Bamboo charcoal enhances cellulase and urease activities during chicken manure composting: Roles of the bacterial community and metabolic functions

Hybrid mechanism of microplastics degradation via biological and chemical process during composting

Little is known about the synergistic effects of abiotic aging and biodegradation on microplastics (MPs) transformation in the environment. Herein, a hybrid process of MPs degradation was proposed by analyzing the effect of microorganisms and abiotic aging on aging MPs and non-aging MPs degradation during composting. The results showed that composting facilitated the oxidation and depolymerization of aging MPs, and its degradation efficiency was about three times that of non-aging MPs. Further investigation revealed that aging MPs contained higher abundance of plastic-degrading bacteria and enzyme activity than non-aging MPs. In addition, free radicals also influenced the degradation of MPs. However, path model and shielding experiments confirmed that free radicals mainly facilitated the non-aging MPs degradation (contribution was 68.8 %), while aging MPs was easily degraded by microorganisms (contribution was 72.6 %). This study provides promising strategies for scaling up plastic treatment in bioreactors through a hybrid collaboration of biological and abiotic processes.

The regulation pathways of biochar and microorganism in soil-plant system by multiple statistical methods: The forms of carbon participation in coastal wetlands

Coastal wetlands possess significant carbon storage capabilities. However, in coastal soil-plant systems augmented with biochar and microorganisms, the mechanisms of these amendments and carbon participation remain unclear. This study utilized pot experiments to explore how Enteromorpha prolifera biochar and Arbuscular mycorrhizal fungi (AMF) affect soil organic carbon (SOC), carbon-related microbes, photosynthetic and osmotic system of Suaeda salsa. The results showed biochar reduced exchangeable sodium percentage by 6.9% through adsorption and ion exchange, and increased SOC content by 34.4%. The abundance of carbon-related microorganisms (Bacteroidota and Chloroflexi) was increased and carbon metabolizing enzyme (cellulase and sucrase) activity in the soil was enhanced. AMF significantly improved plant growth compared with CK, as evidenced by the enhanced dry weight by 2.34 times. A partial least squares pathway model (PLS-PM) and correlation analysis suggested that the combined effect of biochar and AMF could be outlined as two pathways: soil and plant. Biochar increased SOC, improved the growth of soil carbon metabolizing microorganisms, and further promoted the activity of carbon-related enzymes. Additionally, AMF facilitated nutrient absorption by plants through root symbiosis, with biochar further enhancing this process by acting as a nutrient adsorber. These combined effects of biochar and AMF at soil and plant level enhanced the photosynthetic process of Suaeda salsa. The transport of photosynthetic products to the roots can increase the carbon storage in the soil. This study provides quantitative evidence supporting the increase of carbon storage in coastal wetland soil-plant systems through a combined application of biochar and AMF.

Evaluation of gases emission and enzyme dynamics in sheep manure compost occupying with peach shell biochar

The effect of peach shell biochar (PSB) amendment on sheep manure (SM) composting was investigated. Five different ratios of PSB were applied (0%, 2.5%, 5%, 7.5%, and 10% PSB), and named T1 to T5, and run 50 days of composting experiment. It was found that PSB (especially 7.5% and 10%) could improve the compost environment, regulate the activity of microorganisms and related enzymes, and promote the decomposition of compost. 7.5% and 10% PSB advanced the heap into the thermophilic stage and increased the maximum temperature, while also increasing the germination index by 1.40 and 1.39 times compared to control. Importantly, 10% PSB effectively retained more than 60% of carbon and 55% of nitrogen by inhibiting the excess release of NH3 and greenhouse gases. High proportion PSB amendment increased the activity of dehydrogenase and cellulase, but inhibited protease and urease. The correlation results indicated that PSB changed the key bacterial genus, and there was a stronger association with environmental factors at 7.5% and 10%. Therefore, 7.5% and 10% peach shell biochar can be used as appropriate proportions to improve composting conditions.

How does the biochar-supported sulfidized nanoscale zero-valent iron affect the soil environment and microorganisms while remediating cadmium contaminated paddy soil?

In previous studies, iron-based nanomaterials, especially biochar (BC)-supported sulfidized nanoscale zero-valent iron (S-nZVI/BC), have been widely used for the remediation of soil contaminants. However, its potential risks to the soil ecological environment are still unknown. This study aims to explore the effects of 3% added S-nZVI/BC on soil environment and microorganisms during the remediation of Cd contaminated yellow-brown soil of paddy field. The results showed that after 49 d of incubation, S-nZVI/BC significantly reduced physiologically based extraction test (PBET) extractable Cd concentration (P < 0.05), and increased the immobilization efficiency of Cd by 16.51% and 17.43% compared with S-nZVI and nZVI/BC alone, respectively. Meanwhile, the application of S-nZVI/BC significantly increased soil urease and sucrase activities by 0.153 and 0.446 times, respectively (P < 0.05), improving the soil environmental quality and promoting the soil nitrogen cycle and carbon cycle. The results from the analysis of the 16S rRNA genes indicated that S-nZVI/BC treatment had a minimal effect on the bacterial community and did not appreciably alter the species of the original dominant bacterial phylum. Importantly, compared to other iron-based nanomaterials, incorporating S-nZVI/BC significantly increased the soil organic carbon (OC) content and decreased the excessive release of iron (P < 0.05). This study also found a significant negative correlation between OC content and Fe(II) content (P < 0.05). It might originate from the reducing effect of Fe-reducing bacteria, which consumed OC to promote the reduction of Fe(III). Accompanying this process, the redistribution of Cd and Fe mineral phases in the soil as well as the generation of secondary Fe(II) minerals facilitated Cd immobilization. Overall, S-nZVI/BC could effectively reduce the bioavailability of Cd, increase soil nutrients and enzyme activities, with less toxic impacts on the soil microorganisms.

