The evolution of structural characteristics and redox properties of humin during the composting of sludge and corn straw.

Humins (HMs), the insoluble faction of humic substances (HSs), play a pivotal role in the bioremediation of pollutants by acting as electron shuttles that modulate the interactions between microorganisms and pollutants. This crucial function is intricately linked to their structural composition and electron transfer capabilities. However, the dynamics of the electron transfer capacity (ETC) of HM extracted during the composting process and its determinants have yet to be fully elucidated. This study undertakes a comprehensive analysis of the ETC of HM derived from composting, employing electrochemical techniques alongside spectroscopic methods and elemental analysis to explore the influencing factors, including the electron accepting capacity (EAC), electron donating capacity (EDC), and electron reversible rate (ERR). Our findings reveal substantial variations in the EAC and EDC of HM throughout the composting process, with EAC values ranging from 133.03-220.98 µmol e- gC-1 and EDC values from 111.17-229.33 µmol e- gC-1. Notably, the composting process enhances the ERR and EDC of HM while diminishing their EAC. This shift is accompanied by an augmented presence of aromatic structures, polar functional groups, quinones, and nitrogen - and sulfur-containing moieties, thereby boosting the HM's EDC. Conversely, the reduction in EAC is associated with a decline in lignin carbon content and the abundance of oxygen-containing moieties, as well as the diminishment of visible fulvic-like and protein-like substances within HM. Importantly, humic-like substances and nitrogen-containing moieties within HM demonstrated the capacity for repeated electron transfer, underscoring their significance in the context of environmental remediation.

Risk level and removal performance of antibiotic resistance genes and bacterial pathogens in static composting with different temperatures.

The effect of different levels of temperature on resistance genes is not clear in mesophilic static composting (<50 °C). This study conducted livestock manure composting with different temperature gradients from 20 to 50 °C, it was found that the reduction rates of risk rank-I antibiotic resistance genes (from 3 % to 66 %), metal resistance genes (from -50 % to 76 %) and bacterial pathogens (from 72 % to 91 %) all increased significantly with increasing temperature from 20 to 50°C. The vulnerability of bacterial communities increased significantly, and the assembly process of bacterial communities changed from deterministic to stochastic with the increase of composting temperature. Higher temperature could accelerate the removal of thermolabile resistance genes hosts or pathogenic hosts carrying mobile genetic elements by directly or indirectly affecting organic acids content. Therefore, for soil safety, the temperature of the manure recycling process should be increased as much as possible.

A novel micro-CT approach for in situ visualization of the spatial dynamics of mesovoids in aerobic composting piles.

The spatial configuration of mesovoids profoundly affects the aerobic composting microenvironment, which governs vital processes such as greenhouse gas production and emission, thermal conduction, and overall composting efficiency. Nondestructive in-situ characterization of the composting spatial structure is crucial to better understand its interaction mechanism with the microenvironment. In this study, a valuable contribution to the field of composting research was made by introducing micro-computed tomography (micro-CT) tool for in situ three-dimensional (3D) visual characterizing the void structure dynamics of straw and manure compost pile units at the mesoscale. Representative samples at different composting stages derived from wheat straw and cow manure were procured by pre-embedding samplers in laboratory-based aerobic composting reactor systems. Based on an advanced Skyscan 1275 micro-CT system, scanning conditions and image processing algorithms were determined, and the void structure and their dynamic changes in the pile unit during composting were in-situ 3D visualized for the first time. The micro-CT images effectively reveal well-developed void structures exhibiting spatiotemporal dynamics during composting, and they exhibit excellent consistency with conventional macrophysical effects and wet chemical analyses. Micro-CT quantification results of the void structure parameters changes in pile unit during composting were as follows: percentage of the total voidage and the connected voidage in pile unit were in the range of 52.34%-58.56%, indicating a very suitable composting spatial structural microenvironment. This new micro-CT method provides a valuable perspective for analyzing and understanding the complex aerobic composting process.

Insights from meta-analysis on carbon to nitrogen ratios in aerobic composting of agricultural residues.

