Maturity indices as an index to evaluate the quality of sulphur enriched municipal solid waste compost using variable byproduct of sulphur

Exogenous additive ferric sulfate regulates sulfur-oxidizing bacteria in cow manure composting to promote carbon fixation

Enhancing carbon fixation in the composting process was of great significance in the era of massive generation of organic solid waste. In this study, the experimental results showed that the contents of dissolved organic matter (DOM) in the experimental group (CT) were 37.58% higher than those in the control group (CK). The CO2 emission peaked on day 5, and the value of CK was 1.34 times that of CT. Significant differences were observed between the contents of sulfur fractions in CT and CK. This phenomenon may be due to the suppression of sulfur-reducing gene expression in CT. On day 51 of composting, the abundance of sulfur-oxidizing bacteria (SOB) Rhodobacter (5.33%), Rhodovulum (14.76%), and Thioclava (23.83%) in CT was higher than that in CK. In summary, the composting fermentation regulated by Fe2(SO4)3 increased the sulfate content, enhanced the expression of sulfur-oxidizing genes and SOB, and ultimately promoted carbon sequestration during composting.

Optimization of organic solid waste composting process through iron-related additives: A systematic review

Composting is an environmentally friendly method that facilitates the biodegradation of organic solid waste, ultimately transforming it into stable end-products suitable for various applications. The element iron (Fe) exhibits flexibility in form and valence. The typical Fe-related additives include zero-valent-iron, iron oxides, ferric and ferrous ion salts, which can be targeted to drive composting process through different mechanisms and are of keen interest to academics. Therefore, this review integrated relevant literature from recent years to provide more comprehensive overview about the influence and mechanisms of various Fe-related additives on composting process, including organic components conversion, humus formation and sequestration, changes in biological factors, stability and safety of composting end-products. Meanwhile, it was recommended that further research be conducted on the deep action mechanisms, biochemical pathways, budget balance analysis, products stability and application during organic solid waste composting with Fe-related additives. This review provided guidance for the subsequent targeted application of Fe-related additives in compost, thereby facilitating cost reduction and promoting circular economy objectives.

Nutrient-cycling functional gene diversity mirrors phosphorus transformation during chicken manure composting

Elucidating ecological mechanism underlying phosphorus transformation mediated by phosphate-solubilizing bacteria (PSB) during manure composting is an important but rarely investigated subject. The research objective is to disentangle ecological functions of the inoculation of PSB Pseudomonas sp. WWJ-22 during chicken manure composting based on gene quantification and amplicon sequencing. There are large dynamic changes in phosphorus fractions, gene abundances, and bacterial community structure. The PSB addition notably increased available phosphorus from 0.29-0.89 g kg-1 to 0.49-1.39 g kg-1 and significantly affected phosphorus fractionation. The PSB inoculation significantly affected composition of nutrient-cycling functional genes (NCFGs), and notably influenced bacterial community composition and function. Compost bacteria showed significant phylogenetic signals in response to phosphorus fractions, and stochastic processes dominated bacterial community assembly. Results emphasized that PSB addition increased functional redundancy, phylogenetic conservatism, and stochasticity-dominated assembly of bacterial community. Overall, findings highlight NCFG diversity can be a bio-indicator to mirror phosphorus transformation.

Management of plant nutrient dynamics under alkaline soils through graded application of pressmud and gypsum

An incubation experiment was conducted to monitor the effect of different organic matter inputs with the graded application of gypsum at different time intervals on soil pH, sodium (Na) content and available plant nutrients like nitrogen (N) and sulphur (S) in alkaline soil. The experiment was formulated with nine treatments, i.e. control (T1), recommended dose of fertilizer (RDF) (T2), RDF+Gyp1 (T3), RDF+FYM5+Gyp2 (T4), RDF+FYM10+Gyp1 (T5), RDF+PM5+Gyp2 (T6), RDF+PM10+Gyp1 (T7), RDF+FYM2.5+PM2.5+Gyp2 (T8), RDF+FYM5+PM5+Gyp1 (T9) with three replications. Periodical soil samples were taken at six and twelve months intervals. Results showed that the addition of organic matter reduced the pH and Na content in the soil. More reduction was observed at one year period as compared to six months. The addition of farmyard manure (FYM) and pressmud (PM) at 10 t/ha with gypsum (1 t/ha) improved available N and available S content as compared to organic inputs (5 t/ha) with gypsum (2 t/ha) in soil. Pressmud application with FYM showed better availability of plant nutrients and a reduction of soil pH (8.39 to 7.79) and Na content from 626 to 391 mEq/L in the soil during the incubation period. During the study, the application of treatment T9 (FYM and PM in equal ratio with 1 t/ha gypsum) showed a better availability of available N (175 to 235 kg/ha) and S (15.44 to 23.24 kg/ha) and reduced the active ion concentration of Na. This study is very useful for the management of sodium toxicity, improving soil health and the mineralization rate of organic matter through the application of organic inputs for sustainable crop production.

