Functional characteristics and influence factors of microbial community in sewage sludge composting with inorganic bulking agent

Enhancement of microbial community dynamics and metabolism in compost through ammonifying cultures inoculation

The efficient use of livestock and poultry manure waste has become a global challenge, with microorganisms playing an important role. To investigate the impact of novel ammonifying microorganism cultures (NAMC) on microbial community dynamics and carbon and nitrogen metabolism, five treatments [5% (v/w) sterilized distilled water, Amm-1, Amm-2, Amm-3, and Amm-4] were applied to cow manure compost. Inoculation with NAMC improved the structure of bacterial and fungal communities, enriched the populations of the functional microorganisms, enhanced the role of specific microorganisms, and promoted the formation of tight modularity within the microbial network. Further functional predictions indicated a significant increase in both carbon metabolism (CMB) and nitrogen metabolism (NMB). During the thermophilic phase, inoculated NAMC treatments boosted carbon metabolism annotation by 10.55%-33.87% and nitrogen metabolism annotation by 26.69%-63.11. Structural equation modeling supported the NAMC-mediated enhancement of NMB and CMB. In conclusion, NAMC inoculation, particularly with Amm-4, enhanced the synergistic interaction between bacteria and fungi. This collaboration promoted enzymatic catabolic and synthetic processes, resultng in positive feedback loops with the endogenous microbial community. Understanding these mechanisms not only unravels how ammonifying microorganisms influence microbial communities but also paves the way for the development of the composting industry and global waste management practices.

Effects of different proportions of fruit tree branches on nicotine content and microbial diversity during composting of tobacco waste

Adding fruit tree branches to the compost pile in appropriate proportions is one of the methods used to address the challenge of tobacco waste recycling. However, the effects of different proportions of fruit tree branches on nicotine concentration and microbial diversity during tobacco waste composting have not been reported. In this study, a composting system with tobacco waste, cow dung, and fruit tree branches was established in a laboratory fermenter to assess the impact of adding 10%, 20%, and 30% fruit tree branches on quantity changes. In addition, the relationships between nicotine degradation, compost properties, enzyme activities, and microbial diversities were determined using biochemical assay methods and high-throughput sequencing. The results showed that adding appropriate proportions of fruit branch segments affected changes in physical and chemical properties during composting and promoted tobacco waste compost maturity. Aerobic composting effectively degraded nicotine in tobacco waste. Increased proportions of fruit branch segments led to elevations in nicotine degradation rates and enzyme activities related to lignocellulose degradation. The addition of fruit branches influenced the relative abundance and species of dominant bacteria and fungi at the phylum and genus levels. However, it did not significantly affect the relative abundance of the main bacterial genera involved in nicotine degradation. Nevertheless, it reduced the sensitivity of enzyme activity to nicotine content within heaps, increasing reliance on total nitrogen changes. The results of this study provide a theoretical basis for the utilization of tobacco waste in composting systems and indicate that fruit tree branches can enhance nicotine degradation efficiency during tobacco waste composting.

Microbial mechanisms involved in negative effects of amoxicillin and copper on humification during composting of dairy cattle manure

Livestock manure often contains various pollutants. The aim of this study was to investigate how adding amoxicillin (AMX), Cu, and both AMX and Cu (ACu) affected humification during composting and the microbial mechanisms involved. The cellulose degradation rates were 16.96%, 10.86%, and 9.01% lower, the humic acid contents were 18.71%, 12.89%, and 16.78% lower, and the humification degrees were 24.72%, 24.16%, and 15.73% lower for the AMX, Cu, and ACu treatments, respectively, than the control. Adding AMX and Cu separately or together inhibited humic acid formation and decreased the degree of humification, but the degree of humification was decreased less by ACu than by AMX or Cu separately. The ACu treatment decreased the number of core bacteria involved in humic acid formation and decreased carbohydrate and amino acid metabolism during the maturing period, and thereby delayed humic acid formation and humification. The results support composting manure containing AMX and Cu.

Semi-permeable membrane-covered high-temperature aerobic composting: A review

Semi-permeable membrane-covered high-temperature aerobic composting (SMHC) is a suitable technology for the safe treatment and disposal of organic solid waste as well as for improving the quality of the final compost. This paper presents a comprehensive summary of the impact of semi-permeable membranes centered on expanded polytetrafluoroethylene (e-PTFE) on compost physicochemical properties, carbon and nitrogen transformations, greenhouse gas emission reduction, microbial community succession, antibiotic removal, and antibiotic resistance genes migration. It is worth noting that the semi-permeable membrane can form a micro-positive pressure environment under the membrane, promote the uniform distribution of air in the heap, reduce the proportion of anaerobic area in the heap, improve the decomposition rate of organic matter, accelerate the decomposition of compost and improve the quality of compost. In addition, this paper presents several recommendations for future research areas in the SMHC. This investigation aims to guide for implementation of semi-permeable membranes in high-temperature aerobic fermentation processes by systematically compiling the latest research progress on SMHC.

Control of nitrogen and odor emissions during chicken manure composting with a carbon-based microbial inoculant and a biotrickling filter

Although aerobic composting is usually utilized in livestock manure disposal, the emission of odorous gases from compost not only induces harm to the human body and the environment, but also causes loss of nitrogen, sulfur, and other essential elements, resulting in a decline in product quality. The impact of biotrickling filter (BTF) and insertion of carbon-based microbial agent (CBMA) on compost maturation, odor emissions, and microbial population during the chicken manure composting were assessed in the current experiment. Compared with the CK group, CBMA addition accelerated the increase in pile temperature (EG group reached maximum temperature 10 days earlier than CK group), increased compost maturation (GI showed the highest increase of 41.3% on day 14 in EG group), resulted in 36.59% and 14.60% increase in NO3--N content and the total nitrogen retention preservation rate after composting. The deodorization effect of biotrickling filter was stable, and the removal rates of NH3, H2S, and TVOCs reached more than 90%, 96%, and 56%, respectively. Furthermore, microbial sequencing showed that CBMA effectively changed the microbial community in compost, protected the ammonia-oxidizing microorganisms, and strengthened the nitrification of the compost. In addition, the nitrifying and denitrifying bacteria were more active in the cooling period than they were in the thermophilic period. Moreover, the abundance of denitrification genes containing nirS, nirK, and nosZ in EG group was lower than that in CK group. Thus, a large amount of nitrogen was retained under the combined drive of BTF and CBMA during composting. This study made significant contributions to our understanding of how to compost livestock manure while reducing releases of odors and raising compost quality.

Effects of microbial deodorizer on pig feces fermentation and the underlying deodorizing mechanism

Microbial deodorization is a novel strategy for reducing odor in livestock and poultry feces. Herein, 12 strains of ammonia (NH3) and 15 hydrogen sulfide (H2S) removing bacteria were obtained with a removal efficiency of 65.20-79.80% and 34.90-79.70%, respectively. A novel bacteria deodorant named MIX (Bacillus zhangzhouensis, Bacillus altitudinis, and Acinetobacter pittii at a ratio of 1:1:2) were obtained. MIX can shorten the temperature rising stage by 2 days and prolong the thermophilic stage by 4 days. The ability of MIX to remove NH3, H2S, and volatile fatty acids (VFAs) and the underlying removal mechanism were analyzed during pig feces fermentation. MIX can significantly reduce the concentrations of NH3 and H2S by 41.82% and 66.35% and increase the concentrations of NO3--N and SO42- by 7.80% and 8.83% (P < 0.05), respectively, on the 25th day. Moreover, the concentrations of acetic, propionate, iso-valerate, and valerate were significantly reduced. The dominant bacteria communities at the phylum level were Firmicutes, Proteobacteria, Bacteroidetes, and Spirochaetes. B. zhangzhouensis and B. altitudinis could convert NH4+-N to NO3--N, and A. pittii could transfer H2S to SO42-. This study revealed that bacteria deodorant can reduce the concentrations of NH3, H2S, and VFAs in pig feces and increase those of NH4+, NO3-, and SO42- and has excellent potential in deodorizing livestock and poultry feces composting.