Given the heterogeneity of raw materials, the diversity of composting processes, and the complexity of biological transformations, systematically exploring the critical role of the initial carbon-to-nitrogen (C/N) ratio in the aerobic composting of agricultural residues is challenging within a single experimental study. This study employs meta-analysis to investigate this role. Statistical analysis of 192 scholarly articles confirmed that most studies adhere to the recommended optimal initial C/N range of 25 and 30, where enhanced compost maturity and nutrient accumulation are observed. The findings indicate that optimal initial C/N ratios vary by agricultural residue type. A C/N ratio of 20 to 30 facilitates controlling the composting duration within 45 days, while a C/N ratio of 30 to 35 necessitates extending the duration beyond 45 days. The study highlights the effectiveness of adjusting the C/N ratio and applying microbial inoculants and physical amendments to optimize composting outcomes and control the composting duration.

Cattle manure composting driven by a microbial agent: A coupled mechanism involving microbial community succession and organic matter conversion.

Aerobic composting has been used as a mainstream treatment technology for agricultural solid waste resourcing. In the present study, we investigated the effects and potential mechanisms of the addition of a microbial agent (LD) prepared by combining Bacillus subtilis, Bacillus paralicheniformis and Irpex lacteus in improving the efficiency of cattle manure composting. Our results showed that addition of 1.5 % LD significantly accelerated compost humification, i.e., the germination index and lignocellulose degradation rate of the final compost product reached values of 92.20 and 42.29 %, respectively. Metagenomic sequencing results showed that inoculation of cattle manure with LD increased the abundance of functional microorganisms. LD effectively promoted the production of humus precursors, which then underwent reactions through synergistic abiotic and biotic pathways to achieve compost humification. This research provides a theoretical basis for the study of microbial enhancement strategies and humus formation mechanisms in the composting of livestock manure.

Efficient elimination of antibiotics and antibiotic resistance genes in hyperthermophilic sludge composting.

Composting is widely applied in recycling ever-increasing sewage sludge. However, the insufficient elimination of antibiotics and antibiotic resistance genes (ARGs) in conventional compost fertilizer poses considerable threat to agriculture safety and human health. Here we investigated the efficacy and potential mechanisms in the removal of antibiotics and ARGs from sludge in hyperthermophilic composting (HTC) plant. Our results demonstrated that the HTC product was of high maturity. HTC led to complete elimination of antibiotics and potential pathogens, as well as removal of 98.8 % of ARGs and 88.1 % of mobile genetic elements (MGEs). The enrichment of antibiotic-degrading candidates and related metabolic functions during HTC suggested that biodegradation played a crucial role in antibiotic removal. Redundancy analysis (RDA) and structural equation modelling (SEM) revealed that the reduction of ARGs was attributed to the decline of ARG-associated bacteria, mainly due to the high-temperature selection. These findings highlight the feasibility of HTC in sludge recycling and provide a deeper understanding of its mechanism in simultaneous removal of antibiotics and ARGs.

Construction of lignocellulose-degrading compound microbial inoculum and its effects on green waste composting.

The high content of recalcitrant lignocellulose in green waste (GW) makes composting and degradation challenging. Conventional GW composting typically employs single-strain microbial inoculants (MIs) with limited enzyme production capabilities, resulting in low composting efficiency and suboptimal compost product quality. In this study, Bacillus amyloliquefaciens (J1), Clonostachys rogersoniana (B2), and Streptomyces thermoviolaceus (J3) was utilized to optimize cultivation conditions and strain ratios based on enzyme activity indicators. The aim was to develop a potent three-strain lignocellulose-degrading MIs and test the hypothesis that its performance is superior to that of single-strain and two-strain MIs in terms of lignocellulose degradation and compost maturation. The results indicated that, the optimal treatment was T7, which was inoculated with a three-strain MIs composed of the spore suspensions of J1, B2, and J3 with a volume ratio of 3:3:2. Specifically, compared to the control (without MI), T7 increased the content of particle size between 0.25 and 2.00 mm and humic acid by 17% and 291%, respectively. Furthermore, T7 enhanced the degradation rates of cellulose, hemicellulose, and lignin by 197%, 145%, and 113%, respectively, and increased the activities of laccase, manganese peroxidase, lignin peroxidase, and carboxymethyl cellulase by 605%, 269%, 180%, and 228%, respectively. Additionally, T7 increased the relative abundance of bacteria (e.g. Pseudomonas) and fungi (e.g. Parascedosporium) that facilitated lignocellulose degradation, enhanced the alpha diversity index and promoted the formation of a microbial community structure characterized by prominent dominant species and greater diversity. Remarkably, the inoculation with the three-strain MI yielded high-quality compost within 32 days.