Biochar improves compost humification, maturity and mitigates nitrogen loss during the vermicomposting of cattle manure-maize straw

Maintaining humidification and inhibiting nitrogen losses during vermicomposting process have emerged to be key factors for high-quality productions. Previous data have showed outstanding functions of biochar addition in improving vermicomposting quality. In this study, the influence of bamboo biochar (BB) and rice husk biochar (RHB) addition on compost maturity, humification and nitrogen loss was evaluated in the vermicomposting of cattle manure and maize straw. Results revealed that BB or RHB amendment improved organic matter decomposition, enhanced humification and maturity of compost, particularly in the 10% BB treatment, which exerted the highest humic acids content and GI value. Furthermore, BB or RHB addition significantly reduced nitrogen losses, in which the volatilization of NH₃ and N₂O were reduced by 24.93%-66.23% and 14.91%-55.12%. The fewest nitrogen loss was detected in the treatment of 10% BB. Biochar inhibited nirK, nirS but promoted AOB-amoA, nosZ expression; fewer N₂O producing bacteria (Pseudomonas, Devosia, Luteimonas genus) were observed in the biochar treatment, and thereby decreased the N₂O emission. Therefore, 10% BB addition for co-vermicomposting cattle manure and maize straw is an efficient way to increase humification, maturity, and reduce nitrogen loss, and future applications following this strategy is believed to generate better productions.

Pressmud overcome lead toxicity by improving spinach biomass in lead-contaminated soils

Lead (Pb) pollution is a severe problem that primarily affects food chain in developing countries. Continuous use of Pb containing effluent for growing food crops builds up measurable concentration of Pb in soils; and adversely affects the soil properties and crop produce quality. To reduce the Pb metal toxicity in contaminated soil, a pot experiment was conducted with graded doses of pressmud (PM) (0, 2.5, 5.0, and 10.0 g/kg) and Pb (0, 100, 150, and 300 mg/kg soil). Various metal dynamics parameters were computed after spinach crop was harvested. Result showed that higher doses of Pb (300 mg/kg) diminished the spinach root and shoot biomass during the study; whereas, application of PM improved the spinach biomass. However, increasing the pressmud reduced the Pb concentration in shoot from 6.16, 5.99, 4.94, and 3.39 µg/g. Maximum reduction was measured in highest PM applied treatment in shoot (44.92%) and root (57.33%). In this experiment, increasing level of Pb significantly uptake was recorded with higher application rate of Pb (150 and 300 mg/kg). However, elevated doses of PM from control initially enhanced the small chunk of Pb and drastically reduced the shoot Pb uptake (0.060 to 0.049 mg/pot) in maximum level of PM applied treatment. This study is very useful to improve the soil health by immobilizing the labile fraction of Pb by addition of PM in Pb-contaminated soils.

A novel multi-criteria decision-making framework for selecting municipal solid waste management alternative with 2-dimensional uncertain linguistic sets

Municipal solid waste management (MSWM) has been considered as a complicated multi-criteria decision-making problem for the uncertain context and related criteria. To select an optimal MSWM scenario, this paper provides a comprehensive MCDM framework for decision-makers under 2-dimensional uncertain linguistic (2-DUL) environment. Distinguished from traditional approaches, this framework not only guarantees the consistency of comparison matrix but improves effectiveness and efficiency in the decision process. Moreover, it accurately solves the cardinal and ordinal information of MSWM scenarios. Firstly, due to ambiguous and uncertain decision context, the 2-DUL set, characterized by I class of the linguistic evaluation information and II class of the reliability of the assessment results, is adopted to describe decision-makers' preference. An expectation reduced-dimension is developed to effectively handle 2-DUL set. Secondly, to guarantee consistency and reduce numerical pairwise comparisons, a best-worst-method (BWM)-based analytic network process (ANP) is utilized to form the local priority vectors of the main criteria and sub-criteria. Main criteria weights and sub-criteria weights are then obtained by aggregating all local priority vectors. Thirdly, an extended QUALIFLEX approach is employed to rank all alternative MSWM scenarios by comparing the weighted concordance/discordance index among overall possible permutations of all alternative scenarios. Finally, the developed framework is applied in a case study to determine an optimal MSWM scenario in Beijing. Additionally, a comparison analysis is complemented. The results demonstrate that the proposed framework is feasible, efficient, and superior in MSWM scenarios selection.