Humification and fungal community succession during pig manure composting: Membrane covering and mature compost addition

The objective of this study was to elucidate the combined effect of a semi-permeable membrane (M) and mature compost (MC) on humification and fungal community succession in pig manure composting. Compared with the control, the concentrations of humic substances (HSs) increased by 44.54 % (M + 15 % MC) and 43.90 % (M). During the thermophilic phase, Aspergillus (67.26 %) was the dominant genus in the M + 15 % MC treatment. Membrane covering increased the relative abundance (RA) of other phyla (except for Ascomycetes and Basidiomycetes) on the 14th day and Basidiomycetes on the 80th day in M treatment. Humic acid, HSs were positively correlated with the RA of genera Myceliophthora, Kernia, and Mycothermus. Myceliophthora was the key genus in the M + 15 % MC treatment on the 80th day. The results showed that 15 % MC addition under membrane covering optimizes the quality of composting products.

Dynamics and functions of biomarker taxa determine substrate-specific organic waste composting

Bacteria are an influential component of diverse composting microbiomes, but their structure and underlying dynamics are poorly understood. This study analyzed the bacterial communities of 577 compost datasets globally and constructed a substrate-dependent catalog with more than 15 million non-redundant 16S rRNA gene sequences. Using a random-forest machine-learning model, 30 biomarker taxa were identified that accurately distinguish between the food, sludge and manure waste composting microbiomes (accuracy >98 %). These biomarker taxa were closely associated with carbon and nitrogen metabolic processes, during which they contributed to the predominant stochastic process and are influenced by different factors in the substrate-specific composts. This is corroborated by the community topological characteristics, which feature the biomarkers as keystone taxa maintaining the bacterial network stability. These findings provide a theoretical basis to identify and enhance the biomarker-functional bacteria for optimizing the composting performance of different organic wastes.

Effects of sludge retention time (SRT) on nitrogen and phosphorus removal and the microbial community in an ultrashort-SRT activated sludge system

The ultrashort-sludge retention time activate sludge (USAS) process is considered promising for the recovery of energy and resource from wastewater. In this study, we developed five USAS systems (with sludge retention time (SRT) of 0.5, 1, 2, 3, and 4 d), and investigated the nitrogen and phosphorus removal, as well as the microbial community, in the USAS systems. The results revealed that the activated sludge in the USAS system with a shorter SRT can capture more organic matter from wastewater, with organic matter mineralization, capture, and loss rates of 12.9-45.9, 42.4-62.3, and 18.2-24.8%, respectively. In addition, ammonia oxidization only occurred in the USAS systems with SRTs of 3 and 4 d, and all the USAS systems with different SRTs exhibited phosphorus-removal ability. The microbial community analysis results revealed that the relative abundance of nitrifying and denitrifying bacteria (such as Thauera) increased with an increase in the SRT.

Dry and wet seasonal variations of the sediment fungal community composition in the semi-arid region of the Dali River, Northwest China

Microbial communities play an important role in water quality regulation and biogeochemical cycling in freshwater ecosystems. However, there has been a lack of research on the seasonal variation of sediment microorganisms in the sediments of small river basins in typical semi-arid region. In this study, high-throughput DNA sequencing was used to investigate the fungal community and its influencing factors in the sediment of the Dali River in the dry and wet seasons. The results showed that there were obvious seasonal differences in fungal alpha diversity. The diversity and richness of fungi in the dry season were greater than that in the wet season, but the evenness of fungi in the dry season was lower than that in the wet season. In addition, Ascomycota and Basidiomycota were the most important phyla in the Dali River fungal community, but their distributions showed clear seasonal differences. In the dry season, the relative abundance of Ascomycota and Basidiomycota were 12.34-46.42% and 17.59-27.20%, respectively. In the wet season, the relative abundances of these two phyla were 24.33-36.56% and 5.75-12.26%, respectively. PICRUSt2 was used to predict the metabolic function of fungal community in the sediment, and it was found that at the first level, the proportion of biosynthesis in the dry season was higher than that in the wet season. The ecological network structure showed that the fungal community in the wet season was more complex and stable than that in the dry season. The characteristic fungi in the dry season sediment were chytrid fungi in the family Rhizophydiaceae and the order Rhizophydiales, whereas those in the wet season sediment were in the orders Eurotiales and Saccharomycetales. Canonical correspondence analysis (CCA) showed that the physicochemical properties of water and sediment together explained a greater proportion of the dry-season fungal community changes than of the wet-season changes. In the dry season, temperature and ammonia nitrogen in the water were the main factors affecting the change of fungal community, whereas in the wet season, total nitrogen concentration of the water, electrical conductivity, total organic carbon and available phosphorus of the sediment, pH, and temperature were the main factors affecting the changes in fungal community composition. The results of this study enhanced our understanding of microbial communities in semi-arid river ecosystems, and highlight the importance of the management and protection in river ecosystems.

Effects of different concentrations of biological maturity agents on nitrogen and microbial diversity of Auricularia heimuer residue compost

This study investigated the effects of different concentrations of biological maturity agents on the composting process of Auricularia heimuer residue by adding them to the composting process. By measuring the changes in physical and chemical indicators and microbial diversity during composting, the results showed that the addition of biological maturity agents had a certain promoting effect on compost temperature, humidity, pH, seed germination index, and vitality index. Appropriate composting days can promote the accumulation of ammonium nitrogen. The carbon content of humin and E4/E6 of treatments A, B, and E were significantly higher than those of the initial treatment. D0.CK treatment had the most types of resistance genes and the most abundant resistance genes. As composting progresses, the abundance of 13 resistance genes decreased. Adding high concentrations of biological maturity agents can activate the defense mechanism during the composting process, greatly ensuring the safety of fungi residue as a fertilizer.

Assessing the suitability of municipal sewage sludge and coconut bran as breeding medium for Oryza sativa L. seedlings and developing a standardized substrate

The utilization of organic solid waste (OSW) for preparing standardized seedling substrates is a main challenge due to its temporal and spatial variability. This study aims to form models based on data from the literature and validate them through experiments to explore a standardized seedling substrate. The typical OSW in Hainan Province, including municipal sewage sludge (MSS), coconut bran (CB), seaweed mud (SM), and municipal sewage sludge biochar (MSSB), was used as raw material. A series of six mixing ratios was tested, namely: T1 (0% MSS: 90% CB), T2 (10% MSS: 80% CB), T3 (30% MSS: 60% CB), T4 (50% MSS: 40% CB), T5 (70% MSS: 20% CB), and T6 (90% MSS: 0% CB). SM and MSSB were added as amendment materials at 5% (w/w) for each treatment. The physicochemical properties of substrates, agronomic traits of rice seedlings and microbial diversity were analyzed. The results showed that the four kinds of OSW played an active role in providing rich sources of nutrients. The dry weight of the above-ground part was 2.98 times greater in T3 than that of the commercial substrate. Furthermore, the microbial analysis showed a higher abundance of Actinobacteria in T3, representing the stability of the composted products. Finally, the successful fitting of the results with the linear regression models could establish relationship equations between the physicochemical properties of the substrate and the growth characteristics of seedlings. The relevant parameters suitable for the growth of rice seedlings were as follows: pH (6.46-7.01), EC (less than 2.12 mS cm-1), DD (0.13-0.16 g cm-3), and TPS (65.68-82.73%). This study proposed relevant parameters and models for standardization of seedling substrate, which would contribute to ensuring the quality of seedlings and OSW resource utilization.

