Selection of sensitive seeds for evaluation of compost maturity with the seed germination index

The effect of auxiliary conditioning on humification of high-solids anaerobic digestion residues in aerobic composting processes

This study investigated the impact of cornstalk, bagasse, and spent mushroom substrate (SMS) as auxiliary materials on the nitrogen cycling and humification during the aerobic composting of high-solids anaerobically digested residues using high-throughput 16S rRNA sequencing and PICRUSt2 functional prediction. Results showed that cornstalk and SMS accelerated compost warming and upregulated the expression of nitrogen-cycling-related genes (e.g. ureC, narH, and narG), thereby significantly reducing (P < 0.05) N2O and NH3 emissions and increasing the NO3--N content in the compost. Furthermore, cornstalk enriched the microbial diversity and abundance of key bacteria involved in degradation and humification (e.g. Sphingobacterium and Moheibacter), which increased the humic acid content (HA) (78.4 g/kg DM). Although bagasse promoted aerobic conditions, it had less effect on nitrogen cycling and humification. The study highlights the intricate relationship between nitrogen metabolism and humification, demonstrating how selection of auxiliary materials can optimize composting for environmental sustainability.

Palygorskite enhances microbial necromass carbon accumulation and drives heavy metal immobilization during chicken manure composting

Microbial necromass carbon (MNC) is a critical component of stable organic matter in compost. However, its role in shaping compost microbial communities and influencing heavy metals (HMs), as well as the effect of palygorskite amendment on MNC and HMs, remains unclear. This study investigated MNC accumulation in chicken manure compost, assessed its impact on microbial communities and HM bioavailability, and evaluated the effects of 5 %, 10 %, and 15 % palygorskite additions. Results showed that palygorskite significantly increased the MNC proportion in total organic carbon, with the 15 % palygorskite enhancing 7.2 % compared to CK. This was primarily due to enhanced bacterial necromass carbon (BNC), which contributed 39.6 %-48.6 % of total MNC. Thermal stress and nutrient limitation were key drivers of MNC accumulation. Fungal necromass carbon (FNC), the dominant MNC component, was positively correlated with compost maturity indices. Palygorskite also markedly reduced HM bioavailability, increasing the passivation rates of Cd, Cu, and Zn by 4.3 %-24.4 %, 10.2 %-11.3 %, and 5.4 %-16.1 %, respectively. Structural equation modeling identified palygorskite, MNC, and pH as the main factors controlling HM bioavailability, explaining up to 83 % of the variation. However, the contribution of MNC to HM immobilization declined as palygorskite addition increased. This study clarifies the relationship between microbial necromass and HMs, highlighting the dual role of palygorskite in stabilizing MNC and reducing HM toxicity.

Regulation of antibiotic resistance gene rebound by degrees of microecological niche occupation by microbiota carried in additives during the later phases of swine manure composting

The occupation of microecological niches (MNs) by bacteria carrying lower antibiotic resistance genes (ARGs) has been demonstrated an effective strategy for reducing ARGs in compost, thereby mitigating the associated land use risks. In this study, humus soil (HS), matured compost (MC), and their respective isolated microbial agents (HSM and MCM), which exhibit varying abundances of ARGs, were introduced as additives after the thermophilic phase to investigate their influence on ARG removal and the mechanisms underlying effective MN occupation. The addition of HS resulted in the most favorable outcomes, including the highest carbon degradation, minimized nitrogen loss, and an 83.16 % reduction in ARG abundance during the later composting stages. In comparison, ARG rebound levels were 61.77 %-285.33 % across other treatments and 729.23 % in the control. Distinct dominant bacterial genera and potential ARG-host bacterial communities were observed, which varied with different additives and contributed to MN occupation dynamics. The addition of the HS additive intensified competition among non-host bacteria, and diversified the interactions both between genes and between bacteria. These changes suppressed horizontal gene transfer (HGT) mediated by mobile genetic elements (MGEs) and altered the abundance and composition of both dominant and non-dominant potential host species. Furthermore, it shifted the relative importance of key physicochemical parameters, collectively enhancing ARG removal during composting. These findings elucidate the mechanisms by which MN adjustments contribute to ARG reduction, providing actionable insights for designing composting strategies that mitigate environmental ARG dissemination risks more effectively.

Toxicological screening of PM2.5 from wildfires involving different biomass fuels

Wildfires are becoming increasingly frequent and severe, particularly in Southern Europe. In addition to their immediate environmental and socioeconomic impacts, wildfires release significant amounts of particulate matter (PM), which poses serious health and ecological risks. Gaseous (CO and CO2) and PM2.5 samples were collected directly from smoke plumes, and the modified combustion efficiency (MCE) was calculated to characterise combustion conditions. This study aims to assess the cytotoxicity, mutagenicity and ecotoxicity of PM2.5 collected during wildfires in Portugal, with a focus on how varying biomass types and combustion conditions impact these effects. Ecotoxicity assessments using Aliivibrio fischeri showed that PM2.5 samples ranged from toxic to extremely toxic, with mixed vegetation burns (eucalyptus, acacia, ferns) exhibiting the highest toxicity levels. Cytotoxicity tests on human lung epithelial cells (A549) demonstrated a dose-dependent decrease in metabolic activity and no membrane damage, while mutagenicity assays identified direct-acting mutagens from smouldering acacia debris combustion, specifically inducing frameshift mutations in Salmonella typhimurium strain TA98. Root growth inhibition tests showed no toxicity, with some samples, instead, promoting growth probably due to nutrient content. Peroxidase activity responses indicated that, at higher concentrations, the enzyme function could be reduced if defence mechanisms are overwhelmed or stimulated due to high nutrient levels. These findings highlight the complex and varying toxicological profiles of wildfire PM, emphasising the need for further research.

Next-Generation Fertilizers: A TiO2-Chitosan Composite Superabsorbent as a Sustained Release N-Fertilizer

This work aims to develop a sustained-release fertilizer by synthesizing a TiO2-chitosan composite superabsorbent. For this purpose, chitosan was modified with TiO2 nanoparticles, and terephthalaldehyde was used as a cross-linker. The reaction follows the Schiff base condensation mechanism. Confirmatory characterization of the synthesized material was done using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy-energy dispersive X-ray analysis, and X-ray photoelectron spectroscopy. Thermal gravimetric analysis-differential scanning calorimetry was performed to study the thermal behavior of the synthesized material. Rheology was performed for the mechanical studies. The superabsorbent showed excellent swelling behavior. The swelling was studied in different environments; a swelling percentage of 706.6% was observed at room temperature, categorizing the synthesized hydrogel as a superabsorbent. The urea loading at different pHs was also investigated, and a loading capacity of 90% was observed at an acidic pH. Finally, the release of fertilizer from the loaded hydrogel in different media was studied using UV-visible spectrophotometry. Various mathematical models were applied, and the results were fitted to the Korsmeyer-Peppas model. At pH 4, the highest correlation coefficient of 0.89 and an n-value of 0.27 were obtained, showing that the release corresponds to Fickian diffusion. Further, to compare the urea-loaded hydrogel with pure urea, a real-time experiment on the germination of Brassica oleracea var. viridis (Kashmiri saag) seeds was performed and a germination index of 274.69% was observed in the case of urea-loaded hydrogel. According to the results, the synthesized superabsorbent showed excellent controlled release in acidic medium and could be employed in soil for agricultural purposes.

Unraveling the impact of intervention strategies and oxygen disparity in humification during domestic waste composting

This study constructs three different photovoltaic assisted composting systems to treat rural domestic waste, and explores the interaction pathways between biomacromolecules and other factors under oxygen disparity at gradient heights of the compost. The optimized mode of regular turning and ventilation-dehydration significantly reduced the moisture content by 53.6% and increased the seed germination index by 35.6%. The oxygen content at different heights under the optimized mode significantly affects the physicochemical properties of the compost, and the degradation of cellulose, hemicellulose, and protein in the middle is higher than other parts. The structural equation model shows that the physicochemical properties at the bottom are affected by biomacromolecules, which may be related to volatile fatty acids(VFAs) produced under low oxygen conditions.The research results show that using manual turning and ventilation-dehydration as the optimized process can promote compost maturity, and oxygen concentration has an important impact on the humification process of the compost.

