Assessment of the agronomic value of digestate from cashew nut shell and cow dung anaerobic digestion

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Somda, Amidou S. Ouili, Assièta Ouattara, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5188149/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 16 You are reading this latest preprint version Abstract This study investigated agronomic characteristics of digestates from cashew nut shell and cow dung anaerobic digestion. General characteristics and agronomic value of digestates were determined using standard methods. Gaseous emissions (biogas, CH 4 , CO 2 ) were evaluated. Microbiological quality of digestates was evaluated, as well as phytotoxicity on maize, okra, tomato and lettuce seeds. Higher conductivity indicated a greater potential for salinity to affect germination and plant growth. High C/N ratio and degree of humification greater than 0.7 are indicative of immature digestate. Total nitrogen, organic nitrogen and phosphorus contents in g/Kg were 11.26, 0.49 and 5.35 for cashew shell digestate and 18.15, 17.12 and 0.16 for cow dung digestate, respectively. Potassium content was 0.32 and 0.98 g K/Kg in cashew shell and cow dung digestate, respectively. Mineral nitrogen content of cashew nut shell digestate was 0.19 g NH 4 + /kg, 1.28 g NO 2 − /kg, and 0.0016 g NO 3 − /kg. These characteristics showed amending and fertilizing effect of digestates. Physical parameters indicate digestate can improve soil structure. Both digestates are significant source of greenhouse gas. Microbiological analysis revealed spore-forming bacteria and coliforms, with proportions that are acceptable for spreading. Germination test on okra, tomato and lettuce seeds indicated high phytotoxicity. Maize showed significant results for seed germination, root elongation, germination index and germination speed with values of 100%, 100%, 118.63% and 67.21% respectively. The study indicates that digestates present root growth-promoting properties that can be advantageous for plant development. Digestates could be improved by an integrated system in which digestates are composted downstream of anaerobic digestion. Anaerobic digestion cashew nut shell digestate cow dung digestate agronomic value phytotoxicity Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction The cashew nut sector is experiencing increasingly important development in Burkina Faso. Processing units, whether semi-industrial or artisanal, generate thousands of tons of cashew nut shells, which present a significant environmental challenge. Biogas production from anaerobic digestion showed possibility of bioenergy recovery of old cashew shells that can cover energy needs of processing units. Methanization, also called anaerobic digestion, is a process that not only allows production of bioenergy (biomethane) but also the sanitation of living environment of populations ( 1 ). The anaerobic digestion of cashew nut shells has been shown to yield biomethane production from old shells ( 2 ). Nikiema et al.( 2 ) showed interesting biomethane production yields from old cashew nut shells. Pandiyan et al. ( 3 ) showed different rates of CNSL cake would have variation in influencing plant growth, but propagation methods were varied between these plants. Cashew nut consists of a hard woody shell containing cashew nut shell liquid or CNSL. The nut is topped with a false fruit, called a "cashew apple". The shells and films constitute the waste rejected during production. CNSL consists of 70–90% anacardic acid, 10–18% cardol and approximately 5% cardanol ( 4 ). Joshi et al.( 5 ) showed addition of CNSL cake at land preparation would exacerbate phorbol ester content in soil which was reported to decompose at time of harvesting. In addition, the use of this technology would lead to a significant digestate production that could constitute a fertilizer for cashew orchards. According to Möller and Müller ( 6 ) digestates are compared to original feedstock, which are relevant for plant availability of macro and micronutrients after field application. Studies showed that despite their toxicity, Jatropha curcas seed cake used as a fertilizer is detoxified and does not pose any dangers for crops or the environment ( 7 )( 8 )( 9 ). Piperidou et al. ( 10 ) showed possible use of olive mill wastewater as biofertilizer after biodegradation by Azotobacter vinelandii . Rais et al.( 11 ) showed that treated olive mill wastewater acted very favorably on germination of tomato seeds. Ofosu-budu et al.( 12 ) and Szulc et al.( 13 ) reported that compost maturity determination is based on physico-chemical and biological parameters such as C/N ratio, humidity, pH, nitrification index, conductivity, total carbon, humification index, phytotoxicity test and germination index. Leite et al.( 14 ) reported antioxidant, antifungal, antimicrobial and larvicidal activities of CNSL. Tampio et al.( 15 , 16 ) demonstrated that using digestate in agriculture is an effective method of recycling materials and reducing the reliance on mineral fertilizers. The authors asserted that the agronomic characteristics of digestates can enhance plant growth and soil properties following fertilization with digestate. However, adverse effects may also result from the quality of digestates, including factors such as pH, organic matter, and heavy metal content.Alburquerque et al.( 17 ) showed that digestate or cow dung, used as a base treatment, was not sufficient to meet the crop's nitrogen demand throughout its growth cycle, could be the main reason why winter cauliflower is difficult to grow. Barry et al. ( 18 ) showed that the digestate gave highest yield of maize (4.67 t/ha − 3.39 t/ha), and the control gave the lowest yield (1.62 t/ha). For analysis of maize kernels biochemical quality, the fluctuation of the crude fiber content is greater between the variants than that of mineral content. Maize plants grew more from the start of spring until the end, especially in the control group. Adding organic matter to soil helps plants grow better. The content of total nitrogen in the tested samples ranged from 1.63 g/kg to 13.22 g/kg. Czekała ( 19 ) demonstrated that digestate contains a wealth of valuable nutrients, including nitrogen, phosphorus, and potassium. Bolzonella et al. ( 20 ) showcased the potential for recovering nutrients from anaerobic digestate produced in farm-scale plants with specific technologies. The results were impressive, with average yields consistently exceeding 50% for both nitrogen and phosphorus, and costs comparable to those observed in other European experiences documented in literature. Studies showed that the addition of digestate from anaerobic digestion to soil could have environmental impacts, such as CH 4 , CO 2 , and N 2 O gas emissions, which do not affect the fertilizer value of the digestate but have a significant environmental impact ( 21 ). Like olive mill wastewater effluents, cashew nut shells contain phenolic compounds that can be degraded by microorganisms and thus allow their use as a biofertilizer ( 22 , 23 , 24 ). Traoré ( 25 ) showed that contributions of compost made from cashew shells and compost from cotton stems allowed significant improvements in seed cotton yields compared to the control without compost. The agronomic value of digestate from cashew nut shells anaerobic digestion is not known. The substances, a mixture of phenolic molecules, could end up in digestates and contribute to altering their safety. Research questions on Jatropha curcas seed cake toxicities and similar substrates, may raise concerns because phorbol esters (EP) can be transferred to cultivated edible plants, accumulate in soil, and therefore impact on soil fauna and flora. According to Bustamante et al. ( 26 ), the application of unripe compost would decrease the oxygen level and redox potential of the soil, which could lead to reduction of nitrates and organic acid formation. Studies showed possible toxicity with similar substrates such as Jatropha curcas seed cake, olive mill wastewater used as compost for crops ( 22 )( 11 ). The agronomic and ecotoxicological characteristics of cashew nut shell digestate have not yet been studied. It is therefore necessary to carry out a study to determine their digestates safety before their use in plant growth. Cashew nut processing industries could benefit from the energy produced and cashew orchards from organic fertilizer to boost their growth and improve production efficiency. As cow dung is employed as an inoculum in the production of biogas from cashew nut shells, the digestate from cow dung could be utilized for a comparative study. The aim of this study was to evaluate the agronomic characteristics of digestates from cashew nut shell and cow dung anaerobic digestion. MATERIALS AND METHODS Origin of materials This study evaluated the agronomic characteristics of cashew shell and cow dung digestate obtained from scale digester with 200 l of capacity. After anaerobic digestion, digestate was sun-dried at 30–45°C. Figure 1 showed digestate production process. The seeds used in our study were obtained from a seed sales outlet developed by the Institut National de l'Environnement et de la Recherche Agricole (INERA). Fore seed were used for phytotoxicity test: early maize variety F.B.C. 6. (Farako Bk Composite nƒ 6.) developed in Farako Bâ, Burkina (INERA), Maha F1 Okra seeds from Ivory Coast, F1 COBRA 26 tomato from TECHNISEM in France and lettuce variety PACK. Evaluation of the agronomic characteristics of digestates General characteristics The pH was determined using a VWR pH100 pH-analyzer (VWR International). Electrical conductivity (EC) and salinity were measured by filtering the digestate sample through Whatman filter paper using a digital conductivity meter. The gravimetric method was employed to determine the moisture (H) and total solids (TS) content by drying the compost sample (at 105°C for 24 h) and weighing the loss. The organic carbon (OC) and volatile solids (VS) contents were calculated following the burning of the sample at 550°C. OC (%) was obtained by multiplying organic matter by a factor of 1.8. Total nutrient determination Total Nitrogen was determined using LCK 338 Total Nitrogen. Inorganically and organically bonded nitrogen is oxidized to nitrate by digestion with peroxodisulphate. The nitrate ions react with 2.6-dimethylphenol in a solution of sulphuric and phosphoric acid to form a nitrophenol. The method described by Agrawal et al.( 27 ) was used to determine total phosphorus (Pt) in the samples by distilled water dilution to fall within the analytical range of the colorimetric molybdovanadate method with acid persulfate digestion Test 'N Tube procedure, Method 10127 (Hach, Co, USA). The organic N (Norg) in the digestates was calculated from the difference between TKN and the sum of mineral nitrogen (NH 4 -N + NO 3 -N). Water soluble nutrient determination Soluble nutrient was analyzed from 1:5 water extractions described by. Samples were shaken for one hour and filtered through a cellulose filter with a pore size of approximately 8 mm. The concentrations of ammonium (NH 4 + -N), nitrate (NO 3 − -N), nitrite (NO 2 − -N), orthophosphorus (PO 4 − -P) and sulfate (SO 4 2− ) were determined using a lachat autoanalyzer, employing the respective Nessler, Nitraver, Nitriver, Phosver and Sufaver reagents. Physical parameter determination The method adapted from Woessner and Poeter ( 28 ) was used. A graduated cylinder was filled halfway with digestate and tamped down (50 ml). The measured digestate was added to a test tube containing 70 ml of distilled water. The mixture was stirred with a rod and left to stand for 5 min. The final volume of the digestate/water mixture was recorded. Porosity is obtained by the ratio between the volume of the pore space and the volume of the packed sample. The volume of the pore space is the difference between the volume of packed sample and volume of solids (ml). The water holding capacity of digestate (ml/dm3) was determined by multiplying the volume of water retained in 100 ml of digestate by the factor 10. Distilled water 200 ml was gradually added to cover the digestate sample. Distilled water/digestate mixture was stirred gently until saturation was reached. The volume of drained water was measured after draining was complete. The method reported by Achkari-Begdouri and Goodrich ( 29 ) was used to determine bulk density of digestate. The flasks were filled with digestate with great care, then placed on an electronic equilibrator. The bulk density was then calculated by dividing the dry mass of each sample by its volume. Major and secondary nutrients The concentrations of major and secondary nutrients, sodium (Na) and potassium (K), were determined using a BWB flame photometer. The concentrations of water hardness, calcium and magnesium were determined using the standard EDTA titration method (Standard Methods for the Examination of Water and Wastewater ( 30 )). Measure indicators of digestate stability and maturity Measurement of chemical indicators of digestate stability and maturity The color of the humus was determined from alkaline extracts of the compost and the absorbance at 400 and 600 nm was measured using a spectrometric technique. The variation in absorbance (log K value) was calculated as follows: log K 400-log K 600 = log (K400/K600), where K400 and K600 are the absorbances at 400 and 600 nm, respectively ( 31 ) ; Ofosu-budu et al., 2010). Measurement of biological indicators of digestate stability and maturity Respirometry test The method described by Germon ( 32 ) was used with slight modifications. The dried digestate was crushed to a size ≤ 1 mm. A 100 g mass of moistened digestate was placed in 300 ml septum-capped flasks. The flasks were hermetically sealed and incubated at room temperature (25 ± 2°C). The volume of biogas produced was measured by liquid displacement, using the technique adapted from Esposito et al. ( 33 ). The proportions of CH 4 and CO 2 in the biogas were estimated by gas chromatography. Determination of microbiological parameters in digestates Viable count refers to the enumeration of the living microorganisms’ number that form colonies on solid media. Total aerobic flora was quantified using Plate Count Agar, coliforms on Eosin Methylene Blue, spore-forming bacteria on Tryptone-Soja Agar and yeasts and fungi on Sabouraud chloramphenicol agar. Plates were incubated at 37°C for 2–5 days. The observed colonies were enumerated and expressed as colony-forming units per gram (cfu/g) using the Eq. (3) (21): N = \(\:\frac{\sum\:C}{Vi*\left(n1+0,2*n2\right)d}\) x Fd ( 3 ) Where N is the number of colony-forming units per gram (cfu/g), ƩC = Sum of colonies, Vi = volume inoculated, n1 = Number of microorganisms in first dilution, n2 = Number of microorganisms at second dilution, d = First dilution, Fd = dilution factor for digestate Digestate phytotoxicity test Three varieties were used for testing: maize ( Zea mays Komsaya variety), tomato ( Lycopersicum esculentum L. Var. Tropimech), and lettuce ( Lactuca sativa L.). These varieties were purchased from a seed sales outlet developed by the Institut National de l'Environnement et de la Recherche Agricole (INERA). Phytotoxicity was evaluated using the germination test modified from Zucconi et al.( 34 ). A compost extract was prepared by mixing digestate with demineralized water in a 1:5 (weight/volume) ratio for one hour, followed by filtration. Two filter papers were placed in Petri dish, which was then moistened with 15 ml of the digestate water extract. Ten seeds were added to the Petri dish, and a similar set-up was prepared using demineralized water as control. Both set-ups were replicated five times. The experiment involved placing closed petri dishes containing tomato and cabbage seeds in the dark under ambient conditions for 7 days. The germination percentage, root length of germinated seeds, and germination speed were determined. The germination percentage was determined at 96 h, 144 h, and 184 h, with the length of primary roots, fresh weight, dry weight of root biomass and number of lateral roots measured during the final reading. The seed germination (SG), root elongation (RE), germination index (GI), and germination speed (T50) were calculated using the formulas described by Bae et al. ( 35 ). Data analysis Data were analyzed using the XLSAT software version 2018. Analysis of variance (ANOVA) was performed to compare mean values of the different variables using Fisher's tests at probability p = 5%. Results Physical and chemical parameters of digestates The physical and chemical characteristics of digestates from shells and cow dung anaerobic digestion are summarized in Table 1 . For two types of digestates, the pH was 6.81 and 6.61, respectively, for shell digestate and cow dung digestate. The electrical conductivity (EC) and salinity were 2.94 mS/cm and 1.45 mg/l for shell digestate and 7.57 mS/cm and 4.25 mg/l for cow dung digestate. Total solid (TS), solid volatile (SV) and ash content were respectively, 94,20%, 88,86% and, 11,13% for digestate cashew nut shell. The values of 91.27%, 89.70%, and 10.29% were determined for TS, VS and ash, respectively, for cow dung digestate. Both digestates have high SV contents, reaching 88.86 and 89.70% respectively. Overall, nutrient concentrations in cashew shell digestate were lower than cow dung digestate. In fact, Nt, Pt, Norg were respectively 11.26 g N/Kg, 5.35 g (P 2 O 5 ) /Kg and 0.49 g Norg /Kg for cashew sell digestate and 18.15 g N/Kg, 17.12g (P 2 O 5 ) /Kg and 0.16 g Norg/Kg for cow dung digestate. Potassium K was 0.32 g/Kg and 0.98 g/Kg for cashew shell and cow dung digestate. The water-soluble nutrients exhibited mineral nitrogen contents of 0.19 g NH 4 + /kg, 1.28 g NO 2 − /kg, and 1.6 mg NO 3 − /kg for cashew nut shell digestate. The levels were slightly higher in cow dung digestate, with values of 0.69 g NH 4 + /kg, 1.86 g NO 2 − /kg, and 5 mg NO 3 − /kg. The degree of humification determined was 0.99. The levels of phosphorus in the cashew nut shell digestate were found to be slightly higher than in the cow dung digestate (1.31 g/kg versus 1.71 g/kg). Sulfates were found to be 0.11 g SO4 2+ /kg and 0.27 g SO4 2+ /Kg, respectively, in the cashew nut shell and cattle dung digestates. The C/N ratio of the digestates was 43.84 and 22.7 for cashew nut shell digestate and cow dung digestate respectively. In dry matter, the content of micronutrients was as follows: 0.32 g/kg K, 1092.001 mg/Kg Na, 272 mg/Kg Ca, 149.4 mg/Kg Mg, and 0.25 mg/Kg Fe for cashew nut digestate and 0.98 g/kg K, 962.27 mg/Kg Na, 580 mg/Kg Ca, 936 mg/Kg Mg, and 0.2 mg/Kg Fe for cow dung digestate. Micronutrients or trace elements play an important role in plant health and growth. Physical parameters like Water holding capacity, density and porosity, were measured. Cow dung digestate showed higher values for Water holding capacity (979 ml/dm 3 ), density (1 g/cm 3 ) and porosity (78%). Water holding capacity, density and porosity were respectively 870 ml/dm 3 , 0.83 g/cm 3 and 70% for cashew nut shell digestate. Digestates are a significant source of CH 4 , NH 3 and N 2 O emissions into the atmosphere. Our study shows that under the right conditions, cashew