Effect of inoculating thermophilic bacterial consortia on compost efficiency and quality

The objective of this study was to investigate the potential effects of thermophilic bacterial consortia on compost efficiency and quality. The application of bacterial consortia resulted in an earlier onset of the thermophilic period (THP), an increased upper temperature limit, and an extended duration of the THP by 3-5 days compared to the control group (CK). Microbial inoculation significantly improved the efficiency of organic matter degradation, as well as the content of water-soluble nitrogen (WSN) and humic acid-carbon (HAC). In the case of consortium Ⅱ inoculation (T2), the activities of cellobiohydrolase, β-glucosidase, and protease were increased by 81.81 %, 70.13 %, and 74.09 % at the THP respectively compared to CK. During the maturation stage, T2 also exhibited the highest PV, n/PIII, n value (1.33) and HAC content (39.53 mg·g-1), indicating that inoculation of consortium Ⅱ effectively promoted substrate maturity and product quality. Moreover, this inoculation effectively optimized the bacterial communities, particularly the growth of Planococcus, Chelatococcus, and Chelativorans during the composting, which were involved in carbon and nitrogen conversion or HAC synthesis. Carbohydrate and amino acid metabolism, and membrane transport were predominant in the consortia-inoculated samples, with an increased gene abundance, suggesting that inoculation contributed to promoting the biodegradation of lignocellulose and the exchange of favorable factors. In conclusion, this study demonstrates that inoculating thermophilic bacterial consortia has a positive impact on enhancing the resource utilization efficiency of agricultural waste and improving the quality of compost products.

Effects of magnesium-modified biochar on antibiotic resistance genes and microbial communities in chicken manure composting

Abatement of antibiotic resistance genes (ARGs) in livestock manure by composting has attracted attention. This study investigated the effect of adding magnesium-modified biochar (MBC) on ARGs and microbial communities in chicken manure composting. Twelve genes for tetracyclines, sulfonamides, and macrolides, and mobile genetic elements were measured in the compost pile. The results showed that after 45 days of the composting, the treatment groups of MBC had longer high temperature periods, significantly higher germination indices (GI) and lower phytotoxicity. There were four major dominant phyla (Firmicutes, Actinobacteriota, Proteobacteria, and Bacteroidota) in the compost. The abundance of Firmicutes decreased significantly during the compost cooling period; tetracycline resistance genes demonstrated an extremely significant positive correlation with Firmicutes, showing a trend of the same increase and decrease with composting time; tetT, tetO, tetM, tetW, ermB, and intI2 were reduced in the MBC group; the total abundance of resistance genes in the 2% MBC addition group was 0.67 times that of the control; Proteobacteria and Chloroflexi were also significantly lower than the other treatment groups. Most ARGs were significantly associated with mobile genetic elements (MGEs); MBC can reduce the spread and diffusion of ARGs by reducing the abundance of MGEs and inhibiting horizontal gene transfer (HGT).

Nitrogen retention and emissions during membrane-covered aerobic composting for kitchen waste disposal

The composting performance and nitrogen transformation during membrane-covered aerobic composting of kitchen waste were investigated. The aerobic composting products of the kitchen waste had a high seed germination index of ∼180%. The application of the membrane increased the mean temperature in the early cooling stage of composting by 4.5℃, resulted in a lower moisture content, and reduced the emissions of NH3 and N2O by 48.5% and 44.1%, respectively, thereby retaining 7.9% more nitrogen in the compost. The adsorption of the condensed water layer under inner-membrane was the reason for reducing NH3 emissions, and finite element modeling revealed that the condensed water layer was present throughout the composting process with a maximum thickness of ∼2 mm in the thermophilic stage. The reduction of N2O emissions was related to the micro-positive pressure in the reactor, which promoted the distribution of oxygen, thus weakening denitrification. In addition, the membrane cover decreased the diversity of the bacterial community and increased the diversity of ammonia-oxidizing strains. This study confirmed that membrane-covered composting was suitable for kitchen waste management and could be used as a strategy to mitigate NH3 and N2O emissions.

Effects of dissolved organic matter derived from cow manure on heavy metal(loid)s and bacterial community dynamics in mercury-thallium mining waste slag

Organic amendments in aided phytostabilization of waste slag containing high levels of heavy metal (loid)s (HMs) are an important way to control the release of HMs in situ. However, the effects of dissolved organic matter (DOM) derived from organic amendments on HMs and microbial community dynamics in waste slag are still unclear. Here, the effect of DOM derived from organic amendments (cow manure) on the geochemical behaviour of HMs and the bacterial community dynamics in mercury (Hg)-thallium (Tl) mining waste slag were investigated. The results showed that the Hg-Tl mining waste slag without the addition of DOM continuously decreased the pH and increased the EC, Eh, SO42-, Hg, and Tl levels in the leachate with increasing incubation time. The addition of DOM significantly increased the pH, EC, SO42-, and arsenic (As) levels but decreased the Eh, Hg, and Tl levels. The addition of DOM significantly increased the diversity and richness of the bacterial community. The dominant bacterial phyla (Proteobacteria, Firmicutes, Acidobacteriota, Actinobacteriota, and Bacteroidota) and genera (Bacillus, Acinetobacter, Delftia, Sphingomonas, and Enterobacter) were changed in association with increases in DOM content and incubation time. The DOM components in the leachate were humic-like substances (C1 and C2), and the DOC content and maximum fluorescence intensity (FMax) values of C1 and C2 in the leachate decreased and first increased and then decreased with increasing incubation time. The correlations between HMs and DOM and the bacterial community showed that the geochemical behaviours of HMs in Hg-Tl mining waste slag were directly influenced by DOM-mediated properties and indirectly influenced by DOM regulation of bacterial community changes. Overall, these results indicated that DOM properties associated with bacterial community changes increased As mobilization but decreased Hg and Tl mobilization from Hg-Tl mining waste slag.

Comparison of the basic processes of aerobic, anaerobic, and aerobic-anaerobic coupling composting of Chinese medicinal herbal residues

Chinese medicinal herbal residues (CMHRs) are waste generated after extracting Chinese medicinal materials, and they can be used as a renewable bioresource. This study aimed to evaluate the potential of aerobic composting (AC), anaerobic digestion (AD), and aerobic-anaerobic coupling composting (AACC) for the treatment of CMHRs. CMHRs were mixed with sheep manure and biochar, and composted separately under AC, AD, and AACC conditions for 42 days. Physicochemical indices, enzyme activities, and bacterial communities were monitored during composting. Results showed that AACC- and AC-treated CMHRs were well-rotted, with the latter exhibiting the lowest C/N ratio and maximal germination index (GI) values. Higher phosphatase and peroxidase activities were detected during the AACC and AC treatments. Better humification was observed under AACC based on the higher catalase activities and lower E4/E6. AC treatment was effective in reducing compost toxicity. This study provides new insights into biomass resource utilisation.