Firmicutes primarily drive odor emission profiles in poultry manure treatments.

Odor emission during livestock manure treatment poses a threat to the environment and human health. However, the odor emission profiles and related factors of commonly employed poultry manure treatments have rarely been studied. Here, we explored the odor emission profiles of 3 common poultry manure treatments in China, namely, ectopic fermentation beds (EFB), annular composting troughs (ACT) and air-drying rooms (ADR). The results revealed that the total odor concentrations in the EFB, ACT and ADR groups were 2407.67 ± 512.94, 13444.00 ± 1269.92 and 621.33 ± 59.27, respectively. The ACT had the greatest number of odorants (31), followed by the ADR (27) and the EFB (24). Methyl mercaptan, acetic acid, acetaldehyde, hydrogen sulfide, ammonia and acrolein were the key odorous compounds detected in all the treatments. ACT contained the greatest number of key odorants (11) and exhibited an extensive co-occurrence relationship with the bacterial community. The 3 poultry manure treatments exhibited significant differences in the beta diversities of the bacterial community. The phylum of most bacteria associated with key odorants was Firmicutes, and Enterococcus and Oceanobacillus were significantly positively correlated with methyl mercaptan. The bacterial functional groups were enriched in carbohydrate metabolism, amino acid metabolism and energy metabolism, and the functional genes shaped the odor emission patterns in the poultry manure treatments. Redundancy analysis demonstrated that odor emission in the 3 treatments was positively correlated with Firmicutes abundance, pH, electrical conductivity and moisture. Thus, our study provides a good understanding of odor emission profiles in poultry manure treatments and data for precise odor emission control during livestock production.

Microbial fuel cell-assisted composting shows stronger capacity to immobilize phosphorus: Emphasized on bacterial structures and functional enzymes.

Limited scientific evidence exists on phosphorus immobilization under autogenetic electrochemical reactions in composting systems. This study exploited a composting procedure using microbial fuel cell (MFC) to ascertain phosphorus redistribution during composting process. Compared to the control without MFC equipment, MFC-assisted treatment yielded a 13 % decrease in phosphorus availability due to the transformation of exchangeable fraction (Ex-P) to aluminum-bound (Al-P) and calcium-bound (Ca-P) fractions. During the composting process, organic humification primarily controlled phosphorus redistribution and immobilization. Biotic factors, including bacterial communities (i.e., Firmicutes, Proteobacteria, Bacteroidota, and Gemmatimonadota) and functional enzymes (i.e., acid phosphatase, alkaline phosphatase, phytase, and C-P lyase), significantly influenced phosphorus availability in the composting systems. Temperature-dependent composting phases restricted microbial actions on phosphorus transformation. These findings highlight the mechanisms underlying phosphorus transformation in composting systems, and provide valuable insights for advancing composting technology and protecting agricultural ecosystems.

Improved humification and Cr(VI) immobilization by CaO2 and Fe3O4 during composting.

The current research studied how Fe3O4 nanomaterials (NMs) and CaO2 affect humification and Cr(VI) immobilization and reduction during the composting of oil-tea Camellia meal and Cr-contaminated soil. The results showed that Fe3O4 NMs and CaO2 successfully construct a Fenton-like reaction in this system. The excitation-emission matrix-parallel factor (EEM-PARAFAC) demonstrated that this Fenton-like treatment increased the generation of humic acids and accelerated the humification. Meantime, RES-Cr increased by 5.91 % and Cr(VI) decreased by 16.36 % in the treatment group with CaO2 and Fe3O4 NMs after 60 days. Moreover, the microbial results showed that Fe3O4 NMs and CaO2 could promote the enrichment of Cr(VI) reducing bacteria, e.g., Bacillus, Pseudomonas, and Psychrobacter, and promote Cr(VI) reduction. This study gives a novel view and theoretical reference to remediate Cr(VI) pollution through composting.

Inoculation of Saccharomyces cerevisiae for facilitating aerobic composting of acidified food waste.

