, and partly because fulvic acid acts as a precursor to humic acid, which offers greater structural stability. As composting proceeded, the changes in fulvic acid content became less pronounced. This smoothing-out effect was mainly due to a reduction in microbial activity within the compost. Eventually, ZZ (14.55 g/kg), EM (18.42 g/kg), and CK (22.77 g/kg) maintained low levels of fulvic acid content.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec26\" class=\"Section3\"\u003e\n \u003ch2\u003e2.4.2 OM\u003c/h2\u003e\n \u003cp\u003eOM experiences a gradual reduction throughout the composting process (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ec). This decline directly correlates with the decomposition rate of agricultural organic waste\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e71\u003c/span\u003e\u003c/sup\u003e, and it primarily results from the degradation of OM by relevant microorganisms present in the compost pile\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e. Initial composting levels showed ZZ (527.24 g/kg), EM (547.91 g/kg), and CK (531.75 g/kg), whereas, at the end of composting, the levels were ZZ (355.16 g/kg), EM (390.96 g/kg), and CK (398.05 g/kg). The degradation of OM mainly occurred within the first 22 days of composting. Analyzing the trend of OM content reveals that the rate of decline during the pre-composting period exceeds that of the later stages. This can be attributed to the high concentration of readily absorbable substances in the heap during the initial phase\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e72\u003c/span\u003e\u003c/sup\u003e, which stimulates microbial activity and promotes OM degradation.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec27\" class=\"Section3\"\u003e\n \u003ch2\u003e2.4.3 Lignocellulosic changes during composting\u003c/h2\u003e\n \u003cdiv id=\"Sec28\" class=\"Section4\"\u003e\n \u003ch2\u003e2.4.3.1 Cellulose and hemicellulose\u003c/h2\u003e\n \u003cp\u003eTomato straw compost exhibits significant amounts of cellulose and hemicellulose, leading to a reduced rate of microbial decomposition due to their hydrophobic nature\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e73\u003c/span\u003e\u003c/sup\u003e. Initially, ZZ (39.90%/9.33%), EM (37.92%/9.72%), and CK (37.4%/9.86%) displayed higher relative contents of cellulose and hemicellulose at the onset of composting. These relative contents gradually declined as composting progressed, reaching their lowest values by the end of the process (see Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ed and e). The graphs illustrate a rapid decrease in the relative content of cellulose, particularly for hemicellulose, during the early stages of composting. However, the changes in relative content for both components gradually slowed down during the compost maturation stage, indicating that the degradation of cellulose and hemicellulose predominantly occurs during the thermophilic and high-temperature phases of composting\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. This decrease in relative content at the initial stages of composting may be attributed to their higher biodegradability compared to lignin, which consequently becomes the preferred carbon source for microbial activity\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e74\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec29\" class=\"Section2\"\u003e\n \u003ch2\u003e2.4.3.2 Lignin\u003c/h2\u003e\n \u003cp\u003eLignin exhibits a highly irregular three-dimensional structure, rendering it one of the most challenging aromatic compounds for microorganisms to degrade\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. Its degradation, as opposed to cellulose and hemicellulose, predominantly transpires during the rotting phase of composting (see Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ef) \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. During the initial stage of composting, the easier degradation of cellulose and hemicellulose results in an observed tendency towards an increase in the relative content of lignin. The maximum relative content of lignin was achieved on day 38 in ZZ (16.30%), EM (16.01%), and CK (15.12%), after which its content gradually decreased. Moreover, the degradation of lignin within the compost pile is primarily associated with the compost maturation stage, likely attributed to the lower cellulose and hemicellulose content in the compost and the loss of nitrogen, which further facilitates lignin degradation\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e75\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003c/div\u003e\n\u003ch3\u003e2.4 Enzyme activities associated with the composting process\u003c/h3\u003e\n\u003cdiv id=\"Sec31\" class=\"Section2\"\u003e\n \u003ch2\u003e2.4.1 Cellulase activity\u003c/h2\u003e\n \u003cp\u003eCellulase activity plays a crucial role in the composting process of agricultural organic waste by facilitating the hydrolysis of cellulose into D-glucose\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e76\u003c/span\u003e\u003c/sup\u003e. Consequently, the level of cellulose during composting is closely associated with compost quality. Initially, cellulase activity remained low in ZZ (0.34 U/g), EM (0.31 U/g), and CK (0.39 U/g) at the onset of composting. However, as composting progressed (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ea), cellulase activity increased. This upsurge can be attributed to the proliferation of cellulase-producing microorganisms during the initial stages of composting, leading to an augmentation in cellulase activity. Nonetheless, as composting continued, the heap\u0026apos;s nutrient reserves were progressively depleted, resulting in reduced activity of these microorganisms and a subsequent decline in cellulase activity. During the decomposition phase of composting, a decline in the pile\u0026apos;s temperature and the accumulation of nutrients during the high-temperature phase rejuvenated some cellulase-secreting microorganisms, causing their activity to resurge. This resurgence resulted in a subsequent increase in cellulase activity in the compost pile on day 38. Thus, understanding the dynamics of cellulase activity during the composting process is crucial for optimizing compost quality.