Microbial inoculants and struvite improved organic matter humification and stabilized phosphorus during swine manure composting: Multivariate and multiscale investigations

Pyrolysis of pig waste from intensive farming operations: Kinetics, product distribution, and transformation of endogenous heavy metals

This study addresses the critical challenge of safe disposal and resource utilization of pig waste from intensive farming by investigating its pyrolysis behavior, product mechanisms, and heavy metal immobilization. The pyrolysis process was divided into four distinct stages, with kinetic parameters determined using the model-free FWO and KAS methods, ensuring accuracy without prior assumptions, complemented by the master plot method to elucidate reaction mechanisms. The optimal kinetic models identified as f(α)=4α34, f(α)=3(1-α)[-ln(1-α)]23, f(α)=3α23, f(α)=2α12. The volatile products, identified via TG-FTIR and Py-GC/MS, included CO₂, H₂O, CH₄, CO, carbonyl compounds, while pyrolysis oils were enriched with nitrogen-containing organics and ketones. Biochar produced at 450-750 °C demonstrated rich porosity, aromaticity, and high biochemical stability, with heavy metals predominantly immobilized in oxidizable and residual fractions (F3 +F4). FactSage 7.1 simulations provided novel insights into the phase transformations and migration trends of Zn, Mn, Cu, and Cr, highlighting the formation of stable slag or solid compounds at elevated temperatures, consistent with experimental findings. TCLP tests and ecological risk assessments confirmed the environmental safety of pig waste biochars, emphasizing the potential of pyrolysis for heavy metal stabilization. This work advances the understanding of pyrolysis mechanisms for pig waste from intensive farming and offers innovative solutions for sustainable pig waste management.

Effect of selenium and compost on physiological, biochemical, and productivity of chili under chromium stress

In the era of industrialization, chromium (Cr) as a metal poses a substantial threat to the ecosystem. Selenium (Se) is essential for minimizing heavy metal stress in crops and effectively reducing their accumulation in edible plant parts. This research work aimed to evaluate the synergistic effect of compost and Se for alleviation of Cr stress in chili plants. A greenhouse trail was conducted to investigate the individual and combined effects of foliage applied selenium (Na2SeO4 = 3 µM) and soil applied compost (250 mg kg-1, w/w) on the growth, physio-biochemical, antioxidant and of chili grown under varying levels of induced Cr stress (0, 100, and 200 mg kg-1 using K2Cr2O7). Findings revelaed that a significant linear reduction was observed in growth, biomass, and physiological parameters of chili plant with an increasing level of Cr concentrations. Maximum decrease in relative water content (20.04 and 27.21%) and total chlorophyll concentrations (11.73 and 20.57%) and increased in electrolyte leakage (59.14 and 130.52%) was observed at 100 and 200 mg kg-1 of Cr levels in soil in comparison with the control, respectively. Combined application of compost and selenium showed significant increase regardless of Cr concentrations in the soil. Synergistic approach of compost and selenium showed improved growth in comparison with the sole application in limiting the movement and uptake of Cr in the roots and fruits of chili plants. Moreover, improved physiological and antioxidant potential of chili plants helped to cope with higher levels of Cr stress by limiting the lipid peroxidation and membrane damange. The combined use of compost and selenium induces the physio-biochemical defense responses against of the varying levels of Cr stress in chili plants. This promising approach highlights the significant potential for growing chili crop in Cr-contaminated soils to achieve better quality and higher yields.

Harnessing the potential of exogenous microbial agents: a comprehensive review on enhancing lignocellulose degradation in agricultural waste composting

Composting converts organic agricultural wastes into value-added products, yet the presence of significant non-biodegradable lignocelluloses hinders its efficiency. The introduction of various exogenous microbial agents has been shown to effectively addresses this challenge. In this context, basing on the microbial enzymatic mechanism for lignocellulose degradation, this paper synthesizes the latest research advancements and practical applications of exogenous microbial agents in agricultural waste composting. Given that the effectiveness of lignocellulose degradation is highly dependent on the waste's inherent characteristics, it is crucial to carefully consider the composition of fungi and bacteria, the dosage of microbial agents, and the composting process operation, tailored to the specific type of agricultural waste. Moreover, the combination of additives with exogenous microbial agents can further enhance the degradation of lignocelluloses and the humification of organic matters. Furthermore, insights into the future research and application trends of exogenous microbial agents in agricultural waste composting was prospected.