Promoting role of nitrogen-fixing bacteria and biochar on nitrogen retention and degradation of PBAT plastics during composting

Since the increasing number of polybutylene adipate terephthalate (PBAT)-based plastics entering the environment, the search for sustainable treatment methods has become a primary focus of contemporary research. Composting offers a novel approach for managing biodegradable plastics. However, a significant challenge in the composting process is how to control nitrogen loss and enhance plastic degradation. In this context, the effect of various additives on nitrogen retention, PBAT plastics degradation, and microbial community dynamics during composting was investigated. The findings revealed that the addition of nitrogen-fixing bacteria Azotobacter vinelandii and biochar (AzBC) significantly improved nitrogen retention and accelerated PBAT rupture within 40 days of composting. Specifically, the PBAT degradation rate in the AzBC group reached 29.6%, which increased by 12.14% (P < 0.05) compared to the control group. In addition, the total nitrogen (TN) content increased by 6.20% (P < 0.05), and the Nitrogen-fixing enzyme (NIT) content increased by 190 IU/L (P < 0.05). Further analysis of GC-MS confirmed the presence of low molecular weight fragmentation products, such as 6-(4-hydroxybutoxy)-6-oxohexanoic acid. The AzBC treatment promoted the proliferation of Klebsiella at the genus level that could enhance nitrogen retention and the bacteria that have the ability to degrade PBAT, such as Proteobacteria and Firmicutes at the phyla level, and Pseudoxanthomonas, Pseudomonas, and Flavobacterium genera at the genera level (P < 0.05). Correlation analysis indicated that the degradation of PBAT is positively correlated with Temperature (T), NIT, and TN, but negatively correlated with the organic matter (OM) content and germination index (GI). In conclusion, the co-application of biochar and Azotobacter vinelandii offers promising sustainable prospects for enhancing PBAT plastic degradation and reducing nitrogen loss during composting.

Nanoscale Biochar for Fertilizer Quality Optimization in Waste Composting: Microbial Community Regulation

Conventional composting faces challenges of nitrogen loss, product instability, and limited humic substance formation. This study investigated the effects of nanoscale biochars (nano-BCs) derived from rice straw (nano-RSB) and corn stover (nano-CSB) on manure composting. A randomized design with five treatments was used: control, regular biochars (RSB and CSB), and nano-BCs. Nano-BCs, especially nano-CSB, significantly improved compost maturity and reduced phytotoxicity, achieving a 146.20 % germination index. They increased total nitrogen (55.09-63.64 %) and phosphorus (10.25-12.33 %) retention, reduced NH4+-N loss, and promoted nitrification. Nano-CSB showed the highest final NO3--N content (8.63 g/kg). Bacterial richness and diversity increased by 25-30 % in nano-BC treatments, with selective enrichment of beneficial species. The unique properties of nano-BCs, including high surface area and microporous structure, improved nutrient retention and compost quality. Nano-BCs offers a promising solution for sustainable waste management and high-quality compost production in agriculture, significantly enhancing nutrient retention and microbial community regulation during composting process.

Sustainable control of invasive plants: Compost production, quality and effects on wheat germination

Invasive plant species pose significant ecological threats worldwide, affecting the stability and biodiversity of local ecosystems. As a result of their control, a considerable amount of plant biomass is produced, which can be used to produce various value-added products. Five different composts were prepared from three invasive plant species found in Latvia - Reynoutria japonica, Solidago canadensis, Lupinus polyphyllus. The stages of composting have been investigated and recommendations for process optimization have been made based on the quality characterization of the final compost. The quality of the prepared invasive plant biomass composts has been evaluated based on the main plant nutrient concentration, humic substance concentration, and mineral contents. The allelopathic lupin alkaloid concentration throughout the composting process has been evaluated and shows a consistent reduction. Obtained compost quality complies with the EU regulations for fertilizing products and soil amendments thus it can be considered equivalent to industrially produced compost and vermicompost. Seed germination tests confirm that compost prepared from invasive plants is suitable for plant growth and comparable to commercial composts. Based on pilot-scale composting results, recommendations for invasive plant composting have been suggested.

Phytotoxicity assessment of treated vegetable oily wastewater via environmentally coagulation/flocculation and membrane filtration technologies using lettuce (Lactuca sativa) seeds

The present investigation highlights the necessity of monitoring some basic physico-chemical water quality indicators and their phytotoxic effect using ecotoxicological bioassays such as "seed germination tests." The phytotoxicity of raw and treated vegetable oil refinery wastewater (VORW) using different treatment processes was assessed through some physiological responses (relative seed germination (RSG), seedling elongation, and germination index (GI)) using Lactuca sativa cultivar. Biotest results of different raw water samples revealed a noticeable correlation between the organic matter content and water phytotoxicity. In fact, VORW showed a very low RSG (17 ± 0.7 to -47 ± 0.58%) and high phytotoxic effects (GI < 50%). The use of coagulation/flocculation (CF) allowed a satisfactory phytotoxicity removal where RSG obtained ranged from 83 ± 1.58 to 90 ± 1.2%. However, the effluent still presents high to moderate phytotoxicity since GI remained below 80% which indicates the presence of toxic elements remaining after CF treatment. When VORW were treated using membrane processes, their phytotoxicity was gradually decreased with the decrease in the membrane pore size. The use of microfiltration membranes (MF), with pore size of 5 µm, 1.2 µm, 0.45 µm, and 0.22 µm, showed RSG values ranged from 37 ± 1.15 to 77 ± 1.68% and GI of less than 80% indicating a moderate to high phytotoxicity. However, the use of ultrafiltration (UF) membranes with molecular weight cut-off (MWCO) of 100 kDa, 30 kDa, and 10 kDa made it possible to achieve an RSG of 100% and an IG exceeding 80% showing that the VORW-treated using UF does not exhibit any phytotoxicity effect. Hence, UF appears to be the most efficient and environmentally friendly technology that could be used for safely treated VORW irrigation purposes compared to CF and MF processes.

Coating of maize seeds with acephate for precision agriculture: Safety assessment in earthworms, bees, and soil microorganisms

Acephate is commonly used as a seed treatment (ST) in precision agriculture, but its impact on pollinators, earthworms, and soil microorganisms remains unclear. This study aimed to compare the fate of acephate seed dressing (SD) and seed coating (SC) treatments and assess potential risks to bees, earthworms, and soil microorganisms. Additionally, a follow-up study on maize seeds treated with acephate in a greenhouse was conducted to evaluate the maize growth process and the dissipation dynamics of the insecticide. The results indicated that acephate SC led to greater uptake and translocation in maize plants, resulting in lower residue levels in the soil. However, high concentrations of acephate metabolites in the soil had a negative impact on the body weight of earthworms, whereas acephate itself did not. The potential risk to bees from exposure to acephate ST was determined to be low, but dose-dependent effects were observed. Furthermore, acephate ST had no significant effect on soil bacterial community diversity and abundance compared to a control. This study provides valuable insights into the uptake and translocation of acephate SD and SC, and indicates that SC is safer than SD in terms of adverse effects on bees and nontarget soil organisms.