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec32\" class=\"Section2\"\u003e\n \u003ch2\u003e2.4.3 Xylanase activity\u003c/h2\u003e\n \u003cp\u003eXylanase serves as the primary enzyme responsible for hemicellulose degradation in the compost heap, facilitating the breakdown of xylan into xylose and oligosaccharides\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. At the outset of the composting period, all treatments, namely ZZ (12.06 U/g), EM (12.15 U/g), and CK (12.44 U/g), exhibited the highest xylanase activity. However, as composting progressed (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003eb), xylanase activity gradually decreased, consistent with findings by Zhu et al\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. The decline in xylanase activity in the compost can be attributed to the increasing temperature of the heap, which inhibits the activity of microorganisms responsible for xylanase secretion. Notably, on day 8, all treatments experienced a sharp reduction in enzyme activity, with the CK treatment (1.27 U/g) reaching the lowest value. This substantial decline in enzyme activity warrants further investigation to comprehend its implications for the overall composting process.\u003c/p\u003e\n \u003cdiv id=\"Sec33\" class=\"Section3\"\u003e\n \u003ch2\u003e2.4.2 Lignin peroxidase activity\u003c/h2\u003e\n \u003cp\u003eAt the commencement of the composting period, all treatments, including ZZ (5.32 U/g), EM (5.24 U/g), and CK (5.11 U/g), exhibited higher lignin peroxidase activity. However, as composting progressed, the enzyme activity gradually declined and maintained a relatively stable level until the conclusion of the composting process (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ec). Notably, during the initial 0\u0026ndash;26 days, lignin peroxidase activity sharply decreased across all treatments, indicating that Lignin peroxidase activity was predominantly produced by thermophilic microorganisms during composting\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. In contrast, only the ZZ treatment (1.64 U/g) displayed a slight increase in lignin peroxidase activity during the later stages of composting, while EM (1.10 U/g) and CK (0.71 U/g) treatments remained nearly constant. This phenomenon can be attributed to two possible reasons. Firstly, the decreasing temperature of the compost heap during the later stages of composting might suppress the activity of the involved microorganisms. Secondly, as the compost heap matured, the available nutrients for microorganisms became scarce, posing challenges for their reactivation. Understanding the dynamics of lignin peroxidase activity during composting sheds light on the role of thermophilic microorganisms and the influence of environmental factors on enzyme behavior throughout the composting process. Further investigations can deepen our comprehension of these phenomena and their implications for composting efficiency and nutrient cycling.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec34\" class=\"Section3\"\u003e\n \u003ch2\u003e2.4.4 Urease enzyme activity\u003c/h2\u003e\n \u003cp\u003eUrease plays a pivotal role in the composting process by catalyzing the hydrolysis of urea into ammonium and CO2\u003csup\u003e77\u003c/sup\u003e. Throughout composting, urease activity exhibited a consistent decreasing trend until the late stage of composting (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ed), aligning with findings by Zhu et al\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. Initially, the enzyme activities of ZZ (2021.95 U/g), EM (1856.25 U/g), and CK (1705.47 U/g) were maintained at high levels. However, as composting progressed, especially during the high-temperature stage, urease activities experienced a drastic decline. This decline can be attributed to the inhibitory effect of the high-temperature environment on urease activity. As composting advanced, urease activity remained low during the later stages. Two primary reasons may explain this phenomenon. Firstly, the decreasing water-soluble nitrogen and organic value content in the compost pile hinder the availability of substrates necessary for urease activity. Secondly, the ongoing decomposition processes may result in a reduced abundance of the substrates required for urease activity. Understanding the dynamics of urease activity during composting provides valuable insights into nitrogen transformation processes, which are essential for optimizing composting strategies and enhancing nutrient management in agricultural practices. Further research is warranted to delve deeper into these mechanisms and their implications for composting efficiency.