Prediction of compost organic matter via color sensor.

Composted materials serve as an effective soil nutrient amendment. Organic matter in compost plays an important role in quantifying composted materials overall quality and nutrient content. Measuring organic matter content traditionally takes considerable time, resources, and various laboratory equipment (e.g., oven, muffle furnace, crucibles, precision balance). Much like the quantitative color indices (e.g., sRGB R, sRGB G, sRGB B, CIEL*a* b*) derived from the low-cost NixPro2 color sensor have proven adept at predicting soil organic matter in-situ, the NixPro2 color sensor has the potential to be effective for predicting organic matter in composted materials without the need for traditional laboratory methods. In this study, a total of 200 compost samples (13 different compost types) were measured for organic matter content via traditional loss-on-ignition (LOI) and via the NixPro2 color sensor. The NixPro2 color sensor showed promising results with an LOI-prediction model utilizing the CIEL*a* b* color model through the application of the Generalized Additive Model (GAM) algorithm yielding an excellent prediction accuracy (validation R2 = 0.87, validation RMSE = 4.66 %). Moreover, the PCA scoreplot differentiated the three lowest organic matter compost types from the remaining 10 compost types. These results have valuable practical significance for the compost industry by predicting compost organic matter in real time without the need for laborious, time-consuming methods.

Incorporation of compost and biochar enhances yield and medicinal compounds in seeds of water-stressed Trigonella foenum-graecum L. plants cultivated in saline calcareous soils.

BACKGROUND: The combination of compost and biochar (CB) plays an important role in soil restoration and mitigation strategies against drought stress in plants. In the current study, the impact of CB was determined on the characteristics of saline calcareous soil and the productivity of fenugreek (Trigonella foenum-graecum L.) plants. The field trials examined CB rates (CB0, CB10 and CB20 corresponding to 0, 10, and 20 t ha‒1, respectively) under deficit irrigation [DI0%, DI20%, and DI40% receiving 100, 80, and 60% crop evapotranspiration (ETc), respectively] conditions on growth, seed yield (SY), quality, and water productivity (WP) of fenugreek grown in saline calcareous soils. RESULTS: In general, DI negatively affected the morpho-physio-biochemical responses in plants cultivated in saline calcareous soils. However, amendments of CB10 or CB20 improved soil structure under DI conditions. This was evidenced by the decreased pH, electrical conductivity of soil extract (ECe), and bulk density but increased organic matter, macronutrient (N, P, and K) availability, water retention, and total porosity; thus, maintaining better water and nutritional status. These soil modifications improved chlorophyll, tissue water contents, cell membrane stability, photosystem II photochemical efficiency, photosynthetic performance, and nutritional homeostasis of drought-stressed plants. This was also supported by increased osmolytes, non-enzymatic, and enzymatic activities under DI conditions. Regardless of DI regimes, SY was significantly (P ≤ 0.05) improved by 40.0 and 102.5% when plants were treated with CB10 and CB20, respectively, as similarly observed for seed alkaloids (87.0, and 39.1%), trigonelline content (43.8, and 16.7%) and WP (40.9, and 104.5%) over unamended control plants. CONCLUSIONS: Overall, the application of organic amendments of CB can be a promising sustainable solution for improving saline calcareous soil properties, mitigating the negative effects of DI stress, and enhancing crop productivity in arid and semi-arid agro-climates.

Optimizing biochar, vermicompost, and duckweed amendments to mitigate arsenic uptake and accumulation in rice (Oryza sativa L.) cultivated on arsenic-contaminated soil.

