Evaluation of maturity and stability parameters of composts prepared from agro-industrial wastes

Degradation of high concentrations of commercial polylactide packaging on food waste composting in pilot-scale test

The increasing use of synthetic biodegradable polymers, such as aliphatic polyesters, has led to a greater need to understand their behavior in an end-of-life scenario as food packaging materials. The aim of this work was to investigate the effect on composting of high to 10 wt% concentration of commercial polylactide packaging in food waste during a 98-day pilot-scale test. Members of the genera Bacillus, Geobacillus, Caldibacillus, Compostibacillus, Novibacillus, Planifilum and Aeribacillus accounted for 77 % of the bacterial community at the initial stage. Significant fragmentation of the polylactide packaging was observed after 14 days, and the appearance of low-molecular weight (approximately 5.4 kDa) hydrolytic degradation products led to an increase in biodiversity and a prolongation of the thermophilic stage by 12 days. The results obtained show the possibility of efficient disposal of food waste with high concentration of polylactide packaging under industrial composting conditions.

Effects of tomato straw fermentation on nutrients and bacterial community structure

Unsustainable straw treatment methods detrimentally affect the environment and ecology. Aerobic fermentation (AE) and anaerobic fermentation (AN) are environmentally friendly treatments that better utilise straw resources. In this study, high-throughput sequencing was used to investigate the effects of AE and AN on nutrient content and microbial community structure during tomato straw fermentation. Nitrate nitrogen, available phosphorus, available potassium, and fulvic acid contents following AE were 1250.04 mg/kg, 80.34 %, 161.39 %, and 49.31 %, respectively, which were higher than those following AN. Ammonium nitrogen, humic acid, and humic substance levels following AN were 309.07 %, 31.18 %, and 17.38 %, respectively, which were higher than those following AE. Firmicutes (24.76 %) and Actinobacteria (12.93 %) were more abundant following AE, whereas Proteobacteria (33.82 %) and Bacteroidetes (33.82 %) exhibited higher abundance following AN. AE more effectively eliminated pathogenic bacteria (22.01%-0.26 %) and encouraged stronger interactions between dominant bacterial genera. Redundancy and Mantel test analyses revealed that electrical conductivity and temperature were the most important environmental factors affecting bacterial communities in AE and AN, respectively. AE had a stronger effect on effective nutrient release from tomato straw, implying its greater application potential as a fertiliser. Overall, our study provides a theoretical basis for the optimisation of fermentation methods and processes.

Insights from meta-analysis on carbon to nitrogen ratios in aerobic composting of agricultural residues

Given the heterogeneity of raw materials, the diversity of composting processes, and the complexity of biological transformations, systematically exploring the critical role of the initial carbon-to-nitrogen (C/N) ratio in the aerobic composting of agricultural residues is challenging within a single experimental study. This study employs meta-analysis to investigate this role. Statistical analysis of 192 scholarly articles confirmed that most studies adhere to the recommended optimal initial C/N range of 25 and 30, where enhanced compost maturity and nutrient accumulation are observed. The findings indicate that optimal initial C/N ratios vary by agricultural residue type. A C/N ratio of 20 to 30 facilitates controlling the composting duration within 45 days, while a C/N ratio of 30 to 35 necessitates extending the duration beyond 45 days. The study highlights the effectiveness of adjusting the C/N ratio and applying microbial inoculants and physical amendments to optimize composting outcomes and control the composting duration.

Effect of initial moisture content, resulting from different ratios of vegetable waste to maize straw, on compost was mediated by composting temperatures and microbial communities at low temperatures