Co-composting of tail vegetable with flue-cured tobacco leaves: analysis of nitrogen transformation and estimation as a seed germination agent for halophyte

Resource utilization of tail vegetables has raised increasing concerns in the modern agriculture. However, the effect and related mechanisms of flue-cured tobacco leaves on the product quality, phytotoxicity and bacterially-mediated nitrogen (N) transformation process of tail vegetable composting were poorly understood. Amendments of high-dosed (5% and 10% w/w) tobacco leaves into the compost accelerated the heating process, prolonged the time of thermophilic stage, increased the peak temperature, thereby improving maturity and shortening composting duration. The tobacco leaf amendments at the 10% (w/w) increased the N conservation (TN and NH4-N content) of compost, due to the supply of N-containing nutrient and promotion of organic matter degradation by tobacco leaves. Besides, tobacco leaf amendments promoted the seed germination and root development of wild soybean, exhibiting the feasibility of composting product for promoting the growth of salt-tolerant plants, but no dose-dependent effect was found for tobacco leaf amendments. Addition of high dosed (5% and 10% w/w) tobacco leaves shifted the bacterial community towards lignocellulosic and N-fixing bacteria, contributing to increasing the compost maturity and N retention. PICRUSt 2 functional prediction revealed that N-related bacterial metabolism (i.e., hydroxylamine oxidation and denitrifying process) was enhanced in the tobacco leaf treatments, which contributed to N retention and elevated nutrient quality of composting. To the best knowledge, this was the first study to explore the effect of tobacco waste additives on the nutrient transformation and halophyte growth promotion of organic waste composting. These findings will deepen the understanding of microbially-mediated N transformation and composting processes involving flue-cured tobacco leaves.

Microbial electrochemical enhanced composting of sludge and kitchen waste: Electricity generation, composting efficiency and health risk assessment for land use

To realize the energy and resource utilization from organic solid waste, a two-phase microbial desalination cell (TPMDC) was constructed using dewatered sludge and kitchen waste as the anode substrate. The performance of electricity generation and composting efficacy was investigated, along with a comprehensive assessment of the potential health risks associated with the land use of the resulting mixed compost products. Experimental outcomes revealed a maximum open-circuit voltage of 0.893 ± 0.005 V and a maximum volumetric power density of 0.797 ± 0.009 W/m³. After 90 days of composting enhanced by microbial electrochemistry, a significant organic matter removal rate of 31.13 ± 0.44 % was obtained, and the anode substrate electric conductivity was reduced by 30.02 ± 0.04 % based on the anode desalination. Simultaneously, there was an increase in the content of available nitrogen, phosphorus, and potassium, as well as an improvement in the seed germination index. The forms of heavy metals shifted from bioavailable to stable residual states. The non-carcinogenic hazard index (HI) values for heavy metals and polycyclic aromatic hydrocarbons (PAHs) during the land use of compost products were less than 1, and the total carcinogenic risk (TCR) values for heavy metals and PAHs were below the acceptable threshold of 10-4. The occupational population risk of infection from five pathogens was higher than that of the general public, with all risk values ranging from 8.67 × 10-8 to 1, where the highest risk was attributed to occupational exposure to Legionella. These outcomes demonstrated that the mixture of dewatered sludge and kitchen waste was an appropriate anode substrate to enhance TPMDC stability for electricity generation, and its compost products have promising land use suitability and acceptable land use risk, which will provide important guidance for the safe treatment and disposal of organic solid waste.

Bio-stabilization of toxic weeds (Xanthium strumarium and Lantana camara) implementing mono- and polyculture of Eisenia fetida and Eudrilus eugeniae

The present study investigates the synergistic impact of earthworms (Eisenia fetida and Eudrilus eugeniae) and microbes during vermicomposting of invasive weed phytomass (Xanthium strumarium and Lantana camara). This study aims introducing an onsite solution for weed control while producing valuable organic manure. Vermitransformation and detailed characterization of mono- (VC1, VC2, VC4, VC5) and polyculture (VC3, VC6) of X. strumarium and L. camara has been reported for the first time employing E. fetida and E. eugeniae. The study achieved 45.16 ± 2.48-76.73 ± 1.37% vermiconvertion rate. The pH, conductivity, and concentration of heavy metals are effectively stabilized. Furthermore, it observed a significant reduction in total organic carbon (TOC) alongside the augmentation of nitrogen, phosphorus, potassium, calcium, and other trace elements (Zn, Ni, Fe). The ash content, humification index, and C/N ratio analysis established the maturity of the vermicompost. The macronutrient enhancement in the vermicompost samples was recorded 1.5- to 2.47-fold for total N, 1.19- to 1.48-fold in available P, 1.1- to 1.2-fold in total K, and 1.1- to 1.18-fold in total Ca. The germination index reveals a significant reduction in phytotoxicity, suggesting the production of mature and suitable vermicompost for agricultural use. Evaluating mono- and polyculture techniques, the research highlights the superiority of E. fetida over E. eugeniae. Further, the earthworm population and biomass have significantly increased by the end of 60-day experimental trial.

Recirculating frass from food waste bioconversion using black soldier fly larvae: Impacts on process efficiency and product quality

Biowaste generation is increasing worldwide and inadequate disposal has strong negative impacts on food systems and ecosystems. Biodigestion of biowaste using black soldier fly (Hermetia illucens) larvae (BSFL) generates valuable by-products such as animal feed (larval biomass) and organic fertiliser (frass). However, the latter is typically unstable immediately after waste conversion and is thus unsafe for use as a fertilizer in terms of maturity. This study evaluated recirculation of frass within bioconversion of post-consumer food waste (FW) as a dietary component for BSFL to improve the quality of the subsequent frass obtained. Frass was introduced at increasing inclusion levels replacing food waste (2.5-100% on wet-weight basis) as part of the larvae's feeding substrate. Bioconversion efficiency and material reduction were significantly reduced by frass inclusion, while larval yield per experimental unit remained unchanged. When considering only the waste component in the larval diet, larval yield (dry-weight basis) ranged between 207 (0% frass inclusion) and 403 (40% frass inclusion) kg tonne FW-1, thus increasing by up to 94% at higher frass inclusion. With increasing dietary inclusion rate of frass from 0% to 100%, crude protein content of larval biomass increased by 41%, while fat content was reduced by 32%. The recirculated frass (obtained after including frass in the larval diet) had elevated concentrations of P, K, S, Na and B and around 6% lower organic matter content, demonstrating a higher degree of decomposition. Frass inclusion in the larval diet generated recirculated frass that were more stable and mature, as indicated by self-heating capacity, CO2 and NH3 volatilisation, seed germination bioassays and other parameters. It was concluded that frass recirculation improves waste bioconversion efficiency in relation to food waste unit, as well as larval biomass and frass quality, ensuring safer use as a fertilizer.

Investigating inhibiting factors affecting seed germination index in kitchen waste compost products: Soluble carbon, nitrogen, and salt insights

The seed germination index (GI) serves as the principal determinant that impedes the integration of aerobic composting products into agricultural lands. The current research work predominantly focuses on exploring the correlation between physical and chemical indicators of the compost products and GI, neglecting the fundamental cause. This study systematically analyzed the composition of GI aqueous extracts from compost products derived from kitchen waste under various composting methodologies, with nitrogen, carbon, and inorganic salt as critical factors. The analytical work concluded that acetic acid, formic acid, and ammonium were the inhibitory factors influencing GI. Validation experiments introduced inhibitory factors, yielding a functional relationship formula depicting GI variations due to a single influential factor. This study conclusively identified acetic acid as the primary constraint, establishing that its inhibitory concentration corresponded to 70 % GI stands at 85 mg/L. This study will provide guidelines for the future research on enhancing aerobic composting techniques.

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.

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.

The Seed Germination Test as a Valuable Tool for the Short-Term Phytotoxicity Screening of Water-Soluble Polyamidoamines

Six differently charged amphoteric polyamidoamines, synthesized by the polyaddition of N,N'-methylenebisacrylamide to alanine, leucine, serine, arginine (M-ARG), glutamic acid (M-GLU) and a glycine/cystine mixture, were screened for their short-term phytotoxicity using a seed germination test. Lepidium sativum L. seeds were incubated in polyamidoamine water solutions with concentrations ranging from 0.156 to 2.5 mg mL-1 at 25 ± 1 °C for 120 h. The seed germination percentage (SG%), an indicator of acute toxicity, and both root and shoot elongation, related to plant maturation, were the considered endpoints. The germination index (GI) was calculated as the product of relative seed germination times relative radical growth. The SG% values were in all cases comparable to those obtained in water, indicating no detectable acute phytotoxicity of the polyamidoamines. In the short term, the predominantly positively charged M-ARG proved to be phytotoxic at all concentrations (GI < 0.8), whereas the predominantly negatively charged M-GLU proved to be biostimulating at intermediate concentrations (GI > 1) and slightly inhibitory at 2.5 mg mL-1 (0.8 < GI < 1). Overall, polyamidoamine phytotoxicity could be correlated to charge distribution, demonstrating the potential of the test for predicting and interpreting the eco-toxicological behavior of water-soluble polyelectrolytes.