The accumulation of arsenic (As) in rice (Oryza sativa L.) grain poses a significant health concern in Bangladesh. To address this, we investigated the efficacy of various organic amendments and phytoremediation techniques in reducing As buildup in O. sativa. We evaluated the impact of five doses of biochar (BC; BC0.1: 0.1%, BC0.28: 0.28%, BC0.55: 0.55%, BC0.82: 0.82% and BC1.0: 1.0%, w/w), vermicompost (VC; VC1.0: 1.0%, VC1.8: 1.8%, VC3.0: 3.0%, VC4.2: 4.2% and VC5.0: 5.0%, w/w), and floating duckweed (DW; DW100: 100, DW160: 160, DW250: 250, DW340: 340 and DW400: 400 g m- 2) on O. sativa cultivated in As-contaminated soil. Employing a three-factor five-level central composite design and response surface methodology (RSM), we optimized the application rates of BC-VC-DW. Our findings revealed that As contamination in the soil negatively impacted O. sativa growth. However, the addition of BC, VC, and DW significantly enhanced plant morphological parameters, SPAD value, and grain yield per pot. Notably, a combination of moderate BC-DW and high VC (BC0.55VC5DW250) increased grain yield by 44.4% compared to the control (BC0VC0DW0). As contamination increased root, straw, and grain As levels, and oxidative stress in O. sativa leaves. However, treatment BC0.82VC4.2DW340 significantly reduced grain As (G-As) by 56%, leaf hydrogen peroxide by 71%, and malondialdehyde by 50% compared to the control. Lower doses of BC-VC-DW (BC0.28VC1.8DW160) increased antioxidant enzyme activities, while moderate to high doses resulted in a decline in these activities. Bioconcentration and translocation factors below 1 indicated limited As uptake and translocation in plant tissues. Through RSM optimization, we determined that optimal doses of BC (0.76%), VC (4.62%), and DW (290.0 g m- 2) could maximize grain yield (32.96 g pot- 1, 44% higher than control) and minimize G-As content (0.189 mg kg- 1, 54% lower than control). These findings underscore effective strategies for enhancing yield and reducing As accumulation in grains from contaminated areas, thereby ensuring agricultural productivity, human health, and long-term sustainability. Overall, our study contributes to safer food production and improved public health in As-affected regions.

Optimizing wheat productivity through integrated management of irrigation, nutrition, and organic amendments.

Enhancing wheat productivity by implementing a comprehensive approach that combines irrigation, nutrition, and organic amendments shows potential for collectively enhancing crop performance. This study examined the individual and combined effects of using irrigation systems (IS), foliar potassium bicarbonate (PBR) application, and compost application methods (CM) on nine traits related to the growth, physiology, and yield of the Giza-171 wheat cultivar. Analysis of variance revealed significant (P ≤ 0.05) main effects of IS, PBR, and CM on wheat growth, physiology, and yield traits over the two growing seasons of the study. Drip irrigation resulted in a 16% increase in plant height, leaf area index, crop growth rate, yield components, and grain yield compared to spray irrigation. Additionally, the application of foliar PBR at a concentration of 0.08 g/L boosted these parameters by up to 22% compared to the control. Furthermore, the application of compost using the role method resulted in enhanced wheat performance compared to the treatment including mix application. Importantly, the combined analysis revealed that the three-way interaction between the three factors had a significant effect (P ≤ 0.05) on all the studied traits, with drip irrigation at 0.08 g PBR rate and role compost application method (referred as Drip_0.08g_Role) resulting in the best performance across all traits, while sprinkle irrigation without PBR and conventional mixed compost method (referred as sprinkle_CK_Mix) produced the poorest results. This highlights the potential to synergistically improve wheat performance through optimized agronomic inputs.

Molecular insights into effects of chemical conditioning on dissolved organic phosphorus transformation and bioavailability during sludge composting.

Phosphorus is enriched in waste activated sludge (WAS) during wastewater treatment, and organic phosphorus (OP) is a potential slow-release P fertilizer. The chemical coagulants used in sludge dewatering leave numerous residues in WAS that affect sludge composting. In this study, the effects of polyaluminum chloride (PAC) and polyferric sulfate (PFS) on the bioconversion of dissolved OP (DOP) during sludge composting were investigated. The results revealed that PFS conditioning promoted the transformation and bioavailability of DOP, whereas PAC conditioning inhibited. Results indicated that PFS conditioning enhanced the transformation of OP molecules in the thermophilic phase. Through oxidation and dehydrogenation reactions, 1-hydroxy-pentane-3,4-diol-5-phosphate and D-ribofuranose 5-phosphate with high bioactivity were generated in the PFS-conditioned compost. Enzymatic hydrolysis experiments further verified that PFS conditioning enhanced the DOP bioavailability in the compost, whereas PAC conditioning inhibited it. The study has provided molecular insights into the effects of chemical conditioning on DOP conversion during sludge composting.