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003ch3\u003e2.4.5 Sucrase activity\u003c/h3\u003e\n\u003cp\u003eSucrase plays a significant role in compost by hydrolyzing glucose from sucrose analogues, thereby providing a carbon source for microorganisms. The sucrase activity of each treatment initially increased during the composting period, peaking on day 26 in ZZ (61.30 U/g) and EM (71.61 U/g) treatments, with CK (28.33 U/g) showing a different trend (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ee). The higher sucrase activity in both ZZ and EM treatments at the beginning of composting may be attributed to the inoculation of microbial agents, which led to an increase in sucrase-secreting microorganisms in the compost. Subsequently, the decrease in sucrase activity in both ZZ and EM treatments could be attributed to the reduction of nutrients available for microbial utilization within the compost pile, along with the inhibitory effect of high temperatures on the associated microbes. During the putrefaction phase of composting, as the pile\u0026apos;s temperature decreases and nutrients increase, the involved microorganisms become active again, leading to a resurgence in sucrase secretion. Understanding the dynamics of sucrase activity during composting provides valuable insights into carbon cycling and microbial activity. Further investigations into the factors influencing sucrase-secreting microorganisms can enhance composting efficiency and promote nutrient recycling in composting processes.\u003c/p\u003e\n\u003ch3\u003e2.5 Changes in straw structure before and after composting\u003c/h3\u003e\n\u003cdiv id=\"Sec37\" class=\"Section2\"\u003e\n \u003ch2\u003e2.5.1 FTIR\u003c/h2\u003e\n \u003cp\u003eComposting treatment induces discernible modifications in the lignocellulosic structure of the composted material, evident through distinct absorbance patterns in the FTIR spectra. The FTIR spectrograms before and after composting treatment exhibited minimal changes in overall shape but variations in absorption peak intensities (Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003ea). Notably, at 340 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, the hydroxyl (-OH) stretching vibration peak showed a decrease in absorption intensity after treatment, indicating partial lignin removal\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e78\u003c/span\u003e,\u003cspan class=\"CitationRef\"\u003e79\u003c/span\u003e\u003c/sup\u003e. Similarly, the peak near 2926 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, representing the methyl (-OCH3) group\u0026apos;s C-H vibrational band within cellulose, experienced further reduction post-composting, signifying the composting process\u0026apos;s capacity to cleave the carbon chain of lignocellulose\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e80\u003c/span\u003e\u003c/sup\u003e. Moreover, the absorption peak near 1641 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, associated with the carbon-carbon double bond (C\u0026thinsp;=\u0026thinsp;C), exhibited a decrease, indicating depolymerization of lignin and partial benzene ring degradation\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e81\u003c/span\u003e\u003c/sup\u003e. We observed weak C-H and aromatic backbone bonds at 1420 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1100 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, suggesting enhanced biodegradation of lignin and hemicellulose during composting\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e82\u003c/span\u003e\u003c/sup\u003e. Additionally, the peak at 1046 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, representing the ether bond (C-O-C), and the aromatic C-H bond deformation from lignin, together with the C-O-C glycosidic bond from hemicellulose and cellulose, demonstrated alterations, further affirming the composting-induced changes in lignocellulose composition\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e83\u003c/span\u003e\u003c/sup\u003e. The peak around 895 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e weakened during composting, indicating partial microbial utilization of sugars and glycocycle cleavage. These findings shed light on the structural changes in lignocellulose during composting and offer valuable insights into the degradation processes and potential applications in waste management and organic recycling.\u003c/p\u003e\n \u003cdiv id=\"Sec38\" class=\"Section3\"\u003e\n \u003ch2\u003e2.5.2 XRD\u003c/h2\u003e\n \u003cp\u003eThe formation of a crystal structure in the cellulose region of tomato straw compost poses a significant obstacle to the invasion of hydrolysis enzymes and water molecules\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e84\u003c/span\u003e\u003c/sup\u003e. This phenomenon accounts for the challenges encountered during lignocellulose degradation in tomato straw compost. However, composting has proven effective in reducing cellulose crystallinity to varying degrees. Comparing the crystallinity index of all treatments to that of 0CK (28.36%), reductions of 6.96% (65CK), 8% (65EM), and 7.73% (65ZZ) were observed, respectively (Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003eb). The XRD peaks\u0026apos; positions remained relatively stable across all treatments after composting, with only slight changes in the intensity of the diffraction peaks. Notably, the smaller reduction in cellulose crystallinity observed in 65CK compared to 65EM and 65ZZ could be attributed to the presence of microbial agents in 65EM and 65ZZ, which facilitated the degradation of lignocellulose. These results emphasize the role of composting in mitigating cellulose crystallinity and its implications for improving lignocellulose breakdown in tomato straw compost.