Plastic particles in urban compost and their grain size distribution

Gathering information on plastic particles in composts and the processes they undergo is important in terms of potentially limiting their further entry into the environment, for example, in improving the fertilising properties of soils. Microplastics (MPs) were determined in composts produced from urban greenery. They are present in decreasing order: polyethylene terephthalate, polystyrene, polyethylene, and polypropylene. The determination of polymers and additives used to improve their properties was performed by pyrolysis and gas chromatography with mass spectrometric detection (Py-GC/MS). Additives and microplastics are most concentrated in composts in the 0.315-0.63 and 0.63-1.25 mm grain size class, together with the carbon contained in the compost dry matter. Additives form 0.11-0.13% of MPs in dry matter of compost. The average concentration of microplastics in the particle size class from 0.63 to 1.25 mm is 2434 ± 224 mg/kg; in the total sample of composts, it is 1368 ± 286 mg/kg of P-MPs. For composts with particle size <2.5 mm, a relationship between the C/N ratio and the plastic particle concentration was statistically significant. It documents a similar behaviour of lignocellulose and plastic particles during the degradation processes. A relationship between the concentration of polymer markers and additives in the compost dry matter and their concentrations in the leachate has been demonstrated. The leachability from compost is higher for additives than for chemical compounds originating from the decomposition of the main components of MPs. The suitability of the use of the compost for agricultural purposes was monitored by the germination index (GI) for watercress. The lowest value of the GI was determined in the particle size class from 0.63 to 1.25 mm. The leachability of polymer markers and additives alone cannot explain the low GI value in this grain size class. The GI value is also influenced by the leachability of chemical compounds characterised by the value of dissolved organic carbon (DOC) and water-leachable nitrogen (Nw). A statistically significant dependence between DOC/Nw and the germination index value was found.

Germination responses of Lens Culiunaris L. seeds to osmotic potentials at cardinal temperatures using hydrothermal time model

BACKGROUND

Lentil is a significant legume that are consumed as a staple food and have a significant economic impact around the world. The purpose of the present research on lentil was to assess the hydrothermal time model's capacity to explain the dynamics of Lens culinaris L. var. Markaz-09 seed germination, as well as to ascertain the germination responses at various sub-optimal temperatures (T) and water potentials (Ψ). In order to study lentil seed germination (SG) behavior at variable water potentials (Ψs) and temperatures (Ts). A lab experiment employing the hydrothermal time model was created. Seeds were germinated at six distinct temperatures: 15 0С, 20 0С, 25 0С, 30 0С, 35 0С, and 40 0С, with five Ψs of 0, -0.3, -0.6, -0.9, and - 1.2 MPa in a PEG-6000 (Polyethylene glycol 6000) solution.

RESULTS

The results indicated that the agronomic parameters like Germination index (GI), Germination energy (GE), Timson germination index (TGI), were maximum in 25 0C at (-0.9 MPa) and lowest at 40 0C in 0 MPa. On other hand, mean germination time (MGT) value was highest at 15 0C in -1.2 MPa and minimum at 40 0C in (-0.6 MPa) while Mean germination rate (MGR) was maximum at 40 0C in (0 MPa) and minimum at 15 0C in (-0.6 MPa).

CONCLUSIONS

The HTT model eventually defined the germination response of Lens culinaris L. var. Markaz-09 (Lentil) for all Ts and Ψs, allowing it to be employed as a predictive tool in Lens culinaris L. var. Markaz-09 (Lentil) seed germination simulation models.

Effects of thermophilic bacteria inoculation on maturity, gaseous emission and bacterial community succession in hyperthermophilic composting

Hyperthermophilic composting, characterized by temperatures equal to or exceeding 75 °C, offers superior compost maturity and performance. Inoculation with thermophilic bacteria presents a viable approach to achieving hyperthermophilic composting. This study investigates the effects of inoculating thermophilic bacteria, isolated at different temperatures (50 °C, 60 °C, and 70 °C) into compost on maturity, gaseous emissions, and microbial community dynamics during co-composting. Results indicate that the thermophilic bacteria inoculation treatments exhibited peak temperature on Day 3, with the maximum temperature of 75 °C reached two days earlier than the control treatment. Furthermore, these treatments demonstrated increased bacterial richness and diversity, along with elevated relative abundances of Firmicutes and Proteobacteria. They also fostered mutualistic correlations among microbial species, enhancing network connectivity and complexity, thereby facilitating lignocellulose degradation. Specifically, inoculation with thermophilic bacteria at 60 °C increased the relative abundance of Thermobifida and unclassified-f-Thermomonosporaceae (Actinobacteriota), whereas Bacillus, a thermophilic bacterium, was enriched in the 70 °C inoculation treatment. Consequently, the thermophilic bacteria at 60 °C and 70 °C enhanced maturity by 36 %-50 % and reduced NH3 emissions by 1.08 %-27.50 % through the proliferation of thermophilic heterotrophic ammonia-oxidizing bacteria (Corynebacterium). Moreover, all inoculation treatments decreased CH4 emissions by 6 %-27 % through the enrichment of methanotrophic bacteria (Methylococcaceae) and reduced H2S, Me2S, and Me2SS emissions by 1 %-25 %, 47 %-63 %, and 15 %-53 %, respectively. However, the inoculation treatments led to increased N2O emissions through enhanced denitrification, as evidenced by the enrichment of Truepera and Pusillimonas. Overall, thermophilic bacteria inoculation promoted bacteria associated with compost maturity while attenuating the relationship between core bacteria and gaseous emissions during composting.

In Vitro Screening of Ecotoxic and Cytotoxic Activities of Ailanthus altissima Leaf Extract against Target and Non-Target Plant and Animal Cells

Ailanthus altissima, an invasive plant species, exhibits pharmacological properties, but also some allergic effects on humans. This study aimed to evaluate the potential toxicity of A. altissima leaves, using a complex approach towards different organisms. The ecotoxic impact of a crude extract was investigated on seeds germination and brine shrimp lethality. Cytotoxicity was studied in vitro using non-target (haemolysis, liposomal model, fibroblast), and target (cancer cells) assays. Leaf extract at 1000 µg/mL significantly inhibited wheat and tomato germination, while no significant effects were found on parsley germination. A slight stimulatory effect on wheat and tomato germination was found at 125 µg/mL. In a brine shrimp-test, the extract showed a low toxicity at 24 h post-exposure (LC50 = 951.04 ± 28.26 μg/mL), the toxic effects increasing with the exposure time and extract concentration. Leaf extract caused low hematotoxicity. The extract was biocompatible with human gingival fibroblasts. No anti-proliferative effect was found within the concentration range of 10-500 µg/mL on malignant melanoma (MeWo) and hepatocellular carcinoma (HepG2). In a liposomal model-test, the extract proved to possess low capability to alter the eukaryotic cell-mimicking membranes within the tested concentration range. Given the low to moderate toxicity on tested organisms/cells, the A. altissima autumn leaves may find useful applications.