nut shell digestate and cow dung digestate produce 12.12 l biogas/Kg and 4.68 l biogas/Kg respectively. Emissions were 2.68 l CH 4 /kg of cashew nut shell digestate and 2.46 l CH 4 /kg of cow dung digestate. Emissions reached 7.07 l CO 2 /kg cashew nut shell digestate and 0.74 l CO 2 /kg cow dung digestate. Cow dung digestate had lower emissions than cashew nut shell digestate. Methane has a global warming potential (GWP) 28 times greater than that of CO₂. It is the second-largest contributor to total greenhouse gas radiative forcing, accounting for 17% in 2018, after CO₂ (66%) and ahead of N₂O (6%) (Dessus and Laponche, 2008 ; Durand et al. 2020). Table 1 Physical chemical characteristics of digestates from hulls and cow dung anaerobic digestion Parameters Unit DC BD p value General characteristics pH - 6.81 a ± 0,02 6.61 a ± 0.16 0.227 Humidity % 5.79 b ± 0.89 8.72 a ± 0.53 0.026 EC mS/cm 2.94 b ± 0.03 7.57 a ± 0.23 0.001 Salinity mg/l 1.45 b ± 0.07 4.25 a ± 0.07 0.0006 TS % 94.20 a ± 0.89 91.27 b ± 0.53 0.026 Ash % 11.13 a ± 0.27 10.29 a ± 0.13 0.07 Organics characteristics VS % 88.86 b ± 0.27 89.70 a ± 0.13 0.026 Carbon % 49.37 ± 0.16 a 49.83 a ± 0.08 ˂0.05 Humification - 0.99 ± 0.0006 1 ± 0.01 0.4 Total nutrients Nt g/Kg 11.26 b ± 0.11 18.15 a ± 0.21 0.0006 Pt g/Kg ( PO 4 3− ) 7.17 b ± 0.03 22.92 a ± 0.03 ˂0.05 Pt g/Kg (P 2 O 5 ) 5.35 b ± 0.0 17.12 a ± 0.03 0.005 Norg g/Kg 0.49 a ± 0.002 0.16 b ± 0.005 ˂0.05 C :N ratio 43.84 a ± 0.004 22.7 b ± 0.198 0.004 1 :5 water soluble nutrients NH 4 + g/Kg 0.19 b ± 0.001 0.69 a ± 0.005 < 0.0001 NO 2 − g/kg 1.28 b ± 0.002 1.86 a ± 0.0003 < 0.0001 NO 3 − mg/Kg 1.6 b ± 0.000003 5 a ± 0.003 < 0.0001 Orthophosphate g/Kg 1.71 a ± 0.00007 1.31 b ± 0.0001 < 0.0001 Sulfates g/Kg 0.11 b ± 0.021 0.27 a ± 0.01 0.002 NO 3 − /NH 4 + 0,0008 b ± 0,0 0.007 a ± 0.0 < 0.05 Physical parameters Water holding capacity ml/dm 3 870 ± 0.02 979 ± 0.009 0.003 Bulk Density g/cm 3 0.83 ± 0.02 1 ± 0.05 0.038 Porosity % 27 ± 1 38 ± 1 0.014 Gaseous emissions Biogas l/Kg 12.12a ± 2.2 4.68b ± 0.96 0.014 CH 4 l/Kg 2.68a ± 0.8 2.46a ± 0.38 0.068 CO 2 l/Kg 7.07a ± 1.4 0.74a ± 0.3 0.014 Major and secondary nutrients K g/kg 0.32 ± 0.004 0.98 ± 0.015 < 0.0001 Na mg/Kg 1092.001 ± 15.29 962.27 ± 15.29 < 0.0001 Ca mg/Kg 272 ± 22.63 580 ± 28.28 < 0.0001 Mg mg/Kg 149.4 ± 5.94 936 ± 0.0 < 0.0001 Fe mg/Kg 0.25 ± 0.07 0.2 ± 0.0 < 0.0001 DC : Digestate from cashew nut shell ; BD : Digestate from cow dung ; Electrical conductivity (EC) ; TS : Total Solid ; SV : Solids Volatile Determination of microbiological parameters in digestates The microbiological characteristics of the digestates are presented in Fig. 2 . Cow dung digestate showed a higher number of microbial groups than cashew nut shell digestate ( p ˂ 0.05). The total number of microorganisms (total aerobic flora) in digestate were 5.5×10 4 CFU g − 1 and 1.13×10 5 CFU g − 1 , respectively for cashew nut shell and cow dung digestate. Coliforms were 1.98×10 2 and 3.07×10 2 CFU g − 1 respectively for cashew nut and cow dung digestates, and spores forming bacteria, 6.59×10 2 CFU g − 1 and 2.02×10 3 CFU g − 1 , respectively for cashew nut shell and cow dung digestate. Spore-forming bacteria included Bacillus (aerobic) and Clostridium (anaerobic) species. Yeasts and fungi were more numerous than others, with concentrations of 1.02×10 4 CFU g − 1 of cashew nut shell digestate and 2.86×10 4 CFU g − 1 of cow dung digestate. Digestate phytotoxicity test Germination test The results of germination test on Petri dishes are presented in Table 2 . The germination test of digestates using maize, okra, tomato and lettuce seeds demonstrated a range of germination rates, from 0–100%. Maize seeds exhibited 100% germination with cashew nut shell and cow dung digestates. The seed germination (SG), root elongation (RE), germination index (GI) and germination speed (T50) values were 100, 97.19%, 97.19% and 69.82% for cashew nut shell digestates and 100%, 118.63%, 118.63% and 67.21% for cow dung digestates. The cow dung digestate exhibited high phytotoxicity on tomato and lettuce seeds, with a zero GI due to the absence of germination. In contrast, the cashew nut shell digestate demonstrated seed germination (SG) of 40% and 30% for tomato and lettuce seeds, respectively. Okra seed germination was 52.5% and 45.8% for digestate from cashew nut shell and cow dung digestate, respectively. The results of digestates on okra, tomato and lettuce seeds demonstrated low to practically zero germination percentages, which indicated a high phytotoxicity of the samples. Table 2 Phytotoxic effect of digestate on seed germination, radical elongation and germination index Traitment SG RE GI T50 DC Maize 100 97,2 97,2 69,8 BV Maize 100 118,6 118,6 67,2 DC Okra 52,5 nd nd nd BV Okra 45,8 nd nd nd DC Tomato 40 nd nd nd BV Tomato 0 nd nd nd DC Laituce 30 nd nd nd BV Laituce 0 nd nd nd DC : Cashew nut Shell digestate, BV : Bouse Bovine digestate; nd :no determine, SG : Seed Germination, RE : Root Elongation, GI : Germination Index, T50 : Germination Speed Figure 3 showed images of the germination test. The maize germinated well compared with other seeds. Roots growing The graphs of Fig. 4 Fig. 3 presents roots growth results according to the nature of digestate. The results show that the primary length of the roots reached 11.33, 16.27 and 22.60 cm respectively, for cashew nut shell digestate, control and cow dung digestate (Fig. 4 ). The length of primary root reached 11.33, 16.27 and 22.60 cm for cashew nut shell digestate, control and cow dung digestate, respectively. Seminal roots averaged 10.67, 9.00 and 6.33 cm for shells, cow dung digestates and control, respectively. In both types of digestate, no significant differences were observed for the parameters primary root length, fresh weight, dry weight of root biomass and number of seminal roots. However, a significant difference was found for the number of seminal roots, with an average of 11.33, 7.67 and 4.67 for the shell digestates, cattle dung and the control, respectively. Figure 5 presents root development images in cow dung digestate (DB), shell digestate (DC), and control (T). Results was found that the lateral roots were more developed in the digestates than in the control. Discussion The composition of the digestate is strongly dependent on the composition of the feedstock, the inoculum source, the operating conditions of the anaerobic digestion and the presence or absence of post-fermenters ( 38 ). Table 1 summarizes physical and chemical characteristics of digestates from hulls and cow dung anaerobic digestion. For two the types of digestates, pH was 6.81 and 6.61, respectively for shell and cow dung digestate. According to Monlau et al. ( 38 ), digestate was characterized by pH values > 7.5. This slightly-alkaline condition was caused by the degradation of volatile fatty acids (VFAs) and ammonia (NH 3 ) production during the process as well as the addition of strong bases or carbonates to control both the pH and buffer capacity of the system. According to many studies, the digestate pH value is mainly controlled by interaction of fluxes of NH 4 + and NH 3, CO 2 , HCO 3 −, H +, and CO 3 and finally CH 3 COOH and CH 3 COO − ( 39 ). The lower values obtained in our study would be due to the digestate drying process. Indeed, drying causes the volatilization of volatile fatty acids and ammonia (NH 3 ) contained in the liquid digestate. If too much ammonia is lost, the pH will fall. The loss is even greater with cattle dung digestate (pH 6.61) (Table 1 ). Amery et al.( 40 ) found a pH compost range between 6 and 9.53. According to these authors, the lowest values were for plant-based composts and the highest for manure-based composts. A low pH indicate that the compost is immature ( 40 ). The compost pH could influence positively or negatively on plant growth according to the type of plant cultivated. Indeed, Costello and Sullivan ( 41 ) have reported that low-pH composts should be used for acid-loving plants. Acidic and alkaline environments make it difficult for plants to assimilate phosphorus. Also, Barrow and Hartemink ( 42 ) showed the effects of pH on nutrient availability depend on both soils and plants. Liu et al. ( 43 ) showed that the overall effects of pH on the availability of nutrients for the plants are a combination of the effects of pH on sorption by soils and the effects of pH on plant uptake. A pH greater than 7 (alkaline) will have more base (-OH) than hydrogen. A neutral pH of 7 is best, but plants can't tolerate hydrogen until the pH is below 4.5. Aluminium, iron and manganese can cause toxicity in acid soils. A pH of 7 is considered neutral while anything lower is acidic in the soil. The pH of the digestate is suitable for spreading. The higher conductivity value was associated with higher salinity. Cations and anions from dissolved salts in soil water carry electrical charges and conduct electricity. This largely explains the link between salinity and electrical conductivity. Salinity may affect how nutrients are absorbed, which could limit photosynthesis and reduce chlorophyll production. This could result in plants with nutritional deficiencies ( 44 , 45 , 46 ). It has been demonstrated that elevated electrical conductivity (EC) can be indicative of salinity issues, with electrical conductivity values exceeding 4 dS/m. Such conditions impede crop growth, as plants are unable to absorb water even when it is present, and also affect microbial activity. It would seem that soils with a high electrical conductivity, resulting from a high concentration of sodium, often have poor structure and drainage. This can result in sodium becoming toxic to plants. Frankenberger and Bingham ( 47 ) suggested that dehydrogenase activity may be significantly affected by changes in soil extract electrical conductivity (EC), with inhibition levels ranging from 30 to 81% when the EC is increased from 0.2 to 22 dS/m. It is also worth noting that a high salt content (> 1500 µS/cm) can potentially induce salt stress, particularly when compost is used in growing media. Digestate conductivity values are high, above the threshold that could induce stress. It would appear that both digestates have high TS contents, reaching 88.86 and 89.70% respectively. This suggests that both digestates may have the potential to enhance soil organic matter (OM) content, which could contribute to improved soil bio-functioning. Czekała ( 19 ), studying the characteristics of digestates and extracts from different biogas plants, showed that organic matter content in material exhibited greater diversity than the dry matter content, with values ranging from 38.89–94.26%. Additionally, the solid volatile content in the raw pulp exhibited a range of 63.87–83.46%. Möller and Müller ( 48 ) reported that the digestate contained between 1.5% and 13.2% dry matter and between 63.8% and 75.0% organic matter. The low dry matter content in our study could be explained by the process of drying the digestate after anaerobic digestion. Mammarella et al.( 49 ) reported ash contents in different types of digestates from biogas production ranging from 10.2 to 55.5%. Bauer et al.( 50 ) determined that 61.8% and 58% of dry material and organic matter respectively that were present in the inflow were retrieved in the digestate solid phase The ash contents of the two digestates studied, which were 11.13 and 10.29 respectively for cashew nut shell and cow dung digestates, are in agreement with these results. With lower SV levels, the application of digestates could help to increase soil SV levels. The results reported by many authors are in agreement regarding the capacity of biosolids, such as anaerobic digestate or sewage sludge, to increase the organic matter content of the soil ( 51 , 52 ). Bonet-Garcia et al. ( 53 ) showed that municipal solid waste (MSW) digestate application increased the organic matter content and the macro and micronutrients in the marginal soil, indicating a potentially suitable use in soil reclamation. Tambone et al. ( 54 ) reported a high concentration of organic carbon in the organic municipal solid waste (OFMSW) digestate. Overall, nutrient concentrations in cashew shell digestate were lower than cow dung digestate (Table 1 ). Nutrient concentrations are in line with the work of several authors. Möller and Müller ( 48 ) reported total N contents of 1.20–9.10 g Kg − 1 for digestates from agricultural residues and animal excrements. Gell et al.( 55 ) found high levels of potassium (14.38 g K + Kg − 1 ) in cow dung digestate. Total phosphorus concentrations of 0.4–2.6 g Kg − 1 in digestate were reported by Möller and Müller ( 48 ). The values found were higher than those digestates obtained through anaerobic digestion of FW, such as those reported by ( 56 ) (4.93 g N kg − 1 and 0.90 g P kg − 1 ). Cathcart et al.( 57 ) demonstrated that the nitrogen content of the liquid fractions produced from the digestates exhibited a considerable range, varying from 2.14 g/kg to 2.96 g/kg. Additionally, the authors observed a higher proportion of nitrogen in the solid fractions, with concentrations ranging from 3.69 g/kg to 4.91 g/kg. In the same study, the concentrations of phosphorus (P) and potassium (K) in the solids exhibited a range of values from 0.76 g/kg to 2.40 g/kg and 2.70 g/kg to 3.64 g/kg, respectively. According to Valorgas ( 58 ), the total nutrient concentration in European (UK, Finland, and Italy) food wastes, was total-N concentrations, which varied between 24 and 34 g/kg TS, total-P between 2.7 and 6.4 and total-K between 8.6 and 14.3 g/kgTS. Our results show lower values, and those reported by Valorgas ( 58 ), except for the phosphate content of cattle manure digestate, which was excessive at 17.12 g/Kg. For water-soluble nutrients, similar results were found by Reuland et al. ( 59 ), who reported NH 4 + -N contents ranging from 0 to 100.5 g kg − 1 in digestates and composts elaborated from distinct feedstock profiles. All digestates and composts studied had 0.0 g kg − 1 NO 3 -N content, except for commercial compost COM_1, which had a low content of 0.7 g kg − 1 . According to, Amery et al.( 40 ), there are specific differences in nitrogen concentrations between digestate from anaerobic digestion of energy crops and digestate from organic waste and industrial by-products. Mineral nitrogen (NO 3 -N and NH 4 + -N) is the nitrogen that is directly available for the plant, in contrast to the total nitrogen content. In a well-matured compost, the concentration of NH 4 + -N is typically low, with values below 0.4 g/kg. This is accompanied by a high concentration of NO 3 − -N, resulting in a NO 3 − -N/NH 4 + -N ratio greater than 1, which indicates a degree of compost maturity. The NO 3 /NH 4 ratio in this case was 23.34. Sánchez-Monedero et al.( 60 ) indicate that mature compost should have a NO 3 /NH 4 ratio greater than 6.3. The degree of humification determined was 0.99. According to Ofosu-budu et al.( 12 ), a degree of humification of less than 0.7 indicates mature compost. The degree of humification obtained is greater than 0.7, so the digestate is considered immature. Möller & Müller,( 48 ) reported total NH 4 + contents in digestate of 1.5–6.8 g Kg − 1 . The authors stated that the characteristics of digestate depend on the original feedstock. Anaerobic digestion process degrades organic nitrogen compounds, releasing ammonium NH 4 -N, which is immediately bioavailable for growing plants. The content of ammonium in digestate is directly related to the total N content in the substrate. As pig slurry has higher N-total and NH 4 -N contents than cattle slurry, this will be reflected directly in the digestate dominated by such substrates ( 61 ). The levels of orthophosphates in the cashew nut shell digest was found to be slightly higher than in the cattle dung digest (1.31 g/kg versus 1.71 g/kg). Sulfates were found to be 0.11 g SO4 2+ /kg and 0.27 g SO4 2+ /Kg, respectively, in cashew nut shell and cow dung digestates. The C/N ratios were high. These ratios are in agreement with the results reported by Larbi ( 62 ), who found values between 70 and 80 for straw and 10 and 30 for green waste. The high C/N ratios could be explained by the presence of lignified compounds. Muniz et al. ( 63 ) showed that the pericarp of Anacardium has an outer layer composed of highly lignified cells. Reuland et al.( 59 ) found C/N ratios ranging from 1.99 to 26.97 for digestates and composts elaborated from distinct feedstock profiles. Research into the initial chemical characteristics of compostable wastes has shown that wastes such as green waste, bio-waste and municipal solid waste have C/N ratios ranging from 11 to 65It may be the case that a high C/N ratio (greater than 20–25) could indicate that the compost is not yet fully mature. Brust ( 64 ) reported that a C:N ratio of 1 to 15 is more likely to trigger rapid N release, whereas C:N ratios > 35 generally favor net N immobilization ( 64 ). According to Howell ( 65 ), soil microorganisms have a C:N ratio of around 8. In order to maintain this ratio in their cells, they must acquire sufficient carbon and nitrogen from the soil. Research has shown that they perform best on a "diet" with a C:N ratio of 24. Given that the C:N ratio of cashew nut shell digestate is 43.84 (Table 1 ), it will lead to less nitrogen mineralization in the soil. Should the organic matter exhibit a higher C:N ratio, the requisite nitrogen for microbial activity will exceed the quantity present in the organic matter. Consequently, the nitrogen will be extracted from the soil. Microbes get more nitrogen from soil than crops. In the absence of sufficient nitrogen for both microbes and crops, crop growth will be limited. Nevertheless, it is challenging to augment humus by > 1% in intensively managed organic vegetable production systems unless residues with elevated C:N ratios are employed ( 64 ). Cashew nut shell digestate could be used in cover crops and may be useful in managing excess nitrogen by promoting microbial immobilization and slowing the rate of mineralization ( 66 ). Nevertheless, the C/N ratio of the end product may not be an appropriate indicator of maturity or stability ( 67 ). This is because it is primarily influenced by the initial C/N ratio of the feedstock ( 68 ) and may reach a plateau before the compost has stabilized ( 69 ). The degree of humification was greater than 0.7. The degree of humification was greater than 0.7, as reported by Ofosu-budu et al. ( 12 ), who indicated that a degree of humification of less than 0.7 indicates mature compost. The degree of humification obtained is greater than 0.7, thus indicating that the digestate is considered immature. In terms of micronutrients, the digestates exhibited values that were consistent with those reported in previous studies. Micronutrients or trace elements play an important role in plant health and growth. The pH of digestate is also influenced by the concentration of basic cations, including sodium (Na + ), calcium (Ca 2+ ), magnesium (Mg 2+ ), and potassium (K + ). These cations increase the pH of the digestate solution by maintaining a neutral electric charge balance, which results in a reduction in the concentration of hydrogen ions (H + ). The precipitation of iron (Fe 2+ ) phosphates releases protons and lowers the pH. Additionally, the reaction between magnesium (Mg 2+ ) ions, ammonium (NH 4 + ) ions, and phosphate (PO43-) ions causes the release of hydrogen ions (H + ) from the solution. Bonet-Garcia ( 53 ) suggest the migration of Zn, Cu, Pb, Cr, Ni, and Mn from municipal solid waste digestate-amended soil to the soil layer beneath (0.1–0.2 m) during the first 21 days after municipal solid waste digestate application. Compost can help balance soil nutrients. It can be used to add specific nutrients, such as potassium or calcium, to improve soil health ( 67 ). Effect of application of increasing amounts of compost on soil carbon organic content and cation exchange capacity (CEC). In general, the CEC of decomposed soil organic matter is much higher than that of clay minerals ( 70 ). The physical parameters of Water holding capacity, bulk density and porosity demonstrated an improvement in the physical quality of the soil. The addition of digestate increases soil fertility by reducing specific sedimentation mass and increasing Water holding capacity, but only short-term trials have been conducted ( 71 ). The dry density is the ratio of oven-dried solids to the volume of soil. It reflects the structural condition of the soil at a given depth. Schroeder et al. ( 72 ) reported than densities of mineral soils may range from 1.75 g/cm 3 . Organic matter enrichment can therefore contribute to a significant increase in CEC, especially in light soils with low absorptive capacity ( 73 ). Digestates are a significant source of CH 4 , NH 3 and N 2 O emissions to the atmosphere. Cow dung digestate had lower emissions than cashew nut shell digestate (Table 1 ). The high values of biogas emissions could be explained by the fact that biogas consists of several gases such as CO 2 , CH 4 , N 2 O, NH 3 , N 2 and O 2 . The main gases released during the biodegradation of the organic fraction are CH 4 and CO 2 . Amon et al.