In aerobic composting of food waste, acidification of the material (acidified food waste, AFW) often occurs and consequently leads to failure of fermentation initiation. In this study, we solved this problem by adding Saccharomyces cerevisiae inoculants. The results showed that the inoculation with S. cerevisiae effectively promoted the composting process. In 2 kg composting, inoculation with S. cerevisiae significantly elevated the pile temperatures by 4 ~ 14 °C, accompanied by a rapid increase in pH from 4.5 to 6.0. In 15 kg composting, total acid decreased faster and the thermophilic stage above 50 °C was prolonged by 3 days longer than in the control. The residual oxygen content in the reactor indicated that S. cerevisiae, which proliferated during composting, increased microbial activity and reduced ammonia emission during the thermophilic phase. Cell density analysis showed that compost inoculated with S. cerevisiae promoted thermophilic bacterial propagation. Metagenomic analysis showed that the dominant bacteria in the AFW compost were Firmicutes, Proteobacteria, Bacteroidetes, and Actinobacteria, and the relative abundance of Bacillus, Thermobacillus, and Thermobifida increased when inoculated with S. cerevisiae. These results indicate that the inoculation of S. cerevisiae is an effective strategy to improve the aerobic composting process of AFW by accelerating the initial phase and altering microbial community structure in the thermophilic phase. Our findings suggest that S. cerevisiae can be applied to aerobic composting of organic wastes to effectively address the problem of acidification.

Contributions of the bacterial communities to the microcystin degradation and nutrient transformations during aerobic composting of algal sludge.

Aerobic composting is a useful method for managing and disposing of salvaged algal sludge. To optimize the composting process and improve compost quality, it is necessary to understand the functions and responses of microbial communities therein. This work studied the degradation process of organic matter and the assemblage of bacterial communities in algal sludge composting via 16S rRNA amplicon sequencing. The results showed that 77.08% of the microcystin was degraded during the thermophilic stage of composting, which was the main period for microcystin degradation. Bacterial community composition and diversity changed significantly during the composting, and gradually stabilized as the compost matured. Different composting stages may be dominated by different module groups separately, as shown in the co-occurrence networks of composting bacterial communities. In the networks, all bacteria associated with microcystin degradation were identified as connectors between different module groups. The algal sludge composting process was driven primarily by deterministic processes, and the main driving forces for bacterial community assembly were temperature, dissolved organic carbon, ammonium, and microcystin. At last, by applying the structural equation modeling method, the bacterial communities under influences of physiochemical properties were proved as the main mediators for the microcystin degradation. This study provides valuable insights into the optimization of bacterial communities in composting to improve the efficiency of microcystin degradation and the quality of the compost product.

(Bio)degradable Biochar Composites of PLA/P(3HB-co-4HB) Commercial Blend for Sustainable Future-Study on Degradation and Electrostatic Properties.

Interesting alternatives to expensive biodegradable polymers are their composites with natural fillers. The addition of biochar to a blend of poly(lactic acid) (PLA) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) was studied, and the resulting materials were evaluated for their properties and changes during degradation. Introducing biochar as a filler brought a noticeable improvement in electrostatic properties. Surface resistivity decreased from 3.80 × 1012 for the sample without biochar to 1.32 × 1012 for the sample with 30% filler content. Degradation tests revealed distinct differences in the degradation profile for composites due to the presence of filler. Composites with a lower biochar content displayed curling crack edges during hydrolytic degradation, and when the filler content reached 20 wt%, PLA loss accelerated. This study suggests that biochar-based composites have potential to be used as sustainable materials with improved properties.

Efficient reduction of antibiotic resistance genes and mobile genetic elements in organic waste composting via fenton-like treatment.

Livestock manure harbors antibiotic resistance genes (ARGs), and aerobic composting (AC) is widely adopted for waste management. However, mitigating ARG resurgence in later stages remains challenging. This work aims to curb ARGs rebounding through a Fenton-like reaction during food waste and swine manure co-composting. Results revealed that 0.025 % zerovalent iron (ZVI) + 0.5 % hydrogen peroxide (H2O2) facilitated maximum ARG, mobile genetic elements (MGEs), and 16 s rRNA removal with reductions of 2.68, 2.69, and 1.4 logs. Spectroscopic analysis confirmed Fenton-like reaction and cell apoptosis analysis indicated that 0.025 % ZVI and 0.5 % H2O2 treatment had the maximum early apoptosis, least observed, and normal cells on day 30. Redundancy analysis highlighted the influence of bacterial communities and physicochemical properties on ARGs, with MGEs playing a crucial role in Fenton treatments. Our findings suggest incorporating ZVI and H2O2 in composting can significantly reduce ARGs and enhance waste management practices.