Mitigating cadmium contamination in soil using Biochar, sulfur-modified Biochar, and other organic amendments

Biochar is a novel approach to remediating heavy metal-contaminated soil. Using various organic amendments like phyllosilicate-minerals (PSM), compost, biochar (BC) and sulfur-modified biochar (SMB), demonstrates superior adsorption capacity and stability compared to unmodified biochar (BC). The adsorption mechanisms of SMB are identified for its potential to increase soil-pH and reduce available cadmium (Cd). The study reveals the potential of BC and SMB in immobilizing Cd in contaminated soil. SMB demonstrated the highest adsorption capacity for Cd, followed by BC, PSM, and compost, with capacities ranging from 7.47 to 17.67 mg g-1. Both BC and SMB exhibit high adsorption capacities (12.82 and 17.67 mg g-1, respectively) and low desorption percentages (4.46-6.23%) at ion strengths of 0.01 to 0.1 mol-L-1 and pH levels ranging from 5 to 7. SMB showed a higher adsorption capacity (17.67 mg g-1) and lower desorption percentage (4.46-6.23%) compared to BC. The adsorption mechanism involves surface-precipitation, ion exchange, and the formation of Cd(OH)2 and CdCO3 precipitates, as well as interactions between Cd and organic sulfur, leading to more stable-Cd and CdHS+ compounds. Adding 1% SMB increased soil pH and significantly reduced available Cd, demonstrating its potential for pollutant remediation. The study underscores the promise of SMB in providing a sustainable solution for Cd-contaminated soil remediation.

Microbial fuel cell-assisted composting yields higher performance on metals passivation, antibiotics degradation, and resistance genes removal

Little scientific evidence on metal passivation, antibiotic degradation and resistance genes removal, is available under autogenetic electrochemical reactions during composting process. This study established microbial fuel cell (MFC)-assisted composting procedure to ascertain the removal performance and detoxification mechanisms involving metals, antibiotics and their resistance genes. Compared to control treatment, the bioavailability of zinc (Zn) and copper (Cu) in MFC-assisted treatment decreased by 7.8% and 26.9%, while the content of tetracycline (TCL) and oxytetracycline (OCL) reduced by 100% and 89%, respectively. Organics mineralization and humification were responsible for 80% and 70% of the variations in metal passivation and antibiotic degradation during composting process. A decrease of 54% was found for tetW gene, while copA gene increased by 42% in MFC-assisted composting treatment. These findings highlight the detoxification mechanisms underlying metal passivation and antibiotic degradation during composting process, and potentially offer valuable insights for environmental source protection and agricultural sustainable development.

Synergistic effects of heterogeneous mature compost and aeration rate on humification and nitrogen fixing during kitchen waste composting

Sludge mature compost (SMC) is notable for its high production, easy accessibility, and stable supply. This study investigated the impact of the SMC addition and different aeration rates on the humification and nitrogen fixing process during kitchen waste composting. The results demonstrated that addition of SMC prolonged the thermophilic phase, as a comparison, increased aeration shortened this phase. The addition of SMC and increased aeration enhanced humus formation and nitrogen retention. SMC introduced more amide and polysaccharide compounds into the compost, promoting the Maillard humification pathway. Additionally, both SMC and high aeration inhibited denitrification: the SMC reduced the abundance of the nirK gene, while high aeration decreased the abundance of nosZ gene. Network analysis revealed that higher aeration enhanced fungal interactions but diminished bacterial interactions. Conversely, SMC addition bolstered both bacterial and fungal interactions. The final compost product with SMC addition showed a 11.56%-44.19% reduction in antibiotic resistance gene content compared with the control group, and heavy metal contents remained within safe application limits. The combination of high SMC addition and high aeration achieved optimal humification and nitrogen retention, underscoring its potential as a promising solution for kitchen waste composting.

Impact of cellulolytic nitrogen-fixing composite inoculants on humification pathways and nitrogen cycling in kitchen waste composting

Low humification and nitrogen loss pose substantial challenges to the resource utilization in kitchen waste composting. This study investigated the effects of brown-rot fungi (BRF), cellulolytic nitrogen fixing bacteria (CNFB), and their composite microbial inoculants (CMI) during composting. Results indicated that microbial inoculants extended the thermophilic phase and enhanced cellulose degradation. Compared with the control, the degree of polymerization (HA/FA) in BRF, CNFB, and CMI was 2.28, 1.85, and 2.68 times higher, respectively, while increasing total nitrogen by 11.15%, 15.50%, and 19.73%. BRF and CMI primarily enhanced the Maillard humification pathway, while CNFB promoted the polyphenol humification pathway. Additionally, BRF enhanced nitrification and reduced denitrification, whereas CNFB and CMI improved nitrification, nitrogen fixation, and ammonification while reducing denitrification. Overall, BRF primarily promoted humification, while CNFB excelled in nitrogen retention. The CMI achieved optimal humification and nitrogen retention, indicating a potential sustainable solution for kitchen waste composting.