( 74 ) showed anaerobic digestion was a very effective means to reduce greenhouse gas emissions (GHG) 37.9 kg CO 2 eq. m -3 were lost. These authors showed slurry aeration reduces CH 4 and GHG emissions. These digestates must undergo upstream treatment before being used. The microbiological analysis revealed the presence of total aerobic flora, coliforms, and spore-forming bacteria (Fig. 1 ). Spore-forming bacteria included Bacillus (aerobic) and Clostridium (anaerobic) species. Yeasts and fungi were more numerous than other microorganisms, with concentrations of 1.02×10 4 CFU/g of cashew nut shell digest and 2.86×10 4 CFU/g of cow dung digestate. The characteristics observed on the Petri dishes showed that fungi were in the majority. The cashew nut shell contains phenolic compounds that can have toxic effects on microorganisms, particularly bacteria ( 75 )( 76 )( 77 ). Although anaerobic digestion plays a significant role in reducing the concentration of toxic substances in cockles, cashew nut shell digestate is not exempt from this process ( 78 ). While anaerobic digestion contributes significantly to the reduction of toxic substances in the shell, the digestate from cashew nut shell is not exempt from this toxicity. Microorganisms have been shown to be involved in each stage of anaerobic digestion by Demirel and Scherer ( 79 ) and Alvarado et al. ( 80 ). The hydrolysis phase is inhabited by a diverse array of microorganisms, including bacteria belonging to the genera Bacillus , Pseudomonas and Aminobacterium , as well as fungi of the genus Aspergillus . The majority of these microorganisms, particularly coliforms, originate from cow dung inoculum. Similar results was found by Panuccio et al. ( 81 ) with bacteria (CFU g − 1 ) 57.5×10 5 and fungi (CFU g − 1 ) 2×10 4 . A high level of fungi in digestate used as a soil improver could lead to risks of post-harvest contamination. In addition, fungi of the following genera are the main cause of contamination of agricultural produce in the field ( 82 ). Fungi are also associated with the deterioration of the physico-chemical quality of seeds ( 83 ). El Asri et al. ( 21 ) found that the concentration of total aerobic mesophilic flora in cow dung was 25×10 9 CFU g − 1 , while that of coliforms was 28×10 3 CFU g − 1 and that of yeasts and fungi were 11×10 9 CFU g − 1 . El Asri et al. ( 21 ) indicated that the quality of digestate depends on. According to ( 84 ), the biological quality of a soil is its capacity to host a large quantity and diversity of living organisms involved in its functioning and in the ecosystem services it provides. Most of the studies showed neutral or positive effects, while 7% of the results showed an alteration in microbial parameters, indicating that there is a small but significant risk associated with the addition of digestates to soil microbial communities. In fact, reported that microorganisms play a role within the soil by means of the resolution of carbon and nitrogen, as well as the synthesis of exopolysaccharides. These processes enhance soil fertility and water retention, as well as soil shape and stability. They use the atmosphere to help them synthesis cellular proteins. Microorganisms solubilize soil phosphorous, beautify nitrogen fixation, and bring siderophores that sell its boom and suppresses the boom of pathogens. The quality criteria established by United States Environmental Protection Agency was used ( 85 ). While criteria show the degree of compliance of the final treated sludge with the digestate. Coliform concentrations in the digestate are less than 1.1×10 3 CFU g − 1 , as indicated by the criteria of the Environmental Protection Agency (2003) ( 86 ). National Research Council ( 87 ) established two categories of biosolids: Class A biosolids, which have no detectable concentrations of pathogens, and Class B biosolids, which have detectable concentrations of pathogens with fecal coliform count of less than 2×10 6 g − 1 of dry solids at the time of disposal. On the other hand, microbial biomass, the active organic fraction, is an important source of nutrients for the plant, and increasing microbial biomass, and amending compost can improve soil fertility in the long term. The results of phytotoxicity tests indicated that maize seeds exhibited satisfactory performance. Conversely, seeds of okra, tomato and lettuce demonstrated sensitivities, with low germination percentages. Qian et al.( 88 ) showed that the GI values varied from 68% (day 30) to 129% (day 90) in swine manure composting and from 88% (day 30) to 119% (day 90) in dairy manure composting. In addition, the GI values of commercial compost of swine manure and dairy manure reached 145% and 126%, respectively. The cow dung digestate exhibited high phytotoxicity on tomato and lettuce seeds due to absence of germination. In contrast, the cashew nut shell digestate demonstrated very low seeds germination (SG) for tomato and lettuce seeds, respectively. Okra seeds germination was observed to be relatively higher between 45 and 52%. The results of the digestates on okra, tomato and lettuce seeds demonstrated low to practically zero germination percentages, which indicated a high phytotoxicity of the samples. ( 89 ) reported that a GI equal to or higher than 80% indicates the absence of phytotoxic effects. Our results showed that the digestates reduced the root elongation (RE), germination index (GI), germination speed (T50) and affect seed germination (SG). Pluschke et al. ( 90 ) reported that a dilution of with distilled water improved germination by 50% and 23%, respectively. However, the tolerance to salinity depends on the plants, wheat is highly tolerant to soil salinity while tomato is moderately tolerant (conductivity should not exceed 3000 µs/cm) ( 91 ). Authors have reported that digestate phytotoxicity is related to NH 4 + -N and organic acid concentrations ( 92 , 93 ). The growth-promoting effect of digestates is evidenced by the development of roots. Root development is important in the presence of digestate. Digestates had positive effect on maize root development. No significant differences were not observed for parameters main root length, fresh weight, dry weight of root biomass and number of seminal roots (p > 0.05). Cashew nut shell digestate showed a significantly higher number of seminales roots than the other forms of treatment. Mollier et al. ( 94 ) reported that the maize root system is made up of seminal roots preformed in the seed and neoformed adventitious primary roots appearing at the base of successive internodes. The nomenclature used to number the successive root stages was that proposed by Girardin et al. ( 95 ). The number of seminal roots was significantly higher in cashew nut shell digest than in cow dung. The high salinity of the cow dung digestate could be a limit to root development. Khaled et al. ( 96 ) showed that salinity has a depressive effect on growth, accompanied by biochemical and ultrastructural changes. The development of the root system was less sensitive. According to Rahnama et al.( 97 ), salt inhibits root length in a dose-dependent manner in wheat. In Arabidopsis , salt concentrations could inhibit both primary root (PR) and lateral root (LR) growth. The rhizosphere is a habitat for a multitude of microorganisms that interact with the plant and influence its growth. Some of these microorganisms are deleterious, while others, known as plant growth-promoting rhizobacteria, are beneficial to plant growth. It is possible that digestates could harbour these microbial types capable of promoting plant growth ( 98 – 100 ). A number of studies have demonstrated the significance of microorganisms in the development of plant roots ( 101 ). Conclusion The study of the physical-chemical, agronomic, microbiological and phytotoxicity parameters of the two digestates from cashew nutshells and cow dung reflects the importance of waste treatment by anaerobic digestion. The Physical and chemical characteristics of the digestates demonstrate that they can contribute to improving the amending value of soils, which is defined as the organic matter content and bio-functioning of soils. The agronomic characteristics of the digestates indicate the presence of total nutrients (NPK), water-soluble nutrients, and major and secondary nutrients with fertilizing value. However, some parameters require improvement, including gas emissions (Biogas, CH 4 , CO 2 ) and the degree of humification, which suggest that the digestate is not yet mature. The microbiological quality appears to align with the assessment criteria, although further investigation may be necessary to identify other microorganisms. The phytotoxicity tests demonstrated that only maize seeds exhibited resistance to the effects of digestates, particularly cow dung. The study indicates that digestates possess root growth-promoting properties that can be advantageous for plant development. It was therefore concluded that these digestates could be improved by creating an integrated system where the digestates undergo a composting process after anaerobic digestion. Declarations Acknowledgements This work was financially supported by a research grant from the International Foundation for Science (IFS_ I-3-E-6204-2). Therefore, the authors are grateful to this funding and support of this research. Author contribution MN was responsible for the conceptualization and design of the study. MN worked in acquisition and interpretation of data through field and laboratory work. MN drafted the article and MKS, ASO, AO, JBS, NB, YM, COTC, IM, CATO and ASO revised it critically. All authors read and approved the final manuscript. Funding This work was financially supported by a research grant from the International Foundation for Science (IFS_ I-3-E-6204-2). Data availability All data generated in this study are provided in the submitted article. Conflict of interest The authors declare no competing interests. Plant Guidelines The authors confirm that the use of plants in the present study complies with international, national and/or institutional guidelines. 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Valorisation of Food Waste to Biogas. 2010. http://www.valorgas.soton.ac.uk/Deliverables/ VALORGAS_241334_D2-1_rev[1]_130106.pdf Reuland G, Sigurnjak I, Dekker H, Sleutel S, Meers E. Assessment of the Carbon and Nitrogen Mineralisation of Digestates Elaborated from Distinct Feedstock Profiles. Agronomy. 2022;12(2):1–21. Sánchez-Monedero MA, Roig A, Paredes C, Bernal MP. Nitrogen transformation during organic waste composting by the Rutgers system and its effects on pH, EC and maturity of the composting mixtures. Bioresour Technol. 2001;78(3):301–8. Fouda SE sayed. Nitrogen availability of biogas residues. Technische Universitat Munchen; 2011. Larbi M. Influence de la qualité des composts et de leurs extraits sur la protection des plantes contre les maladies fongiques. These Dr l’Université Neuchâtel. 2006;161. Muniz CR, Freire FCO, Soares AA, Cooke PH, Guedes MIF. The ultrastructure of shelled and unshelled cashew nuts. Micron [Internet]. 2013;54–55(January):52–6. Available from: http://dx.doi.org/10.1016/j.micron.2013.08.006 Brust GE. Management strategies for organic vegetable fertility [Internet]. Safety and Practice for Organic Food. Elsevier Inc.; 2019. 193–212 p. Available from: http://dx.doi.org/10.1016/B978-0-12-812060-6.00009-X Howell J. Organic Matter: Key to Soil Management [Internet]. 2005. Available from: http://www.hort.uconn.edu/ipm/veg/croptalk/croptalk1_4/%0Apage8.html Poudel DD, Horwath WR, Mitchell JP, Temple SR. Impacts of cropping systems on soil nitrogen storage and loss. Agric Syst. 2001;68(3):253–68. Vandecasteele B, Willekens K, Steel H, D’Hose T, Van Waes C, Bert W. Feedstock Mixture Composition as Key Factor for C/P Ratio and Phosphorus Availability in Composts: Role of Biodegradation Potential, Biochar Amendment and Calcium Content. Waste and Biomass Valorization. 2017;8(8):2553–67. Nolan T, Troy SM, Healy MG, Kwapinski W, Leahy JJ, Lawlor PG. Characterization of compost produced from separated pig manure and a variety of bulking agents at low initial C/N ratios. Bioresour Technol [Internet]. 2011;102(14):7131–8. Available from: http://dx.doi.org/10.1016/j.biortech.2011.04.066 Zmora-Nahum S, Markovitch O, Tarchitzky J, Chen Y. Dissolved organic carbon (DOC) as a parameter of compost maturity. Soil Biol Biochem. 2005;37(11):2109–16. Blume H peter, Brümmer GW, Horn R, Kögel-knabner I. Soil Science. Vol. 70. 2019. Beni C, Servadio P, Marconi S, Neri U, Aromolo R, Diana G. Anaerobic Digestate Administration: Effect on Soil Physical and Mechanical Behavior. Commun Soil Sci Plant Anal. 2012;43(5):821–34. Schroeder R, Fleige H, Hoffmann C, Vogel HJ, Horn R. Mechanical Soil Database—Part I: Impact of Bulk Density and Organic Matter on Precompression Stress and Consequences for Saturated Hydraulic Conductivity. Front Environ Sci. 2022;10(February):1–15. Mohamed Hafidi. Impact of applying composted biosolids on wheat growth and yield parameters on a calcimagnesic soil in a semi-arid region. African J Biotechnol. 2012;11(41):9805–15. Amon B, Kryvoruchko V, Amon T, Zechmeister-Boltenstern S. Methane, nitrous oxide and ammonia emissions during storage and after application of dairy cattle slurry and influence of slurry treatment. In: Agriculture, Ecosystems and Environment. 2006. p. 153–62. Watanabe Y, Suzuki R, Koike S, Nagashima K, Mochizuki M, Forster RJ, et al. In vitro evaluation of cashew nut shell liquid as a methane-inhibiting and propionate-enhancing agent for ruminants. J Dairy Sci [Internet]. 2010;93(11):5258–67. Available from: http://dx.doi.org/10.3168/jds.2009-2754 Souza N de O, Cunha DA, Rodrigues N de S, Pereira AL, Medeiros EJT, Pinheiro A de A, et al. Cashew nut shell liquids: Antimicrobial compounds in prevention and control of the oral biofilms. Arch Oral Biol. 2022;133(July 2021):0–9. Abbas J, Ariani N, Ria Andayanie W. Antibacterial Activity from The Cashew Nut Shell Extracts. E3S Web Conf. 2024;503:1–15. Nikiema M, Sawadogo JB, Somda MK, Maiga Y, Mogmenga I, Ouattara CAT, et al. Influence of Inoculums Source and Pretreatment on Biogas Production from Cashew Nut Shells (Anacardium occidentale). Int J Environ Agric Biotechnol. 2021;6(6):73–83. Demirel B, Scherer P. Production of methane from sugar beet silage without manure addition by a single-stage anaerobic digestion process. Biomass and Bioenergy. 2008;32(3):203–9. Alvarado A, Montañez-Hernández LE, Palacio-Molina SL, Oropeza-Navarro R, Luévanos-Escareño MP, Balagurusamy N. Microbial trophic interactions and mcrA gene expression in monitoring of anaerobic digesters. Front Microbiol. 2014;5(NOV):1–14. Panuccio MR, Romeo F, Mallamaci C, Muscolo A. Digestate Application on Two Different Soils: Agricultural Benefit and Risk. Waste and Biomass Valorization [Internet]. 2021;12(8):4341–53. Available from: https://doi.org/10.1007/s12649-020-01318-5 Broydé H, Doré T. Effets des pratiques agricoles sur la contamination des denrées par les mycotoxines issues de Fusarium et Aspergillus spp. Cah Agric. 2013;22(3):182–94. Leal PC, Massuquetto A, dos Santos MC, Bruno LDG, Krabbe EL, Felix AP, et al. Fungus Damage Effect on Physical-Chemical Characteristics of Corn Grains. Arch Vet Sci. 2021;26(4):69–76. Karimi B, Sadet-bourgeteau S, Cannavacciuolo M, Flamin C, Haumont A, Jean-baptiste V, et al. Review of the impact of biogas digestates on the microbiological quality of agricultural soils To cite this version : Impact des digestats de méthanisation sur la qualité microbiologique des sols agricoles : 2023; United States Environmental Protection Agency (US EPA). Guideline on Air Quality Models, Revised. Office of Air Quality Planning & Standards, Research Triangle Park [Internet]. 2003. Available from: http://www.epa.gov/scram001/guidance/appw_03.pdf USEPA. United States Environmental ProtectionAgency (USEPA) Control of Pathogens and Vector Attraction in Sewage Sludge [Internet]. 2003. Available from: https://www.epa.gov/sites/production/files/2015-07/documents/epa-625-r-92-013.pdf National Research Council. Biosolids Applied to Land: Advancing Standards and Practices Chapter: 6 Evaluation of EPA’s Approach to Setting Pathogen Standards. In: DC: The National Academies Press [Internet]. 2002. p. 257–321. Available from: https://doi.org/10.17226/10426 Qian X, Shen G, Wang Z, Guo C, Liu Y, Lei Z, et al. Co-composting of livestock manure with rice straw: Characterization and establishment of maturity evaluation system. Waste Manag [Internet]. 2014;34(2):530–5. Available from: http://dx.doi.org/10.1016/j.wasman.2013.10.007 Luo Y, Liang J, Zeng G, Chen M, Mo D, Li G, et al. Seed germination test for toxicity evaluation of compost: Its roles, problems and prospects. Waste Manag [Internet]. 2018;71:109–14. Available from: https://doi.org/10.1016/j.wasman.2017.09.023 Pluschke J, Faßlrinner K, Hadrich F, Loukil S, Chamkha M, Geißen SU, et al. Anaerobic Digestion of Olive Mill Wastewater and Process Derivatives—Biomethane Potential, Operation of a Continuous Fixed Bed Digester, and Germination Index. Appl Sci. 2023;13(17). Daliakopoulos IN, Tsanis IK, Koutroulis A, Kourgialas NN, Varouchakis AE, Karatzas GP, et al. The threat of soil salinity: A European scale review. Sci Total Environ [Internet]. 