Enhancing C and N turnover, functional bacteria abundance, and the efficiency of biowaste conversion using Streptomyces-Bacillus inoculation

Microbial inoculation plays a significant role in promoting the efficiency of biowaste conversion. This study investigates the function of Streptomyces-Bacillus Inoculants (SBI) on carbon (C) and nitrogen (N) conversion, and microbial dynamics, during cow manure (10% and 20% addition) and corn straw co-composting. Compared to inoculant-free controls, inoculant application accelerated the compost's thermophilic stage (8 vs 15 days), and significantly increased compost total N contents (+47%) and N-reductase activities (nitrate reductase: +60%; nitrite reductase: +219%). Both bacterial and fungal community succession were significantly affected by DOC, urease, and NH4+-N, while the fungal community was also significantly affected by cellulase. The contribution rate of Cupriavidus to the physicochemical factors of compost was as high as 83.40%, but by contrast there were no significantly different contributions (∼60%) among the top 20 fungal genera. Application of SBI induced significant correlations between bacteria, compost C/N ratio, and catalase enzymes, indicative of compost maturation. We recommend SBI as a promising bio-composting additive to accelerate C and N turnover and high-quality biowaste maturation. SBI boosts organic cycling by transforming biowastes into bio-fertilizers efficiently. This highlights the potential for SBI application to improve plant growth and soil quality in multiple contexts.

Synergistic improvement of humus formation in compost residue by fenton-like and effective microorganism composite agents

Improving the humification of compost through a synergistic approach of biotic and abiotic methods is of great significance. This study employed a composite reagent, comprising Fenton-like agents and effective microorganisms (EM) to improve humification. This composite reagent increased humic-acid production by 37.44 %, reaching 39.82 g kg-1, surpassing the control group. The composite reagent synergistically promoted micromolecular fulvic acid and large humic acid production. Collaborative mechanism suggests that Fenton-like agents contributed to bulk residue decomposition and stimulated the evolution of microbial communities, whereas EMs promoted highly aromatic substance synthesis and adjusted the microbial community structure. Sequencing analysis indicates the Fenton-like agent initiated compost decomposition by Firmicutes, and EM reduced the abundance of Virgibacillus, Lentibacillus, and Alcanivorax. Applied as an organic fertilizer in Brassica chinensis L. plantations, the composite reagent considerably improved growth and photosynthetic pigment content. This composite reagent with biotic and abiotic components provides a learnable method for promoting humification.

Biochar improves the humification process during pig manure composting: Insights into roles of the bacterial community and metabolic functions

Biochar could promote humification in composting, nevertheless, its mechanism has not been fully explored from the perspective of the overall bacterial community and its metabolism. This study investigated the effects of bamboo charcoal (BC) and wheat straw biochar (WSB) on the humic acid (HA) and fulvic acid (FA) contents during pig manure composting. The results showed that BC enhanced humification more than WSB, and significantly increased the HA content and HA/FA ratio. The bacterial community structure under BC differed from those under the other treatments, and BC increased the abundance of bacteria associated with the transformation of organic matter compared with the other treatments. Furthermore, biochar enhanced the metabolism of carbohydrates and amino acids in the thermophilic and cooling phases, especially BC. Through Mantel tests and network analysis, we found that HA was mainly related to carbon source metabolism and the bacterial community, and BC might change the interaction patterns among carbohydrates, amino acid metabolism, Bacillales, Clostridiales, and Lactobacillales with HA and FA to improve the humification process during composting. These results are important for understanding the mechanisms associated with the effects of biochar on humification during composting.

Enhancing humification and microbial interactions during co-composting of pig manure and wine grape pomace: The role of biochar and Fe2O3

Phenol-rich wine grape pomace (WGP) improves the conversion of pig manure (PM) into humic acid (HA) during composting. However, the impact of using combinations of Fe2O3 and biochar known to promote compost maturation remains uncertain. This research explored the individual and combined influence of biochar and Fe2O3 during the co-composting of PM and WGP. The findings revealed that Fe2O3 boosts microbial network symbiosis (3233 links), augments the HA yield to 3.38 by promoting polysaccharide C-O stretching, and improves the germination index to 124.82 %. Limited microbial interactions, increased by biochar, resulted in a lower HA yield (2.50). However, the combination weakened the stretching of aromatics and quinones, which contribute to the formation of HA, resulting in reduced the humification to 2.73. In addition, Bacillus and Actinomadura were identified as pivotal factors affecting HA content. This study highlights Fe2O3 and biochar's roles in phenol-rich compost humification, but combined use reduces efficacy.