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

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

Role of cow dung and sawdust during the bioconversion of swine waste through the rotary drum composting process

The demand for strategic and environment-friendly swine waste (SW) management is critical in the northeastern states of India, which account for 46.7% of the country's total swine population. This paper examines nutrient-rich compost production from SW with minimal negative environmental fallout, using cow dung microbiological inoculum and sawdust bulking agent for expeditious rotary drum composting. Aerobic biodegradation conducted in a rotary drum composter (RDC), raised the feedstock temperature to > 40 °C in just 24 h, which stimulated thermophilic decomposition. The thermophilic phase remained for 16 days in the cow dung-amended 10:1:1 (swine waste:cow dung:sawdust) trial (RDC1) versus 7 days for the sawdust-amended 10:1 (swine waste:sawdust) trial (RDC2). After 20 days, the RDC1 product exhibited superior nutritional characteristics, with a total nitrogen content of 2.52%, a significantly reduced coliform population, and an overall weight loss of 25%. These findings highlight that incorporating cow dung (10% w/w) into SW and bulking agents through RDC produces high-quality compost in just 20 days. Thus, the livestock industry benefits significantly from this laboratory-scale method of improved waste management by producing valuable bioproducts via RDC.

Performance of co-composting Pholiota nameko spent mushroom substrate and pig manure at different proportions: Chemical properties and humification process

Co-composting is the controlled aerobic degradation of organics, using more than one feedstock. By combining the spent mushroom substrate of Pholiota nameko (SMS) and pig manure (PM), the benefits of each could be used to optimize the composting process and the final product. This study introduced a comprehensive evaluation strategy aimed at identifying the optimal co-composting ratio for these two substrates. A 120-day composting trial was conducted, blending SMS and PM in various ratios to evaluate the benefits of co-composting SMS-PM. The results indicated that dissolved organic matter (DOM) in SMS-derived compost primarily originated from plants, whereas PM-derived compost predominantly consisted of microbial metabolic products, and co-composting combined both sources. An increase in aromaticity and humification degree of DOM occurred during the composting process itself rather than being derived from autochthonous origin. Carbohydrates like phenols and alcohols broke down during composting, and microbes utilized polysaccharides as an energy source for humus formation. As co-composting progressed, the treatments with varying mass ratios of SMS to PM, including 8:2, 7:3, 6:4, 5:5, 4:6, and 3:7 were observed to result in a decline in aliphatic hydroxylated chains alongside an enhancement in aromaticity within the compost. Additionally, there was a conversion from organic carbon (C) to carboxyl C within humic acid (HA) due to oxidation and dehydrogenation processes that facilitated the formation of stable nitrogen-containing compounds characterized by condensed aromatic structures. Following thorough evaluation, it was determined that optimal composting efficacy occurred at a mass ratio of SMS to PM equal to 6:4. Post-compost analysis revealed increases in nutrient content; specifically, germination index (GI) value reached 132.7%, while organic matter content attained 45.3%. Conversely, electrical conductivity (EC), C contents of water-soluble substances and humin (Cwss and CHu) decreased by approximately 11.8%, 73.4%, and 29.8% respectively; meanwhile, C contents of humic-extracted acid and HA (CHE and CHA), along with degree of polymerization (DP), increased by 17.3%, 20.3% and 9.9% respectively. The proposed co-compost formula not only facilitated simultaneous recycling of both SMS and PM waste but also transformed them into high-quality organic fertilizers suitable for soil enrichment-effectively addressing challenges faced by both edible fungi cultivation and livestock industries while augmenting organic fertilizer sources for Black land protection.

Seaweed-derived etherified carboxymethyl cellulose for sustainable tissue engineering

Biodegradability, biocompatibility, abundant supply from renewable sources, and affordability are the outstanding properties of cellulose that have prompted substantial studies into its potential in biomedical applications. Beyond terrestrial sources of cellulose, seaweeds have attracted much attention as a potential source of cellulose because they are widely available. Cellulose and its byproducts may be extracted from various macroalgae species, including red, green, and brown algae. The extracted cellulose's qualities vary depending on the algae species, age, and extraction process utilized. Cellulose's characteristics are enhanced through chemical modifications, specifically etherification and esterification, which substitute functional groups for hydroxyl groups, yielding a range of products, including cellulose acetate (CA), cellulose nitrate, cellulose sulfate, methylcellulose, and carboxymethyl cellulose (CMC). The ability to modify CMC characteristics for particular applications is explored through techniques including grafting processes mixing, and cross-linking with other polymers. Moreover, tissue engineering is given significant consideration in the growing use of CMC and its altered forms in biological applications. These alterations allow for the production of scaffolds that promote tissue regeneration and cell proliferation, enabling CMC-based scaffolds for various tissue engineering uses. This review provides a comprehensive overview of CMC's properties, modifications, and potential in tissue engineering.