2016;573:727–39. http://dx.doi.org/10.1016/j.scitotenv.2016.08.177 Salminen E, Rintala J. Anaerobic digestion of organic solid poultryslaughterhouse waste – a review. Bioresour Technol. 2002;83:13–26. Drennan MF, DiStefano TD. Characterization of the curing process from high-solids anaerobic digestion. Bioresour Technol [Internet]. 2010;101(2):537–44. Available from: http://dx.doi.org/10.1016/j.biortech.2009.08.029 Mollier A, Mollier A, Paris DLU, Orsay XI. Croissance racinaire du maïs ( Zea mays L .) sous déficience en phosphore . Etude expérimentale et modélisation To cite this version : HAL Id : tel-02840596 Thèse présentée Croissance racinaire du maïs ( Zea mays L .) sous déficience en phosphore . Etude. Hal [Internet]. 2020;185. Available from: https://hal.inrae.fr/tel-02840596 Girardin P, Jordan MO, Picard D, Trendel R. Harmonisation des notations concernant la description morphologique d’un pied de maïs ( Zea mays L.). Agronomie. 1986;6(9):873–5. Khaled L Ben, Gõmez A, Honrubia M, Oihabi A. Review article Methods for studying root colonization by introduced. Agronomie. 2003;23:407–18. Rahnama A, Munns R, Poustini K, Watt M. A screening method to identify genetic variation in root growth response to a salinity gradient. J Exp Bot. 2011;62(1):69–77. Welbaum GE, Sturz A V., Dong Z, Nowak J. Managing soil microorganisms to improve productivity of agro-ecosystems. CRC Crit Rev Plant Sci. 2004;23(2):175–93. Compant S, Clément C, Sessitsch A. Plant growth-promoting bacteria in the rhizo- and endosphere of plants: Their role, colonization, mechanisms involved and prospects for utilization. Soil Biol Biochem. 2010;42(5):669–78. Kirdi B. Rôle des PGPR Plant Growth Promotion Rhizobacteria dans la croissance végétale et la lutte contre les phanérogames parasites. Ecole Nationale Supérieure Agronomique-El Harrach-Alger; 2011. http://repositorio.unan.edu.ni/2986/1/5624.pdf%0Ahttp://fiskal.kemenkeu.go.id/ejournal%0Ahttp://dx .doi.org/10.1016/j.cirp.2016.06.001%0Ahttp://dx.doi.org/10.1016/j.powtec.2016.12.0 55%0Ahttps://doi.org/10.1016/j.ijfatigue.2019.02.006%0Ahttps://doi.org/10.1 Watt M, Silk WK, Passioura JB. Rates of root and organism growth, soil conditions, and temporal and spatial development of the rhizosphere. Ann Bot. 2006;97(5):839–55. Additional Declarations No competing interests reported. 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T.","lastName":"Ouattara","suffix":""},{"id":380845133,"identity":"6205593d-e3b7-4bca-8782-98e068bc0a49","order_by":10,"name":"Aboubakar S. Ouattara","email":"","orcid":"","institution":"Université Joseph Ki Zerbo","correspondingAuthor":false,"prefix":"","firstName":"Aboubakar","middleName":"S.","lastName":"Ouattara","suffix":""}],"badges":[],"createdAt":"2024-10-01 14:53:24","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5188149/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5188149/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":70559985,"identity":"a4add9bb-6d25-41b7-af50-37efc86ebc1e","added_by":"auto","created_at":"2024-12-04 11:51:49","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":195119,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFictorial representation of digestate production process\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-5188149/v1/7c25b7b0002b5c2bfbb53f2b.png"},{"id":70559987,"identity":"aae4451a-ade9-47a4-9f95-f42d729f6b46","added_by":"auto","created_at":"2024-12-04 11:51:49","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":20522,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMicroorganisms in digestate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDC : Cashew nut shell digestate ; DB : Cow dung digestate ; a, b and c showed significant value with p˂0,05\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-5188149/v1/a06ee000ae2680fb557f39d0.png"},{"id":70559532,"identity":"2c054cd0-6cf6-4095-b4d7-86a58a1b4382","added_by":"auto","created_at":"2024-12-04 11:43:49","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":444263,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMaize and okra seed germination test using digestate extract\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eA : Maize seeds ; B : Okra seeds\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-5188149/v1/8091f71fe9b228b72d5461aa.png"},{"id":70559528,"identity":"6a4c6c83-8cc7-4cdd-a13a-9db097f0416f","added_by":"auto","created_at":"2024-12-04 11:43:49","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":25839,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eGermination parameters of maize\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA/lenght primary root ; B/ Number seminal roots and C/Root dry and fresh weight ; a, b and c showed significant value with p˂0,05\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-5188149/v1/6fe599e7239b21a674ab7894.png"},{"id":70561390,"identity":"739cdf91-9ec0-4416-bc2a-fb89ccccadc8","added_by":"auto","created_at":"2024-12-04 11:59:49","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":445506,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMaize root development in different types of treatment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDB: Cow dung digestate, DC: shells digestate, T: control\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-5188149/v1/b7572be754f1b8c63dc53717.png"},{"id":70561392,"identity":"34796a05-b8d0-452f-b144-aedb648cb64a","added_by":"auto","created_at":"2024-12-04 11:59:55","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2306393,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5188149/v1/ded407eb-04cd-41de-a0d6-c3385485fdfa.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Assessment of the agronomic value of digestate from cashew nut shell and cow dung anaerobic digestion","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe cashew nut sector is experiencing increasingly important development in Burkina Faso. Processing units, whether semi-industrial or artisanal, generate thousands of tons of cashew nut shells, which present a significant environmental challenge. Biogas production from anaerobic digestion showed possibility of bioenergy recovery of old cashew shells that can cover energy needs of processing units. Methanization, also called anaerobic digestion, is a process that not only allows production of bioenergy (biomethane) but also the sanitation of living environment of populations (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e). The anaerobic digestion of cashew nut shells has been shown to yield biomethane production from old shells (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e). Nikiema et al.(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) showed interesting biomethane production yields from old cashew nut shells. Pandiyan et al. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) showed different rates of CNSL cake would have variation in influencing plant growth, but propagation methods were varied between these plants. Cashew nut consists of a hard woody shell containing cashew nut shell liquid or CNSL. The nut is topped with a false fruit, called a \"cashew apple\". The shells and films constitute the waste rejected during production. CNSL consists of 70\u0026ndash;90% anacardic acid, 10\u0026ndash;18% cardol and approximately 5% cardanol (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e). Joshi et al.(\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e) showed addition of CNSL cake at land preparation would exacerbate phorbol ester content in soil which was reported to decompose at time of harvesting.\u003c/p\u003e \u003cp\u003eIn addition, the use of this technology would lead to a significant digestate production that could constitute a fertilizer for cashew orchards. According to M\u0026ouml;ller and M\u0026uuml;ller (\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e) digestates are compared to original feedstock, which are relevant for plant availability of macro and micronutrients after field application. Studies showed that despite their toxicity, \u003cem\u003eJatropha curcas\u003c/em\u003e seed cake used as a fertilizer is detoxified and does not pose any dangers for crops or the environment (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e)(\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e)(\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e). Piperidou et al. (\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e) showed possible use of olive mill wastewater as biofertilizer after biodegradation by \u003cem\u003eAzotobacter vinelandii\u003c/em\u003e. Rais et al.(\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e) showed that treated olive mill wastewater acted very favorably on germination of tomato seeds. Ofosu-budu et al.(\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e) and Szulc et al.(\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e) reported that compost maturity determination is based on physico-chemical and biological parameters such as C/N ratio, humidity, pH, nitrification index, conductivity, total carbon, humification index, phytotoxicity test and germination index. Leite et al.(\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e) reported antioxidant, antifungal, antimicrobial and larvicidal activities of CNSL. Tampio et al.(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e) demonstrated that using digestate in agriculture is an effective method of recycling materials and reducing the reliance on mineral fertilizers. The authors asserted that the agronomic characteristics of digestates can enhance plant growth and soil properties following fertilization with digestate. However, adverse effects may also result from the quality of digestates, including factors such as pH, organic matter, and heavy metal content.Alburquerque et al.(\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e) showed that digestate or cow dung, used as a base treatment, was not sufficient to meet the crop's nitrogen demand throughout its growth cycle, could be the main reason why winter cauliflower is difficult to grow. Barry et al. (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e) showed that the digestate gave highest yield of maize (4.67 t/ha \u0026minus;\u0026thinsp;3.39 t/ha), and the control gave the lowest yield (1.62 t/ha). For analysis of maize kernels biochemical quality, the fluctuation of the crude fiber content is greater between the variants than that of mineral content. Maize plants grew more from the start of spring until the end, especially in the control group. Adding organic matter to soil helps plants grow better. The content of total nitrogen in the tested samples ranged from 1.63 g/kg to 13.22 g/kg. Czekała (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e) demonstrated that digestate contains a wealth of valuable nutrients, including nitrogen, phosphorus, and potassium. Bolzonella et al. (\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e) showcased the potential for recovering nutrients from anaerobic digestate produced in farm-scale plants with specific technologies. The results were impressive, with average yields consistently exceeding 50% for both nitrogen and phosphorus, and costs comparable to those observed in other European experiences documented in literature. Studies showed that the addition of digestate from anaerobic digestion to soil could have environmental impacts, such as CH\u003csub\u003e4\u003c/sub\u003e, CO\u003csub\u003e2\u003c/sub\u003e, and N\u003csub\u003e2\u003c/sub\u003eO gas emissions, which do not affect the fertilizer value of the digestate but have a significant environmental impact (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e). Like olive mill wastewater effluents, cashew nut shells contain phenolic compounds that can be degraded by microorganisms and thus allow their use as a biofertilizer (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e). Traor\u0026eacute; (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e) showed that contributions of compost made from cashew shells and compost from cotton stems allowed significant improvements in seed cotton yields compared to the control without compost. The agronomic value of digestate from cashew nut shells anaerobic digestion is not known. The substances, a mixture of phenolic molecules, could end up in digestates and contribute to altering their safety. Research questions on \u003cem\u003eJatropha curcas\u003c/em\u003e seed cake toxicities and similar substrates, may raise concerns because phorbol esters (EP) can be transferred to cultivated edible plants, accumulate in soil, and therefore impact on soil fauna and flora. According to Bustamante et al. (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e), the application of unripe compost would decrease the oxygen level and redox potential of the soil, which could lead to reduction of nitrates and organic acid formation. Studies showed possible toxicity with similar substrates such as \u003cem\u003eJatropha curcas\u003c/em\u003e seed cake, olive mill wastewater used as compost for crops (\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e)(\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e). The agronomic and ecotoxicological characteristics of cashew nut shell digestate have not yet been studied. It is therefore necessary to carry out a study to determine their digestates safety before their use in plant growth. Cashew nut processing industries could benefit from the energy produced and cashew orchards from organic fertilizer to boost their growth and improve production efficiency. As cow dung is employed as an inoculum in the production of biogas from cashew nut shells, the digestate from cow dung could be utilized for a comparative study. The aim of this study was to evaluate the agronomic characteristics of digestates from cashew nut shell and cow dung anaerobic digestion.\u003c/p\u003e"},{"header":"MATERIALS AND METHODS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eOrigin of materials\u003c/h2\u003e \u003cp\u003eThis study evaluated the agronomic characteristics of cashew shell and cow dung digestate obtained from scale digester with 200 l of capacity. After anaerobic digestion, digestate was sun-dried at 30\u0026ndash;45\u0026deg;C. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e showed digestate production process. The seeds used in our study were obtained from a seed sales outlet developed by the Institut National de l'Environnement et de la Recherche Agricole (INERA). Fore seed were used for phytotoxicity test: early maize variety F.B.C. 6. (Farako Bk Composite nƒ 6.) developed in Farako B\u0026acirc;, Burkina (INERA), Maha F1 Okra seeds from Ivory Coast, F1 COBRA 26 tomato from TECHNISEM in France and lettuce variety PACK.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eEvaluation of the agronomic characteristics of digestates\u003c/h3\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eGeneral characteristics\u003c/h2\u003e \u003cp\u003eThe pH was determined using a VWR pH100 pH-analyzer (VWR International). Electrical conductivity (EC) and salinity were measured by filtering the digestate sample through Whatman filter paper using a digital conductivity meter. The gravimetric method was employed to determine the moisture (H) and total solids (TS) content by drying the compost sample (at 105\u0026deg;C for 24 h) and weighing the loss. The organic carbon (OC) and volatile solids (VS) contents were calculated following the burning of the sample at 550\u0026deg;C. OC (%) was obtained by multiplying organic matter by a factor of 1.8.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eTotal nutrient determination\u003c/h3\u003e\n\u003cp\u003eTotal Nitrogen was determined using LCK 338 Total Nitrogen. Inorganically and organically bonded nitrogen is oxidized to nitrate by digestion with peroxodisulphate. The nitrate ions react with 2.6-dimethylphenol in a solution of sulphuric and phosphoric acid to form a nitrophenol. The method described by Agrawal et al.(\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e) was used to determine total phosphorus (Pt) in the samples by distilled water dilution to fall within the analytical range of the colorimetric molybdovanadate method with acid persulfate digestion Test 'N Tube procedure, Method 10127 (Hach, Co, USA). The organic N (Norg) in the digestates was calculated from the difference between TKN and the sum of mineral nitrogen (NH\u003csub\u003e4\u003c/sub\u003e-N\u0026thinsp;+\u0026thinsp;NO\u003csub\u003e3\u003c/sub\u003e-N).\u003c/p\u003e\n\u003ch3\u003eWater soluble nutrient determination\u003c/h3\u003e\n\u003cp\u003eSoluble nutrient was analyzed from 1:5 water extractions described by. Samples were shaken for one hour and filtered through a cellulose filter with a pore size of approximately 8 mm. The concentrations of ammonium (NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e-N), nitrate (NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e-N), nitrite (NO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e-N), orthophosphorus (PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e-P) and sulfate (SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e) were determined using a lachat autoanalyzer, employing the respective Nessler, Nitraver, Nitriver, Phosver and Sufaver reagents.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003ePhysical parameter determination\u003c/h2\u003e \u003cp\u003eThe method adapted from Woessner and Poeter (\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e) was used. A graduated cylinder was filled halfway with digestate and tamped down (50 ml). The measured digestate was added to a test tube containing 70 ml of distilled water. The mixture was stirred with a rod and left to stand for 5 min. The final volume of the digestate/water mixture was recorded. Porosity is obtained by the ratio between the volume of the pore space and the volume of the packed sample. The volume of the pore space is the difference between the volume of packed sample and volume of solids (ml).\u003c/p\u003e \u003cp\u003eThe water holding capacity of digestate (ml/dm3) was determined by multiplying the volume of water retained in 100 ml of digestate by the factor 10. Distilled water 200 ml was gradually added to cover the digestate sample. Distilled water/digestate mixture was stirred gently until saturation was reached. The volume of drained water was measured after draining was complete.\u003c/p\u003e \u003cp\u003eThe method reported by Achkari-Begdouri and Goodrich (\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e) was used to determine bulk density of digestate. The flasks were filled with digestate with great care, then placed on an electronic equilibrator. The bulk density was then calculated by dividing the dry mass of each sample by its volume.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eMajor and secondary nutrients\u003c/h3\u003e\n\u003cp\u003eThe concentrations of major and secondary nutrients, sodium (Na) and potassium (K), were determined using a BWB flame photometer. The concentrations of water hardness, calcium and magnesium were determined using the standard EDTA titration method (Standard Methods for the Examination of Water and Wastewater (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e)).