Pilot-scale membrane-covered composting of food waste: Initial moisture, mature compost addition, aeration time and rate

The impact of different operational parameters on the composting efficiency and compost quality during pilot-scale membrane-covered composting (MCC) of food waste (FW) was evaluated. Four factors were assessed in an orthogonal experiment at three different levels: initial mixture moisture (IMM, 55 %, 60 %, and 65 %), aeration time (AT, 6, 9, and 12 h/d), aeration rate (AR, 0.2, 0.4, and 0.6 m3/h) and mature compost addition ratio (MC, 2 %, 4 %, and 6 %). Results indicated that 55 % IMM, 6 h/d AT, 0.4 m3/h AR, and 4 % MC addition ratio simultaneously provided the compost with the maximum cumulative temperature and the minimum moisture. It was shown that the IMM was the driving factor of this optimum composting process. On contrary, the optimal parameters for reducing carbon and nitrogen loss were 65 % IMM, 6 h/d AT, 0.4 m3/h AR, and 2 % MC addition ratio. The AR had the most influence on reducing carbon and nitrogen losses compared to all other factors. The optimal conditions for compost maturity were 55 % IMM, 9 h/d AT, 0.2 m3/h AR, and 6 % MC addition ratio. The primary element influencing the pH and electrical conductivity values was the AR, while the germination index was influenced by IMM. Protein was the main organic matter limiting the composting efficiency. The results of this study will provide guidance for the promotion and application of food waste MCC technology, and contribute to a better understanding of the mechanisms involved in MCC for organic solid waste treatment.

Modifying humus-phosphorus-arsenic interactions in sludge composting: The strengthening of phosphorus availability and arsenic efflux detoxification mechanisms

Arsenic (As) in sewage sludge poses a significant threat to environmental and human health, which has attracted widespread attention. This study investigated the value of adding sodium percarbonate (SP) on phosphorus (P) availability and As efflux detoxification through HS-P-As interactions. Due to the unique structure of humus (HS) and the similar chemical properties of P and As, the conditions for HS-P-As interaction are provided. This study discussed the content, morphology and microbial communities of HS, P and As by using metagenomic and correlation analysis. The results showed that the humification index in the experiment group (SPC) was 2.34 times higher than that in the control group (CK). The available phosphorus (AP) content of SPC increased from 71.09 mg/kg to 126.14 mg/kg, and SPC was 1.11 times that of CK. The relative abundance of ACR3/ArsB increased. Pst, Actinomyces and Bacillus commonly participated in P and As conversion. The correlation analysis revealed that the humification process was enhanced, the AP was strengthened, and the As was efflux detoxified after SP amendment. All in all, this study elucidated the key mechanism of HS-P-As interaction and put forward a new strategy for sewage sludge resource utilization and detoxification.

Predicting maturity and identifying key factors in organic waste composting using machine learning models

The measurement of germination index (GI) in composting is a time-consuming and laborious process. This study employed four machine learning (ML) models, namely Random Forest (RF), Artificial Neural Network (ANN), Support Vector Regression (SVR), and Decision Tree (DT), to predict GI based on key composting parameters. The prediction results showed that the coefficient of determination (R2) for RF (>0.9) and ANN (>0.9) was higher than SVR (<0.6) and DT (<0.8), suggesting that RF and ANN displayed superior predictive performance for GI. The SHapley additive exPlanations value result indicated that composting time, temperature, and pH were the important features contributing to GI. Composting time was found to have the most significant impact on GI. Overall, RF and ANN were suggested as effective tools for predicting GI in composting. This study offers the reliable approach of accurately predicting GI in composting processes, thereby enabling intelligent composting practices.

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.

Novel perspective on qualitative assessment of swine manure compost maturity using organic carbon density fractions

Mature compost is safe and stable, yet quality assessments are challenging owing to current maturity indicators' limitations. This study employed density fractionation to separate organic carbon into light and heavy fractions, offering a new perspective for assessing maturity. Results showed that light fraction organic carbon progressively transitioned into heavy fraction during composting, reducing the proportion of total organic carbon from 82.82% to 44.03%, while heavy fraction organic carbon increased to 48.58%. During the first seven days, the reduction rate of light fraction organic carbon decreased slowly, while the increase rate of heavy fraction declined sharply, levelling off thereafter. Light/heavy fraction organic carbon ratio was significantly correlated with existing maturity indicators (carbon/nitrogen ratio, humic acid/fulvic acid ratio, biological growth-related indicators), with the ratio below 1.33 serving as a potential compost maturity marker. Thus, given its simplicity and reliability, organic carbon density fractions is an innovative indicator for compost maturity assessments.

Comparison analysis of microbial agent and different compost material on microbial community and nitrogen transformation genes dynamic changes during pig manure compost

This study aimed to assess the impact of microbial agent and different compost material, on physicochemical parameters dynamic change, nitrogen-transfer gene/bacterial community interaction network during the pig manure composting. Incorporating a microbial agent into rice straw-mushroom compost reduced the NH3 and total ammonia emissions by 25.52 % and 14.41 %, respectively. Notably, rice straw-mushroom with a microbial agent reduced the total ammonia emissions by 37.67 %. NH4+-N and pH emerged as primary factors of phylum-level and genus-level microorganisms. Microbial agent increased the expression of narG, nirK, and nosZ genes. Rice straw-mushroom elevated the content of amoA, nirK, nirS, and nosZ genes. Alcanivorax, Luteimonas, Pusillimonas, Lactobacillus, Aequorivita, Clostridium, Moheibacter and Truepera were identified as eight core microbial genera during the nitrogen conversion process. This study provides a strategy for reducing ammonia emissions and analyzes the potential mechanisms underlying compost processes.

Continuous thermophilic composting of distilled grain waste improved organic matter stability and succession of bacterial community

Continuous thermophilic composting (CTC) is potentially helpful in shortening the composting cycle. However, its universal effectiveness and the microbiological mechanisms involved are unclear. Here, the physicochemical properties and bacterial community dynamics during composting of distilled grain waste in conventional and CTC models were compared. CTC accelerated the organic matter degradation rate (0.2 vs. 0.1 d-1) and shortened the composting cycle (24 vs. 65 d), mainly driven by the synergism of bacterial genera. Microbial analysis revealed that the abundance of Firmicutes was remarkably improved compared to that in conventional composting, and Firmicutes became the primary bacterial phylum (relative abundance >70 %) during the entire CTC process. Moreover, correlation analysis demonstrated that bacterial composition had a remarkable effect on the seed germination index. Therefore, controlling the composting process under continuous thermophilic conditions is beneficial for enhancing composting efficiency and strengthening the cooperation between bacterial genera.

DOM hydrophilic components of organic fertilizers increased the soil nitrogen retention capacity and succession of the microbial community

Introduction

Application of organic fertilizers affects soil properties and microbial communities, which in turn alters soil N transformation processes. Unfortunately, it is not clear how the difference in the character of the organic fertilizer DOM affects the soil nitrogen retention capacity and its microbial processes.

Methods

According to the principle of equal nutrients, the treatments of chemical fertilizer alone (treatment CF), chemical fertilizer with organic fertilizer DOM hydrophilic components (treatment H), and chemical fertilizer with organic fertilizer DOM hydrophobic components (treatment P) were set up, where the characteristics of soil nitrogen transformation and changes in microbial community structure were studied with soil culture conditions for 24 days.

Results

It was discovered that the addition of organic fertilizer DOM components (H and P) slowed nitrification rate and increased protease activity resulting in a higher NH4+-N content compared to the CF treatment. The DOM addition (H and P) increased the microbial biomass nitrogen (MBN) levels in the soil and increased the soil nitrogen pool capacity.

Conclusions

Moreover, the carbon use efficiency of the hydrophilic components is higher than that of the hydrophobic components, resulting in its further increase in nitrogen reservoir capacity and higher nitrogen retention capacity. Network analysis showed that the addition of organic fertilizer DOM hydrophilic components increased network complexity and synergy between microorganisms. In combination with random forest analysis, it was shown that Sphingomonas and Massilia were key species influencing soil nitrogen retention capacity and nitrogen availability characteristics.