Self-ignition behaviour of corn cob, wheat bran and rice husk residues in ambient air from biomass gasification

The possibility of different agrowastes to self-ignite under ambient condition, due to exothermic reactions between their surface molecules and air or other oxidizing agents which are conveyed into the void volume between the particles, exists. It is imperative to investigate the self-ignition ability of these harzadous waste products causing environmental pollution after the milling process to avoid sudden fire outbreaks. In this study, the self-ignition attributes of corn cob, wheat bran and rice husk residues in ambient air from biomass gasification was investigated by evaluating their self-ignition temperatures using DIN EN 15188:2021 standard and Frank-Kamenetzkii's theory of thermal explosion at varying basket volume. The results revealed decrease in the ignition temperature of dust samples as ignition time and dust basket volume were increased. Sample C (rice husk dust residue) was considered to be the most hazardous with respect to its propensity to self-heating possessing the lowest self-ignition temperature of 173 °C at 800 mL cubic mesh. Its moisture content and activation energy of 1.41 % and 46.52 kJ/mol respectively were the lowest. Its thermal conductivity, carbon content, heating value and bulk density of 0.07 W/mK, 78.98 wt%, 26,895 kJ/kg and 255.4 kg/m3 respectively were the highest. Correlation coefficient from the Arrhenius plot showing the self-ignition behaviour of dust samples using the model of Frank-Kamenetzkii were 0.9976, 0.9910 and 0.9962 for corn cob, wheat bran and rice husk residues respectively. In conclusion, the data presented are effective in predicting the self-ignition ability of corn cob, wheat bran and rice husk residues in ambient air from biomass gasification in order to prevent sudden fire attack that may arise based on storage of their dust particles in food processing industries.

Eco-friendly natural rubber-based hydrogel loaded with nano-fertilizer as soil conditioner and improved plant growth

This study addresses the dual challenge of agricultural cost and waste management by harnessing agrarian waste to produce nano-fertilizers (NF) to enhance crop yield while mitigating environmental impacts. Recognizing the limitations of traditional hydrogels' non-biodegradability and their inability to sustain root zone moisture and nutrient levels, we developed an LNR/AAc/pectin hydrogel. This innovative hydrogel offers a viable solution that provides a consistent NF supply and improves water retention efficiently. Additionally, we utilized Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy-energy dispersive x-ray (SEM-EDX), and thermogravimetric analysis (TGA) to analyze the hydrogel's structure, stability, and form. Transmission electron microscopy (TEM) and X-ray fluorescence spectroscopy (XRF) were employed to ascertain the NF concentration. The optimization of the hydrogel's swelling and NF release was conducted through a 5-level, 2-factor Response Surface Methodology (RSM), focusing on the effects of the AAc: LNR ratio and pectin weight while maintaining constant concentrations of potassium persulfate (KPS) and MBA. Results revealed a high correlation between predicted and experimental values, with determination coefficients (R2) of 0.9982 for swelling and 0.9979 for NF release. Furthermore, the hydrogel exhibited a 96.30 % biodegradation rate after 120 days of soil burial. Our findings demonstrate the hydrogels' potential to significantly impact farming and gardening by ensuring a sustainable supply of nutrients to enhance soil moisture retention.

A comprehensive review on agricultural waste utilization through sustainable conversion techniques, with a focus on the additives effect on the fate of phosphorus and toxic elements during composting process

The increasing trend of using agricultural wastes follows the concept of "waste to wealth" and is closely related to the themes of sustainable development goals (SDGs). Carbon-neutral technologies for waste management have not been critically reviewed yet. This paper reviews the technological trend of agricultural waste utilization, including composting, thermal conversion, and anaerobic digestion. Specifically, the effects of exogenous additives on the contents, fractionation, and fate of phosphorus (P) and potentially toxic elements (PTEs) during the composting process have been comprehensively reviewed in this article. The composting process can transform biomass-P and additive-born P into plant available forms. PTEs can be passivated during the composting process. Biochar can accelerate the passivation of PTEs in the composting process through different physiochemical interactions such as surface adsorption, precipitation, and cation exchange reactions. The addition of exogenous calcium, magnesium and phosphate in the compost can reduce the mobility of PTEs such as copper, cadmium, and zinc. Based on critical analysis, this paper recommends an eco-innovative perspective for the improvement and practical application of composting technology for the utilization of agricultural biowastes to meet the circular economy approach and achieve the SDGs.

Modifying row-configuration and vermicompost application reduces intercropped peanut (Arachis hypogaea L.) yield instability and penalty in sorghum at Babile, Eastern Ethiopia