Owing to the huge amounts and perishable character of vegetable wastes, composting is one of the best options for recycling vegetable wastes post-harvest. The initial moisture content (MC) is critical for optimizing composting process, but the effect of high MC in undehydrated vegetable wastes on composting was rarely reported. For this, the plant-scale windrows were prepared by mixing cauliflower waste and maize straw at different ratios to control initial MC of 70 % (T1-70) and 80 % (T2-80), respectively, and composted in winter. As composting progressed, substantial organic matter degradation, progressive humification, decreases in electrical conductivity and increases of pH and germination index (GI) were observed in both treatments. Nonetheless, T1-70 accelerated heating rate early during composting, prolonged high temperature period (>50 °C) by 30 d, thus increased the harmless level of composting, and significantly improved the humification of end-products compared to T2-80. Results also revealed that T1-70 activated more indigenous microbes and enhanced microbial interactions early during composting, with the fungi enriched in T1-70 playing an important role in accelerating the composting process. Remarkably, the difference in composting temperatures, humification degree, and microbial communities between the two treatments was most significant during the maturation phase. In this phase, MWH_CFBk5, Planktosalinus, Pseudopedobacter, and Luteimonas enriched in T1-70 were positively correlated with humification indices. It is suggested that the effect of initial MC, resulting from different ratios of vegetable waste to maize straw, on their composting was mediated by the composting temperature and microbial communities at low temperatures.

Changes in the Glucose Concentration Affect the Formation of Humic-like Substances in Polyphenol-Maillard Reactions Involving Gibbsite

The polyphenol-Maillard reaction is considered one of the important pathways in the formation of humic-like substances (HLSs). Glucose serves as a microbial energy source that drives the humification process. However, the effects of changes in glucose, particularly its concentration, on abiotic pathways remain unclear. Given that the polyphenol-Maillard reaction requires high precursor concentrations and elevated temperatures (which are not present in soil), gibbsite was used as a catalyst to overcome energetic barriers. Catechol and glycine were introduced in fixed concentrations into a phosphate-buffered solution containing gibbsite using the liquid shake-flask incubation method, while the concentration of glucose was controlled in a sterile incubation system. The supernatant fluid and HLS components were dynamically extracted over a period of 360 h for analysis, thus revealing the influence of different glucose concentrations on abiotic humification pathways. The results showed the following: (1) The addition of glucose led to a higher degree of aromatic condensation in the supernatant fluid. In contrast, the supernatant fluid without glucose (Glu0) and the control group without any Maillard precursor (CK control group) exhibited lower degrees of aromatic condensation. Although the total organic C (TOC) content in the supernatant fluid decreased in all treatments during the incubation period, the addition of Maillard precursors effectively mitigated the decreasing trend of TOC content. (2) While the C content of humic-like acid (CHLA) and the CHLA/CFLA ratio (the ratio of humic-like acid to fulvic-like acid) showed varying increases after incubation, the addition of Maillard precursors resulted in a more noticeable increase in CHLA content and the CHLA/CFLA ratio compared to the CK control group. This indicated that more FLA was converted into HLA, which exhibited a higher degree of condensation and humification, thus improving the quality of HLS. The addition of glycine and catechol without glucose or with a glucose concentration of 0.06 mol/L was particularly beneficial in enhancing the degree of HLA humification. Furthermore, the presence of glycine and catechol, as well as higher concentrations of glucose, promoted the production of N-containing compounds in HLA. (3) The presence of Maillard precursors enhanced the stretching vibration of the hydroxyl group (-OH) of HLA. After the polyphenol-Maillard reaction of glycine and catechol with glucose concentrations of 0, 0.03, 0.06, 0.12, or 0.24 mol/L, the aromatic C structure in HLA products increased, while the carboxyl group decreased. The presence of Maillard precursors facilitated the accumulation of polysaccharides in HLA with higher glucose concentrations, ultimately promoting the formation of Al-O bonds. However, the quantities of phenolic groups and phenols in HLA decreased to varying extents.

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.