Bentonite addition enhances the biodegradation of petroleum pollutants and bacterial community succession during the aerobic co-composting of waste heavy oil with agricultural wastes

Soil contamination with petroleum significantly threatens the ecological equilibrium and human health. In this context, aerobic co-composting of waste heavy oil with agricultural wastes was performed in the present study to remediate petroleum pollutants through four treatments: CK (control), T1 (petroleum pollutant), T2 (petroleum pollutant with bentonite), and T3 (petroleum pollutant with humic acid-modified bentonite). Comprehensive analyses were conducted to determine the physicochemical parameters, enzymatic activities, removal of petroleum pollutants, microbial community structure, and water-extractable organic matter in different composting systems. Structural equation modeling was employed to identify the key factors influencing the removal of petroleum pollutants. According to the results, petroleum pollutant removal percentages of 44.94%, 79.09%, and 79.67% could be achieved with T1, T2, and T3, respectively. In addition, the activities of polyphenol oxidase (51.21 U/g) and catalase (367.91 U/g), which are the enzymes related to petroleum hydrocarbon degradation, were the highest in T3. Moreover, bentonite addition to the treatment increased the nitrate nitrogen storage in the compost from 10.95 mg/kg in T1 to 18.63 and 17.41 mg/kg in T2 and T3, respectively. Humic acid-modified bentonite could enhance the degree of compost humification, thereby leading to a higher-quality compost product. Collectively, these findings established bentonite addition as an efficient approach to enhance the compost remediation of petroleum pollutants.

Piriformospora indica colonization enhances remediation of cadmium and chromium co-contaminated soils by king grass through plant growth promotion and rhizosphere microecological regulation

Poor plant growth and low pollutant bioavailability in contaminated soils limit phytoremediation efficiency. Pot experiments were conducted to investigate the effects and mechanisms of Piriformospora indica inoculation on the phytoremediation of Cd-Cr co-contaminated soils from farmland using king grass. P. indica colonization increased plant biomass by 20.4-24.6% and enhanced Cd/Cr accumulation in root, stem and leave tissues. Root vascular cylinder and cortex were the major structures for Cd/Cr transportation in plants. The amounts of Cd and Cr extracted by king grass considerably increased in the presence of P. indica (by 31.5-88.9% and 22.4-38.4%, respectively), as did the removal efficiency of both metals from soils (by 13.2-32.2% and 23.2-33.5%, respectively). Cd/Cr phytoextraction was closely related to the contents of alkanes, lipids and acids in root exudates. Following inoculation, the respiration of microbial sulfur compounds was promoted in soils at low and medium pollution levels, whereas nitrogen fixation and nitrification were reduced at high pollution level. This study demonstrates that P. indica inoculation enhances the phytoremediation efficiency of king grass for Cd-Cr co-contaminated soils through multiple regulation of plant growth, rhizosphere environment, root exudation and soil microbial function.

β-Glucosidase-producing microbial community in composting: Response to different carbon metabolic pressure influenced by biochar

Poor management of agricultural waste will cause a lot of environment pollution and the composting process is one of the most effective measures for resource reuse of agricultural waste. β-Glucosidase-producing microbial communities play a vital role in cellulose degradation during composting and regulate cellulase production via differentially expressed glucose/non-glucose tolerant β-glucosidase genes. Biochar is widely used as an amendment in compost to accelerate cellulose degradation during composting. However, Biochar-mediated impacts on β-glucosidase-producing microbial communities in compost are unclear. Here, different carbon metabolism pressures were set in natural and biochar compost to elucidate the regulation mechanism and interaction of the β-glucosidase microbial community. Results showed that the addition of biochar decreased the transcription of β-glucosidase genes and led to a reduction of β-glucosidase activity. Micromonospora and Cellulosimicrobium were the predominant functional communities determining cellulose degradation during biochar compost. Biochar addition strengthened the response of the functional microbial community to carbon metabolism pressure. And adding biochar altered the key β-glucosidase-producing microbial communities, influencing cellulase and the interaction between these communities to respond to the different carbon metabolic pressure of compost. Biochar also shifted the co-occurrence network of β-glucosidase-producing microbial community by changing the keystone species. Furthermore, co-occurrence network analysis revealed that high glucose decreased the complexity and stability of the functional microbial network. Most functional microorganisms from Streptomyces produce non-glucose tolerant β-glucosidase, which were the key bacterial communities affecting β-glucosidase activity in the non-glucose treatment. This study provides new insights into the response of functional microbial communities and the regulation of enzyme production during the transformation of cellulosic biomass.

Regulation of fungal communities during pig manure composting

The role of protein shell (PS) amendment in altering the fungal community during pig manure (PM) composting was investigated. Six different dosages of PS based on the dry weight of PM (0 %, 2.5 %, 5 %, 7.5 %, 10 %, and 12 %; T1-T6, respectively) were mixed with wheat straw to make the initial feedstock and composted for 42 days. The results showed that Ascomycota, Basidiomycota, and Giomeromycota were the most abundant phyla in all treatments. However, the relative abundance of Giomeromycota was the highest in the control treatment, although a substantially greater population was observed in all treatments. Genus abundance declined steadily from T1 to T6; however, T4 and T6 had smaller populations. Correlation analysis also suggested that T6 amendment increased the overall fungal dynamics and organic matter degradation. Thus, T6 was more efficient to enhance the overall fungal population and dynamics with considerable network connections among all the analyzed parameters.