\u003c/p\u003e\n\u003ch3\u003eMeasure indicators of digestate stability and maturity\u003c/h3\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eMeasurement of chemical indicators of digestate stability and maturity\u003c/h2\u003e \u003cp\u003eThe color of the humus was determined from alkaline extracts of the compost and the absorbance at 400 and 600 nm was measured using a spectrometric technique. The variation in absorbance (log K value) was calculated as follows: log K 400-log K 600\u0026thinsp;=\u0026thinsp;log (K400/K600), where K400 and K600 are the absorbances at 400 and 600 nm, respectively (\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e) ; Ofosu-budu et al., 2010).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eMeasurement of biological indicators of digestate stability and maturity\u003c/h2\u003e \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e \u003ch2\u003eRespirometry test\u003c/h2\u003e \u003cp\u003eThe method described by Germon (\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e) was used with slight modifications. The dried digestate was crushed to a size\u0026thinsp;\u0026le;\u0026thinsp;1 mm. A 100 g mass of moistened digestate was placed in 300 ml septum-capped flasks. The flasks were hermetically sealed and incubated at room temperature (25\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C). The volume of biogas produced was measured by liquid displacement, using the technique adapted from Esposito et al. (\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e). The proportions of CH\u003csub\u003e4\u003c/sub\u003e and CO\u003csub\u003e2\u003c/sub\u003e in the biogas were estimated by gas chromatography.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eDetermination of microbiological parameters in digestates\u003c/h2\u003e \u003cp\u003eViable count refers to the enumeration of the living microorganisms\u0026rsquo; number that form colonies on solid media. Total aerobic flora was quantified using Plate Count Agar, coliforms on Eosin Methylene Blue, spore-forming bacteria on Tryptone-Soja Agar and yeasts and fungi on Sabouraud chloramphenicol agar. Plates were incubated at 37\u0026deg;C for 2\u0026ndash;5 days. The observed colonies were enumerated and expressed as colony-forming units per gram (cfu/g) using the Eq.\u0026nbsp;(3) (21):\u003c/p\u003e \u003cp\u003eN = \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\frac{\\sum\\:C}{Vi*\\left(n1+0,2*n2\\right)d}\\)\u003c/span\u003e\u003c/span\u003e x Fd (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eWhere N is the number of colony-forming units per gram (cfu/g), ƩC\u0026thinsp;=\u0026thinsp;Sum of colonies, Vi\u0026thinsp;=\u0026thinsp;volume inoculated, n1\u0026thinsp;=\u0026thinsp;Number of microorganisms in first dilution, n2\u0026thinsp;=\u0026thinsp;Number of microorganisms at second dilution, d\u0026thinsp;=\u0026thinsp;First dilution, Fd\u0026thinsp;=\u0026thinsp;dilution factor for digestate\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eDigestate phytotoxicity test\u003c/h2\u003e \u003cp\u003eThree varieties were used for testing: maize (\u003cem\u003eZea mays\u003c/em\u003e Komsaya variety), tomato (\u003cem\u003eLycopersicum esculentum\u003c/em\u003e L. Var. Tropimech), and lettuce (\u003cem\u003eLactuca sativa\u003c/em\u003e L.). These varieties were purchased from a seed sales outlet developed by the Institut National de l'Environnement et de la Recherche Agricole (INERA). Phytotoxicity was evaluated using the germination test modified from Zucconi et al.(\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e). A compost extract was prepared by mixing digestate with demineralized water in a 1:5 (weight/volume) ratio for one hour, followed by filtration. Two filter papers were placed in Petri dish, which was then moistened with 15 ml of the digestate water extract. Ten seeds were added to the Petri dish, and a similar set-up was prepared using demineralized water as control. Both set-ups were replicated five times. The experiment involved placing closed petri dishes containing tomato and cabbage seeds in the dark under ambient conditions for 7 days. The germination percentage, root length of germinated seeds, and germination speed were determined. The germination percentage was determined at 96 h, 144 h, and 184 h, with the length of primary roots, fresh weight, dry weight of root biomass and number of lateral roots measured during the final reading. The seed germination (SG), root elongation (RE), germination index (GI), and germination speed (T50) were calculated using the formulas described by Bae et al. (\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eData analysis\u003c/h2\u003e \u003cp\u003eData were analyzed using the XLSAT software version 2018. Analysis of variance (ANOVA) was performed to compare mean values of the different variables using Fisher's tests at probability \u003cem\u003ep\u003c/em\u003e\u0026thinsp;=\u0026thinsp;5%.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec18\"\u003e\n \u003ch2\u003ePhysical and chemical parameters of digestates\u003c/h2\u003e\n \u003cp\u003eThe physical and chemical characteristics of digestates from shells and cow dung anaerobic digestion are summarized in Table \u003cspan\u003e1\u003c/span\u003e. For two types of digestates, the pH was 6.81 and 6.61, respectively, for shell digestate and cow dung digestate. The electrical conductivity (EC) and salinity were 2.94 mS/cm and 1.45 mg/l for shell digestate and 7.57 mS/cm and 4.25 mg/l for cow dung digestate. Total solid (TS), solid volatile (SV) and ash content were respectively, 94,20%, 88,86% and, 11,13% for digestate cashew nut shell. The values of 91.27%, 89.70%, and 10.29% were determined for TS, VS and ash, respectively, for cow dung digestate. Both digestates have high SV contents, reaching 88.86 and 89.70% respectively. Overall, nutrient concentrations in cashew shell digestate were lower than cow dung digestate. In fact, Nt, Pt, Norg were respectively 11.26 g N/Kg, 5.35 g (P\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e) /Kg and 0.49 g Norg /Kg for cashew sell digestate and 18.15 g N/Kg, 17.12g (P\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e) /Kg and 0.16 g Norg/Kg for cow dung digestate. Potassium K was 0.32 g/Kg and 0.98 g/Kg for cashew shell and cow dung digestate. The water-soluble nutrients exhibited mineral nitrogen contents of 0.19 g NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e/kg, 1.28 g NO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e/kg, and 1.6 mg NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e/kg for cashew nut shell digestate. The levels were slightly higher in cow dung digestate, with values of 0.69 g NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e/kg, 1.86 g NO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e/kg, and 5 mg NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e/kg. The degree of humification determined was 0.99. The levels of phosphorus in the cashew nut shell digestate were found to be slightly higher than in the cow dung digestate (1.31 g/kg versus 1.71 g/kg). Sulfates were found to be 0.11 g SO4\u003csup\u003e2+\u003c/sup\u003e /kg and 0.27 g SO4\u003csup\u003e2+\u003c/sup\u003e/Kg, respectively, in the cashew nut shell and cattle dung digestates. The C/N ratio of the digestates was 43.84 and 22.7 for cashew nut shell digestate and cow dung digestate respectively. In dry matter, the content of micronutrients was as follows: 0.32 g/kg K, 1092.001 mg/Kg Na, 272 mg/Kg Ca, 149.4 mg/Kg Mg, and 0.25 mg/Kg Fe for cashew nut digestate and 0.98 g/kg K, 962.27 mg/Kg Na, 580 mg/Kg Ca, 936 mg/Kg Mg, and 0.2 mg/Kg Fe for cow dung digestate. Micronutrients or trace elements play an important role in plant health and growth. Physical parameters like Water holding capacity, density and porosity, were measured. Cow dung digestate showed higher values for Water holding capacity (979 ml/dm\u003csup\u003e3\u003c/sup\u003e), density (1 g/cm\u003csup\u003e3\u003c/sup\u003e) and porosity (78%). Water holding capacity, density and porosity were respectively 870 ml/dm\u003csup\u003e3\u003c/sup\u003e, 0.83 g/cm\u003csup\u003e3\u003c/sup\u003e and 70% for cashew nut shell digestate. Digestates are a significant source of CH\u003csub\u003e4\u003c/sub\u003e, NH\u003csub\u003e3\u003c/sub\u003e and N\u003csub\u003e2\u003c/sub\u003eO emissions into the atmosphere. Our study shows that under the right conditions, cashew nut shell digestate and cow dung digestate produce 12.12 l biogas/Kg and 4.68 l biogas/Kg respectively. Emissions were 2.68 l CH\u003csub\u003e4\u003c/sub\u003e/kg of cashew nut shell digestate and 2.46 l CH\u003csub\u003e4\u003c/sub\u003e/kg of cow dung digestate. Emissions reached 7.07 l CO\u003csub\u003e2\u003c/sub\u003e/kg cashew nut shell digestate and 0.74 l CO\u003csub\u003e2\u003c/sub\u003e/kg cow dung digestate. Cow dung digestate had lower emissions than cashew nut shell digestate. Methane has a global warming potential (GWP) 28 times greater than that of CO₂. It is the second-largest contributor to total greenhouse gas radiative forcing, accounting for 17% in 2018, after CO₂ (66%) and ahead of N₂O (6%) (Dessus and Laponche, 2008 ; Durand et al. 2020).\u003c/p\u003e\n \u003cdiv\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 1\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003ePhysical chemical characteristics of digestates from hulls and cow dung anaerobic digestion\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eParameters\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eUnit\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDC\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eBD\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003ep\u003c/em\u003e value\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e\u003cem\u003eGeneral characteristics\u003c/em\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003epH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.81\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0,02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.61\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.227\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHumidity\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.79\u003csup\u003eb\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.72\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.026\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eEC\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003emS/cm\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.94\u003csup\u003eb\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.57\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSalinity\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003emg/l\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.45\u003csup\u003eb\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.25\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0006\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e94.20\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e91.27\u003csup\u003eb\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.026\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAsh\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.13\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10.29\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.07\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003eOrganics characteristics\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e88.86\u003csup\u003eb\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.27\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e89.70\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.026\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCarbon\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e49.37\u0026thinsp;\u0026plusmn;\u0026thinsp;0.16\u003csup\u003ea\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e49.83\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e˂0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHumification\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.99\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0006\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal nutrients\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNt\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eg/Kg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11.26\u003csup\u003eb\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e18.15\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.0006\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePt\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eg/Kg ( PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.17\u003csup\u003eb\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22.92\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e˂0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePt\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eg/Kg (P\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.35\u003csup\u003eb\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17.12\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.005\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNorg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eg/Kg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.49\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.002\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.16\u003csup\u003eb\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.005\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e˂0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eC\u0026nbsp;:N ratio\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e43.84\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.004\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22.7\u003csup\u003eb\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.198\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.004\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003e1\u0026nbsp;:5 water soluble nutrients\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eg/Kg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.19\u003csup\u003eb\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.69\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.005\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eg/kg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.28\u003csup\u003eb\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.002\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.86\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0003\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003emg/Kg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.6\u003csup\u003eb\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.000003\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.003\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eOrthophosphate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eg/Kg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.71\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.00007\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.31\u003csup\u003eb\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSulfates\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eg/Kg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.11\u003csup\u003eb\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.021\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.27\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.002\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eNO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e/NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0,0008\u003csup\u003eb\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0,0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.007\u003csup\u003ea\u003c/sup\u003e\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003ePhysical parameters\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eWater holding capacity\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eml/dm\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e870\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e979\u0026thinsp;\u0026plusmn;\u0026thinsp;0.009\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.003\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eBulk Density\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eg/cm\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.83\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.038\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePorosity\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e27\u0026thinsp;\u0026plusmn;\u0026thinsp;1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e38\u0026thinsp;\u0026plusmn;\u0026thinsp;1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.014\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003e\u003cstrong\u003eGaseous emissions\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eBiogas\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003el/Kg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12.12a\u0026thinsp;\u0026plusmn;\u0026thinsp;2.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.68b\u0026thinsp;\u0026plusmn;\u0026thinsp;0.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.014\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCH\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003el/Kg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.68a\u0026thinsp;\u0026plusmn;\u0026thinsp;0.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.46a\u0026thinsp;\u0026plusmn;\u0026thinsp;0.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.068\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003el/Kg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.07a\u0026thinsp;\u0026plusmn;\u0026thinsp;1.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.74a\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.014\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003e\u003cstrong\u003eMajor and secondary nutrients\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eK\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eg/kg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.32\u0026thinsp;\u0026plusmn;\u0026thinsp;0.004\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.98\u0026thinsp;\u0026plusmn;\u0026thinsp;0.015\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003emg/Kg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1092.001\u0026thinsp;\u0026plusmn;\u0026thinsp;15.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e962.27\u0026thinsp;\u0026plusmn;\u0026thinsp;15.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003emg/Kg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e272\u0026thinsp;\u0026plusmn;\u0026thinsp;22.