The yield of intercropped peanut (Arachis hypogaea L.) in cereal crops was drastically reduced by 20-55 %, presumably due to high interspecific competition caused by illogical field layout and imbalanced fertilizer application. Field experiments were conducted in the Babile district of Eastern Ethiopia during the main cropping seasons of 2021 and 2022 to assess the possibilities of minimizing the peanut yield penalty and instability while improving sorghum production. The treatments consisted of two monocrops (SM = sole sorghum, GM = sole peanut), three row-configurations (S1G1 = 1-row sorghum with 1-row peanut, S1G2 = 1-row sorghum with 2-row peanut, MBILI = Managing Beneficial Interactions in Legume Intercrops via modifying 2-rows of sorghum with 2-rows of peanut), and four vermicompost levels (0, 1.5, 3, and 4.5 t/ha), which were factorial arranged in a randomized complete block design and replicated three times. Peanut under MBILI with 4.5 t/ha vermicompost boosted peanut seed/pod and dry pod yield by 17.5 % and 20 %, respectively, with a corresponding rise of sorghum grain yield by 72 % and net profit by 48 %. Unlike GM, intercropping peanut with sorghum significantly increases yield with time, which shows the high yield stability and sustainability of intercropping over monocropping. Interestingly, peanut yield in this treatment was statistically on par with pure stand, supporting the concept that MBILI row-configuration is necessary for maintaining the potential yield of the peanut crop. Similarly, the assessment of bio-ecological indices infers the superiority of the MBILI in terms of land use efficiency, yield advantage, and profitability compared to other combinations. This implies that modifying the planting geometry along with balanced nutrient supply could alleviate the detrimental effects of sorghum over peanut by minimizing interspecific competition, thereby giving better yield and economic value for subsistence farmers.

Lead stabilization and remediation strategy with soil amendment in situ immobilization in contaminated range lands

In situ immobilization is a potential approach that can be used to remediate low-to-medium levels of heavy-metal in contaminated-soil. There is little known about how modifications to soil characteristics may affect Pb's release from soil. The four different amendments, triple-superphosphate and attapulgite were combined in Ad-1; zeolite and triple-superphosphate were in Ad-2; hydroxyapatite and humus were in Ad-3; and nano-carbon. These amendments are mostly made of phyllosilicate minerals, humus, base minerals, and nano-carbon, respectively. Results revealed that the test amendments' maximal Pb-adsorption capacity varied from 7.47 to 17.67 mg g-1. Surface precipitation and ion-exchange were found to be the main mechanisms for Pb-adsorption by Ad-1 and Ad-2, while Ad-3 and Ad-4 were promising among the all, according to analysis of the modifications both before and after Pb loading. When the pH dropped (7-1) or the ion-strength rose (0-0.2 M), there was a discernible rise in the Pb-desorption percentages from the amendments. It was determined that Ad-3 and Ad-4 were more effective in situ immobilizing lead in contaminated-soils because of their high adsorption capacities (12.82 and 17.67 mg g-1) and low-desorption percentages (4.46-6.23%) at ion-strengths of 0.01-0.1 mol L-1 and pH levels ranging from 5 to 7.

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.

Green and efficient synthesis of cellulose nanocrystals from Hamelia patens leftover via hydrolysis of microwave assisted-ionic liquid (MWAIL) pretreated microcrystalline cellulose

The efficient bioconversion of the lignocellulosic agro-waste has immense importance in biorefinery processing in extracting the cellulose and saccharide fractions. To achieve this, a series of chemical pretreatments is employed, thus concerning environmental threats limit its use. Therefore, an ionic liquid is employed for pretreatment before sustainable extractions owing to its safe manipulation, recycling, and reusability. Specifically, microwave-assisted ionic liquid (MWAIL) pretreatment has significant importance in extracting high cellulose yield at less thermal power consumption. In this study, the leftover stalks of Hamelia patens were subjected to MWAIL pretreatment at 60, 70, 80, and 90 °C to extract microcrystalline cellulose (MCC). Subsequently, the MCC was fabricated into cellulose nanocrystals (CNC) through hydrolytic treatment using acidic and ionic liquids and denoted as CNC-AH and CNC-ILH. Thus obtained CNC was characterized by FTIR, FESEM, XRD, and TGA to investigate the influence of solvent on its morphology, crystallinity, and thermal stability of CNC. The results support that the CNC-ILH has comparatively more thermal and dispersal stability with a reduced crystallinity index than CNC-AH. The surprising results of CNC-ILH signify its utilization in diverse applications in the food and industrial sectors.

Responses of soil enzymatic activities and microbial biomass phosphorus to improve nutrient accumulation abilities in leguminous species

Fertilizers application are widely used to get a higher yield in agricultural fields. Nutrient management can be improved by cultivating leguminous species in order to obtain a better understanding of the mechanisms that increase the amount of available phosphorus (P) and potassium (K) through fertilizer treatments. A pot experiment was conducted to identify the leguminous species (i.e., chickpea and pea) under various fertilizer treatments. Experimental design is as follows: T0 (control: no fertilizer was applied), T1: P applied at the level of (90 kg ha-1), T2: (K applied at the level of 90 kg ha-1), and T3: (PK applied both at 90 kg ha-1). All fertilizer treatments significantly (p < 0.05) improved the nutrient accumulation abilities and enzymes activities. The T3 treatment showed highest N uptake in chickpea was 37.0%, compared to T0. While T3 developed greater N uptake in pea by 151.4% than the control. However, T3 treatment also increased microbial biomass phosphorus in both species i.e., 95.7% and 81.5% in chickpeas and peas, respectively, compared to T0 treatment. In chickpeas, T1 treatment stimulated NAGase activities by 52.4%, and T2 developed URase activities by 50.1% higher than control. In contrast, T3 treatment enhanced both BGase and Phase enzyme activities, i.e., 55.8% and 33.9%, respectively, compared to the T0 treatment. Only the T3 treatment improved the activities of enzymes in the pea species (i.e., BGase was 149.7%, URase was 111.9%, Phase was 81.1%, and NAGase was 70.0%) compared to the control. Therefore, adding combined P and K fertilizer applications to the soil can increase the activity of enzymes in both legume species, and changes in microbial biomass P and soil nutrient availability make it easier for plants to uptake the nutrients.