Microbial dynamics and nitrogen retention during sheep manure composting employing peach shell biochar

In this study, the effects of peach shell biochar (PSB) and microbial agent (EM) amendment on nitrogen conservation and bacterial dynamics during sheep manure (SM) composting were examined. Six treatments were performed including T1 (control with no addition), T2 (EM), T3 (EM + 2.5 %PSB), T4 (EM + 5 %PSB), T5 (EM + 7.5 %PSB), and T6 (EM + 10 %PSB). The results showed that the additives amendment reduced NH3 emissions by 6.12%∼32.88% and N2O emissions by 10.96%∼19.76%, while increased total Kjeldahl nitrogen (TKN) content by 8.15-9.13 g/kg. Meanwhile, Firmicutes were the dominant flora in the thermophilic stages, while Proteobacteria, Actinobacteriota, and Bacteroidota were the dominant flora in the maturation stages. The abundance of Bacteroidota and Actinobacteriota were increased by 17.49%∼32.51% and 2.31%∼12.60%, respectively, which can accelerate the degradable organic materials decomposition. Additionally, redundancy analysis showed that Proteobacteria, Actinobacteriota, and Bacteroidota were positively correlated with NO3--N, TKN, and N2O, but a negative correlation with NH3 and NH4+-N. Finally, results confirmed that (EM + 10 %PSB) additives were more effective to reduce nitrogen loss and improve bacterial dynamics.

Bacterial community dynamics and co-occurrence network patterns during different stages of biochar-driven composting

Bacterial communities were dynamically tracked at four stages of biochar-driven sheep manure pile composting, and the co-occurrence networks with keystone taxa were established. The succession of bacterial community obvious varied during the composting process, Proteobacteria predominant in initial stage (39%) then shifted into Firmicutes in thermophilic (41%) and mesophilic (27%) stages, finally the maturation stage dominant by Bacteroidota (26%). Visualizations of bacterial co-occurrence networks demonstrate more cooperative mutualism and complex interactions in the thermophilic and mesophilic phases. Noticeably, the 7.5 and 10% biochar amended composts shown highest connections (736 and 663 total links) and positive cooperation (97.37 and 97.13% positive link) as well as higher closeness centrality and betweenness centrality of keystone taxa. Overall, appropriate biochar addition alters bacterial community succession and strengthens connection between keystone taxa and other bacteria, with 7.5 and 10% biochar amended composts has intense mutualistic symbiosis among bacterial communities.

Short-term exposure to enrofloxacin causes hepatic metabolism disorder associated with intestinal flora dysbiosis in adult marine medaka (Oryzias melastigma)

Enrofloxacin (ENR) is a widely used fluoroquinolone antibiotic that is frequently detected in the environment. Our study assessed the impact of short-term ENR exposure on the intestinal and liver health of marine medaka (Oryzias melastigma) using gut metagenomic shotgun sequencing and liver metabolomics. We found that ENR exposure resulted in imbalances of Vibrio and Flavobacteria and enrichments of multiple antibiotic resistance genes. Additionally, we found a potential link between the host's response to ENR exposure and the intestinal microbiota disorder. Liver metabolites, including phosphatidylcholine, lysophosphatidylcholine, taurocholic acid, and cholic acid, in addition to several metabolic pathways in the liver that are closely linked to the imbalance of intestinal flora were severely maladjusted. These findings suggest that ENR exposure has the potential to negatively affect the gut-liver axis as the primary toxicological mechanism. Our findings provide evidence regarding the negative physiological impacts of antibiotics on marine fish.

Biochar enhanced organic matter transformation during pig manure composting: Roles of the cellulase activity and fungal community

Fungal degradation of cellulose is a key step in the conversion of organic matter in composting. This study investigated the effects of adding 10% biochar (including, prepared from corn stalk and rape stalk corresponding to CSB and RSB) on organic matter transformation in composting and determined the role of cellulase and fungal communities in the conversion of organic matter. The results showed that biochar could enhance the conversion of organic matter, especially in RSB treatment. Biochar could increase cellulase activity, and RSB could enhance 33.78% and 30.70% the average activity of cellulase compared with the control and CSB treatments in the mesophilic to thermophilic phase, respectively. The results of high throughput sequencing demonstrated that Basidiomycota dominant in mesophilic phase, and Ascomycota dominant in other phases of composting. The redundancy analysis showed that Alternaria, Thermomycees, Aspergillus, Wallemia, and Melanocarpus might be the key fungi for the degradation of organic matter, and Fusarium, Penicillium, and Scopulariopsis may promote the conversion of organic matter. Network showed that the addition of RSB changed the interactions between fungal communities and organic matter transformation, and RSB treatment enriched members of Ascomycota related to organic matter transformation and cellulase activity. These results indicated that RSB improved organic matter conversion by enhancing the role of cellulase and fungal communities.

Biochar Can Improve Absorption of Nitrogen in Chicken Manure by Black Soldier Fly

(1) Background: There is growing interest in using insects to treat nutrient-rich organic wastes, such as the black soldier fly (BSF), one of the most efficient organic waste recyclers for upcycling nutrients into the food system. Although biochar (BC) was shown to enhance nutrient retention and the final product quality during the composting of livestock and poultry manure in many previous studies, little information is available on the effect of BC on livestock manure bioconversion by black soldier fly larvae (BSFL). (2) Methods: This study investigated the effect of adding a small amount of BC to chicken manure (CM) on the bioconversion system of the black soldier fly (including N2O and NH3 emissions and the final distribution of nitrogen during the treatment process). (3) Results: The lowest N2O and NH3 emission and highest residual nitrogen in the substrate were observed in the 15% BC treatment. The highest bioconversion rate of CM (8.31%) and the peak of larval biomass was obtained in the 5% BC treatment. (4) Conclusions: The results demonstrate the feasibility of adding 5% BC to reduce pollution and achieve a satisfactory BSFL-based CM bioconversion efficiency.