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e580\u0026thinsp;\u0026plusmn;\u0026thinsp;28.28\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003emg/Kg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e149.4\u0026thinsp;\u0026plusmn;\u0026thinsp;5.94\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e936\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFe\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003emg/Kg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.2\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0.0001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\"\u003eDC : Digestate from cashew nut shell ; BD : Digestate from cow dung ; Electrical conductivity (EC) ; TS : Total Solid ; SV : Solids Volatile\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cdiv\u003e\u003cbr\u003e\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec19\"\u003e\n \u003ch2\u003eDetermination of microbiological parameters in digestates\u003c/h2\u003e\n \u003cp\u003eThe microbiological characteristics of the digestates are presented in Fig. \u003cspan\u003e2\u003c/span\u003e. Cow dung digestate showed a higher number of microbial groups than cashew nut shell digestate (\u003cem\u003ep\u003c/em\u003e ˂ 0.05). The total number of microorganisms (total aerobic flora) in digestate were 5.5\u0026times;10\u003csup\u003e4\u003c/sup\u003e CFU g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1.13\u0026times;10\u003csup\u003e5\u003c/sup\u003e CFU g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively for cashew nut shell and cow dung digestate. Coliforms were 1.98\u0026times;10\u003csup\u003e2\u003c/sup\u003e and 3.07\u0026times;10\u003csup\u003e2\u003c/sup\u003e CFU g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e respectively for cashew nut and cow dung digestates, and spores forming bacteria, 6.59\u0026times;10\u003csup\u003e2\u003c/sup\u003e CFU g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 2.02\u0026times;10\u003csup\u003e3\u003c/sup\u003e CFU g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively for cashew nut shell and cow dung digestate. Spore-forming bacteria included \u003cem\u003eBacillus\u003c/em\u003e (aerobic) and \u003cem\u003eClostridium\u003c/em\u003e (anaerobic) species. Yeasts and fungi were more numerous than others, with concentrations of 1.02\u0026times;10\u003csup\u003e4\u003c/sup\u003e CFU g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e of cashew nut shell digestate and 2.86\u0026times;10\u003csup\u003e4\u003c/sup\u003e CFU g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e of cow dung digestate.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec20\"\u003e\n \u003ch2\u003eDigestate phytotoxicity test\u003c/h2\u003e\n \u003cdiv id=\"Sec21\"\u003e\n \u003ch2\u003eGermination test\u003c/h2\u003e\n \u003cp\u003eThe results of germination test on Petri dishes are presented in Table \u003cspan\u003e2\u003c/span\u003e. The germination test of digestates using maize, okra, tomato and lettuce seeds demonstrated a range of germination rates, from 0\u0026ndash;100%. Maize seeds exhibited 100% germination with cashew nut shell and cow dung digestates. The seed germination (SG), root elongation (RE), germination index (GI) and germination speed (T50) values were 100, 97.19%, 97.19% and 69.82% for cashew nut shell digestates and 100%, 118.63%, 118.63% and 67.21% for cow dung digestates. The cow dung digestate exhibited high phytotoxicity on tomato and lettuce seeds, with a zero GI due to the absence of germination. In contrast, the cashew nut shell digestate demonstrated seed germination (SG) of 40% and 30% for tomato and lettuce seeds, respectively. Okra seed germination was 52.5% and 45.8% for digestate from cashew nut shell and cow dung digestate, respectively. The results of digestates on okra, tomato and lettuce seeds demonstrated low to practically zero germination percentages, which indicated a high phytotoxicity of the samples.\u0026nbsp;\u003c/p\u003e\n \u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 2\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003ePhytotoxic effect of digestate on seed germination, radical elongation and germination index\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTraitment\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSG\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eRE\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eGI\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eT50\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\u003eDC Maize\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e97,2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e97,2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e69,8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eBV Maize\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e118,6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e118,6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e67,2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDC Okra\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e52,5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003end\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003end\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003end\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eBV Okra\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e45,8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003end\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003end\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003end\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDC Tomato\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e40\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003end\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003end\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003end\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eBV Tomato\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003end\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003end\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003end\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDC Laituce\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e30\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003end\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003end\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003end\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eBV Laituce\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003end\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003end\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003end\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"5\"\u003eDC : Cashew nut Shell digestate, BV : Bouse Bovine digestate; nd :no determine, SG : Seed Germination, RE : Root Elongation, GI : Germination Index, T50 : Germination Speed\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003cp\u003eFigure \u003cspan\u003e3\u003c/span\u003e showed images of the germination test. The maize germinated well compared with other seeds. \u0026nbsp;\u003c/p\u003eRoots growing\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec22\"\u003e\n \u003cdiv id=\"Sec23\"\u003e\n \u003cp\u003eThe graphs of Fig. \u003cspan\u003e4\u003c/span\u003e Fig. \u003cspan\u003e3\u003c/span\u003e presents roots growth results according to the nature of digestate. The results show that the primary length of the roots reached 11.33, 16.27 and 22.60 cm respectively, for cashew nut shell digestate, control and cow dung digestate (Fig. \u003cspan\u003e4\u003c/span\u003e). The length of primary root reached 11.33, 16.27 and 22.60 cm for cashew nut shell digestate, control and cow dung digestate, respectively. Seminal roots averaged 10.67, 9.00 and 6.33 cm for shells, cow dung digestates and control, respectively. In both types of digestate, no significant differences were observed for the parameters primary root length, fresh weight, dry weight of root biomass and number of seminal roots. However, a significant difference was found for the number of seminal roots, with an average of 11.33, 7.67 and 4.67 for the shell digestates, cattle dung and the control, respectively. Figure \u003cspan\u003e5\u003c/span\u003e presents root development images in cow dung digestate (DB), shell digestate (DC), and control (T). Results was found that the lateral roots were more developed in the digestates than in the control.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe composition of the digestate is strongly dependent on the composition of the feedstock, the inoculum source, the operating conditions of the anaerobic digestion and the presence or absence of post-fermenters (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e). Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e1\u003c/span\u003e summarizes physical and chemical characteristics of digestates from hulls and cow dung anaerobic digestion. For two the types of digestates, pH was 6.81 and 6.61, respectively for shell and cow dung digestate. According to Monlau et al. (\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e), digestate was characterized by pH values\u0026thinsp;\u0026gt;\u0026thinsp;7.5. This slightly-alkaline condition was caused by the degradation of volatile fatty acids (VFAs) and ammonia (NH\u003csub\u003e3\u003c/sub\u003e) production during the process as well as the addition of strong bases or carbonates to control both the pH and buffer capacity of the system. According to many studies, the digestate pH value is mainly controlled by interaction of fluxes of NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e and NH\u003csub\u003e3,\u003c/sub\u003e CO\u003csub\u003e2\u003c/sub\u003e, HCO\u003csub\u003e3\u003c/sub\u003e \u0026minus;, H +, and CO\u003csub\u003e3\u003c/sub\u003e and finally CH\u003csub\u003e3\u003c/sub\u003eCOOH and CH\u003csub\u003e3\u003c/sub\u003eCOO\u003csup\u003e\u0026minus;\u003c/sup\u003e (\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e). The lower values obtained in our study would be due to the digestate drying process. Indeed, drying causes the volatilization of volatile fatty acids and ammonia (NH\u003csub\u003e3\u003c/sub\u003e) contained in the liquid digestate. If too much ammonia is lost, the pH will fall. The loss is even greater with cattle dung digestate (pH 6.61) (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Amery et al.(\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e) found a pH compost range between 6 and 9.53. According to these authors, the lowest values were for plant-based composts and the highest for manure-based composts. A low pH indicate that the compost is immature (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e). The compost pH could influence positively or negatively on plant growth according to the type of plant cultivated. Indeed, Costello and Sullivan (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e) have reported that low-pH composts should be used for acid-loving plants. Acidic and alkaline environments make it difficult for plants to assimilate phosphorus. Also, Barrow and Hartemink (\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e) showed the effects of pH on nutrient availability depend on both soils and plants. Liu et al. (\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e) showed that the overall effects of pH on the availability of nutrients for the plants are a combination of the effects of pH on sorption by soils and the effects of pH on plant uptake. A pH greater than 7 (alkaline) will have more base (-OH) than hydrogen. A neutral pH of 7 is best, but plants can't tolerate hydrogen until the pH is below 4.5. Aluminium, iron and manganese can cause toxicity in acid soils. A pH of 7 is considered neutral while anything lower is acidic in the soil. The pH of the digestate is suitable for spreading.\u003c/p\u003e \u003cp\u003eThe higher conductivity value was associated with higher salinity. Cations and anions from dissolved salts in soil water carry electrical charges and conduct electricity. This largely explains the link between salinity and electrical conductivity. Salinity may affect how nutrients are absorbed, which could limit photosynthesis and reduce chlorophyll production. This could result in plants with nutritional deficiencies (\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e, \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e, \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e). It has been demonstrated that elevated electrical conductivity (EC) can be indicative of salinity issues, with electrical conductivity values exceeding 4 dS/m. Such conditions impede crop growth, as plants are unable to absorb water even when it is present, and also affect microbial activity. It would seem that soils with a high electrical conductivity, resulting from a high concentration of sodium, often have poor structure and drainage. This can result in sodium becoming toxic to plants. Frankenberger and Bingham (\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e) suggested that dehydrogenase activity may be significantly affected by changes in soil extract electrical conductivity (EC), with inhibition levels ranging from 30 to 81% when the EC is increased from 0.2 to 22 dS/m. It is also worth noting that a high salt content (\u0026gt;\u0026thinsp;1500 \u0026micro;S/cm) can potentially induce salt stress, particularly when compost is used in growing media. Digestate conductivity values are high, above the threshold that could induce stress.\u003c/p\u003e \u003cp\u003eIt would appear that both digestates have high TS contents, reaching 88.86 and 89.70% respectively. This suggests that both digestates may have the potential to enhance soil organic matter (OM) content, which could contribute to improved soil bio-functioning. Czekała (\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e), studying the characteristics of digestates and extracts from different biogas plants, showed that organic matter content in material exhibited greater diversity than the dry matter content, with values ranging from 38.89\u0026ndash;94.26%. Additionally, the solid volatile content in the raw pulp exhibited a range of 63.87\u0026ndash;83.46%. M\u0026ouml;ller and M\u0026uuml;ller (\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e) reported that the digestate contained between 1.5% and 13.2% dry matter and between 63.8% and 75.0% organic matter. The low dry matter content in our study could be explained by the process of drying the digestate after anaerobic digestion. Mammarella et al.(\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e) reported ash contents in different types of digestates from biogas production ranging from 10.2 to 55.5%. Bauer et al.(\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e) determined that 61.8% and 58% of dry material and organic matter respectively that were present in the inflow were retrieved in the digestate solid phase The ash contents of the two digestates studied, which were 11.13 and 10.29 respectively for cashew nut shell and cow dung digestates, are in agreement with these results. With lower SV levels, the application of digestates could help to increase soil SV levels. The results reported by many authors are in agreement regarding the capacity of biosolids, such as anaerobic digestate or sewage sludge, to increase the organic matter content of the soil (\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e, \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e). Bonet-Garcia et al. (\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e) showed that municipal solid waste (MSW) digestate application increased the organic matter content and the macro and micronutrients in the marginal soil, indicating a potentially suitable use in soil reclamation. Tambone et al. (\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e) reported a high concentration of organic carbon in the organic municipal solid waste (OFMSW) digestate.\u003c/p\u003e \u003cp\u003eOverall, nutrient concentrations in cashew shell digestate were lower than cow dung digestate (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Nutrient concentrations are in line with the work of several authors. M\u0026ouml;ller and M\u0026uuml;ller (\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e) reported total N contents of 1.20\u0026ndash;9.10 g Kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for digestates from agricultural residues and animal excrements. Gell et al.(\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e) found high levels of potassium (14.38 g K\u003csup\u003e+\u003c/sup\u003e Kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) in cow dung digestate. Total phosphorus concentrations of 0.4\u0026ndash;2.6 g Kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in digestate were reported by M\u0026ouml;ller and M\u0026uuml;ller (\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e). The values found were higher than those digestates obtained through anaerobic digestion of FW, such as those reported by (\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e) (4.93 g N kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 0.90 g P kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). Cathcart et al.(\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e) demonstrated that the nitrogen content of the liquid fractions produced from the digestates exhibited a considerable range, varying from 2.14 g/kg to 2.96 g/kg. Additionally, the authors observed a higher proportion of nitrogen in the solid fractions, with concentrations ranging from 3.69 g/kg to 4.91 g/kg. In the same study, the concentrations of phosphorus (P) and potassium (K) in the solids exhibited a range of values from 0.76 g/kg to 2.40 g/kg and 2.70 g/kg to 3.64 g/kg, respectively. According to Valorgas (\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e), the total nutrient concentration in European (UK, Finland, and Italy) food wastes, was total-N concentrations, which varied between 24 and 34 g/kg TS, total-P between 2.7 and 6.4 and total-K between 8.6 and 14.3 g/kgTS. Our results show lower values, and those reported by Valorgas (\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e), except for the phosphate content of cattle manure digestate, which was excessive at 17.12 g/Kg.\u003c/p\u003e \u003cp\u003eFor water-soluble nutrients, similar results were found by Reuland et al. (\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e), who reported NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e-N contents ranging from 0 to 100.5 g kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in digestates and composts elaborated from distinct feedstock profiles. All digestates and composts studied had 0.0 g kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e NO\u003csub\u003e3\u003c/sub\u003e-N content, except for commercial compost COM_1, which had a low content of 0.7 g kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. According to, Amery et al.(\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e), there are specific differences in nitrogen concentrations between digestate from anaerobic digestion of energy crops and digestate from organic waste and industrial by-products. Mineral nitrogen (NO\u003csub\u003e3\u003c/sub\u003e-N and NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e-N) is the nitrogen that is directly available for the plant, in contrast to the total nitrogen content. In a well-matured compost, the concentration of NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e-N is typically low, with values below 0.4 g/kg. This is accompanied by a high concentration of NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e-N, resulting in a NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e-N/NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e-N ratio greater than 1, which indicates a degree of compost maturity. The NO\u003csub\u003e3\u003c/sub\u003e/NH\u003csub\u003e4\u003c/sub\u003e ratio in this case was 23.34. S\u0026aacute;nchez-Monedero et al.