Compost-assisted revegetation of highly phytotoxic sulfidic tailings with Medicago sativa L. plants grown from the seed to seedpod stage under greenhouse experimental mesocosms conditions

The revegetation of highly phytotoxic sulfidic tailings is a challenging task which may often be successfully accomplished only following the addition of soil amendments. This study evaluated the use of green compost at increasing rates (10, 25 and 50% v/v) for the revegetation of extremely acidic sulfidic tailings of the North Mathiatis mine, Cyprus, with the use of alfalfa (Medicago sativa L.) plants, under greenhouse conditions. Alfalfa seeds were successfully germinated in tailings amended either with 25% or 50% (v/v) compost (52 and 85%, respectively). Plants managed to complete their life cycle and produce seeds only in the tailings amended with 50% (v/v) compost, since plants grown in tailings amended with lower rates of compost (i.e., 10 or 25% v/v) showed severe symptoms of phytotoxicity and eventually died. The amendment of tailings with 50% (v/v) green compost resulted in increased pH values, water holding capacity and organic content levels, soil respiration rates, as well as changes in soil elemental composition compared with tailings alone treatment, which in turn facilitated the growth and development of alfalfa plants during the whole experimental period (140 days). Plants managed to reach the late seedpod growth stage, indicating their potential regeneration and continual existence to the amended tailings, simultaneously uncovering the development of favorable conditions in the rhizosphere for the successful revegetation of studied tailings.

Effect of ferrous ions combined with zeolite on humification degree during food waste composting

The research aims to clarify role of ferrous sulfate (FeSO4) combined with zeolite (Z) on humification degree based on investigation of concentration and structural stability of humic acid (HA) during food waste composting. Four treatments were set up, namely CK (control), Fe (5 %), Z (5 %) and Fe + Z (2.5 %+2.5 %). Results demonstrated that concentration and polymerization degree of HA were 53.4 % and 97.3 % higher in composting amended with Fe + Z than in the control, respectively. Meanwhile, formation of aromatic functional groups and recalcitrant fluorescent components (HAC3) was significantly promoted, indicating that Fe + Z treatment enhanced HA structure stability. The bacterial networks became tighter, and the proportion of core bacteria in dominant modules increased at Fe + Z treatment. Additionally, key factors affecting HAC3 and product quality were identified by structural equation models, which verified potential mechanism of humification enhancement. Overall, this study provided theoretical support for improving humification degree and product quality.

Improved carbon sequestration by utilization of ferrous ions during different organic wastes composting

The humic acid (HA) possesses a more recalcitrant structure, making it crucial carbon components that improve carbon sequestration. Moreover, ferrous ions could improve microbial activity and enhance compost humification, and their oxidation into iron oxides could adsorb carbon components for sequestration. Based on the advantages of low cost and easy availability of ferrous sulfate (FeSO4), this study investigated the effect of FeSO4 on carbon sequestration during composting. Chicken manure (CM) and food waste (FW) composting were carried out in four treatments, namely control (CM, FW) and 5% (w/w) FeSO4 treated groups (CM+, FW+). Results indicated that FeSO4 increased HA content, improved organic carbon stability. Carbon loss for CM, CM+, FW and FW + treatments were 48.5%, 46.2%, 45.0%, and 40.3%, respectively. Meanwhile, FeSO4 enhanced the function of bacterial taxa involved in HA synthesis in CM + treatment, and improved the number of core bacteria significantly associated with formation of HA and iron oxide. SEM analysis verified that role of FeSO4 was significant in promoting HA synthesis during CM + composting, while it was remarkably in enhancing HA sequestration during FW + composting. This article provided fundamental theoretical backing for enhancing HA production and improving carbon sequestration during different materials composting.

Occurrences of typical PPCPs during wastewater treatment and the composting of sewage sludge with micron-sized and nano-sized Fe3O4

New pollutants, pharmaceuticals and personal care products (PPCPs), accumulate in sewage sludge (SS) in wastewater treatment plants (WWTPs), posing risks to the environment and to human health. In the present study, the fates of typical PPCPs, carbamazepine (CBZ), triclosan (TCS), ibuprofen (IBU) and galaxolide (HHCB), were examined during WW treatment. Additionally, SS collected from a WWTP was used for aerobic composting to investigate the influences of micron-sized Fe3O4 (M-Fe) and nano-sized Fe3O4 (N-Fe) on the degradation of these PPCPs and the succession of microbial communities during the composting process. The results showed that the mean concentrations of CBZ, TCS, IBU and HHCB in the influent of the WWTP were 926.5, 174.4, 8869, and 967.3 ng/g, respectively, and in the effluent were 107.6, 47.0, 283.4, and 88.4 ng/g, respectively. The removal rate averaged ∼80%, while the enrichment rates of the PPCPs in SS ranged from 37.2% to 60.5%. M-Fe and N-Fe reduced NH3 emissions by 32.9% and 54.1% and N2O emissions by 26.2% and 50.8%, respectively. Moreover, the addition of M-Fe and N-Fe effectively increased PPCP degradation rates 1.12-1.66-fold. During the whole process, the additions of M-Fe and N-Fe significantly shifted microbial community structure, and the abundances of Proteobacteria, Chloroflexi, and Actinobacteria were increased during the thermophilic stage, marking them as key PPCP-degrading phyla. Taken together, our results indicated that the addition of M-Fe and N-Fe is an effective method for improving the quality of end compost and accelerating the degradation of PPCPs.

Effect of the inoculation of Phanerochaete chrysosporium on nitrogen migration and organic matter conversion during electrolytic manganese residue composting

Composting has made it practicable to dispose electrolytic manganese residues (EMR) in a less toxic way, nevertheless, the decomposition and the loss of nitrogen is a critical issue. This study aimed to investigate the role of Phanerochaete chrysosporium (PC) inoculation on nitrogen migration and promotion of decomposing organic matter (OM), as well as the effect on bacterial community structure during EMR composting. The results exhibited that nitrogen loss tallied with the first-order kinetic model. PC inoculation increased the relative microbial abundance of Firmicutes, which improved the efficiency of nitrogen nitrification and OM degradation, and increased the germination index and total nitrogen content by 13.8% and 2.95 g/kg, respectively. Moreover, aromatic benzenes replaced heteropolysaccharides, alcohols and ethers as the main components of OM in fertilizer, leading up to a more stable humus structure. This study provides a rationale and a novel perspective on the resource and nutrient conservation of EMR-contaminated soils.

Enhanced biodegradation of endocrine disruptor bisphenol A by food waste composting without bioaugmentation: Analysis of bacterial communities and their relative abundances

Composting with food waste was assessed for its efficacy in decontaminating Bisphenol A (BPA). In a BPA-treated compost pile, the initial concentration of BPA 847 mg kg-1 fell to 6.3 mg kg-1 (99% reduction) over a 45-day composting period. The biodegradation rate was at its highest when bacterial activity peaked in the mesophilic and thermophilic phases. The average rate of total biodegradation was 18.68 mg kg-1 day-1. Standard methods were used to assess physicochemical parameters of the compost matrix and gas chromatography combined with mass spectrometry (GC/MS) was used to identify BPA intermediates. Next-generation sequencing (NGS) was used to detect BPA degraders and the diverse bacterial communities involved in BPA decomposition. These communities were found consist of 12 phyla and 21 genera during the composting process and were most diversified during the maturation phase. Three dominant phyla, Firmicutes, Pseudomonadota, and Bacteroidetes, along with Lactobacillus, Proteus, Bacillus, and Pseudomonas were found to be the most responsible for BPA degradation. Different bacterial communities were found to be involved in the food waste compost biodegradation of BPA at different stages of the composting process. In conclusion, food waste composting can effectively remove BPA, resulting in a safe product. These findings might be used to expand bioremediation technologies to apply to a wide range of pollutants.