Upgrade from aerated static pile to agitated bed systems promotes lignocellulose degradation in large-scale composting through enhanced microbial functional diversity.

Composting presents a viable management solution for lignocellulose-rich municipal solid waste. However, our understanding about the microbial metabolic mechanisms involved in the biodegradation of lignocellulose, particularly in industrial-scale composting plants, remains limited. This study employed metaproteomics to compare the impact of upgrading from aerated static pile (ASP) to agitated bed (AB) systems on physicochemical parameters, lignocellulose biodegradation, and microbial metabolic pathways during large-scale biowaste composting process, marking the first investigation of its kind. The degradation rates of lignocellulose including cellulose, hemicellulose, and lignin were significantly higher in AB (8.21%-32.54%, 10.21%-39.41%, and 6.21%-26.78%) than those (5.72%-23.15%, 7.01%-33.26%, and 4.79%-19.76%) in ASP at three thermal stages, respectively. The AB system in comparison to ASP increased the carbohydrate-active enzymes (CAZymes) abundance and production of the three essential enzymes required for lignocellulose decomposition involving a mixture of bacteria and fungi (i.e., Actinobacteria, Bacilli, Sordariomycetes and Eurotiomycetes). Conversely, ASP primarily produced exoglucanase and ß-glucosidase via fungi (i.e., Ascomycota). Moreover, AB effectively mitigated microbial stress caused by acetic acid accumulation by regulating the key enzymes involved in acetate conversion, including acetyl-coenzyme A synthetase and acetate kinase. Overall, the AB upgraded from ASP facilitated the lignocellulose degradation and fostered more diverse functional microbial communities in large-scale composting. Our findings offer a valuable scientific basis to guide the engineering feasibility and environmental sustainability for large-scale industrial composting plants for treating lignocellulose-rich waste. These findings have important implications for establishing green sustainable development models (e.g., a circular economy based on material recovery) and for achieving sustainable development goals.

Insights into effects of thermotolerant nitrifying and sulfur-oxidizing inoculants on nitrogen-sulfur co-metabolism in sewage sludge composting.

In this study, high temperature thermotolerant nitrifying bacteria (TNB) and high temperature thermotolerant sulfide oxidizing bacteria (TSOB) were obtained from compost samples and inoculated into sewage sludge (SS) compost. The effects of inoculation on physical and chemical parameters, ammonia and hydrogen sulfide release, nitrogen form and sulfur compound content change and physical-chemical properties during nitrogen and sulfur conversion were studied. The results showed that inoculation of TNB and TSOB increased the temperature, pH, OM degradation, C/N ratio and germination index (GI) of compost. Compared with the control treatment (CK), the addition of inoculants reduced the release of NH3 and H2S, and transformed them into nitrogen and sulfur compounds, the hydrolysis of polymeric ferrous sulfate was promoted, resulting in relatively high content of sulfite and sulfate. At the same time, the physical and chemical properties of SS have a strong correlation with nitrogen and sulfur compounds.

Micro-positive pressure significantly decreases greenhouse gas emissions by regulating archaeal community during industrial-scale dairy manure composting.

In this study, the effects of micro-positive pressure formed by covering with a semipermeable membrane in the heating phase of dairy manure composting on greenhouse gas emissions and the mechanism of reducing methane emissions by the archaeal community were investigated. A large-scale experiment was conducted with semipermeable membrane-covered composting (SMC), forced aeration composting (FAC), and traditional static composting (TSC) groups. The results showed that the oxygen concentration and methanogen abundance were key factors in regulating methane emissions. In the heating phase of SMC, the micro-positive pressure could enhance the O2 utilization rate and heating rate, resulting in Methanobrevibacter and Methanobacterium greatly decreasing, and the abundance of mcrA decreased by 90.03%, while that of pmoA did not increase. Compared with FAC and TSC, the cumulative methane emissions in SMC decreased by 51.75% and 96.04%, respectively. Therefore, the micro-positive pressure could effectively reduce greenhouse gas emissions by inhibiting the growth of methanogens.