Shifts in bacterial diversity characteristics during the primary and secondary fermentation stages of bio-compost inoculated with effective microorganisms agent

Microbial inoculation was an effective way to improve product quality of composting and solve traditional composting shortage. However, the effect mechanism of microbial inoculation on compost microorganisms remains unclear. Here, Shifts in bacterial community, metabolic function and co-occurrence network during the primary and secondary fermentation stages of bio-compost inoculated with effective microorganisms (EM) agent were analyzed by high-throughput sequencing and network analysis. Microbial inoculation promoted organic carbon transformation in early stage of secondary fermentation (days 27 to 31). The beneficial biocontrol bacteria were main dominant genera at the second fermentation stage. Microbial inoculation can be good for the survival of beneficial bacteria. Inoculation with microbes promoted amino acid, carbohydrate and lipid metabolism, and inhibited energy metabolism and citrate cycle (TCA cycle). Microbial inoculation could enhance complexity of bacterial network and enhance mutual cooperation among bacteria during composting.

Aerobic co-composting of mature compost with cattle manure: organic matter conversion and microbial community characterization

The production of organic fertilizer by aerobic composting of cattle manure is an important way of its resource utilization. This study evaluated the effects of adding mature compost on the decomposition and microbial communities in the aerobic composting of cattle manure. The addition of mature compost shortens the composting cycle and results in a final lignocellulosic degradation rate of 35%. Metagenomic analysis showed that this was due to the proliferation of thermophilic and organic matter-degrading functional microorganisms, which enhanced the activity of carbohydrate-active enzymes. With the addition of mature compost, the microbial community exhibited stronger metabolic functions, especially carbohydrate and amino acid metabolism, which are the driving forces of organic matter degradation. This study deepens the understanding of organic matter conversion and microbial community metabolic functions when mature compost is used for livestock manure composting and provides a promising technology for livestock manure composting.

High oil content inhibits humification in food waste composting by affecting microbial community succession and organic matter degradation

Composting is an effective technology to realize resource utilization of food waste in rural China. However, high oil content in food waste limits composting humification. This study investigated the effects of blended plant oil addition at different proportions (0, 10, 20, and 30%) on the humification of food waste composting. Oil addition at 10%-20% enhanced lignocellulose degradation by 16.6%-20.8% and promoted humus formation. In contrast, the high proportion of oil (30%) decreased the pH, increased the electrical conductivity, and reduced the seed germination index to 64.9%. High-throughput sequencing showed that high oil inhibited the growth and reproduction of bacteria (Bacillus, Fodinicurvataceae, and Methylococcaceae) and fungi (Aspergillus), attenuated their interaction, thus, reducing the conversion of organic matter, such as lignocellulose, fat, and total sugar, to humus, consequently leading to negative impacts on composting humification. The results can guide composting parameter optimization and improve effective management of rural food waste.

Response characteristics of Flax retting liquid addition during chicken manure composting: Focusing on core bacteria in organic carbon mineralization and humification

To explore the applicability of flax retting liquid (FRL) addition, the physicochemical properties, microbial community structure and function, carbon conversion and humus (HS) formation were assessed during chicken manure (CM) aerobic composting. Compared with the control group, the addition of FRL increased the temperature at thermophilic phase, while the microbial mass carbon content (MBC) in SCF and FRH groups raised to 96.1±0.25 g/Kg and 93.33±0.27 g/Kg, respectively. Similarly, FRL also improved the concent of humic acid (HA) to 38.44±0.85 g/Kg, 33.06±0.8 g/Kg, respcetively. However, fulvic acid (FA) decreased to 30.02±0.55g/Kg, 31.4±0.43 g/Kg, respectively and further reduced CO₂ emissions. FRL influenced the relative abundance of Firmicutes at thermophilic phase and Ornithinimicrobium at maturity phase. Additionally, FRL strengthen the association among flora and reduce the number of bacteria, which was negative correlated with HA and positive with CO₂ during composting. These findings offer powerful technological support for improving agricultural waste recycling.

Effect of the lignocellulolytic Psychrotroph Lelliottia sp. on bacterial community succession in corn straw compost

This study aimed to explore the effect of an inoculation, Lelliottia sp., on the corn straw compost's physico-chemical properties, composition, and the succession of bacterial community structure. The compost community composition and succession changed after Lelliottia sp. inoculation. Inoculation increased the bacterial community diversity and abundance in the compost to promote composting. The inoculated group entered the thermophilic stage on the first day, lasting 8 days. Judging the pile maturity based on the carbon:nitrogen ratio and germination index values, the inoculated group reached the maturity standard, which was 6 days faster than the control group. The relationship between environmental factors and bacterial communities was comprehensively analyzed using redundancy analysis. Temperature and carbon:nitrogen ratio were the main environmental factors driving the succession of bacterial communities, to provide basic information on the changes of physicochemical indexes and bacterial community succession in Lelliottia sp. inoculated maize straw composting, providing assistance for practical composting applications of this strain.

Effects of micro-positive pressure environment on nitrogen conservation and humification enhancement during functional membrane-covered aerobic composting

Aerobic composting is a humification process accompanied by nitrogen loss. This study is the first research systematically investigating and elucidating the mechanism by which functional membrane-covered aerobic composting (FMCAC) reduces nitrogen loss and enhances humification. The variations in bioavailable organic nitrogen (BON) and humic substances (HSs) in different composting systems were quantitatively studied, and the functional succession patterns of fungal groups were determined by high-throughput sequencing and FUNGuild. The FMCAC improved oxygen utilization and pile temperature, increased BON by 29.95 %, reduced nitrogen loss by 34.00 %, and enhanced humification by 26.09 %. Meanwhile, the FMCAC increased the competitive advantage of undefined saprotroph and significantly reduced potential pathogenic fungi (<0.10 %). Structural equation modeling indicated that undefined saprotroph facilitated the humification process by increasing the production of BON and storing BON in stable humic acid. Overall, the FMCAC increased the safety, stability, and quality of the final compost product.

Insights into the influence of digestate-derived biochar upon the microbial community succession during the composting of digestate from food waste

The by-product from the anaerobic digestion of food waste (FW) called the digestate (DFW) needs proper disposal because of its high environmental burden. Composting can transform DFW into a nutrient-containing soil improver via a series of microbial metabolic activities. However, the long composting time and high amount of ammonia emission are the key concerns of DFW composting. In the present study, the effect of DFW-derived biochar (BC-DFW) on microbial succession and its involvement in nitrogen transformation and humification during DFW composting were investigated. The results indicated that the BC-DFW accelerated bacterial and fungal evolution, and the bacterial diversity was augmented by increasing the amount of BC-DFW. In particular, Cryomorpha, Castellaniella, Aequorivita, and Moheibacter were enriched by the addition of BC-DFW, thereby enhancing the degradation of organic matter and nitrogen transformation and increasing the germination index. The group with 25% BC-DFW contained a higher relative abundance of Cryomorpha (2.08%, 2.47%) than the control (0.39%, 1.72%) on days 19 and 35 which benefited the degradation of organic matter. The group with 25% BC-DFW quickly enhanced the growth of Nitrosomonas, thereby accelerating the conversion of ammonium-nitrogen to nitrate-nitrogen and reducing the phytotoxicity of the composting product.

Intermittent aeration to reduce gaseous emission and advance humification in food waste digestate composting: Performance and mechanisms

This study investigated the performance and mechanisms of intermittent aeration to regulate gaseous emission and humification during food waste digestate composting. In addition to continuous aeration, three intermittent aeration regimes were conducted with the on-off interval ratio at 3:1, 2:1, and 1:1 within each 30 min, respectively. Results showed that intermittent aeration regimes reduced gaseous emission and enhanced humification during composting. In particular, intermittent aeration with the on/off ratio of 1:1 was more effective to reduce organic mineralization than other regimes, which alleviated the emission of nitrous oxide and ammonia by 63.1% and 75.7% in comparison with continuous aeration, respectively. In addition, this aeration regime also enhanced the content of humic acid by 24.1%. Further analysis demonstrated that prolonging aeration-off intervals could enrich facultative bacteria (e.g. Atopobium and Clostridium) from digestate and inhibit the proliferation of several aerobic bacteria (e.g. Caldicoprobacter and Marinimicrobium) to retard organic mineralization for humification.