\u003c/p\u003e"},{"header":"3. Conclusion","content":"\u003cp\u003eThe study demonstrated that isolating compost from tomato stage piles of compost maturation yielded effective bacteria strains that facilitated compost maturation. Additionally, the research established that lowering the pile temperature and subsequently reintroducing an exogenous carbon source, glucose, could further promote compost maturation. Introducing microbial agents to the compost heap significantly extended the high-temperature phase while reducing the presence of insect pests. The combination of microbial agents and brown sugar in the heap enhanced nutrient content and facilitated straw waste degradation. Furthermore, treatments involving ZZ and EM, combined with brown sugar addition, exhibited superior lignocellulose degradation capacity. Fourier Infrared Transform and XRD analyses were conducted to investigate the structural changes in straw during tomato straw composting. These analyses provided further evidence that adding microbial agents and brown sugar promoted the degradation of relevant substances in the compost and reduced cellulose crystallinity. This study supports scenarios where short high-temperature phases and low composting environment temperatures hinder compost decomposition. However, the high cost associated with brown sugar addition can be mitigated by substituting it with glucose-rich waste materials like sugarcane waste after the initial high-temperature composting phase.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData Availability\u003c/strong\u003e\u003cstrong\u003e：\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAll data generated or analysed during this study are included in this published article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of interests\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003cbr\u003e\u0026nbsp; ☐ The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp; We thank Ⅰ Shaanxi Province Technology Innovation Guidance Special Project (2021QFY08-02); Ⅱ Tibetan plateau facility vegetable key technology innovation and integration (XZ202202YD0002C); Ⅲ Construction of a demonstration base for the introduction and standardization of famous varieties of vegetables, melons and fruits (QYXTZX-AL2023-07) fund for support.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions:\u003c/strong\u003e Conceptualization, P. Xu and X. Li; Methodology, P. Xu; Validation, P. Xu; Formal analysis, S. W. Zhao and L. L. Shu. ; investigation, G. Z. Zhang; resources, Z. C. Yang and Y. j. Wu; writing-original draft preparation, P. Xu; writing-review and editing, visualization, Xue Li; supervision, L. L. Shu.. ; project management, S. W. Zhao. ; Funding acquisition, Z. C. Yang.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe link given cannot be opened; the raw data of the manuscript will be made available to the editors upon request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eDavis, K. F., Rulli, M. C., Seveso, A. \u0026amp; D\u0026rsquo;Odorico, P. Increased food production and reduced water use through optimized crop distribution. Nat. 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B Environ. 184, 285\u0026ndash;298 (2016).\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":"Microbial agents, Brown sugar carbon source, Lignocellulose, Cellulose crystallinity, Compost product quality","lastPublishedDoi":"10.21203/rs.3.rs-3205436/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3205436/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe utilization of microbial agents can enhance the composting process of agricultural organic waste and enhance the quality of compost products. However, several challenges persist in the composting of such waste, including the limited degradation capacity of the introduced microbial agents and the short duration of the high-temperature phase during composting. To enhance the composting efficiency of agro-organic waste, this study investigated the impact of inoculating tomato straw compost with two microbial agents: ZZ, a complex microbial agent, and EM, a commercial microbial agent. Additionally, 10% brown sugar was added as a carbon source to the compost after the initial high-temperature phase, aiming to assess its effect on the composting process. The findings revealed that compared to the control (CK) group, the ZZ and EM treatments extended the first high-temperature phase by 2 and 1 day, respectively. Furthermore, with the addition of 10% brown sugar, the ZZ and EM treatments remained in the second high-temperature phase for 8 and 7 days, respectively, while the CK treatment had already entered the cooling stage by then. Notably, the inoculation of microbial agents and the addition of brown sugar substantially augmented the activity of lignocellulose-related hydrolases, thereby promoting the degradation of lignocellulose in the ZZ and EM treatment groups. This was confirmed by FTIR analysis, which demonstrated that the addition of microbial agents facilitated the degradation of specific substances, leading to reduced absorbance in the corresponding spectra. XRD analysis further indicated a notable reduction in cellulose crystallinity for both the ZZ (8.00%) and EM (7.73%) treatments. Hence, the incorporation of microbial agents and brown sugar in tomato straw compost effectively enhances the composting process and improves the quality of compost products.\u003c/p\u003e","manuscriptTitle":"Brown sugar as a carbon source can make agricultural organic waste compost enter the secondary thermophilic stage and promote compost decomposition","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-08-04 17:07:06","doi":"10.21203/rs.3.rs-3205436/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":"867eab0c-52ce-431d-b57c-a6661a46fc4c","owner":[],"postedDate":"August 4th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":23694937,"name":"Earth and environmental sciences/Environmental sciences/Environmental impact"},{"id":23694938,"name":"Earth and environmental sciences/Environmental sciences/Environmental chemistry/Pollution remediation"}],"tags":[],"updatedAt":"2023-11-09T10:29:23+00:00","versionOfRecord":[],"versionCreatedAt":"2023-08-04 17:07:06","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3205436","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3205436","identity":"rs-3205436","version":["v1"]},"buildId":"ehx78VzkSd0WSzXnipQa-","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}