Correlations between sewage sludge composting physicochemical parameters and emissions of greenhouse gases and ammonia: A statistical analysis.

Mitigating the environmental impact of composting by the reduction of greenhouse gases (N2O, CH4) and ammonia (NH3) emissions is a major challenge. To meet this challenge, the understanding of the relationships between composted substrates initial physicochemical parameters and gas emissions is essential. From a long-term perspective, it will allow to guide the recipe formulation of the initial mixture to be composted, with a view to reducing gas emissions during composting. This study gathered literature data targeting sewage sludge composting and performed statistical correlation analyses between cumulative gas emissions and the following parameters: sewage sludge, bulking agent and composted mixture initial physicochemical parameters (pH, dry matter, total carbon, total nitrogen, C/N), the dry mass ratio of sewage sludge to bulking agent and the duration of composting. The average values of cumulative emissions show a large variability: 1.37 ± 2.71 gC.kg initial mix DM-1, 0.13 ± 0.17 gN.kg initial mix DM-1 and 2.23 ± 2.79 gN.kg initial mix DM-1 for CH4, N2O and NH3 emissions respectively. Although the correlation analysis highlighted some significant interesting correlations between initial physicochemical parameters and gas emissions (p.value < 0.05), reliable multiparametric model could not fit the data, meaning that the actual literature data are not sufficient to explain most part of gas emissions. Among the most interesting relationships, the study showed that the dry matter of the composted mixture is negatively correlated to N2O emissions, while the ratio of sewage sludge to bulking agent and the duration of composting are positively correlated to N2O emissions. It was also shown that the pH of the bulking agent is positively correlated to NH3 emissions. Considering the large part of the emission variability that is not explained and the difficulty to link the correlation with their causality, it will be interesting to improve composting gas emissions knowledge in future research by analyzing free air space, bulking agent adsorption capacity and available and biodegradable organic matter. These parameters are of particular interest in solving the main problems associated with sewage sludge composting, namely porosity and nitrogen retention. This study also highlighted the necessity to extend the duration of the composting studies over 40 days in order to measure possible N2O late release and better identify parameters influencing N2O emissions.

Impact of aeration rate on the transfer range of antibiotic-resistant plasmids during manure composting.

Conjugative plasmids are important vectors of mobile antibiotic resvistance genes (ARGs), facilitating their horizontal transfer within the environment. While composting is recognized as an effective method to reduce antibiotics and ARGs in animal manure, its impact on the bacterial host communities containing antibiotic-resistant plasmids remains unclear. In this study, we investigated the permissiveness of bacterial community during composting when challenged with multidrug-resistant conjugative RP4 plasmids, employing Pseudomonas putida as the donor strain. Ultimately, this represents the first exploration of the effects of aeration rates on the range of RP4 plasmid transfer hosts. Transconjugants were analyzed through fluorescent reporter gene-based fluorescence-activated cell sorting and Illumina sequencing. Overall, aeration rates were found to influence various physicochemical parameters of compost, including temperature, pH, total organic matter, total nitrogen, and potassium. Regarding RP4 plasmid host bacteria, the dominant phylum was determined to shift from Bacteroidetes in the raw material to Proteobacteria in the compost. Notably, a moderate-intensity aeration rate (0.05 L/min/L) was found to be more effective in reducing the diversity and richness of the RP4 plasmid host bacterial community. Following composting, the total percentage of dominant transconjugant-related genera decreased by 66.15-76.62%. Ultimately, this study determined that the aeration rate negatively impacts RP4 plasmid host abundance primarily through alterations to the environmental factors during composting. In summary, these findings enhance our understanding of plasmid host bacterial communities under varying composting aeration rates and offer novel insights into preventing the dissemination of ARGs from animal manure to farmland.

Techno-economic assessment of industrial food waste composting facility: Evaluating bulking agents, processing strategies, and market dynamics.