Investigation of biochar amendments on odor reduction and their characteristics during food waste co-composting

The odor emission such as ammonia (NH₃) and hydrogen sulfide (H₂S) during the composting process is a severe problem that adversely affects the environment and human health. Therefore, this study aimed to (1) evaluate the variation of physicochemical characteristics during the co-composting of food waste, and sawdust mixed biochar; (2) assess the efficiency of biochar-composting combined amendment materials for reducing odor emissions and their maturity. The raw materials including food waste (FW), straw dust (SD), and biochar (BC) were prepared and homogeneously mixed with the weight ranging from 120.0 kg to 135.8 kg with five treatments, BC0 (Control), BC1 (5 % biochar), BC2 (5 % distilled water washed biochar), BC3 (10 % biochar), BC4 (20 % biochar). Adding biochar could change physicochemical properties such as temperature, moisture, and pH during composting. The results indicated applying biochar-composting covering to minimalized NH₃ and H₂S aided by higher porous structure and surface functional groups. Among trials, biochar 20 % obtained the lowest NH₃ (2 ppm) and H₂S (3 ppm) emission on day 16 and stopping their emission on day 17. The NH₃/NH₄⁺ adsorption on large specific surface areas and highly porous micro-structure of biochar lead to reduced nitrogen losses, while nitrification (NH₄⁺ ➔ NO₂^- ➔ NO₃^-) may also contribute to nitrogen retention. The H₂S concentration decreased with increasing the biochar proportion, suggesting that biochar could reduce the H₂S emission. Correlation analysis illustrated that temperature, moisture, and oxygen are the most critical factors affecting H₂S and NH₃ emissions (p <0.05). The physicochemical properties and seed germination index indicated that the compost was mature without phytotoxicity. These novelty findings illustrated that the biochar amendment is an effective solution to reduce odor emission and enhances the maturity of compost mixture, which is promising to approach in real-scale conditions and could apply in agricultural fields.

Biochar reduces bioavailability of phosphorus during swine manure composting: Roles of phoD-harboring bacterial community

The bioavailability of phosphorus is a vital index for evaluating the quality of compost products. This study examined the effects of adding wheat straw biochar (WSB) and bamboo charcoal (BC) on the transformation of various phosphorus fractions during composting, as well as analyzing the roles of the phoD-harboring bacterial community in the transformation of phosphorus fractions. Adding WSB and BC reduced the available phosphorus content in the compost products by 35.2 % and 38.5 %, respectively. Redundancy analysis showed that the alkaline phosphatase content and pH were the most important factors that affected the transformation of phosphorus fractions. The addition of biochar resulted in changes in the composition and structures of the phoD-harboring bacteria communities during composting. In addition, the key bacterial genera that secreted alkaline phosphatase and decomposed different forms of phosphorus under WSB and BC were different compared with those under control. Network and correlation analysis demonstrated that the activities of phoD-harboring bacteria could have been enhanced by biochar to accelerate the consumption of available phosphorus, and the activities of key phosphorus-solubilizing bacteria (Lysobacter, Methylobacterium, and Saccharothrix) might be inhibited when the pH increased, thereby increasing the insoluble phosphorus content.

Effects of biochar on the degradation of organophosphate esters in sewage sludge aerobic composting

In this study, the impact of biochar on the degradation of organophosphate esters (OPEs) during the aerobic composting of sewage sludge was investigated. Three treatments were conducted with different percentages of biochar in the compost, including 5 %, 10 %, and 20 %. The treatment with 10 % of biochar showed the longest thermophilic phase compared to that of 5 % and 20 % of biochar, which greatly promoted the decomposition of organic matter. In addition, the degradation rate of the hard-to-degrade chlorinated-OPEs was significantly increased by 10 % biochar, reaching to 57.2 %. Correspondingly, approximately 43.6 % of the total concentration of OPEs (Σ₆OPEs) was eliminated in the presence of 10 % of biochar, which was higher than the treatments with 5 % and 20 % of biochar. Biochar significantly influenced the microbial community structure of compost, but the previously reported organophosphorus-degrading bacteria did not play a major role in the degradation of OPEs. The redox ability of the increased oxygen-containing functional groups such as quinone on the surface of biochar and the biochar-mediated electron transfer ability may play an essential role in the degradation of OPEs during the composting process.

Effects of hydrolyzed polymaleic anhydride addition combined with vermicomposting on maturity and bacterial diversity in the final vermicompost from the biochemical residue of kitchen waste