Effects of functional membrane coverings on carbon and nitrogen evolution during aerobic composting: Insight into the succession of bacterial and fungal communities

Carbon and nitrogen evolution and bacteria and fungi succession in two functional membrane-covered aerobic composting (FMCAC) systems and a conventional aerobic composting system were investigated. The micro-positive pressure in each FMCAC system altered the composting microenvironment, significantly increased the oxygen uptake rates of microbes (p < 0.05), and increased the abundance of cellulose- and hemicellulose-degrading microorganisms. Bacteria and fungi together influenced the conversion between carbon and nitrogen forms. FMCAC made the systems less anaerobic and decreased CH₄ production and emissions by 22.16 %-23.37 % and N₂O production and emissions by 41.34 %-45.37 % but increased organic matter degradation and NH₃ production and emissions by 16.91 %-90.13 %. FMCAC decreased carbon losses, nitrogen losses, and the global warming potential by 7.97 %-11.24 %, 15.43 %-34.00 %, and 39.45 %-42.16 %, respectively. The functional membrane properties (pore size distribution and air permeability) affected fermentation process and gaseous emissions. A comprehensive assessment indicated that FMCAC has excellent prospects for application.

Review of inventory data for the biological treatment of sewage sludge

The biological treatment of municipal sewage sludge, including anaerobic digestion and composting, was reviewed with the purpose of establishing inventory data to address all the inputs and outputs related to sludge treatment. We identified 193 scientific papers, resulting in 64 datasets on anaerobic digestion and 35 datasets on composting. For anaerobic digestion, biogas production varied significantly (up to a factor of four) depending on the sludge. A useful correlation was identified between the amount of methane produced and the degradation of volatile solids. According to statistical tests, no significant differences were found in biogas production for mesophilic and thermophilic digesters. In addition, methane content varied significantly, and very few data were available for digestate composition or for energy consumption and recovery. For composting, accurate estimates relating to the degradation of sewage sludge could not be made, since organic bulking materials were part of the final composted product. Data on emissions to air are currently scarce, which points to the need for more published information. The inventory data evaluated herein are useful in the feasibility assessment of the biological treatment of sewage sludge, for comparing technologies, for example in LCA studies and as a basis for evaluating the performance of a specific biological sludge treatment plant. However, a great deal of the reviewed data originated from laboratory and pilot-scale studies, and so there is a need for more complete datasets on the performance of full-scale technologies, in order to establish full inventories and identify differences in technologies and operational conditions.

Recognition Method of Sports Training Based on Intelligent Information Platform

With the wide development of sports nowadays, many kinds of sport applications have appeared and changed the living styles of people all around the world. There are many factors that are important for sports, such as the environment and exercise. At present, there are still some shortcomings in sports training management all around the world. For example, the unscientific is unclear, the training purpose is not strong, and the assistant decision-making means are backward. In this way, these issues jointly make the sport training process difficult. In this way, this paper applies the multi-agent technology to the system, designs an intelligent information sports training management and recognition method based on intelligent agents, and carries on the concrete implementation in certain environments. The corresponding experimental results indicate that the accuracy and intelligence of the training recognition system can be improved greatly and effectively.

Co-composting of faecal sludge and carbon-rich wastes in the earthworm's synergistic cooperation system: Performance, global warming potential and key microbiome

Composting is an effective alternative for recycling faecal sludge into organic fertilisers. A microflora-earthworm (Eisenia fetida) synergistic cooperation system was constructed to enhance the composting efficiency of faecal sludge. The impact of earthworms and carbon-rich wastes (rice straw (RS) and sawdust (S)) on compost properties, greenhouse gas emissions, and key microbial species of composting were evaluated. The addition of RS or S promoted earthworm growth and reproduction. The earthworm-based system reduced the volatile solid of the final substrate by 13.19-16.24 % and faecal Escherichia coli concentrations by 1.89-3.66 log10 cfu/g dry mass compared with the earthworm-free system. The earthworm-based system increased electrical conductivity by 0.322-1.402 mS/cm and reduced C/N by 56.16-64.73 %. The NH₄⁺:NO₃^- ratio of the final faecal sludge and carbon-rich waste was <0.16. The seed germination index was higher than 80 %. These results indicate that earthworms contribute to faecal sludge maturation. Earthworm addition reduced CO₂ production. The simultaneous addition of earthworms and RS system (FRS2) resulted in the lowest global warming potential (GWP). The microbial diversity increased significantly over time in the RS-only system, whereas it initially increased and later decreased in the FRS2 system. Cluster analysis revealed that earthworms had a more significant impact on the microbial community than the addition of carbon-rich waste. Co-occurrence networks for earthworm-based systems were simple than those for earthworm-free systems, but the major bacterial genera were more complicated. Highly abundant key species (norank_f_Chitinophagaceae and norank_f_Gemmatimonadaceae) are closely related. Microbes may be more cooperative than competitive, facilitating the conversion of carbon and nitrogen in earthworm-based systems. This work has demonstrated that using earthworms is an effective approach for promoting the efficiency of faecal sludge composting and reducing GWP.

Dynamic changes of microbial community and moisture ratio during bio-drying of sludge after electro-dewatering

Using electro-dewatering as the pretreatment process for sludge bio-drying can improve the dewatering performance. It was innovatively investigated including the microbial mechanism and the kinetics of moisture removal by bio-drying with electro-dewatered sludge in this study. Two bio-drying processes using electro-dewatered sludge (EDS) and sludge added cornstalk conditioner (CSS) were compared. Microbial community analysis showed that the abundance of Bacteroidetes increased from 4.21% to 16.67% after electro-dewatering. The dominant phyla were Bacteroidetes (36.79%), Proteobacteria (32.35%), and Actinobacteria (24.58%) at the end of EDS bio-drying. Network analysis revealed that the co-occurrence patterns in EDS included 40 nodes and 97 edges. The prediction results of the Kyoto Encyclopedia of Genes and Genomes demonstrated that the relative abundances of carbohydrate metabolism and metabolism of terpenoids and polyketides in sludge decreased, while the relative abundances of lipid metabolism, xenobiotic biodegradation and metabolism increased after electro-dewatering. Five thin layer drying kinetic models were analyzed to estimate the bio-drying kinetic parameters. The Page's model could be better fitted to the results and the highest R² was 0.9570 in the EDS. The new coefficients k (0.1637) and n (1.2097) were obtained. The results provided mechanism and data support for exploring and applying bio-drying technology after sludge electro-dewatering.

Metagenomics analysis of the effects of Agaricus bisporus mycelia on microbial diversity and CAZymes in compost

Agaricus bisporus growth alters the lignocellulosic composition and structure of compost. However, it is difficult to differentiate the enzyme activities of A. bisporus mycelia from the wider microbial community owing to the complication of completely speareting the mycelia from compost cultures. Macrogenomics analysis was employed in this study to examine the fermentation substrate of A. bisporus before and after mycelial growth, and the molecular mechanism of substrate utilization by A. bisporus mycelia was elucidated from the perspective of microbial communities and CAZymes in the substrate. The results showed that the relative abundance of A. bisporus mycelia increased by 77.57-fold after mycelial colonization, the laccase content was significantly increased and the lignin content was significantly decreased. Analysis of the CAZymes showed that AA10 family was extremely differentiated. Laccase-producing strains associated with AA10 family were mostly bacteria belonging to Thermobifida and Thermostaphylospora, suggesting that these bacteria may play a synergistic role in lignin decomposition along with A. bisporus mycelia. These findings provide preliminary evidence for the molecular mechanism of compost utilization by A. bisporus mycelia and offer a reference for the development and utilization of strains related to lignocellulose degradation.