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

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

Biodiversity and core microbiota of key-stone ecological clusters regulate compost maturity during cow-dung-driven composting

The primary objectives of this study were to explore the community-level succession of bacteria, fungi, and protists during cow-dung-driven composting and to elucidate the contribution of the biodiversity and core microbiota of key-stone microbial clusters on compost maturity. Herein, we used high-throughput sequencing, polytrophic ecological networks, and statistical models to visualize our hypothesis. The results showed significant differences in the richness, phylogenetic diversity, and community composition of bacteria, fungi, and eukaryotes at different composting stages. The ASV191 (Sphingobacterium), ASV2243 (Galibacter), ASV206 (Galibacter), and ASV62 (Firmicutes) were the core microbiota of key-stone bacterial clusters relating to compost maturity; And the ASV356 (Chytridiomycota), ASV470 (Basidiomycota), and ASV299 (Ciliophora) were the core microbiota of key-stone eukaryotic clusters relating to compost maturity based on the data of this study. Compared with the fungal taxa, the biodiversity and core microbiota of key-stone bacterial and eukaryotic clusters contributed more to compost maturity and could largely predict the change in the compost maturity. Structural equation modeling revealed that the biodiversity of total microbial communities and the biodiversity and core microbiota of the key-stone microbial clusters in the compost directly and indirectly regulated compost maturity by influencing nutrient availability (e.g., NH4+-N and NO3--N), hemicellulose, humic acid content, and fulvic acid content, respectively. These results contribute to our understanding of the biodiversity and core microbiota of key-stone microbial clusters in compost to improve the performance and efficiency of cow-dung-driven composting.

Effects of Bacillus-based inoculum on odor emissions co-regulation, nutrient element transformations and microbial community tropological structures during chicken manure and sawdust composting

This study aims to evaluate whether different doses of Bacillus-based inoculum inoculated in chicken manure and sawdust composting will provide distinct effects on the co-regulation of ammonia (NH3) and hydrogen sulfide (H2S), nutrient conversions and microbial topological structures. Results indicate that the Bacillus-based inoculum inhibits NH3 emissions mainly by regulating bacterial communities, while promotes H2S emissions by regulating both bacterial and fungal communities. The inoculum only has a little effect on total organic carbon (TOC) and inhibits total sulfur (TS) and total phosphorus (TP) accumulations. Low dose inoculation inhibits total potassium (TK) accumulation, while high dose inoculation promotes TK accumulation and the opposite is true for total nitrogen (TN). The inoculation slightly affects the bacterial compositions, significantly alters the fungal compositions and increases the microbial cooperation, thus influencing the compost substances transformations. The microbial communities promote ammonium nitrogen (NH4+-N), TN, available phosphorus (AP), total potassium (TK) and TS, but inhibit nitrate nitrogen (NO3--N), TP and TK. Additionally, the bacterial communities promote, while the fungal communities inhibit the nitrite nitrogen (NO2--N) production. The core bacterial and fungal genera regulate NH3 and H2S emissions through the secretions of metabolic enzymes and the promoting or inhibiting effects on NH3 and H2S emissions are always opposite. Hence, Bacillus-based inoculum cannot regulate the NH3 and H2S emissions simultaneously.

Novel process for organic wastewater treatment using aerobic composting technology: Shifting from pollutant removal towards resource recovery

In this study, an organic wastewater treatment process based on aerobic composting technology was developed in order to explore the transition of wastewater treatment from pollutants removal to resource recovery. The novelty of the process focuses towards the microbial metabolic heat that is often ignored during the composting, and taking advantage of this heat for wastewater evaporation to achieve zero-discharge treatment. Meanwhile, this process can retain the wastewater's nutrients in the composting substrate to realize the recovery of resources. This study determined the optimum condition for the process (initial water content of 50 %, C/N ratio of 25:1, ventilation rate of 3 m3/h), and 69.9 % of the total heat generated by composting was used for wastewater treatment under the condition. The HA/FA ratio of composting substrate increased from 0.07 to 0.53 after wastewater treatment, and the retention ratio of TOC and TN was 52.3 % and 61.7 %, respectively, which proved the high recycling value of the composting products. Thermoduric and thermophilic bacteria accounted for 44.3 % of the community structure at the maturation stage, which played a pivotal role in both pollutant removal and resource recovery.