Inhibitory Effects of the Addition of KNO3 on Volatile Sulfur Compound Emissions during Sewage Sludge Composting

Odor released from the sewage sludge composting process often has a negative impact on the sewage sludge treatment facility and becomes a hindrance to promoting compost technology. This study investigated the effect of adding KNO₃ on the emissions of volatile sulfur compounds, such as hydrogen sulfide (H₂S), dimethyl sulfide (DMS), and carbon disulfide (CS₂), during sewage sludge composting and on the physicochemical properties of compost products, such as arylsulfatase activity, available sulfur, total sulfur, moisture content, and germination index. The results showed that the addition of KNO₃ could inhibit the emissions of volatile sulfur compounds during composting. KNO₃ can also increase the heating rate and peak temperature of the compost pile and reduce the available sulfur loss. The addition of 4% and 8% KNO₃ had the best effect on H₂S emissions, and it reduced the emissions of H₂S during composting by 19.5% and 20.0%, respectively. The addition of 4% KNO₃ had the best effect on DMS and CS₂ emissions, and it reduced the emissions of DMS and CS₂ by 75.8% and 63.0%, respectively. Furthermore, adding 4% KNO₃ had the best effect from the perspective of improving the germination index of the compost.

Reuse of poor-quality water for sustainable crop production in the changing scenario of climate

The availability of freshwater is limited for agriculture systems across the globe. A fast-growing population demands need to enhance the food grain production from a limited natural resources. Therefore, researchers and policymakers have been emphasized on the production potential of agricultural crops in a sustainable manner. On the challenging side, freshwater bodies are shrinking with the pace of time further limiting crop production. Poor-quality water may be a good alternative for fresh water in water scarce areas. It should not contain toxic pollutants beyond certain critical levels. Unfortunately, such critical limits for different pollutants as well as permissible quality parameters for different wastewater types are lacking or poorly addressed. Marginal quality water and industrial effluent used in crop production should be treated prior to application in crop field. Hence, safe reuse of wastewater for cultivation of food material is necessary to fulfil the demands of growing population across the globe in the changing scenario of climate.

Insights into the effect of iron-carbon particle amendment on food waste composting: Physicochemical properties and the microbial community

The effects of iron-carbon (Fe-C) particle amendment on organic matter degradation, product quality and functional microbial community in food waste composting were investigated. Fe-C particles (10%) were added to the material and composted for 32 days in a lab-scale composting system. The results suggested that Fe-C particle enhanced organic matter degradation by 12.3%, particularly lignocellulose, leading to a greater humification process (increased by 15.5%). In addition, NO₃^--N generation was enhanced (15.9%) by nitrification with more active ammonia monooxygenase and nitrite oxidoreductase activities in the cooling and maturity periods. Fe-C particles not only significantly increased the relative abundances of Bacillus and Aspergillus for organic matter decomposition, but also decreased the relative abundances of acid-producing bacteria. RDA analysis demonstrated that the bacterial community was significantly influenced by dissolved organic matter, C/N, NO₃^--N, humic acid, volatile fatty acids and pH, while electrical conductivity was the key factor affecting the fungal community.

Toxicity and physicochemical parameters of composts including distinct residues from agribusiness and slaughterhouse sludge

Composting is useful for treatment of residues from agribusiness, but the potential toxicity of the final compost should be evaluated before its agricultural destination. The objective of this study was to evaluate the physicochemical characteristics and the toxicity of agribusiness residues using onion seeds as bioindicators. All tested treatments were composed by sludge from a swine slaughterhouse and sawdust. Besides the control, which included no additional materials, the other treatments included aviary bedding, rice husk and residue from tobacco industries as structuring materials. After 120 days of composting, for all treatments, the temperature inside the composting piles approached the environmental temperature, the physicochemical parameters indicated that the composts were stabilized and, except for the treatment including tobacco residues, that could be used for agriculture without impairing plant germination. Although the treatments including tobacco residues and rice husk showed evidence of cytotoxicity and genotoxicity at the beginning of the composting period, that was not observed for the treatment including aviary bedding. Such potential toxicity was not observed at the end of composting for any of the tested treatments.

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

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