(\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e) indicate that mature compost should have a NO\u003csub\u003e3\u003c/sub\u003e/NH\u003csub\u003e4\u003c/sub\u003e ratio greater than 6.3. The degree of humification determined was 0.99. According to Ofosu-budu et al.(\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e), a degree of humification of less than 0.7 indicates mature compost. The degree of humification obtained is greater than 0.7, so the digestate is considered immature. M\u0026ouml;ller \u0026amp; M\u0026uuml;ller,(\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e) reported total NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e contents in digestate of 1.5\u0026ndash;6.8 g Kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The authors stated that the characteristics of digestate depend on the original feedstock. Anaerobic digestion process degrades organic nitrogen compounds, releasing ammonium NH\u003csub\u003e4\u003c/sub\u003e-N, which is immediately bioavailable for growing plants. The content of ammonium in digestate is directly related to the total N content in the substrate. As pig slurry has higher N-total and NH\u003csub\u003e4\u003c/sub\u003e-N contents than cattle slurry, this will be reflected directly in the digestate dominated by such substrates (\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e). The levels of orthophosphates in the cashew nut shell digest was found to be slightly higher than in the cattle dung digest (1.31 g/kg versus 1.71 g/kg). Sulfates were found to be 0.11 g SO4\u003csup\u003e2+\u003c/sup\u003e /kg and 0.27 g SO4\u003csup\u003e2+\u003c/sup\u003e/Kg, respectively, in cashew nut shell and cow dung digestates.\u003c/p\u003e \u003cp\u003eThe C/N ratios were high. These ratios are in agreement with the results reported by Larbi (\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e), who found values between 70 and 80 for straw and 10 and 30 for green waste. The high C/N ratios could be explained by the presence of lignified compounds. Muniz et al. (\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e) showed that the pericarp of \u003cem\u003eAnacardium\u003c/em\u003e has an outer layer composed of highly lignified cells. Reuland et al.(\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e) found C/N ratios ranging from 1.99 to 26.97 for digestates and composts elaborated from distinct feedstock profiles. Research into the initial chemical characteristics of compostable wastes has shown that wastes such as green waste, bio-waste and municipal solid waste have C/N ratios ranging from 11 to 65It may be the case that a high C/N ratio (greater than 20\u0026ndash;25) could indicate that the compost is not yet fully mature. Brust (\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e) reported that a C:N ratio of 1 to 15 is more likely to trigger rapid N release, whereas C:N ratios\u0026thinsp;\u0026gt;\u0026thinsp;35 generally favor net N immobilization (\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e). According to Howell (\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e), soil microorganisms have a C:N ratio of around 8. In order to maintain this ratio in their cells, they must acquire sufficient carbon and nitrogen from the soil. Research has shown that they perform best on a \"diet\" with a C:N ratio of 24. Given that the C:N ratio of cashew nut shell digestate is 43.84 (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e1\u003c/span\u003e), it will lead to less nitrogen mineralization in the soil. Should the organic matter exhibit a higher C:N ratio, the requisite nitrogen for microbial activity will exceed the quantity present in the organic matter. Consequently, the nitrogen will be extracted from the soil. Microbes get more nitrogen from soil than crops. In the absence of sufficient nitrogen for both microbes and crops, crop growth will be limited. Nevertheless, it is challenging to augment humus by \u0026gt;\u0026thinsp;1% in intensively managed organic vegetable production systems unless residues with elevated C:N ratios are employed (\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e). Cashew nut shell digestate could be used in cover crops and may be useful in managing excess nitrogen by promoting microbial immobilization and slowing the rate of mineralization (\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e). Nevertheless, the C/N ratio of the end product may not be an appropriate indicator of maturity or stability (\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e). This is because it is primarily influenced by the initial C/N ratio of the feedstock (\u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e68\u003c/span\u003e) and may reach a plateau before the compost has stabilized (\u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e69\u003c/span\u003e). The degree of humification was greater than 0.7. The degree of humification was greater than 0.7, as reported by Ofosu-budu et al. (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e), who indicated that a degree of humification of less than 0.7 indicates mature compost. The degree of humification obtained is greater than 0.7, thus indicating that the digestate is considered immature.\u003c/p\u003e \u003cp\u003eIn terms of micronutrients, the digestates exhibited values that were consistent with those reported in previous studies. Micronutrients or trace elements play an important role in plant health and growth. The pH of digestate is also influenced by the concentration of basic cations, including sodium (Na\u003csup\u003e+\u003c/sup\u003e), calcium (Ca\u003csup\u003e2+\u003c/sup\u003e), magnesium (Mg\u003csup\u003e2+\u003c/sup\u003e), and potassium (K\u003csup\u003e+\u003c/sup\u003e). These cations increase the pH of the digestate solution by maintaining a neutral electric charge balance, which results in a reduction in the concentration of hydrogen ions (H\u003csup\u003e+\u003c/sup\u003e). The precipitation of iron (Fe\u003csup\u003e2+\u003c/sup\u003e) phosphates releases protons and lowers the pH. Additionally, the reaction between magnesium (Mg\u003csup\u003e2+\u003c/sup\u003e) ions, ammonium (NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e) ions, and phosphate (PO43-) ions causes the release of hydrogen ions (H\u003csup\u003e+\u003c/sup\u003e) from the solution. Bonet-Garcia (\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e) suggest the migration of Zn, Cu, Pb, Cr, Ni, and Mn from municipal solid waste digestate-amended soil to the soil layer beneath (0.1\u0026ndash;0.2 m) during the first 21 days after municipal solid waste digestate application. Compost can help balance soil nutrients. It can be used to add specific nutrients, such as potassium or calcium, to improve soil health (\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e). Effect of application of increasing amounts of compost on soil carbon organic content and cation exchange capacity (CEC). In general, the CEC of decomposed soil organic matter is much higher than that of clay minerals (\u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e). The physical parameters of Water holding capacity, bulk density and porosity demonstrated an improvement in the physical quality of the soil. The addition of digestate increases soil fertility by reducing specific sedimentation mass and increasing Water holding capacity, but only short-term trials have been conducted (\u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e71\u003c/span\u003e). The dry density is the ratio of oven-dried solids to the volume of soil. It reflects the structural condition of the soil at a given depth. Schroeder et al. (\u003cspan citationid=\"CR72\" class=\"CitationRef\"\u003e72\u003c/span\u003e) reported than densities of mineral soils may range from \u0026lt;\u0026thinsp;0. 8 to \u0026gt;\u0026thinsp;1.75 g/cm\u003csup\u003e3\u003c/sup\u003e. Organic matter enrichment can therefore contribute to a significant increase in CEC, especially in light soils with low absorptive capacity (\u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e73\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDigestates are a significant source of CH\u003csub\u003e4\u003c/sub\u003e, NH\u003csub\u003e3\u003c/sub\u003e and N\u003csub\u003e2\u003c/sub\u003eO emissions to the atmosphere. Cow dung digestate had lower emissions than cashew nut shell digestate (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The high values of biogas emissions could be explained by the fact that biogas consists of several gases such as CO\u003csub\u003e2\u003c/sub\u003e, CH\u003csub\u003e4\u003c/sub\u003e, N\u003csub\u003e2\u003c/sub\u003eO, NH\u003csub\u003e3\u003c/sub\u003e, N\u003csub\u003e2\u003c/sub\u003e and O\u003csub\u003e2\u003c/sub\u003e. The main gases released during the biodegradation of the organic fraction are CH\u003csub\u003e4\u003c/sub\u003e and CO\u003csub\u003e2\u003c/sub\u003e. Amon et al.(\u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e) showed anaerobic digestion was a very effective means to reduce greenhouse gas emissions (GHG) 37.9 kg CO\u003csub\u003e2\u003c/sub\u003e eq.\u0026nbsp;m\u003csup\u003e-3\u003c/sup\u003e were lost. These authors showed slurry aeration reduces CH\u003csub\u003e4\u003c/sub\u003e and GHG emissions. These digestates must undergo upstream treatment before being used.\u003c/p\u003e \u003cp\u003eThe microbiological analysis revealed the presence of total aerobic flora, coliforms, and spore-forming bacteria (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Spore-forming bacteria included \u003cem\u003eBacillus\u003c/em\u003e (aerobic) and \u003cem\u003eClostridium\u003c/em\u003e (anaerobic) species. Yeasts and fungi were more numerous than other microorganisms, with concentrations of 1.02\u0026times;10\u003csup\u003e4\u003c/sup\u003e CFU/g of cashew nut shell digest and 2.86\u0026times;10\u003csup\u003e4\u003c/sup\u003e CFU/g of cow dung digestate. The characteristics observed on the Petri dishes showed that fungi were in the majority. The cashew nut shell contains phenolic compounds that can have toxic effects on microorganisms, particularly bacteria (\u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e75\u003c/span\u003e)(\u003cspan citationid=\"CR76\" class=\"CitationRef\"\u003e76\u003c/span\u003e)(\u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e77\u003c/span\u003e). Although anaerobic digestion plays a significant role in reducing the concentration of toxic substances in cockles, cashew nut shell digestate is not exempt from this process (\u003cspan citationid=\"CR78\" class=\"CitationRef\"\u003e78\u003c/span\u003e). While anaerobic digestion contributes significantly to the reduction of toxic substances in the shell, the digestate from cashew nut shell is not exempt from this toxicity. Microorganisms have been shown to be involved in each stage of anaerobic digestion by Demirel and Scherer (\u003cspan citationid=\"CR79\" class=\"CitationRef\"\u003e79\u003c/span\u003e) and Alvarado et al. (\u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e80\u003c/span\u003e). The hydrolysis phase is inhabited by a diverse array of microorganisms, including bacteria belonging to the genera \u003cem\u003eBacillus\u003c/em\u003e, \u003cem\u003ePseudomonas\u003c/em\u003e and \u003cem\u003eAminobacterium\u003c/em\u003e, as well as fungi of the genus \u003cem\u003eAspergillus\u003c/em\u003e. The majority of these microorganisms, particularly coliforms, originate from cow dung inoculum. Similar results was found by Panuccio et al. (\u003cspan citationid=\"CR81\" class=\"CitationRef\"\u003e81\u003c/span\u003e) with bacteria (CFU g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) 57.5\u0026times;10\u003csup\u003e5\u003c/sup\u003e and fungi (CFU g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) 2\u0026times;10\u003csup\u003e4\u003c/sup\u003e. A high level of fungi in digestate used as a soil improver could lead to risks of post-harvest contamination. In addition, fungi of the following genera are the main cause of contamination of agricultural produce in the field (\u003cspan citationid=\"CR82\" class=\"CitationRef\"\u003e82\u003c/span\u003e). Fungi are also associated with the deterioration of the physico-chemical quality of seeds (\u003cspan citationid=\"CR83\" class=\"CitationRef\"\u003e83\u003c/span\u003e). El Asri et al. (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e) found that the concentration of total aerobic mesophilic flora in cow dung was 25\u0026times;10\u003csup\u003e9\u003c/sup\u003e CFU g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, while that of coliforms was 28\u0026times;10\u003csup\u003e3\u003c/sup\u003e CFU g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and that of yeasts and fungi were 11\u0026times;10\u003csup\u003e9\u003c/sup\u003e CFU g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. El Asri et al. (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e) indicated that the quality of digestate depends on. According to (\u003cspan citationid=\"CR84\" class=\"CitationRef\"\u003e84\u003c/span\u003e), the biological quality of a soil is its capacity to host a large quantity and diversity of living organisms involved in its functioning and in the ecosystem services it provides. Most of the studies showed neutral or positive effects, while 7% of the results showed an alteration in microbial parameters, indicating that there is a small but significant risk associated with the addition of digestates to soil microbial communities. In fact, reported that microorganisms play a role within the soil by means of the resolution of carbon and nitrogen, as well as the synthesis of exopolysaccharides. These processes enhance soil fertility and water retention, as well as soil shape and stability. They use the atmosphere to help them synthesis cellular proteins. Microorganisms solubilize soil phosphorous, beautify nitrogen fixation, and bring siderophores that sell its boom and suppresses the boom of pathogens. The quality criteria established by United States Environmental Protection Agency was used (\u003cspan citationid=\"CR85\" class=\"CitationRef\"\u003e85\u003c/span\u003e). While criteria show the degree of compliance of the final treated sludge with the digestate. Coliform concentrations in the digestate are less than 1.1\u0026times;10\u003csup\u003e3\u003c/sup\u003e CFU g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, as indicated by the criteria of the Environmental Protection Agency (2003) (\u003cspan citationid=\"CR86\" class=\"CitationRef\"\u003e86\u003c/span\u003e). National Research Council (\u003cspan citationid=\"CR87\" class=\"CitationRef\"\u003e87\u003c/span\u003e) established two categories of biosolids: Class A biosolids, which have no detectable concentrations of pathogens, and Class B biosolids, which have detectable concentrations of pathogens with fecal coliform count of less than 2\u0026times;10\u003csup\u003e6\u003c/sup\u003e g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e of dry solids at the time of disposal. On the other hand, microbial biomass, the active organic fraction, is an important source of nutrients for the plant, and increasing microbial biomass, and amending compost can improve soil fertility in the long term.\u003c/p\u003e \u003cp\u003eThe results of phytotoxicity tests indicated that maize seeds exhibited satisfactory performance. Conversely, seeds of okra, tomato and lettuce demonstrated sensitivities, with low germination percentages. Qian et al.(\u003cspan citationid=\"CR88\" class=\"CitationRef\"\u003e88\u003c/span\u003e) showed that the GI values varied from 68% (day 30) to 129% (day 90) in swine manure composting and from 88% (day 30) to 119% (day 90) in dairy manure composting. In addition, the GI values of commercial compost of swine manure and dairy manure reached 145% and 126%, respectively. The cow dung digestate exhibited high phytotoxicity on tomato and lettuce seeds due to absence of germination. In contrast, the cashew nut shell digestate demonstrated very low seeds germination (SG) for tomato and lettuce seeds, respectively. Okra seeds germination was observed to be relatively higher between 45 and 52%. The results of the digestates on okra, tomato and lettuce seeds demonstrated low to practically zero germination percentages, which indicated a high phytotoxicity of the samples. (\u003cspan citationid=\"CR89\" class=\"CitationRef\"\u003e89\u003c/span\u003e) reported that a GI equal to or higher than 80% indicates the absence of phytotoxic effects. Our results showed that the digestates reduced the root elongation (RE), germination index (GI), germination speed (T50) and affect seed germination (SG). Pluschke et al. (\u003cspan citationid=\"CR90\" class=\"CitationRef\"\u003e90\u003c/span\u003e) reported that a dilution of with distilled water improved germination by 50% and 23%, respectively. However, the tolerance to salinity depends on the plants, wheat is highly tolerant to soil salinity while tomato is moderately tolerant (conductivity should not exceed 3000 \u0026micro;s/cm) (\u003cspan citationid=\"CR91\" class=\"CitationRef\"\u003e91\u003c/span\u003e). Authors have reported that digestate phytotoxicity is related to NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e-N and organic acid concentrations (\u003cspan citationid=\"CR92\" class=\"CitationRef\"\u003e92\u003c/span\u003e, \u003cspan citationid=\"CR93\" class=\"CitationRef\"\u003e93\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe growth-promoting effect of digestates is evidenced by the development of roots. Root development is important in the presence of digestate. Digestates had positive effect on maize root development. No significant differences were not observed for parameters main root length, fresh weight, dry weight of root biomass and number of seminal roots (p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). Cashew nut shell digestate showed a significantly higher number of seminales roots than the other forms of treatment.\u003c/p\u003e \u003cp\u003eMollier et al. (\u003cspan citationid=\"CR94\" class=\"CitationRef\"\u003e94\u003c/span\u003e) reported that the maize root system is made up of seminal roots preformed in the seed and neoformed adventitious primary roots appearing at the base of successive internodes. The nomenclature used to number the successive root stages was that proposed by Girardin et al. (\u003cspan citationid=\"CR95\" class=\"CitationRef\"\u003e95\u003c/span\u003e). The number of seminal roots was significantly higher in cashew nut shell digest than in cow dung. The high salinity of the cow dung digestate could be a limit to root development. Khaled et al. (\u003cspan citationid=\"CR96\" class=\"CitationRef\"\u003e96\u003c/span\u003e) showed that salinity has a depressive effect on growth, accompanied by biochemical and ultrastructural changes. The development of the root system was less sensitive. According to Rahnama et al.