Bioconversion of cow manure through vermicomposting: effects of tylosin concentration on the weight of worms and manure quality.

This study investigated batch-fed vermicomposting of cow manure, with a specific focus on assessing the effects of tylosin on the weight of earthworms and the overall quality of the resulting manure. Five reactors, including three concentrations of tylosin (50, 100, and 150 mg/kg) and two control reactors, were employed. Residual tylosin concentrations were measured using high-performance liquid chromatography (HPLC). Quality parameters such as pH, temperature, volatile solids (VS), organic carbon content (OCC), electrical conductivity (EC), ash content, C/N ratio, total Kjeldahl nitrogen (TKN), and microbial content were evaluated. The toxicity and maturity of vermicompost were assessed by determining the germination index (GI). The study also monitored variations in the earthworm's weight. The results demonstrated a decreasing trend in VS, OCC, C/N, and fecal coliforms, along with increased pH, EC, ash content, and TKN during the vermicomposting process. Furthermore, investigations revealed significant reductions in the reactors with tylosin concentrations of 50, 100, and 150 mg/kg, resulting in the removal of 98%, 90.48%, and 89.38% of the initial tylosin, respectively. This result confirms the faster removal of tylosin in reactors with lower concentrations. Degradation of tylosin also conforms to first-order kinetics. The findings showed a significant influence of tylosin on the weight of Eisenia fetida earthworms and the lowest antibiotic concentration led to the highest weight gain. Finally, the high percentage of germination index (90-100%) showed that the quality and maturity of vermicompost is by national and international standards.

Characteristics of humification, functional enzymes and bacterial community metabolism during manganese dioxide-added composting of municipal sludge.

The aim of this study was to assess effects of MnO2 addition (CK-0%, T1-2% and T2-5%) on humification and bacterial community during municipal sludge (MS) composting. The results suggested that MnO2 addition inhibited the growth of Nitrospira but stimulated Nonomuraea, Actinomadura, Streptomyces and Thermopolyspora, facilitating the lignocellulose degradation and humification with the increase in organic matter degradation by 13.8%-19.2% and humic acid content by 10.9%-20.6%. Compared to CK, the abundances of exoglucanase (EC:3.2.1.91), endo-1,4-beta-xylanase (EC:3.2.1.136) and endomannanase (EC:3.2.1.78) increased by 88-99, 52-66 and 4-15 folds, respectively. However, 5%-MnO2 induced the enrichment of Mizugakiibacter that harms the environment of agricultural production. The addition of 2%-MnO2 was recommended for MS composting. Furthermore, metabolic function analysis indicated that MnO2 addition altered amino acid and carbohydrate metabolism, especially enhancing propanoate metabolism and butanoate metabolism but inhibiting citrate cycle. Structural equation modeling revealed that Nonomuraea and Actinomadura were the main drivers for lignocellulose degradation. This study provided theoretical guidance in regulating humification via MnO2 for MS composting.

Effect of vermicompost on rhizobiome and the growth of wheat on Martian regolith simulant.

As humanity embarks on the journey to establish permanent colonies on Mars, ensuring a reliable source of sustenance will be crucial. Therefore, detailed studies regarding crop cultivation using Martian simulants are of great importance. This study aimed to grow wheat on substrates based on soil and Martian simulants, with the addition of vermicompost, to investigate the differences in wheat development. Basic physical and chemical properties of substrates were examined, including determination of macro- and microelements as well as their microbiological properties. Plant growth parameters were also determined. The addition of vermicompost positively affected wheat grown on soil, but the effect on plants grown on substrate with Martian simulants was negligible. Comparing the microbiological and chemical components, it was observed that plants can defend themselves against the negative effects of growth on the Martian simulants, but their success depends on having the PGPR (Plant growth-promoting rhizobacteria) present, which can provide the plant with additional nitrogen. The presence of beneficial symbiotic microbiota will allow the wheat to wait out the negative growth time rather than adapt to the regolith environment.