Determining the extraction conditions and phytotoxicity threshold for compost maturity evaluation using the seed germination index method

The phytotoxicity of the compost aqueous extracts determines the maturity. To improve the accuracy of compost maturity evaluation using the seed germination index (GI) method, different extraction methods (different moisture content and extraction ratio) were designed to obtain samples with various phytotoxic level. This study analyzed the effects of different extraction condition of compost samples on GI, and established the relationship between phytotoxicity and GI. The results showed that the moisture content and extraction ratio of the compost significantly affected the GI. The extraction ratio for the compost with 60-70 % moisture content was 1:10 (ratio of compost mass to extract volume). However, commercial compost, which must have a moisture content of 30-45 %, had an extraction ratio of 1:30 (w:v). More importantly, compost extraction based on dry weight, with a moisture content of 10-15 %, more effectively reflected the phytotoxicity variations during composting. In such cases, the extraction ratio should be at least 1:30 (w:v) but not exceed 1:50 (w:v). The relationship between phytotoxicity and GI showed that dissolved organic carbon and dissolved nitrogen were the most important factors influencing GI, followed by NH4+, electrical conductivity, K, volatile fatty acids, Zn, and Cu. For composts with a GI greater than 70 %, the dissolved organic carbon, dissolved nitrogen, and NH4+ concentrations were below 257, 164, and 73 mg/L, respectively. These findings provide an optimized standard method for compost maturity evaluation using GI and a concentration threshold of key phytotoxicity is proposed to achieve accurate control of compost maturity.

The integrated study of the effects of infographic design on waste separation behavior and the behavioral outcome implementation on waste composting

This study revealed the effects of designed infographics for waste separation and the implementation of behavioral outcomes using surveys and lab-scale experiments. The designed infographics improved the waste separation behaviors of the respondents in term of subject norm, perceived behavioral control, and intention. These influential factors were increased by 5.84 to 20.5%. The effects of design elements including waste separation mascots, the knowledge of waste separation, and the knowledge of waste management were dependent on the ratio of graphics and messages. Therefore, the careful attention on design elements of the infographic had to be noted. According to survey results, animal bone and shell wastes were the highest miss-sorting waste for the compostable waste bin. Although the contamination rate of these wastes did not significantly affect the decomposition of organic waste in the composting process, the quality of the product was degraded in term of toxicity. The germination index was decreased by 66.0% under a 10% contaminated condition. In contrast, the increased the total Ca of compost was increased. Furthermore, the other chemical components of final composts were similar under various conditions. It could be concluded that the mixture of animal bone and shell in compostable waste is acceptable for the purpose of waste reduction. However, the contamination rate of inappropriate wastes in the compostable waste bin should be minimized to enable effective waste composting. The significant findings of this study will be able to apply to the design of waste separation at the source and the plan of waste management.

Utilizing Black Soldier Fly Larvae to Improve Bioconversion and Reduce Pollution: A Sustainable Method for Efficient Treatment of Mixed Wastes of Wet Distiller Grains and Livestock Manure

Widespread environmental contamination caused by huge amounts of wastes generated by human activities has become a critical global concern that requires urgent action. The black soldier fly (BSFL) has gradually been used to treat different wastes due to high efficiency and low cost. However, little information is available regarding the treatment of mixed wastes by BSFLs. The impact of BSFLs on conversion of cow manure (COM) and pig manure (PM) via the incorporation of wet distiller grains (WDG) was assessed. Results demonstrate that the waste reduction rate was increased by 20% by incorporating 45% WDG to COM and PM. The bioconversion rate of BSFLs in COM and PM also increased from 1.20 ± 0.02% and 0.92 ± 0.02% to 10.54 ± 0.06% and 10.05 ± 0.11%, respectively. Total nitrogen content and δ15N/14N ratios of WDG + COM and WDG + PM were found to be significantly lower than those of COM and PM alone (p < 0.01). The organic matter changes during manure degradation were further analyzed by combing ultraviolet-visible spectrum (UV-vis) with excitation-emission matrix (EEM) spectroscopy techniques and fluorescence area integration (FRI) method. The UV-vis spectra results indicate that the addition of WDG to manures resulted in the decreased aromaticity and molecular weight of the waste. EEM spectra demonstrated that the accumulative Pi,n values of regions III and V in COM, COM + WDG, PM, and PM + WDG were 58%, 49%, 52% and 63%, respectively. These results not only provide new insights into the potential of mixed wastes for BSFL treatment but also contribute to the basis for the formulation of effective management measurements that reduce and/or reuse these wastes.

Comparing the bacterial composition, succession and assembly patterns in plastisphere and kitchen waste composting with PLA/PBAT blends

Biodegradable plastics has aroused increasing concern due to the negative environmental impact of plastic waste, however, the impact of biodegradable plastics mixed into kitchen waste (KW) on composting remains poorly understood, especially focusing on bacterial communities in the unique "plastisphere". Here, KW composting for 120 days with adding poly lactic acid / poly butylene adipate-co-terephthalate (PLA/PBAT) plastics were conducted to reveal the dynamics of bacterial composition, succession, and assembly process in different ecological niches (compost and plastisphere). Results showed that the existence of PLA/PBAT plastics in composting would not significantly affect the safety and maturation of composts. After composting, 80% PLA/PBAT were degraded and there were prominent divergences of bacterial compositions between plastisphere, composts with PLA/PBAT and control. Co-occurrence network suggested that PLA/PBAT plastisphere exhibited higher network complexity and cohesion than that in compost, and PLA/PBAT increased bacterial module hubs, network hubs, and connectors in composting compared to control, but might enrich pathogens. Phylogenetic bin-based null model analysis indicated that stochastic processes obviously shaped the communities on PLA/PBAT plastisphere, but compare to control, PLA/PBAT plastics enhanced the contribution of deterministic processes on composting bacterial community assembly. These findings deeply understood the assembly patterns and diversity of plastisphere and composting processes, laying down a foundation on applying biodegradable plastics under the classification of domestic garbage.

Long-term microbial community succession and mechanisms of regulation of dissolved organic matter derivation in livestock manure fermentation system

Industrial-scale aerobic fermentation was conducted with livestock manures. Microbial inoculation promoted the growth of Bacillaceae and consolidated its position as the dominant microorganism. Microbial inoculation substantially influenced dissolved organic matter (DOM) derivation and variations of related components in the fermentation system. The relative abundance of humic acid-like substances of DOM increased from 52.19% to 78.27% in microbial inoculation system, resulting in a high humification level. Moreover, lignocellulose degradation and microbial utilization were the important factors influencing DOM content in fermentation systems. The fermentation system was regulated by microbial inoculation, thus achieving a high level of fermentation maturity.

Hydrothermal carbonization aqueous phase promotes nutrient retention and humic substance formation during aerobic composting of chicken manure

The aqueous phase (AP) of hydrothermal carbonization is rich in humic substances (HSs), which could influence the poultry manure composting process and the product quality. Here, raw AP and its modified product (MAP) with different nitrogen (N) contents were added into chicken manure composting at low (5%) or high (10%) rate. Results showed that all APs addition decreased the temperature and pH but AP-10% increased total N, HSs, and humic acid (HA) of compost by 12%, 18% and 27%, respectively. MAP applications increased the total phosphorus by 8-9% and MAP-10% enhanced the total potussium content by 20%. Additionally, both AP and MAP additions increased the contents of three major components of dissolved organic matter by 20-64%. In conclusion, both AP and MAP can generally improve the chicken manure compost quality, which provides a new idea for the recycling of APs derived from agro-forestry wastes during hydrothermal carbonization.

Phosphorus transformation behavior and phosphorus cycling genes expression in food waste composting with hydroxyapatite enhanced by phosphate-solubilizing bacteria

This study aimed to explore the effect of phosphate-solubilizing bacteria (PSB) Bacillus inoculation in the cooling stage on hydroxyapatite dissolution, phosphorus (P) forms transformation, and bacterial P cycling genes in food waste composting with hydroxyapatite. Results indicated that PSB inoculation promoted the dissolution of hydroxyapatite, increased P availability of compost by 8.1% and decreased the ratio of organic P to inorganic P by 10.2% based on sequential fractionation and ³¹P nuclear magnetic resonance spectroscopy. Illumina sequencing indicated Bacillus relative abundance after inoculation increased up to one time higher than control after the cooling stage. Network analysis and metabolic function of bacterial community analysis suggested inorganic P solubilizing genes of Bacillus and organic P mineralization genes of other genera were improved after inoculation in the core module. Therefore, bioaugmentation of PSB in the cooling stage may be a potential way to improve P bioavailability of bone and food waste in composting.