A large amount of kitchen waste is produced all over the world. Biochemical disposal is an effective method for the reduction and safe utilization of kitchen waste. However, high salinity, low maturity and poor biocompatibility were encountered when utilizing the biochemical residue of kitchen waste (BRKW) as a kind of soil amendment. To reduce the high salinity, accelerate the maturity and improve the biocompatibility in the BRKW, this study used the BRKW as the main feedstock for earthworms after hydrolyzed polymaleic anhydride (HPMA) was added and focused on revealing the effect of HPMA addition combined with the vermicomposting process on the growth of earthworms and on the basic physicochemical properties and the microbial diversity of the derived vermicompost. The results showed that HPMA addition can promote earthworm growth and reproduction. The pH, electric conductivity, organic matter content, C/N and NH₄⁺-N/NO₃^--N were decreased in the final vermicompost, while total nitrogen, total phosphorus and total potassium contents, and the seed germination index were increased. Scanning electron microscopy analysis showed that there was more disintegration in the final vermicompost. Meanwhile, adding the HPMA also helped to decrease the total number of fungi while increasing the populations of nitrogen-fixing bacteria, phosphorus-solubilizing bacteria and potassium-solubilizing bacteria as well as amount of total bacteria and actinomycetes. The vermicomposting process increased the bacterial phyla that promote the degradation of OM, such as Actinobacteria, Firmicutes and Acidobacteria, decreased the pathogenic Enterobacter and increased the bacterial genera that promote the maturity and quality, such as Cellvibrio and Pseudomonas. Thus, HPMA addition combined with vermicomposting can promote the growth of beneficial bacteria that promote the degradation of lignocelluloses and accelerate maturity while inhibiting some potential bacterial pathogens, which helps guarantee the safety of vermicomposting products from BRKW. Hence, employing HPMA to promote BRKW vermicomposting can possibly reduce salt content and improve the maturity and biocompatibility of the final vermicompost. This approach may help realize the safe utilization of BRKW and further promote the biochemical disposal of kitchen waste.

Independent and combined effects of biochar and microbial agents on physicochemical parameters and microbial community succession during food waste composting

This study evaluated the independent and combined effects of biochar and microbial agents on food waste composting. The results indicated that combined addition increased the peak temperature to 63.5 °C and extended the thermophilic periods to 8 days, resulting in the highest organic matter degradation rate (12.7%). Analysis of enzymatic activity indicated that combined addition increased urease and dehydrogenase activity by 22.9% and 26.5%. Furthermore, the degradation of volatile fatty acids also increased by 37.4% with combined addition. Microbial analysis demonstrated that combined addition effectively increased the relative abundances of Enterobacter, Sphingobacterium and Aspergillus, which could be attributed to the optimal environment provided by biochar and stimulation of microbial agents. Moreover, correlation analysis showed a strong interaction between the microbial community and environment with combined addition. In general, combined addition could be beneficial for composting based on the synergistic effects of biochar and inoculation on microorganism.

Inoculating indoleacetic acid bacteria promotes the enrichment of halotolerant bacteria during secondary fermentation of composting

The secondary fermentation stage is critical for stabilizing composting products and producing various secondary metabolites. However, the low metabolic rate of mesophilic bacteria is regarded as the rate-limiting stage in composting process. In present study, two indoleacetic acid (IAA)-producing bacteria (Bacillus safensis 33C and Corynebacterium stationis subsp. safensis 29B) were inoculated to strengthen the secondary fermentation stage to improve the plant-growth promoting potential of composting products. The results showed that the addition of IAA-producing bacteria promoted the assimilation of soluble salt, the condensation and aromatization of humus, and the accumulation of dissolved organic nitrogen (DON) and dissolved organic carbon (DOC). The bioaugmentation strategy also enabled faster microbial community succession during the medium-late phase of secondary fermentation. However, the colonization of Bacillus and Corynebacterium could not explain the disproportionate increase of IAA yield, which reached up to 5.6 times compared to the control group. Deeper analysis combined with physicochemical properties and microbial community structure suggested that IAA-producing bacteria might induce the increase of salinity, which enriched halotolerant bacteria capable of producing IAA, such as Halomonas, Brachybacterium and Flavobacterium. In addition, the results also proved that it was necessary to shorten secondary fermentation time to avoid IAA degradation without affecting composting maturity. In summary, enhancing secondary fermentation of composting via adding proper IAA-producing bacteria is an efficient strategy for upgrading the quality of organic fertilizer.

Evaluation of key microbial community succession and enzyme activities of nitrogen transformation in pig manure composting process through multi angle analysis

This experiment aimed to investigate changes in enzyme activity, microbial succession, and nitrogen conversion caused by different initial carbon-to-nitrogen ratios of 25:1, 35:1 and 20:1 (namely CK, T1 and T2) during pig manure composting. The results showed that the lower carbon-to-nitrogen ratio (T2) after composting retained 19.64 g/kg of TN which was more than 16.74 and 17.32 g/kg in treatments of CK and T1, respectively, but excessive conversion of ammonium nitrogen to ammonia gas resulted in nitrogen loss. Additional straw in T1 could play the role as a bulking agent. After composting, TN in T1 retained the most, and TN contents were 63.51 %, 67.34 % and 56.24 % in CK, T1 and T2, respectively. Network analysis indicated that many types of microorganisms functioned as a whole community at various stages of nitrogen cycle. This study suggests that microbial community structure modification might be a good strategy to reduce ammonium nitrogen loss.

Deciphering the internal driving mechanism of microbial community for carbon conversion and nitrogen fixation during food waste composting with multifunctional microbial inoculation

In this study, the effects of multifunctional microbial inoculation on food waste composting based on the synergistic property between organic matter degradation and nitrogen fixation were investigated. The results showed that inoculation simultaneously strengthened organic matter degradation by 9.9% and improved the nitrogen content by 20.6% compared with that of the control group. Additionally, spectral analysis demonstrated that inoculation was conducive to the enhanced humification, which was supported by the improvement in polyphenol oxidase activity. Microbial analysis showed that most of the introduced microorganisms (Bacillus, Streptomyces, Saccharomonospora) successfully colonized, and stimulated the growth of other indigenous microorganisms (Enterobacter, Paenibacillus). Meanwhile, the change in microbial community structure was accompanied by the enhanced tricarboxylic acid cycle and amino acid metabolism. Furthermore, network analysis and structural equation model revealed that the enhanced cooperation of microorganisms, in which more carbon sources could be provided by cellulose decomposition for nitrogen fixation.