Effects of oyster shells on maturity and calcium activation in organic solid waste compost

With the rapid development of aquaculture, the production of oyster shells has surged, posing a potential threat to the environment. While oyster shell powder is widely recognized for its inherent alkalinity and rich calcium carbonate content, making it a superior soil conditioner, its role in organic solid waste composting remains underexplored. To investigate the effects of varying concentrations of oyster shell powder on compost maturation and calcium activation, this study employed thermophilic co-composting with acidic sugar residue and bean pulp, incorporating 0% (control), 10% (T1), 20% (T2), 30% (T3), and 40% (T4) oyster shell powder. Findings revealed that appropriate proportions of oyster shell powder significantly enhance temperature stability during composting and elevate maturation levels, notably reducing ammonia emissions between 62.5% and 76.7%. Intriguingly, the calcium in the oyster shell powder was significantly activated during composting, with the 40% addition group achieving the highest calcium activation rate of 48.5%. In summation, the inclusion of oyster shell powder not only optimizes the composting process but also efficiently activates the calcium, resulting in an alkaline organic-inorganic composite soil conditioner with high exchangeable calcium content. This research holds significant implications for promoting the high-value utilization of oyster shells.

Hydrothermal Alkaline Treatment (HALT) of Foam Fractionation Concentrate Derived from PFAS-Contaminated Groundwater

While foam fractionation (FF) process has emerged as a promising technology for removal of per- and polyfluoroalkyl substances (PFASs) from contaminated groundwater, management of the resulting foam concentrates with elevated concentrations of PFASs (e.g., >1 g/L) remains a challenge. Here, we applied hydrothermal alkaline treatment (HALT) to two foam concentrates derived from FF field demonstration projects that treated aqueous film-forming foam (AFFF)-impacted groundwater. Results showed >90% degradation and defluorination within 90 min of treatment (350 °C, 1 M NaOH) of all 62 PFASs (including cations, anions, and zwitterions) identified in foam concentrates. Observed rate constants for degradation of individual perfluoroalkyl sulfonates (PFSAs, CnF2n+1-SO3-), the most recalcitrant class of PFASs, in both foam concentrates were similar to values measured previously in other aqueous matrices, indicating that elevated initial PFAS concentrations (e.g., PFHxSinit = 0.55 g/L), dissolved organic carbon (DOC; up to 4.5 g/L), and salt levels (e.g., up to 325 mg/L chloride) do not significantly affect PFAS reaction kinetics. DOC was partially mineralized by treatment, but a fraction (∼15%) was recalcitrant. Spectroscopic characterization revealed molecular features of the HALT-recalcitrant DOC fraction, and nontarget high-resolution mass spectrometry tentatively identified 129 nonfluorinated HALT-recalcitrant molecules. Analysis of process energy requirements shows that treating PFAS-contaminated foam concentrates with HALT would add minimally (<5%) to the overall energy requirements of an integrated FF-HALT treatment train.

A review of struvite crystallization for nutrient source recovery from wastewater

Nutrient recovery from wastewater not only reduces the nutrient load on water resources but also alleviates the environmental problems in aquatic ecosystems, which is a solution to achieve a sustainable society. Besides, struvite crystallization technology is considered a potential nutrient recovery technology because the precipitate obtained can be reused as a slow-release fertilizer. This review presents the basic properties of struvite and the theory of the basic crystallization process. In addition, the possible influencing variables of the struvite crystallization process on the recovery efficiency and product purity are also examined in detail. Then, the advanced auxiliary technologies for facilitating the struvite crystallization process are systematically discussed. Moreover, the economic and environmental benefits of the struvite crystallization process for nutrient recovery are introduced. Finally, the shortcomings and inadequacies of struvite crystallization technology are presented, and future research prospects are provided. This work serves as the foundation for the future use of struvite crystallization technology to recover nutrients in response to the increasingly serious environmental problems and resource depletion.

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.

The various effect of cow manure compost on the degradation of imazethapyr in different soil types

Adding compost to soil is an effective strategy to promote the degradation of organic pollutants and reduce ecological risks. However, the effect of compost on the degradation of imazethapyr (IMET) in different soil types is not clear. To address this issue, a pot experiment was conducted, and high-throughput sequencing and mass spectrometry technology were used to identify the influence of cow manure compost on the degradation efficiency of IMET in black soil and saline-alkali soil and the role of key microorganisms. The results showed that adding compost to black soil increased the degradation rate of IMET by 12.58% and shortened the half-life by 53.37%, while in saline-alkali soil, the degradation rate of IMET decreased by 6.99% with no significant change in the half-life. High-throughput sequencing results showed that adding cow manure compost (mass ratio of 4%) significantly increased the abundance of bacterial families capable of degrading organic pollutants in black soil, but had an inhibitory effect on this bacterial community in saline-alkali soil. Redundancy analysis (RDA) results showed that total organic carbon (TOC), alkali-hydrolyzable nitrogen (AN), ammonia nitrogen (NH₄⁺-N) and nitrate nitrogen (NO₃^--N) were the main factors driving microbial community variation. Mass spectrometry analysis indicated that IMET generated three metabolites during the degradation process. Sphingomonadaceae and Vicinamibacteraceae could accelerate the breaking of side-chain alkyl groups, while Chitinophagaceae could cause the rearrangement of the imidazole ring structure, gradually metabolizing IMET into small organic molecules. The application of appropriate cow manure compost can promote the development of IMET-degrading bacteria by adjusting the organic carbon and dissolved nitrogen content in black soil. In the future, the quantitative effects of organic fertilizer application on the IMET degradation process in different soil types should be further analyzed, and microbial isolation and purification should be used to enhance the ability of microorganisms to degrade herbicides.