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.

Evaluation of fungal community assembly and function during food waste composting with Aneurinibacillus sp. LD3 inoculant

The objective of this work was to evaluate the fungal community assembly and function during food waste composting with Aneurinibacillus sp. LD3 (LD3) inoculant. Inoculation reduced the content of total organic carbon, moisture content, nitrate nitrogen, and nitrite nitrogen. The LD3 inoculant was able to drive the changes in the assembly of the fungal community. In particular, inoculation with LD3 not only increased the relative abundance of Ascomycota and Trichocomaceae_unclassified for lignocellulose degradation at the mesophilic and cooling stages but also reduced the relative abundances of the opportunistic human pathogen Candida. Saprotroph was the predominant fungal trophic mode in composting, and inoculation with LD3 has a better inactivation effect on animal and plant pathogenic fungi during composting. Furthermore, the variation of the fungal community after inoculation with LD3 was the largest explained by temperature (30.64%). These results implied that LD3 significantly regulated fungal composition and function of food waste composting.

Insight into the fraction variations of selenium and their effects on humification during composting

This study investigated the variation of selenium fractions and their effects on humification during composting. Selenite and selenate were added to a mixture of goat manure and wheat straw for composting. The results demonstrated that the bioavailable Se in the selenite added treatment (9.3-13.8%) was lower than in the selenate added treatment (18.1-47.3%). Meanwhile, the HA/FA of selenite and selenate added treatments were higher than in control, indicating that the selenium addition (especially selenite) promoted the humification of composting. Importantly, selenite enriched the abundance of Tepidimicrobium and Virgibacillus which were responsible to improve humification performance. Selenate increased the abundance of Thermobifida and Cellvibrio which facilitated the composting humification. The genes encoding CAZymes involved in the degradation of organic materials were also analyzed, and selenium could contribute to the synthesis of humus. KEGG pathway analysis revealed that the selenite addition promoted amino acids and carbohydrate metabolism compared to the control.

Analysis of Microbial Community Diversity on the Epidermis of Wine Grapes in Manasi’s Vineyard, Xinjiang

Epiphytic microbial communities significantly impact the health and quality of grape berries. This study utilized high-performance liquid chromatography and high-throughput sequencing to explore the epiphytic microbial diversity and physicochemical indicators in nine different wine grape varieties. In total, 1,056,651 high-quality bacterial 16S rDNA sequences and 1,101,314 fungal ITS reads were used for taxonomic categorization. Among the bacteria, Proteobacteria and Firmicutes were the dominant phyla, and Massilia, Pantoea, Pseudomonas, Halomonas, Corynebacterium, Bacillus, Anaerococcus, and Acinetobacter were the dominant genera. Among the fungi, Ascomycota and Basidiomycota were the dominant phyla, and Alternaria, Filobasidium, Erysiphe, Naganishia, and Aureobasidium were the dominant genera. Notably, Matheran (MSL) and Riesling (RS) exhibited the highest microbial diversity among the nine grape varieties. Moreover, pronounced differences in epiphytic microorganisms in red and white grapes suggested that the grape variety significantly influences the structure of surface microbial communities. Understanding the composition of epiphytic microorganisms on the grape skin can provide a direct guide to winemaking.

Micro-aerobic conditions based on membrane-covered improves the quality of compost products: Insights into fungal community evolution and dissolved organic matter characteristics

This study investigated the effects of micro-aerobic conditions on fungal community succession and dissolved organic matter transformation during dairy manure membrane-covered composting. The results showed that lignocellulose degradation in the micro-aerobic composting group (AC: oxygen concentration < 5 %) was slower than that in the static composting group (SC: oxygen concentration < 1 %), but the dissolved organic carbon in AC was greatly increased. The degree of aromatic polymerization was higher in AC than in SC. But the carboxyl carbon and alcohol/ether biodegradations were faster in SC than in AC, which promoted carbon dioxide and methane emissions, respectively. The relative abundances of pathogenic and dung saprotrophic fungi in AC were 44.6 % and 10.59 % lower than those in SC on day 30, respectively. Moreover, the relative abundance of soil saprotrophs increased by 5.18 % after micro-aerobic composting. Therefore, micro-aerobic conditions improved the quality of compost products by influencing fungal community evolution and dissolved organic matter transformation.

Effect of inoculation with newly isolated thermotolerant ammonia-oxidizing bacteria on nitrogen conversion and microbial community during cattle manure composting

Nitrogen loss during composting is closely related to NH₄⁺-N conversion, and ammonia-oxidizing bacteria (AOB) are important microorganisms that promote NH₄⁺-N conversion. Since the biological activity of conventional AOB agents used for compost inoculation declines rapidly during the thermophilic phase of composting, new compound inoculants should be developed that are active during that phase. In the current study, the effects of inoculating cattle manure compost with newly isolated AOB (5%, v/w) [thermotolerant AOB X-2 strain (T-AOB-2), mesophilic AOB X-4 strain (M-AOB-4), and AOB X-2 combined with AOB X-4 (MT-AOB-2-4)] on the conversion of nitrogen, compost maturity, and the resident microbial community were studied. During 35 days of composting, compared with the control, AOB inoculation reduced NH₃ emissions by 29.98-46.94%, accelerated the conversion of NH₄⁺-N to NO₂^--N, increased seed germination values by 13.00-25.90%, and increased the abundance of the microbial community at the thermophilic phase (16.38-68.81%). Network analysis revealed that Bacillaceae play a crucial role in the composting process, with the correlation coefficients: 0.83 (p < 0.05) with NH₃, 0.64 (p < 0.05) with NH₄⁺-N, and 0.81 (p < 0.05) with NO₂^--N. In addition, inoculation with MT-AOB-2-4 notably increased the total nitrogen content of compost, prolonged the sanitation stage, and promoted compost maturity. Hence, MT-AOB-2-4 may be used to increase the microbial community abundance and improve the efficiency of cattle manure composting.

Insight into the microbial mechanisms for the improvement of composting efficiency driven by Aneurinibacillus sp. LD3

This work explored the microbial mechanisms for the improvement of composting efficiency driven by thermotolerant lignin-degrading bacterium Aneurinibacillus sp. LD3 (LD3). Results showed that LD3 inoculant prolonged the thermophilic period by 4 days, improved the final content of humic acid, total phosphorus (TP), nitrogen, potassium and seed germination index. Inoculating LD3 enhanced the relative abundance of thermotolerant and phosphate-solubilizing microbes including the phyla of Proteobacteria, Bacteroidota, Firmicutes, and Actinobacteriota, and the genus of Bacillus, Thermoactinomyces, and Pseudomonas. Metabolic function analysis showed that sequences involved in carbohydrate and amino acid metabolism were boosted, while sequences associated with human disease were reduced after inoculating LD3. Spearman correlation analysis revealed that Aneurinibacillus has a significant positive correlation with temperature, TP, Bacillus, and Thermoactinomyces. This study provides useful information for understanding the microbial mechanisms of LD3 promoting composting efficiency, and reveals the tremendous potential of LD3 in the resource utilization of organic solid wastes.