Effects of biochar amendment on bioconversion of soybean dregs by black soldier fly

Biochar is known to accelerate composting process and improve the quality of end-products. However, its effects on bioconversion of organic waste by black soldier fly larvae (BSFL) remains largely unexamined. To investigate the effects of corn straw biochar (CS-BC) on bioconversion of soybean dregs (SD) by BSFL, SD was amended with four different dosages of CS-BC [0%, 2%, 5%, and 8% (w/w)] and digested by BSFL for ten days. The results indicated that the peak values of single larva wet weight in the treatments amended with CS-BC were advanced by 2-3 days and the reduction rate of SD increased from 72.09% to 85.37% with the increasing dosage of CS-BC. Meanwhile, SD mixed with 2%, 5% and 8% of CS-BC decreased ammonia (NH3) emission by 2.7%, 3.6% and 18.0%, respectively. The nitrous oxide (N2O) emissions reduced (-23.6%, -29.1% and -49.2%) with 2%, 5% and 8% CS-BC additions, respectively. In addition, the residual nitrogen of SD‑nitrogen proportionally increased with CS-BC application (28.3%, 28.6%, 30.1% and 35.0% for application at the dosage of 0%, 2%, 5% and 8%, respectively). Based on the comprehensive evaluation of bioconversion performance, alleviation of pollutant gas emission, and nitrogen conservation, we recommend the introduction of 8% (w/w) CS-BC during bioconversion of SD by BSFL. This study confirmed the feasibility of CS-BC as an amendment for the BSFL-based bioconversion system.

Reducing Nutrient Loss Caused by Thinning: Effects of Four Composts of Forest Thinning Shreds on Soil Nutrients and Tree Growth in Semimature Pinus tabuliformis Carr., Beijing, China

Traditional methods to deal with thinning shreds (twigs, bark, etc.) include using them as fuelwood (artificially taken out of the forest) and stacking in situ natural decompositions (slow decomposition and nutrient return to the field). These methods will cause the loss of nutrients in the forest, and composting with additives can effectively promote nutrient circulation effectively. The purpose of our study was to explore the effects of composts of forest thinning shreds with different additives on soil and tree growth in semimature Pinus tabuliformis Carr. We selected four composts of forest thinning shreds (T1 adjustment of C/N and C/P + 0.2% priming; T2: adjustment of C/N and C/P + 0.2% common compost; T3: adjustment of C/N and C/P only; T4: raw material grinding of thinning shreds) and applied them in the volume of 900 g·m−2, which were made in the early stage. The soil nutrient content, microbial characteristics, and growing volume of Pinus tabuliformis were measured at 0.5, 1, and 1.5 years after fertilization. The soil became acid after one year of fertilization, having a great impact on the 0–20 cm soil layer. At 0.5 years of fertilization, the total nitrogen (TN) content of the soil with priming compost (T1) was 1.5 times higher than that of the control group (T5); the soil organic matter (SOM) was increased by 4.93–6.41 mg·kg−1. After one year of fertilization, the difference in the soil microbial carbon and nitrogen (MBC and MBN) content of each treatment decreased gradually. Soil sucrase activity was the highest after fertilization, and different composts had the greatest impact on urease activity in the 0–20 cm layer; the alkaline phosphatase (AKPase) activity of soil with common compost (T2) changed the most, and after 0.5 years of fertilization, the acid phosphatase (APase) activity of T1 in the two layers increased by 0.31 mg·g−1 and 0.1 mg·g−1, and the increase in of T2 was slightly lower than that of T1. There were significant differences in the number of bacteria, fungi, and actinomycetes compared to T1 and T2 with other treatments. T1 promoted the height growth (H) of trees three times higher than T5 and T2 promoted the growth of diameter at breast height (DBH) by 2.5 cm. The results showed that T1 and T2 had obvious effects on promoting soil nutrient content, microbial biomass accumulation, and forest growth, and the application of compost had no significant effect on promoting understory regeneration. The findings of this study show that using compost with priming can effectively increase the soil nutrient content, microbial activity, and quantity of Pinus tabuliformis effectively in terms of promoting the growth of trees and reducing the nutrient loss caused by thinning.

Indigenous cellulolytic aerobic and facultative anaerobic bacterial community enhanced the composting of rice straw and chicken manure with biochar addition

Microbial degradation of organic matters is crucial during the composting process. In this study, the enhancement of the composting of rice straw and chicken manure with biochar was evaluated by investigating the indigenous cellulolytic bacterial community structure during the composting process. Compared with control treatment, composting with biochar recorded higher temperature (74 °C), longer thermophilic phase (> 50 °C for 18 days) and reduced carbon (19%) with considerable micro- and macronutrients content. The bacterial community succession showed that composting with biochar was dominated by the cellulolytic Thermobifida and Nocardiopsis genera, which play an important role in lignocellulose degradation. Twenty-three cellulolytic bacterial strains were successfully isolated at different phases of the composting with biochar. The 16S rRNA gene sequencing similarity showed that they were related to Bacilluslicheniformis, Bacillussubtilis,Bacillusaerius, and Bacillushaynesii, which were known as cellulolytic bacteria and generally involved in lignocellulose degradation. Of these isolated bacteria, Bacilluslicheniformis, a facultative anaerobe, was the major bacterial strain isolated and demonstrated higher cellulase activities. The increase in temperature and reduction of carbon during the composting with biochar in this study can thus be attributed to the existence of these cellulolytic bacteria identified.