Greenhouse gas emission during swine manure aerobic composting: Insight from the dissolved organic matter associated microbial community succession

Greenhouse gas emissions during aerobic composting is unavoidable, but good practices can minimize emission. Therefore, to explore the key factors influencing the release of greenhouse gas emissions during composting, the inaction of organic matter conversion, greenhouse gas emissions and bacterial community structure during co-composting with different ratio (pig manure and corn straw) over a 6-week period was studied. The excitation-emission matrix fluorescence spectroscopy with the parallel factor was used to identify that dissolved organic matter associated microbial community succession mainly influenced greenhouse gas emissions. Protein-like fractions of dissolved organic matter were more likely to decompose and promote CH₄ and CO₂ emissions, while the humic-like fractions of dissolved organic matter positively affected N₂O emissions. The largest of greenhouse gas emissions was appeared in MR2 with 12.7 kg CO₂-eq, and the MR3 and MR4 reduced greenhouse gas emissions by 26.8 % and 11.4 %, respectively.

Phosphorus functional microorganisms and genes: A novel perspective to ascertain phosphorus redistribution and bioavailability during copper and tetracycline-stressed composting

There is limited information on the phosphorus availability under copper and tetracycline-amended composting: Insights into microbial communities and genes. Thus, this work investigated the phosphorus redistribution and transformation, illustrated the variation in microbial communities and genes, and ascertained the multiple action-patterns among which within copper and tetracycline-amended composting. Phosphorus bioavailability reduced by 8.96 % ∼ 13.10 % due to the conservation of Ex-P to Ca-P. Copper and tetracycline showed a significant effect on fungal succession, but not to bacteria, as well as inhibited the phosphorus functional genes in fungal communities, while accelerated it in bacterial communities. Under the copper/tetracycline-stressed conditions, bacterial Firmicutes could promote the mineralization of organic phosphorus, and bacterial Proteobacteria might facilitate the dissolution of inorganic phosphorus. These findings could provide theoretical guidance for the further research on phosphorus bioavailability ascribed to microbial communities and genes.

Passivation mechanism of Cu and Zn with the introduction of composite passivators during anaerobic digestion of pig manure

Heavy metals in livestock manure pose a threat to the environment after biogas fertilizer being utilized, while its bioavailability is reduced substantially by passivator during the anaerobic digestion. In this study, an optimal composite passivator of humic acid, fly ash and biochar with proportion of 7.5%:7.5%:7.5% and 5.0%:7.5%:7.5% is obtained and the passivation mechanism on Cu and Zn during anaerobic digestion of pig manure is explored. The content of humic acid (HA) in biogas residue increased by 15.66-27.82%, which promoted the transformation from FA-Cu/Zn to HA-Cu/Zn and was beneficial to the passivation of Cu and Zn. The bioavailability of Cu and Zn was reduced by the adsorption and complexation at the early and middle stages of anaerobic digestion. Humic substances play a major role in the passivation of heavy metals at the late stage. The composite passivator can improve the humification degree of biogas residue and reduce heavy metal biotoxicity.

Rare alkaline phosphatase-harboring bacteria mediate organic phosphorus mineralization during swine manure composting

Deciphering ecological functions of alkaline phosphatase (phoD)-harboring bacteria in composting systems is crucial but poorly understood. High-throughput sequencing, gene quantification, and statistical analyses were applied to investigate effects of abundance and diversity of phoD-harboring bacteria (PHB) on phosphorus availability during swine manure composting. Results showed that available phosphorus notably increased from 0.5 to 1.43 g kg^-1, and physicochemical properties and enzyme activities affected PHB community composition. Phylogenetic signals of PHB responded notably to temperature and phosphorus components, and stochasticity (94.2 %) dominated community assembly. Abundance and diversity of PHB directly and indirectly influenced phosphorus availability, and rare PHB mediated organic phosphorus mineralization. A phosphate-solubilizing bacterium (PSB) Pseudomonas sp. WWJ-22 isolated from compost displayed good efficiency in mineralizing lecithin, demonstrating the highest phosphorus-solubilizing level of 116.3 mg L^-1. This study highlights ecological roles of PHB on phosphorus availability and provides a potential PSB candidate for composting.