Techno-economic assessment (TEA) of a valorization of bulking agent (BA) ratios on the food waste compost value chain is made to assess economic feasibility. TEA was performed with two plans (Plan A: existing composting facilities; Plan B: new composting facilities) and each plan was under four scenarios. The BA (i.e. corn stalks, garden waste, and watermelon seedlings) ratio of 5 % (S1), 10 % (S2), 20 % (S3), and garden waste with a ratio of 20 % (S4). Results indicate that S2, with a net present value (NPV) of 128.9 million, represents Plan A's most economically viable scenario. Although the total operating costs of S4 were 18.9 %-23.5 % higher, 25.6 %-42.2 % higher total revenue made S4 have an NPV of 92.9 million, making it the most viable scenario in Plan B. All scenarios show positive NPV within a ± 20 % fluctuation range. Organic fertilizer price, government subsidies, and processing capacity were the key factors influencing NPV.

Effect of black soldier fly larvae frass addition on humus content during low temperature co-composting.

Initiating aerobic fermentation under low temperature is the main challenge for winter livestock manure composting. This study aims to address this issue by applying black soldier fly larvae (BSFL) frass as a co-composting additive to enhance the low-temperature composting process. Specifically, this work explored the effects of chicken manure and BSFL frass co-composting on the temperature, humus content, and microorganisms with fresh weight ratio of 2:1, 1:1, 1:2 (w/w) at 6 °C. The result showed frass could rapidly rise the temperature to 50 °C and significantly increased the humus content by 15.6 % ∼ 26.3 %. Moreover, microbial analysis revealed that Sphingobacteriaceae accelerated temperature rise via low-temperature reproduction, creating proper temperature for thermophilic bacteria (Truepera and Georgia). Additionally, Cellulomonas and other bacteria promoted organic matter degradation and participated in humus formation. This study presents a novel solution for low-temperature composting, providing practical insights for improving manure management in winter.

Microbial mechanisms of biochar addition on carbon and nitrogen synergistic retention during distilled grain waste composting: Insights from metagenomic analysis.

To elucidate the mechanism of biochar addition on carbon and nitrogen retention during distilled grain (DGW) composting, this study investigated the losses of carbon and nitrogen and functional genes related to carbon and nitrogen metabolisms between biochar-treated and control composts. The addition of biochar significantly increased carbon and nitrogen retention by 13.5% and 33.8%, respectively. The difference in core carbon metabolism genes indicated that biochar addition inhibited CO2 release and promoted carbon fixation during the later composting phase, leading to improved carbon retention. Nitrogen metabolism analysis indicated that biochar addition suppressed early-phase ammoniation and late-phase denitrification and promoted nitrification and ammonia assimilation during the later stages of composting, thereby preserving nitrogen. During the later composting phase, biochar addition enhanced carbon-nitrogen coupling metabolism activity, leading to the synchronous retention of carbon and nitrogen. These findings elucidate the mechanism of biochar addition on carbon and nitrogen retention during DGW composting.

The role of cattle manure-driven polysaccharide precursors in humus formation during composting of spent mushroom substrate.

The study examined the impact of adding cattle manure to the composting process of Agaricus bisporus mushroom substrate on compost humification. A control group CK comprised entirely of Agaricus bisporus mushroom substrate, while the experimental group CD (70 percent Agaricus bisporus mushroom substrate and 30 percent cattle manure) comprised the two composting treatments that were established. The study determined that the addition of cow dung has promoted the formation of humus components. Particularly, humic substance (HS-C) and humic acid (HA) increased by 41.3 and 74.7%, respectively, and the ratio of humic acid to fulvic acid (HA/FA) also increased by 2.78. It showed that the addition of cow dung accelerated the synthesis and decomposition of precursors, such as polysaccharides, polyphenols, and reducing sugars. Thereby promoting the formation of humic acid. Network analysis revealed that adding cow dung promoted microbial interactions increased the complexity and stability of the bacterial and fungal symbiotic network, enhanced cooperation and reciprocity among microbes, and assisted in transforming fulvic acid (FA) components. Structural equation modeling (SEM) is a multivariate data analysis method for analyzing complex relationships among constructs and core indicators. SEM illustrated that introducing cattle manure into the composting process resulted in alterations to the correlation between physicochemical parameters and the microbial community, in addition to humus formation. Polysaccharides are the primary precursors for polymerization to form HA, which is an essential prerequisite for the conversion of fulvic acid to humic acid. Additionally, microbes affected the formation of humus, with bacteria substantially more influential than fungi. These findings provide new ideas for regulating the degree of humification in the composting process and have important practical implications for optimizing mushroom cultivation and composting techniques today.