The risk of viable but non-culturable (VBNC) enterococci and antibiotic resistance transmission during simulated municipal sludge composting.

Sludge composting is a sludge resource utilization method that can reduce pollutants, such as pathogens. Enterococci are regarded as more reliable and conservative indicators of pathogen inactivation than fecal coliforms, which are typically used as indicators of fecal pollution. Non-spore pathogenic bacteria may enter a viable but non-culturable (VBNC) state during composting, leading to residual risk. The VBNC status of bacteria is related to their survival during composting. However, the survival mechanisms of enterococci during sludge composting remain unclear. Therefore, this study aimed to investigate the VBNC state of enterococci in different phases of simulated sludge composting and the fate of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) during the composting process. This study is expected to provide a basis for subsequent exploration of possible methods to completely inactivate enterococci and reduce ARGs during sludge composting. Culturable enterococci were reduced in the thermophilic phase of sludge composting, but the proportion of VBNC subpopulation increased. It was reported for the first time that most VBNC enterococci were killed by extending the cooling phase of sludge compost, and by prolonging the cooling phase the types of ARG were reduced. However, there was a certain quantity (approximately 104/g dry weight) of culturable and VBNC enterococci in the compost products. In addition, MGEs and ARGs exist in both bacteria and compost products, leading to the risk of spreading antibiotic-resistant bacteria and antibiotic resistance when sludge compost products are used.

A critical review on characterization, human health risk assessment and mitigation of malodorous gaseous emission during the composting process.

Composting has emerged as a suitable method to convert or transform organic waste including manure, green waste, and food waste into valuable products with several advantages, such as high efficiency, cost feasibility, and being environmentally friendly. However, volatile organic compounds (VOCs), mainly malodorous gases, are the major concern and challenges to overcome in facilitating composting. Ammonia (NH3) and volatile sulfur compounds (VSCs), including hydrogen sulfide (H2S), and methyl mercaptan (CH4S), primarily contributed to the malodorous gases emission during the entire composting process due to their low olfactory threshold. These compounds are mainly emitted at the thermophilic phase, accounting for over 70% of total gas emissions during the whole process, whereas methane (CH4) and nitrous oxide (N2O) are commonly detected during the mesophilic and cooling phases. Therefore, the human health risk assessment of malodorous gases using various indexes such as ECi (maximum exposure concentration for an individual volatile compound EC), HR (non-carcinogenic risk), and CR (carcinogenic risk) has been evaluated and discussed. Also, several strategies such as maintaining optimal operating conditions, and adding bulking agents and additives (e.g., biochar and zeolite) to reduce malodorous emissions have been pointed out and highlighted. Biochar has specific adsorption properties such as high surface area and high porosity and contains various functional groups that can adsorb up to 60%-70% of malodorous gases emitted from composting. Notably, biofiltration emerged as a resilient and cost-effective technique, achieving up to 90% reduction in malodorous gases at the end-of-pipe. This study offers a comprehensive insight into the characterization of malodorous emissions during composting. Additionally, it emphasizes the need to address these issues on a larger scale and provides a promising outlook for future research.

Assessing the quality and eco-beneficial microbes in the use of silkworm excrement compost.