(\u003cspan citationid=\"CR97\" class=\"CitationRef\"\u003e97\u003c/span\u003e), salt inhibits root length in a dose-dependent manner in wheat. In \u003cem\u003eArabidopsis\u003c/em\u003e, salt concentrations could inhibit both primary root (PR) and lateral root (LR) growth. The rhizosphere is a habitat for a multitude of microorganisms that interact with the plant and influence its growth. Some of these microorganisms are deleterious, while others, known as plant growth-promoting rhizobacteria, are beneficial to plant growth. It is possible that digestates could harbour these microbial types capable of promoting plant growth (\u003cspan additionalcitationids=\"CR99\" citationid=\"CR98\" class=\"CitationRef\"\u003e98\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR100\" class=\"CitationRef\"\u003e100\u003c/span\u003e). A number of studies have demonstrated the significance of microorganisms in the development of plant roots (\u003cspan citationid=\"CR101\" class=\"CitationRef\"\u003e101\u003c/span\u003e).\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe study of the physical-chemical, agronomic, microbiological and phytotoxicity parameters of the two digestates from cashew nutshells and cow dung reflects the importance of waste treatment by anaerobic digestion. The Physical and chemical characteristics of the digestates demonstrate that they can contribute to improving the amending value of soils, which is defined as the organic matter content and bio-functioning of soils. The agronomic characteristics of the digestates indicate the presence of total nutrients (NPK), water-soluble nutrients, and major and secondary nutrients with fertilizing value. However, some parameters require improvement, including gas emissions (Biogas, CH\u003csub\u003e4\u003c/sub\u003e, CO\u003csub\u003e2\u003c/sub\u003e) and the degree of humification, which suggest that the digestate is not yet mature. The microbiological quality appears to align with the assessment criteria, although further investigation may be necessary to identify other microorganisms. The phytotoxicity tests demonstrated that only maize seeds exhibited resistance to the effects of digestates, particularly cow dung. The study indicates that digestates possess root growth-promoting properties that can be advantageous for plant development. It was therefore concluded that these digestates could be improved by creating an integrated system where the digestates undergo a composting process after anaerobic digestion.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was financially supported by a research grant from the International Foundation for Science (IFS_ I-3-E-6204-2). Therefore, the authors are grateful to this funding and support of this research.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMN was responsible for the conceptualization and design of the study. MN worked in acquisition and interpretation of data through field and laboratory work. MN drafted the article and MKS, ASO, AO, JBS, NB, YM, COTC, IM, CATO and ASO revised it critically. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was financially supported by a research grant from the International Foundation for Science (IFS_ I-3-E-6204-2).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAll data generated in this study are provided in the submitted article.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest\u0026nbsp;\u003c/strong\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePlant Guidelines\u0026nbsp;\u003c/strong\u003eThe authors confirm that the use of plants in the\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003epresent study complies with international, national and/or institutional guidelines.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePermissions to collect the plants/plant parts\u003c/strong\u003e Not applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSource of the plant used in your study\u0026nbsp;\u003c/strong\u003eAll plants seeds name and he source of them are in the Methods section.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eZhang J, Chen M, Sui Q, Wang R, Tong J, Wei Y. 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Bioresour Technol. 2006;97(6):847\u0026ndash;53. \u003c/li\u003e\n\u003cli\u003eJoshi C, Mathur P, Khare SK. Degradation of phorbol esters by Pseudomonas aeruginosa PseA during solid-state fermentation of deoiled Jatropha curcas seed cake. Bioresour Technol [Internet]. 2011;102(7):4815\u0026ndash;9. Available from: http://dx.doi.org/10.1016/j.biortech.2011.01.039\u003c/li\u003e\n\u003cli\u003eM\u0026ouml;ller K, M\u0026uuml;ller T. Effects of anaerobic digestion on digestate nutrient availability and crop growth: A review. Eng Life Sci. 2012;12(3):242\u0026ndash;57. \u003c/li\u003e\n\u003cli\u003eDevappa KR, Makkara HPS, Beckera K. Jatropha Toxicity _A Review. J Toxicol Environ Heal. 2010;13(6):476\u0026ndash;507. \u003c/li\u003e\n\u003cli\u003ePunsuvon V, Nokkaew R, Karnasuta S. Determination of toxic phorbol esters in biofertilizer produced with Jatropha curcas seed cake. ScienceAsia. 2012;38:223\u0026ndash;5. \u003c/li\u003e\n\u003cli\u003eSrinophakun P. 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Resour Conserv Recycl. 2010;54:205\u0026ndash;9. \u003c/li\u003e\n\u003cli\u003eSzulc W, Beata Rutkowska B, Gawronski S, Wszelaczy E. Possibilities of Using Organic Waste after Biological and Physical Processing \u0026mdash; An Overview. Process. 2021;9:1501. \u003c/li\u003e\n\u003cli\u003eLeite A de S, Dantas AF, Oliveira GL da S, Gomes J\u0026uacute;nior AL, de Lima SG, Cit\u0026oacute; AM das GL, et al. Evaluation of Toxic, Cytotoxic, Mutagenic, and Antimutagenic Activities of Natural and Technical Cashew Nut Shell Liquids Using the Allium cepa and Artemia salina Bioassays. Biomed Res Int. 2015; \u003c/li\u003e\n\u003cli\u003eTampio E, Ervasti S, Rintala J. Characteristics and agronomic usability of digestates from laboratory digesters treating food waste and autoclaved food waste. J Clean Prod [Internet]. 2015;94:86\u0026ndash;92. Available from: http://dx.doi.org/10.1016/j.jclepro.2015.01.086\u003c/li\u003e\n\u003cli\u003eTampio E, Salo T, Rintala J. 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Micron [Internet]. 2013;54\u0026ndash;55(January):52\u0026ndash;6. Available from: http://dx.doi.org/10.1016/j.micron.2013.08.006\u003c/li\u003e\n\u003cli\u003eBrust GE. Management strategies for organic vegetable fertility [Internet]. Safety and Practice for Organic Food. Elsevier Inc.; 2019. 193\u0026ndash;212 p. Available from: http://dx.doi.org/10.1016/B978-0-12-812060-6.00009-X\u003c/li\u003e\n\u003cli\u003eHowell J. Organic Matter: Key to Soil Management [Internet]. 2005. Available from: http://www.hort.uconn.edu/ipm/veg/croptalk/croptalk1_4/%0Apage8.html\u003c/li\u003e\n\u003cli\u003ePoudel DD, Horwath WR, Mitchell JP, Temple SR. Impacts of cropping systems on soil nitrogen storage and loss. Agric Syst. 2001;68(3):253\u0026ndash;68. \u003c/li\u003e\n\u003cli\u003eVandecasteele B, Willekens K, Steel H, D\u0026rsquo;Hose T, Van Waes C, Bert W. 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In: Agriculture, Ecosystems and Environment. 2006. p. 153\u0026ndash;62. \u003c/li\u003e\n\u003cli\u003eWatanabe Y, Suzuki R, Koike S, Nagashima K, Mochizuki M, Forster RJ, et al. In vitro evaluation of cashew nut shell liquid as a methane-inhibiting and propionate-enhancing agent for ruminants. J Dairy Sci [Internet]. 2010;93(11):5258\u0026ndash;67. Available from: http://dx.doi.org/10.3168/jds.2009-2754\u003c/li\u003e\n\u003cli\u003eSouza N de O, Cunha DA, Rodrigues N de S, Pereira AL, Medeiros EJT, Pinheiro A de A, et al. Cashew nut shell liquids: Antimicrobial compounds in prevention and control of the oral biofilms. Arch Oral Biol. 2022;133(July 2021):0\u0026ndash;9. \u003c/li\u003e\n\u003cli\u003eAbbas J, Ariani N, Ria Andayanie W. Antibacterial Activity from The Cashew Nut Shell Extracts. E3S Web Conf. 2024;503:1\u0026ndash;15. \u003c/li\u003e\n\u003cli\u003eNikiema M, Sawadogo JB, Somda MK, Maiga Y, Mogmenga I, Ouattara CAT, et al. 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Available from: https://doi.org/10.1007/s12649-020-01318-5\u003c/li\u003e\n\u003cli\u003eBroyd\u0026eacute; H, Dor\u0026eacute; T. Effets des pratiques agricoles sur la contamination des denr\u0026eacute;es par les mycotoxines issues de Fusarium et Aspergillus spp. Cah Agric. 2013;22(3):182\u0026ndash;94. \u003c/li\u003e\n\u003cli\u003eLeal PC, Massuquetto A, dos Santos MC, Bruno LDG, Krabbe EL, Felix AP, et al. Fungus Damage Effect on Physical-Chemical Characteristics of Corn Grains. Arch Vet Sci. 2021;26(4):69\u0026ndash;76. \u003c/li\u003e\n\u003cli\u003eKarimi B, Sadet-bourgeteau S, Cannavacciuolo M, Flamin C, Haumont A, Jean-baptiste V, et al. Review of the impact of biogas digestates on the microbiological quality of agricultural soils To cite this version : Impact des digestats de m\u0026eacute;thanisation sur la qualit\u0026eacute; microbiologique des sols agricoles : 2023; \u003c/li\u003e\n\u003cli\u003eUnited States Environmental Protection Agency (US EPA). Guideline on Air Quality Models, Revised. Office of Air Quality Planning \u0026amp; Standards, Research Triangle Park [Internet]. 2003. Available from: http://www.epa.gov/scram001/guidance/appw_03.pdf\u003c/li\u003e\n\u003cli\u003eUSEPA. United States Environmental ProtectionAgency (USEPA) Control of Pathogens and Vector Attraction in Sewage Sludge [Internet]. 2003. Available from: https://www.epa.gov/sites/production/files/2015-07/documents/epa-625-r-92-013.pdf\u003c/li\u003e\n\u003cli\u003eNational Research Council. Biosolids Applied to Land: Advancing Standards and Practices Chapter: 6 Evaluation of EPA\u0026rsquo;s Approach to Setting Pathogen Standards. In: DC: The National Academies Press [Internet]. 2002. p. 257\u0026ndash;321. Available from: https://doi.org/10.17226/10426\u003c/li\u003e\n\u003cli\u003eQian X, Shen G, Wang Z, Guo C, Liu Y, Lei Z, et al. Co-composting of livestock manure with rice straw: Characterization and establishment of maturity evaluation system. Waste Manag [Internet]. 2014;34(2):530\u0026ndash;5. Available from: http://dx.doi.org/10.1016/j.wasman.2013.10.007\u003c/li\u003e\n\u003cli\u003eLuo Y, Liang J, Zeng G, Chen M, Mo D, Li G, et al. Seed germination test for toxicity evaluation of compost: Its roles, problems and prospects. Waste Manag [Internet]. 2018;71:109\u0026ndash;14. Available from: https://doi.org/10.1016/j.wasman.2017.09.023\u003c/li\u003e\n\u003cli\u003ePluschke J, Fa\u0026szlig;lrinner K, Hadrich F, Loukil S, Chamkha M, Gei\u0026szlig;en SU, et al. Anaerobic Digestion of Olive Mill Wastewater and Process Derivatives\u0026mdash;Biomethane Potential, Operation of a Continuous Fixed Bed Digester, and Germination Index. Appl Sci. 2023;13(17). \u003c/li\u003e\n\u003cli\u003eDaliakopoulos IN, Tsanis IK, Koutroulis A, Kourgialas NN, Varouchakis AE, Karatzas GP, et al. The threat of soil salinity: A European scale review. Sci Total Environ [Internet]. 2016;573:727\u0026ndash;39. http://dx.doi.org/10.1016/j.scitotenv.2016.08.177\u003c/li\u003e\n\u003cli\u003eSalminen E, Rintala J. Anaerobic digestion of organic solid poultryslaughterhouse waste \u0026ndash; a review. Bioresour Technol. 2002;83:13\u0026ndash;26. \u003c/li\u003e\n\u003cli\u003eDrennan MF, DiStefano TD. Characterization of the curing process from high-solids anaerobic digestion. Bioresour Technol [Internet]. 2010;101(2):537\u0026ndash;44. Available from: http://dx.doi.org/10.1016/j.biortech.2009.08.029\u003c/li\u003e\n\u003cli\u003eMollier A, Mollier A, Paris DLU, Orsay XI. Croissance racinaire du ma\u0026iuml;s ( \u003cem\u003eZea mays \u003c/em\u003eL .) sous d\u0026eacute;ficience en phosphore . Etude exp\u0026eacute;rimentale et mod\u0026eacute;lisation To cite this version : HAL Id : tel-02840596 Th\u0026egrave;se pr\u0026eacute;sent\u0026eacute;e Croissance racinaire du ma\u0026iuml;s ( \u003cem\u003eZea mays\u003c/em\u003e L .) sous d\u0026eacute;ficience en phosphore . Etude. Hal [Internet]. 2020;185. Available from: https://hal.inrae.fr/tel-02840596\u003c/li\u003e\n\u003cli\u003eGirardin P, Jordan MO, Picard D, Trendel R. Harmonisation des notations concernant la description morphologique d\u0026rsquo;un pied de ma\u0026iuml;s (\u003cem\u003eZea mays\u003c/em\u003e L.). Agronomie. 1986;6(9):873\u0026ndash;5. \u003c/li\u003e\n\u003cli\u003eKhaled L Ben, G\u0026otilde;mez A, Honrubia M, Oihabi A. Review article Methods for studying root colonization by introduced. Agronomie. 2003;23:407\u0026ndash;18. \u003c/li\u003e\n\u003cli\u003eRahnama A, Munns R, Poustini K, Watt M. A screening method to identify genetic variation in root growth response to a salinity gradient. J Exp Bot. 2011;62(1):69\u0026ndash;77. \u003c/li\u003e\n\u003cli\u003eWelbaum GE, Sturz A V., Dong Z, Nowak J. Managing soil microorganisms to improve productivity of agro-ecosystems. CRC Crit Rev Plant Sci. 2004;23(2):175\u0026ndash;93. \u003c/li\u003e\n\u003cli\u003eCompant S, Cl\u0026eacute;ment C, Sessitsch A. Plant growth-promoting bacteria in the rhizo- and endosphere of plants: Their role, colonization, mechanisms involved and prospects for utilization. Soil Biol Biochem. 2010;42(5):669\u0026ndash;78. \u003c/li\u003e\n\u003cli\u003eKirdi B. R\u0026ocirc;le des PGPR Plant Growth Promotion Rhizobacteria dans la croissance v\u0026eacute;g\u0026eacute;tale et la lutte contre les phan\u0026eacute;rogames parasites. Ecole Nationale Sup\u0026eacute;rieure Agronomique-El Harrach-Alger; 2011. http://repositorio.unan.edu.ni/2986/1/5624.pdf%0Ahttp://fiskal.kemenkeu.go.id/ejournal%0Ahttp://dx\u003cbr\u003e.doi.org/10.1016/j.cirp.2016.06.001%0Ahttp://dx.doi.org/10.1016/j.powtec.2016.12.0\u003cbr\u003e55%0Ahttps://doi.org/10.1016/j.ijfatigue.2019.02.006%0Ahttps://doi.org/10.1\u003c/li\u003e\n\u003cli\u003eWatt M, Silk WK, Passioura JB. Rates of root and organism growth, soil conditions, and temporal and spatial development of the rhizosphere. Ann Bot. 2006;97(5):839\u0026ndash;55. \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"discover-applied-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Applied Sciences](https://link.springer.com/journal/42452)","snPcode":"42452","submissionUrl":"https://submission.springernature.com/new-submission/42452/3","title":"Discover Applied Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Anaerobic digestion, cashew nut shell digestate, cow dung digestate, agronomic value, phytotoxicity","lastPublishedDoi":"10.21203/rs.3.rs-5188149/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5188149/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study investigated agronomic characteristics of digestates from cashew nut shell and cow dung anaerobic digestion. General characteristics and agronomic value of digestates were determined using standard methods. Gaseous emissions (biogas, CH\u003csub\u003e4\u003c/sub\u003e, CO\u003csub\u003e2\u003c/sub\u003e) were evaluated. Microbiological quality of digestates was evaluated, as well as phytotoxicity on maize, okra, tomato and lettuce seeds. Higher conductivity indicated a greater potential for salinity to affect germination and plant growth. High C/N ratio and degree of humification greater than 0.7 are indicative of immature digestate. Total nitrogen, organic nitrogen and phosphorus contents in g/Kg were 11.26, 0.49 and 5.35 for cashew shell digestate and 18.15, 17.12 and 0.16 for cow dung digestate, respectively. Potassium content was 0.32 and 0.98 g K/Kg in cashew shell and cow dung digestate, respectively. Mineral nitrogen content of cashew nut shell digestate was 0.19 g NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e/kg, 1.28 g NO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e/kg, and 0.0016 g NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e/kg. These characteristics showed amending and fertilizing effect of digestates. Physical parameters indicate digestate can improve soil structure. Both digestates are significant source of greenhouse gas. Microbiological analysis revealed spore-forming bacteria and coliforms, with proportions that are acceptable for spreading. Germination test on okra, tomato and lettuce seeds indicated high phytotoxicity. Maize showed significant results for seed germination, root elongation, germination index and germination speed with values of 100%, 100%, 118.63% and 67.21% respectively. The study indicates that digestates present root growth-promoting properties that can be advantageous for plant development. Digestates could be improved by an integrated system in which digestates are composted downstream of anaerobic digestion.\u003c/p\u003e","manuscriptTitle":"Assessment of the agronomic value of digestate from cashew nut shell and cow dung anaerobic digestion","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-12-04 11:43:45","doi":"10.21203/rs.3.rs-5188149/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-11-21T09:23:23+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"259496954954829557712332886422422720783","date":"2024-11-19T09:10:00+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-11-18T13:47:12+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"206928320415697416971972631297212459170","date":"2024-11-15T10:40:35+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"171268610941494412620704327278070382335","date":"2024-11-15T03:43:34+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"285920878504300700396877471690936603101","date":"2024-11-14T20:32:38+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"310630033562729640321313753864035910229","date":"2024-11-14T19:58:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"195147296797595909900348165494342118144","date":"2024-11-02T09:38:13+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-10-27T15:32:16+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"20289744511089064660521569501694360335","date":"2024-10-23T19:05:47+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"54513938744737897636718760979992356949","date":"2024-10-22T17:26:00+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"159007400665231850286696707955016340997","date":"2024-10-22T10:03:40+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-10-21T13:29:27+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-10-16T05:22:43+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-10-12T06:38:30+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Applied Sciences","date":"2024-10-01T14:45:06+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-applied-sciences","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Applied Sciences](https://link.springer.com/journal/42452)","snPcode":"42452","submissionUrl":"https://submission.springernature.com/new-submission/42452/3","title":"Discover Applied Sciences","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"663d5c95-60b0-4471-aab8-c8e522e88cc2","owner":[],"postedDate":"December 4th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-01-13T10:39:02+00:00","versionOfRecord":[],"versionCreatedAt":"2024-12-04 11:43:45","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5188149","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5188149","identity":"rs-5188149","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}