Effects of exogenous cellulose-degrading bacteria on humus formation and bacterial community stability during composting

This study aimed to reveal the potential mechanism of influence exogenous cellulose-degrading bacteria (ECDB) exerted on humus synthesis during the co-composting of corn straw and cattle manure. By measuring the changes in physicochemical factors and bacterial communities, it was revealed that inoculation with ECDB enhanced the driving force of cellulose degradation and humus synthesis. ECDB not only directly participated in cellulose degradation as degrading bacteria, but also changed the bacterial community succession, and increased the abundance of bacterial communities associated with cellulose degradation. The results showed that ECDB stimulated the potential functions and interactions of bacterial communities. Structural equation modeling confirmed that ECDB acted mainly as a bioactivator to promote humus formation in co-composting of corn straw and cattle manure. Taken together, these findings offered new strategies which can be effectively utilized to increase the efficiency and quality of corn straw composting.

Succession of Microbial Community during the Co-Composting of Food Waste Digestate and Garden Waste

Microorganisms are of critical importance during the composting process. The aim of this study was to reveal the bacterial and fungal compositions of a composting pile of food waste digestate and garden waste, where the succession of the microbial communities was monitored using Illumina MiSeq sequencing. We explored the efficiency of composting of different microorganisms to judge whether the composting system was running successfully. The results showed that the composting process significantly changed the bacterial and fungal structure. Firmicutes, Proteobacteria, and Bacteroidota were the dominant phyla of the bacterial communities, while Ascomycota was the dominant phylum of the fungal communities. Moreover, the highest bacterial and fungal biodiversity occurred in the thermophilic stage. The physical and chemical properties of the final compost products conformed to the national standards of fertilizers. The efficient composting functional microbes, including Cladosporium, Bacillus and Saccharomonospora, emerged to be an important sign of a successfully operating composting system.

Succession of the Bacterial Communities and Functional Characteristics in Sheep Manure Composting

Bacterial community is a key factor affecting aerobic composting, and understanding bacterial community succession is important to revealing the mechanism of organic matter degradation. In this study, the succession and metabolic characteristics of bacterial communities were explored in 45 days composting of sheep manure and wheat straw by using high-throughput sequencing technology and bioinformatics tools, respectively. Results showed that the alpha diversity of bacterial community significantly decreased in the thermophilic (T2) phase and then recovered gradually in the bio-oxidative (T3) and the maturation (T4) phases. Bacterial communities varied at different stages, but there were 158 genera in common bacterial species. Unclassified_f_Bacillaceae, Oceanobacillus, Bacillus, Pseudogracilibacillus, and Nocardiopsis were identified as keystone bacterial genera. Eleven genera were significantly correlated (p < 0.05), or even extremely significantly correlated (p < 0.001), with the physicochemical factors. Redundancy analysis (RDA) showed that changes of bacterial community diversity correlated with physicochemical factors. The highest relative abundances were amino acid and carbohydrate metabolism among the metabolic groups in the compost. These results will provide theoretical support for further optimizing sheep manure composting conditions and improving the quality of organic fertilizers.

Biochars modify the degradation pathways of dewatered sludge by regulating active microorganisms during gut digestion of earthworms

Biochar can accelerate the degradation and mineralization of organic matter during vermicomposting of sludge and the resulted vermicompost is termed as vermi-char containing active enzymes and microorganisms. However, the mechanisms by which biochars affect vermicomposting of the dewatered sludge during gut digestion of earthworms remain unclear. This study aimed to investigate the effects of biochar on the degradation pathways of organic matter and the involved active microorganisms in dewatered sludge during gut digestion of earthworms. The earthworms Eisenia fetida were fed on three sludge substrates; 1) sludge mixed with 5% corncob biochar, 2) sludge mixed 5% rice husk biochar, and 3) sludge without biochar. The results showed that dissolved organic carbon significantly decreased by 5.65%-21.81% after the 5-day gut digestion of earthworms (P < 0.05) and that biochar addition could accelerate the decomposition of aromatic protein-like substances. Contrarily, the nitrate in earthworms casting with biochars significantly increased by 47.32%-122.64% (P < 0.05) compared with the control. The numbers of active bacteria and eukaryotes in earthworm castings with biochars significantly enhanced by 1.34-1.45 times and 0.45-5.91 times, respectively, than the control (P < 0.05). Active Actinobacteria and Bacteroidetes dominated the castings with biochars significantly enriched by 76.18%-88.83% and 4.02%-18.59% (P < 0.05), respectively, compared to control. As for eukaryotes, the biochars amendment increased Cercozoa abundance by 114.23%-136.31% but decreased Annelida by 55.61%-75.88% in the castings. The partial least squares path model revealed that the biochars could change the content and structure of organic matter in earthworm castings during vermicomposting of sludge by affecting environmental factors, microbial abundance, and microbial community composition.

Feasibility of sewage sludge and food waste aerobic co-composting: Physicochemical properties, microbial community structures, and contradiction between microbial metabolic activity and safety risks

Co-composting of sludge and food waste eliminates the disadvantages of composting these waste products separately. Specifically, co-composing neutralizes the pollutants and improves the organic matter that occur in sewage sludge, and solves the problem of the low pH values and high moisture content of food waste. However, little is known about the functional microorganisms, microbial metabolic capacity, and biosecurity risks involved in sewage sludge and food waste co-composting. Therefore, this study established four lab-scale composting reactors [T1 (separate composting of food waste), T2 (separate composting of sewage sludge), T3 (sewage sludge and food waste co-composting at a C/N ratio of 25), and T4 (equal proportions composting of sewage sludge and food waste)] to assess the feasibility of sewage sludge and food waste aerobic co-composting. Our findings indicated that polysaccharides and proteins in T3 could be effectively degraded, and the total nutrient levels in T3 were higher than those in the other groups. After composting, the microbial diversity and richness of T3 were higher than that of T1. In later composting stages, the functional microorganisms in T1 maintained higher metabolic activity, however, it also had a higher biosecurity risk than T3 due to the presence of pathogenic bacteria such as Enterococcus_faecalis and Bacillus_circulan. Although the product of T3 could not be used as a microbial fertilizer, its biosecurity risk was lower than that of T1 and could therefore be used as an organic fertilizer. Redundancy analysis (RDA) results indicated that changing the microbial community structure by adjusting key environmental factors could improve composting quality and reduce microbial safety risks. Collectively, our results provide a theoretical basis for the development of co-composting strategies for the biodegradation of perishable solid organic waste, in addition to proposing the risk of pathogenic bacteria exposure that could endanger human and animal health.

Sustainability of the rice-crayfish co-culture aquaculture model: microbiome profiles based on multi-kingdom analyses

While the rice-crayfish culture (RCFP) model, an important aquaculture model in Asia, is generally considered a sustainable model, its sustainability in terms of microbial community profiles has not been evaluated. In this study, multi-kingdom analyses of microbiome profiles (i.e., bacteria, archaea, viruses, and eukaryotes) were performed using environmental (i.e., water and sediment) and animal gut (i.e., crayfish and crab gut) microbial samples from the RCFP and other aquaculture models, including the crab-crayfish co-culture, crayfish culture, and crab culture models, to evaluate the sustainability of the RCFP systematically. Results showed that RCFP samples are enriched with a distinct set of microbes, including Shewanella, Ferroplasma, Leishmania, and Siphoviridae, when compared with other aquaculture models. Additionally, most microbes in the RCFP samples, especially microbes from different kingdoms, were densely and positively connected, which indicates their robustness against environmental stress. Whereas microbes in different aquaculture models demonstrated moderate levels of horizontal gene transfer (HGT) across kingdoms, the RCFP showed relatively lower frequencies of HGT events, especially those involving antibiotic resistance genes. Finally, environmental factors, including pH, oxidation-reduction potential, temperature, and total nitrogen, contributed profoundly to shaping the microbial communities in these aquaculture models. Interestingly, compared with other models, the microbial communities of the RCFP model were less influenced by these environmental factors, which suggests that microbes in the latter have stronger ability to resist environmental stress. The findings collectively reflect the unique multi-kingdom microbial patterns of the RCFP model and suggest that this model is a sustainable model from the perspective of microbiome profiles.