Sericulture has become widespread globally, and the utilization of artificial diets produces a substantial quantity of silkworm excrement. Although silkworm excrement can be composted for environmentally friendly disposal, the potential utility of the resulting compost remains underexplored. The aim of this study was to assess the quality of this unique compost and screen for eco-beneficial microbes, providing a new perspective on microbial research in waste management, especially in sustainable agriculture. The low-concentration compost application exhibited a greater plant growth-promoting effect, which was attributed to an appropriate nutritional value (N, P, K, and dissolved organic matter) and the presence of plant growth-promoting bacteria (PGPB) within the compost. Encouraged by the "One Health" concept, the eco-benefits of potent PGPB, namely, Klebsiella pneumoniae and Bacillus licheniformis, in sericulture were further evaluated. For plants, K. pneumoniae and B. licheniformis increased plant weight by 152.44 % and 130.91 %, respectively. We also found that even a simple synthetic community composed of the two bacteria performed better than any single bacterium. For animals, K. pneumoniae significantly increased the silkworm (Qiufeng × Baiyu strain) cocoon shell weight by 111.94 %, which could increase sericulture profitability. We also elucidated the mechanism by which K. pneumoniae assisted silkworms in degrading tannic acid, a common plant-derived antifeedant, thereby increasing silkworm feed efficiency. Overall, these findings provide the first data revealing multiple beneficial interactions among silkworm excrement-derived microbes, plants, and animals, highlighting the importance of focusing on microbes in sustainable agriculture.

Closing the nutrient cycle in urban areas: The use of municipal solid waste in peri-urban and urban agriculture.

Cities face the challenges of supplying food and managing organic municipal solid waste (OMSW) sustainably amid increasing urbanization rates. Urban agriculture (UA) can help with this effort by producing local crops that are fertilized with nutrients recovered from compost generated from OMSW. This research aims to determine the potential of OMSW compost to supply the nitrogen-phosphorus-potassium (NPK) demand of UA and the environmental benefits of replacing mineral fertilizer from a life cycle perspective. The Metropolitan Area of Barcelona (AMB) serves as the case study given its commitment to reuse biowaste according to the Revised Waste Framework Directive and to promote UA as a signing member of the Milan Urban Food Policy Pact. Based on crop requirements and farmer surveys, we find that the annual NPK demands of the agricultural fields of the AMB that cover 5,500 ha and produce 70,000 tons of crops are approximately 769, 113, and 592 tons of NPK, respectively. Spatial material flow analysis and life cycle assessment were applied to found that the current waste management system can potentially substitute 8 % of the total NPK demanded by UA with compost, reduce the impacts by up to 39 % and yield savings in global warming of 130 %. The more ambitious future scenario of 2025 can potentially substitute 21 % of the total NPK demand and reduce environmental impacts up to 1,049 %, depending on the category considered. Avoiding processing of mixed OMSW, mineral fertilizer replacement and cogeneration of electricity from biogas are the major contributors to these environmental savings.

Reducing carbon and nitrogen loss by shortening the composting duration based on seed germination index (SCD@GI): Feasibilities and challenges.

Addressing carbon (C) and nitrogen (N) losses through composting has emerged as a critical environmental challenge recently, and how to mitigate these losses has been a hot topic across the world. As the emissions of carbonaceous and nitrogenous gases were closely correlated with the composting process, the feasibility of composting duration shortening on C and N loss needs to be explored. Therefore, the goal of this paper is to find evidence-based approaches to reduce composting duration, utilizing the seed germination index as a metric (SCD@GI), for assessing its efficiency on C and N loss reductions as well as compost quality. Our findings reveal that the terminal seed germination index (GI) frequently surpassed the necessary benchmarks, with a significant portion of trials achieving the necessary GI within 60 % of the standard duration. Notably, an SCD@GI of 80 % resulted in a reduction of CO2 and NH3 by 21.4 % and 21.9 %, respectively, surpassing the effectiveness of the majority of current mitigation strategies. Furthermore, compost quality, maturity specifically, remained substantially unaffected at a GI of 80 %, with the composting process maintaining adequate thermophilic conditions to ensure hygienic quality and maturity. This study also highlighted the need for further studies, including the establishment of uniform GI testing standards and comprehensive life cycle analyses for integrated composting and land application practices. The insights gained from this study would offer new avenues for enhancing C and N retention during composting, contributing to the advancement of high-quality compost production within the framework of sustainable agriculture.

Revealing mechanism of phenol-amine reaction to form humus in compost based on high-resolution liquid chromatography mass spectrometry and spectroscopy.