Biochar regulates bacterial-fungal diversity and associated enzymatic activity during sheep manure composting

Aimed to evaluate the coexistence of bacterial and fungal diversity and their correlation with enzymatic activity in response to biochar. This study performed aerobic composting based on typical agricultural wastes of sheep manure with additive apple tree branch biochar at distinct concentration (0, 2.5, 5, 7.5, 10 and 12.5% corresponding from T1 to T6). The result demonstrated that appropriate amendment of biochar enriched bacterial diversity (1646-1686 OTUs) but interestingly decreased fungal diversity (542-630 OTUs) compared to control (1444 and 682 OTUs). Biochar addition enhanced all enzymatic activities and its correlation with bacterial was more complex than fungal community (786 and 359 connect edges). The dominant microbes comprised of Firmicutes (45.2-35.2%), Proteobacteria (14.0-17.5%), Basidiomycota (32.4-49.5%) and Ascomycota (11.3-37.5%) among all the treatments. Overall, biochar regulates the composting microenvironment by influencing the microbial diversity and associated enzymatic activities.

Biochar for agronomy, animal farming, anaerobic digestion, composting, water treatment, soil remediation, construction, energy storage, and carbon sequestration: a review

In the context of climate change and the circular economy, biochar has recently found many applications in various sectors as a versatile and recycled material. Here, we review application of biochar-based for carbon sink, covering agronomy, animal farming, anaerobic digestion, composting, environmental remediation, construction, and energy storage. The ultimate storage reservoirs for biochar are soils, civil infrastructure, and landfills. Biochar-based fertilisers, which combine traditional fertilisers with biochar as a nutrient carrier, are promising in agronomy. The use of biochar as a feed additive for animals shows benefits in terms of animal growth, gut microbiota, reduced enteric methane production, egg yield, and endo-toxicant mitigation. Biochar enhances anaerobic digestion operations, primarily for biogas generation and upgrading, performance and sustainability, and the mitigation of inhibitory impurities. In composts, biochar controls the release of greenhouse gases and enhances microbial activity. Co-composted biochar improves soil properties and enhances crop productivity. Pristine and engineered biochar can also be employed for water and soil remediation to remove pollutants. In construction, biochar can be added to cement or asphalt, thus conferring structural and functional advantages. Incorporating biochar in biocomposites improves insulation, electromagnetic radiation protection and moisture control. Finally, synthesising biochar-based materials for energy storage applications requires additional functionalisation.

Research progress and prospects for using biochar to mitigate greenhouse gas emissions during composting: A review

Biochar possesses a unique porous structure and abundant surface functional groups, which can potentially help mitigate greenhouse gas (GHG) emissions from compost. This review summarizes the properties and functions of biochar, and the effects of biochar on common GHGs (methane (CH₄), carbon dioxide (CO₂), and nitrous oxide (N₂O)) and ammonia (NH₃, an indirect GHG) during composting. Studies have shown that it is possible to improve the mitigation of GHG emissions during composting by adjusting the biochar amount, type of raw material, pyrolysis temperature, and particle size. Biochar produced from crop residues and woody biomass has a greater effect on mitigating CH₄, N₂O, and NH₃ emissions during composting, and GHG emissions can be reduced significantly by adding about 10% (w/w) biochar. Biochar produced by high temperature pyrolysis (500-900 °C) has a greater effect on mitigating CH₄ and N₂O emissions, whereas biochar generated by low temperature pyrolysis (200-500 °C) is more effective at reducing NH₃ emissions. Interestingly, adding granular biochar is more beneficial for mitigating CH₄ emissions, whereas adding powdered biochar is better at reducing NH₃ emissions. According to the current research status, developing new methods for producing and using biochar (e.g., modified or combined with other additives) should be the focus of future research into mitigating GHG emissions during composting. The findings summarized in this review may provide a reference to allow the establishment of standards for using biochar to mitigate GHG emissions from compost.

Effects of urease inhibitors on enzymatic activities and fungal communities during the biosolids composting

This study evaluated the influences of urease inhibitors (UIs) on nitrogen conversion, enzyme activities, and fungal communities during aerobic composting. Results showed that UI addition reduced NH₃ emissions by 22.2% and 21.5% and increased the total nitrogen (TN) content by 9.7% and 14.3% for the U1 (0.5% UI of the dry weight of the mixture) and U2 (1% UI of the dry weight of the mixture) treatments, respectively. The addition of UI inhibited the enzyme activity during thermophilic stage while increased enzyme activity during the cool and maturity stages. Ascomycota, Basidiomycota and unclassified fungi were the main phyla, and Ascomycota increased significantly during the maturity period. Network analysis showed that Aspergillus, Penicillium, Trichoderma, Talaromyces, Peseudeurotium, and Exophiala were the main “connecting” genera. The redundancy analysis (RDA) showed that the fungal community was mainly influenced by temperature, DOC, pH, and urease. The results suggested that UI was an effective additive for nitrogen conservation and the increase of enzyme activity reduce nitrogen loss and promote enzyme activity during biosolids composting.

Adding UI was effective for nitrogen conservation and the increase of enzyme activity during biosolid composting.