Coupling network of hydrogen sulfide precursors and bacteria in kitchen waste composting

This study was focused on the changes of hydrogen sulfide (H₂S), its precursors, and microorganisms associated with its transformation during the composting process of kitchen waste. The results showed that the content of cysteine (Cys) and methionine (Met) decreased by 32.3 % and 57.5 % respectively, while the content of sulfate (SO₄^2-) changed little during composting. The main release period of H₂S was during the high-temperature period of composting, Cys was its main precursor. Based on network analysis, a total of 15 core genera associated with the conversion of H₂S precursors were identified, and the transformation of the H₂S precursor was mainly influenced by Filomicrobium. Temperature, pH, and TN levels had a positive effect on Filomicrobium. It could find a balance point by controlling these three factors to reduce the production of H₂S.

Multi-omics analysis provides insight into the phytotoxicity of chicken manure and cornstalk on seed germination

To minimize environmental risks and the phytotoxic influence of organic materials on crop growth, it is necessary to test their phytotoxicity and maturity when they were used in farmland. However, the stress response of seed germination to chicken manure and cornstalks is not clear. This study used multi-omics analysis to investigate the inhibition mechanism of seed germination by chicken manure and cornstalk. Chicken manure caused destructive inhibition of seed germination with higher phytotoxicity (GI = 0). Cornstalk also had a low GI (8.81 %), while it mainly inhibited radicle growth (RL = 9.39 %) rather than seed germination (GR = 93.33 %). The response of radish seed germination to chicken manure and cornstalk phytotoxic stresses was accompanied by metabolic adjustments of storage substance accumulation, antioxidant enzyme activity change, phytohormone induction, and expression of specific proteins and gene regulation. Combined transcriptomic and proteomic analysis revealed that differential expression of 13,090 (5944 upregulated/7146 downregulated) and 3850 (2389 upregulated/1461 downregulated) genes (DEGs), and 1041 (82 upregulated/932 downregulated) and 575 (111 upregulated/464 downregulated) proteins (DEPs) at chicken manure and cornstalk treatment, respectively. Most down-regulated genes and proteins were involved in phenylpropanoid biosynthesis under chicken manure stress, which caused irreversible inhibition of seed germination. Down-regulation of phytohormone signal transduction-related genes under cornstalk stress resulted in inhibition of radicle growth, but the inhibitory stress was restorable. These findings provide new insight into the phytotoxicity of livestock manure and cornstalk on seed germination.

Bacillus subtilis reduces antibiotic resistance genes of animal sludge in vermicomposting by improving heat stress tolerance of Eisenia foetida and bacterial community adjustment

Antibiotic resistance genes (ARGs) in livestock industry have been recognized as a kind of pollutant. The effect of Bacillus subtilis (B. subtilis) as an additive for the reduction of ARGs in animal sludge from livestock and poultry wastewater treatment plant during vermicomposting was investigated. We also evaluated the oxidative stress level and growth of earthworms, Eisenia foetida, bacterial community succession, and the quality of the end products. Two treatments were conducted using B. subtilis, one at 18 °C and another at 28 °C. Controls were setup without the bacteria. The results showed that inoculation of B. subtilis promoted the degradation of organics at 28 °C and increased the germination index to 236%. The increased activities of the superoxide dismutase (1.69 U/mg pr) and catalase (8.05 U/mg pr) and the decreased activity of malondialdehyde (0.02 nmol/mg pr) by B. subtilis at 28 °C showed that the earthworms were relieved of heat stress. The addition of B. subtilis reduced the abundance of 32 target ARGs, including integron (intI-1), transposase (IS613) and resistant genes, such as sulfonamide (sul2), quinolone (oprJ), macrolide-lincosamide-streptogramin group B (ermF, ermB), tetracycline (tetL-02, tetX), β-lactama (blaOXA10-01) and aminoglycoside [strB, aac(6')-Ib(aka aacA4)-01, aac(6')-Ib(aka aacA4)-02]. Organic matter degrading Membranicola, Paludisphaera, Sphingorhabdus and uncultured bacterium belonging to the order Chitinophagales, nitrifying and nitrogen-fixing Singulisphaera and Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium, soil remediating Achromobacter, and plant growth promoting Kaistia, Galbibacter and Ilumatobacter were increased significantly (P < 0.05). However, the growth of harmful bacteria such as Burkholderiaceae was inhibited in the vermicompost. In earthworm guts, the probiotic Mesorhizobium was promoted, while the pathogenic uncultured bacterium belonging to the family Enterobacteriaceae was reduced. Besides, B. subtilis enhanced the host relationships between bacteria and ARGs. These findings might be helpful in the removal of ARGs in animal wastes and in understanding the synergy between earthworms and microorganisms.

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

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

Mechanism analysis of humification coupling metabolic pathways based on cow dung composting with ionic liquids

This study focused on how adding ionic liquids (IL) affects composting humification. During the warming and thermophilic phases, addition of IL increased precursors content, and increased the polymerization of humus (HS) at later stages. Furthermore, the final HS and humic acid (HA) content of experimental groups (T) groups 129.79 mg/g and 79.91 mg/g were higher than in control group (CK) 118.57 mg/g and 74.53 mg/g, respectively (p < 0.05). IL up-regulated the gene abundance of metabolism for carbohydrate and amino acid (AA), and promoted the contributions of Actinobacteria and Proteobacteria, which affected humification. The redundancy analysis (RDA) results showed that the citrate-cycle (TCA cycle)(ko0020), pentose phosphate pathway (ko00030), pyruvate metabolism (ko00620), glyoxylate and dicarboxylate metabolism (ko00630), propanoate metabolism (ko00640), butanoate metabolism (ko00650) positively correlated with HA and HI. HA and humification index (HI) positively correlated with AA metabolic pathways, and fulvic acid (FA) was negatively correlated with these pathways. Overall, metabolism for carbohydrate and AA metabolism favored compost humification. ILs improved metabolism for carbohydrate and amino acid metabolism, thus enhancing humification.

Preparation, biocontrol activity and growth promotion of biofertilizer containing Streptomyces aureoverticillatus HN6

Nowadays, due to the excessive dependence on chemical fertilizers and pesticides in agricultural production, many problems, such as soil hardening and soil-borne diseases, have become increasingly prominent, which seriously restrict the sustainable development of agriculture. The application of microbial fertilizer prepared by biocontrol microorganisms can not only improve soil structure and increase fertility but also have the function of controlling diseases. Streptomyces aureoverticillatus HN6 has obvious disease prevention and growth promotive effect, which can improve the rhizosphere fertility of plants and even regulate the rhizosphere microbial community of plants. Based on the comparison of frame composting and natural composting, we used the response surface method to optimize the preparation conditions of Streptomyces HN6 bacterial fertilizer. The results showed that natural composting not only produced higher composting temperatures and maintained long high temperature periods in accordance with local conditions, but was also more suitable for composting in the field according to local conditions. Therefore, the substrate's conductivity changed more, the ash accumulation increased, and the substrate decomposed more thoroughly. Thus, this composting method is highly recommended. Additionally, Streptomyces HN6 microbial fertilizer EC20 can reduce cowpea fusarium wilt and promote cowpea growth. The number of plant leaves, plant height and fresh weight, increased significantly in the microbial fertilizer EC20. Moreover, Streptomyces HN6 fertilizer EC20 could significantly induce soil invertase, urease and catalase activities. Our study highlights the potential use of Streptomyces HN6 as a biofertilizer to improve plant productivity and biological control of plant pathogenic fungi.