Humus is the stable form of carbon storage in straw compost. The phenol-amine reaction is a pathway for humus formation in straw compost. In this study, two reaction systems, GP group (pyrogallol and glycine) and GCP group (catechol, pyrogallol, and glycine), were constructed in a simulated composting environment and revealed the molecular binding mechanism of the phenol-amine reaction through spectroscopy and mass spectrometry. The results showed that phenolic self-polymerization was faster than phenol-amine reaction. Therefore, the aromatization degree of GP was 27.14 % higher than that of GCP. The phenol-amine reaction first produced fulvic acid, and then formed humus units rich in active functional group structures (i.e., phenolic hydroxyl and carboxyl groups). These units further captured small molecule compounds to form humic acid eventually. This study would provide theoretical support for exploring the humus formation process and the promotion of straw humification by adding phenol or amino acids to compost.

Exploring the promoting effect of nitrilotriacetic acid on hydroxyl radical and humification during magnetite-amended composting of sewage sludge.

The OH production by adding magnetite (MGT) alone has been reported in composting. However, the potential of nitrilotriacetic acid (NTA) addition for magnetite-amended sludge composting remained unclear. Three treatments with different addition [control check (CK); T1: 5 % MGT; T2: 5 % MGT + 5 % NTA] were investigated to characterize hydroxyl radical, humification and bacterial community response. The NTA addition manifested the best performance, with the peak OH content increase by 52 % through facilitating the cycle of Fe(Ⅱ)/Fe(Ⅲ). It led to the highest organic matters degradation (22.3 %) and humic acids content (36.1 g/kg). Furthermore, NTA addition altered bacterial community response, promoting relative abundances of iron-redox related genera, and amino acid metabolism but decreasing carbohydrate metabolism. Structural equation model indicated that temperature and Streptomyces were the primary factors affecting OH content. The study suggests that utilizing chelators is a promising strategy to strengthen humification in sewage sludge composting with adding iron-containing minerals.

Effect of microbial inoculation on nitrogen transformation, nitrogen functional genes, and bacterial community during cotton straw composting.

The effects of microbial agents on nitrogen (N) conversion during cotton straw composting remains unclear. In this study, inoculation increased the germination index and total nitrogen (TN) by 24-29 % and 7-10 g/kg, respectively. Inoculation enhanced the abundance of nifH, glnA, and amoA and reduced that of major denitrification genes (nirK, narG, and nirS). Inoculation not only produced high differences in the assembly process and strong community replacement but also weakened environmental constraints. Partial least squares path modelling demonstrated that enzyme activity and bacterial community were the main driving factors influencing TN. In addition, network analysis and the random forest model showed distinct changing patterns of bacterial communities after inoculation and identified keystone microorganisms in maintaining network complexity and synergy, as well as system function to promote nitrogen preservation. Findings provide a novel perspective on high-quality resource recovery of agricultural waste.

Landfill-mined soil-like fraction (LMSF) use in biopolymer composting: Material pre-treatment, bioaugmentation and agricultural prospects.

Polylactic Acid (PLA) based compostable bioplastic films degrade under thermophilic composting conditions. The purpose of our study was to understand whether sample pre-treatment along with bioaugmentation of the degradation matrix could reduce the biodegradation time under a simulated composting environment. Sepcifically, we also explored whether the commercial composts could be replaced by landfill-mined soil-like fraction (LMSF) for the said application. The effect of pre-treatment on the material was analysed by tests like tensile strength analysis, hydrophobicity analysis, morphological analysis, thermal degradation profiling, etc. Subsequently, the degradation experiment was performed in a simulated composting environment following the ASTM D5338 standard, along with bioaugmentation in selected experimental setups. When the novel approach of material pre-treatment and bioaugmentation were applied in combination, the time necessary for 90% degradation was reduced by 27% using compost and by 23% using LMSF. Beyond the improvement in degradation rate, the water holding capacity increased significantly for the degradation matrices. With pH, C: N ratio and microbial diversity tested to be favourable through 16s metabarcoding studies, material pre-treatment and bioaugmentation allow LMSF to not only replace commercial compost in polymer degradation but also find immense application in the agricultural sector of drought-affected areas (for better water retention) after it has been used for PLA degradation.