Addition of mature compost improves the composting of green waste

Composting is an environmentally friendly and effective way to dispose of green waste (GW), but traditional composting of GW is slow and results in the loss of many nutrients and a poor-quality compost product. In this study, mature compost (MC), which may function as an inexpensive and readily available microbial inoculant, was added to GW at 15, 20, 25, and 30% (w/w, dry weight basis) (treatments T2-T5, respectively); GW with 0.5% (v/w, dry weight basis) commercial microbial inoculum served as T1, and GW without any microbial inoculant served as the control. The treatment that produced the highest quality compost was determined based on the following compost properties: temperature, bulk density, porosity, pH, electric conductivity, contents of organic matter and nutrients, Fourier-transform infrared spectroscopy data, and phytotoxicity. The results showed that addition of 25% MC resulted in the best quality product in only 40 days.

Improving the humification and phosphorus flow during swine manure composting: A trial for enhancing the beneficial applications of hazardous biowastes

Improving the recovery of organic matter and phosphorus (P) from hazardous biowastes such as swine manure using acidic substrates (ASs) in conjunction with aerobic composting is of great interest. This work aimed to investigate the effects of ASs on the humification and/or P migration as well as on microbial succession during the swine manure composting, employing multivariate and multiscale approaches. Adding ASs, derived from wood vinegar and humic acid, increased the degree of humification and thermal stability of the compost. The ³¹P nuclear magnetic resonance spectroscopy and X-ray absorption near-edge structure analyses demonstrated compost P was in the form of struvite crystals, Ca/Al-P phases, and Poly-P (all inorganic P species) as well as inositol hexakisphosphate and Mono-P (organophosphorus species). However, the efficiency of P recovery could be improved by generating more struvite by adding the ASs. The flows among nutrient pools resulted from the diversity in the dominant microbial communities in different composting phases after introducing the ASs and appearance of Bacillus spp. in all phases. These results demonstrate the potential value of ASs for regulating and/or improving nutrients flow during the composting of hazardous biowastes for producing higher quality compost, which may maximize their beneficial benefits and applications.

Enhanced bio-reductive degradation of fluoroglucocorticoids in the groundwater fluctuation zone by external electron donors: Performance, microbial community, and functional genes

This study evaluated the effectiveness of external electron donors on the bio-reductive degradation enhancement of fluoroglucocorticoids (FGCs) in the groundwater fluctuation zone during the wet season when reverse upward fluctuation of the groundwater table occurs and the dry season after the groundwater table declines. The results showed that the external electron donors, provided by the addition of nano zero-valent iron-modified biochar (nZVI@BC), inhibited the migration and enhanced the reductive defluorination of triamcinolone acetonide (TA), a representative FGC. The accumulation rate constant with temporal fluctuation depth and the attenuation rate constant with vertical fluctuation depth were -2.55 × 10^-3 and 4.20 × 10^-2, respectively, in the groundwater of the natural groundwater fluctuation zone (N-FZ). In contrast, the accumulation and attenuation rate constants were, respectively, 35.6% and 2.64 times higher in the groundwater fluctuation zone amended with nZVI@BC (nZVI@BC-FZ) as compared with those observed in the N-FZ. Furthermore, the decay rate constant of the TA residue in the dry season was 0.843 × 10^-2 μg/d in N-FZ and was 2.19 times higher in nZVI@BC-FZ. This enhancement effect, caused by the addition of external electrons, was positively correlated with the evolution of the microbial community and the expression of functional genes. The microbes evolved into functional genera with reductive dehalogenation (Xylophilus and Hydrogenophaga) and iron-oxidizing (Lysobacter, Pseudoxanthomonas, and Sphingomonas) abilities in the nZVI@BC-FZ system, which increased dehalogenation and iron oxide genes by a 4-5 order of magnitude. The utilization proportion of external electrons for TA metabolism was 50.04%, of which 30.82%, 10.26%, and 8.96% were utilized for defluorination, hydrogenation, and ring-opening, respectively. This study provides an effective method to reduce pollutant diffusion and enhance the bio-reductive degradation caused by groundwater table fluctuation.

Effects of further composting black soldier fly larvae manure on toxic metals and resistant bacteria communities by cornstalk amendment

Rapid composting by black soldier fly larvae (BSFL) may be insufficient to maturation and humification of composting and further composting is necessary. The purpose of this study was to explore cornstalk addition on toxic metals (Cu, Zn, Pb and Cd), toxic metals resistance bacterial (TMRB) destiny and their relationship with physicochemical factors during BSFL manure composting. High-throughput sequencing was performed by six treatments, namely T1 to T6, where T1 to T3 were BSFL manures from chicken, pig and dairy manure, respectively, and T4 to T6 were same manures and utilized cornstalk to adjust C/N to 25. The results showed that cornstalk amendment could enhance the toxic metals immobilization rate compared to control treatments in the ultimate product. TMRB indicated that the major potential hosts bacteria were Firmicutes, Bacteroidota, Proteobacteria, Acidobacteriota and Actinobacteriota, and the sum relative abundance were 63.33%, 90.62%, 83.62%, 69.38%, 50.66% and 90.52% in T1 to T6 at the end of composting. Bacteria diversity and heat map revealed composting micro-ecology with additive cornstalk to remarkably effect main resistant bacterial distribution via adjusting environmental factors and potential hosts bacterial. Finally, T5 treatment was able to greatly decrease the TMRB abundance, and improve the ability of composting and ultimate product quality.

Impact of bamboo sphere amendment on composting performance and microbial community succession in food waste composting

The purpose of this study was to find an economical and effective amendment for improving composting performance and product quality, as well as to analyze the microbial community succession in the whole phase of composting. Therefore, the effect of reusable amendment bamboo sphere on composting performance and microbial community succession during food waste composting was investigated. The results showed that 6% bamboo sphere treatment had the highest degree of polymerization (3.7) and humification index (0.18). Compared with control, 6% bamboo sphere amendment increased total nitrogen (TN), phosphorus (TP) and potassium (TK) contents by 13.61%, 19% and 17.42%, respectively. Furthermore, bamboo sphere enhanced bacterial-fungal diversity and improved microbial community composition by enhancing the relative abundance of thermo-tolerance and lignocellulolytic bacteria and fungi. The five most abundant genera in bamboo sphere composting comprised Bacillus (0-71.47%), Chloroplast-norank (0-47.17%), Pusillimonas (0-33.24%), Acinetobacter (0-27.98%) and unclassified Sphingobacteriaceae (0-22.62%). Linear discriminant analysis effect size showed that Firmicutes, Thermoascaceae and Actinobacteriota, which have a relationship with the decomposition of soluble organic matter and lignocellulose, were significantly enriched in bamboo sphere treatment. Canonical correspondence analysis illustrated that total organic carbon (TOC), TK, and TP were the most important environmental factors on microbial community succession in the two composting systems. Together these results suggest that bamboo sphere as a reusable amendment can shorten maturity period, improve humification degree, increase the contents of nutrient and contribute to the succession of microbial community during food waste composting. These findings provide a theoretical basis for improving the efficiency of food waste composting.