Recent Trends and Advances in Additive-Mediated Composting Technology for Agricultural Waste Resources: A Comprehensive Review

Agriculture waste has increased annually due to the global food demand and intensive animal production. Preventing environmental degradation requires fast and effective agricultural waste treatment. Aerobic digestion or composting uses agricultural wastes to create a stabilized and sterilized organic fertilizer and reduces chemical fertilizer input. Indeed, conventional composting technology requires a large surface area, a long fermentation period, significant malodorous emissions, inferior product quality, and little demand for poor end results. Conventional composting loses a lot of organic nitrogen and carbon. Thus, this comprehensive research examined sustainable and adaptable methods for improving agricultural waste composting efficiency. This review summarizes composting processes and examines how compost additives affect organic solid waste composting and product quality. Our findings indicate that additives have an impact on the composting process by influencing variables including temperature, pH, and moisture. Compost additive amendment could dramatically reduce gas emissions and mineral ion mobility. Composting additives can (1) improve the physicochemical composition of the compost mixture, (2) accelerate organic material disintegration and increase microbial activity, (3) reduce greenhouse gas (GHG) and ammonia (NH3) emissions to reduce nitrogen (N) losses, and (4) retain compost nutrients to increase soil nutrient content, maturity, and phytotoxicity. This essay concluded with a brief summary of compost maturity, which is essential before using it as an organic fertilizer. This work will add to agricultural waste composting technology literature. To increase the sustainability of agricultural waste resource utilization, composting strategies must be locally optimized and involve the created amendments in a circular economy.

Enhanced humus synthesis from Chinese medicine residues composting by lignocellulose-degrading bacteria stimulation: Upregulation of key enzyme activity and neglected indirect effects on humus formation

Chinese medicine residues (CMHRs) resource is attracting widespread attention, as it is expected to be produced into Humus-rich fertilizer for soil application. This study aimed to promote effective humus (HS) production through lignocellulose-degrading bacteria (LDB) addition and explore the biological regulation mechanism of LDB affecting lignocellulose-to-humus conversion. The results showed higher HS production was achieved, with 109.73 and 111.44 g·kg-1, and HA/FA was raised by 12.70-16.02 % in compost products by LDB addition stimulation. Significant upregulation of β-glucanase and xylanase activities catalyzed higher decomposition of lignocellulose toward more HS potential precursors supply. Furthermore, exogenous LDB intervention induced microbial community restructure and microbial network establishment via enriching synergism functional bacteria, i.e., Thermobifida, Paenibacillus, Nonomuraea, etc. Mantel test results showed that it was variation of cellulose, hemicellulose and HS that affected microbial community succession (p < 0.01, r > 0.6), which represented the positive action of LDB addition stimulation on HS synthesis upregulation. Further exploration suggested LDB had an indirect effect on HS formation by enhanced lignin and hemicellulose conversion based on the Random Forest model and Partial least-squares path modeling results. This research provides new insights into the trigger effects of LDB introduction on upregulating HS synthesis and is expected to propose new perspectives for HS efficient production in CMHRs composting.

Effects of biochar and volcanic rock addition on humification and microbial community during aerobic composting of cow manure

Additives are important for accelerating humification during aerobic composting. The impacts of porous additives biochar and volcanic rock on the physicochemical parameters, maturity indicators, microbial communities, and bacterial functional metabolism during the aerobic composting of cow manure were investigated in this study. The results showed that the biochar addition decreased the E4/E6 value by 10.42% and increased the abundance of Geobacillus (1.69 times), and volcanic rock addition decreased the E4/E6 value by 11.31% and increased the abundance of Thermobacillus (1.29 times) and Paenibacillus (1.72 times). The network analysis demonstrated that biochar promoted maturity by reducing the abundance of Pseudomonas and increasing the abundance of genes related to the metabolism of other amino acids, while volcanic rock promoted maturity by reducing the abundance of genes related to nucleotide metabolism. These results provided data and theoretical justification for the selection of porous additives for composting.

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.

Composting and vermicomposting of sewage sludge at various C/N ratios: Technological feasibility and end-product quality

Even though sewage sludge (SS) contains a high level of pollutants, it is rich in essential plant nutrients and has the potential to enhance soil fertility. However, the SS must be further treated through pre-composting plus vermicomposting to make it safe for use on food crops. More research and data are needed to determine how different carbon-to-nitrogen ratios (C/N) affect the feasibility and quality of composting vs vermicomposting of SS. Therefore, in this study we comprehensively evaluated the feasibility and end-product quality of compost and vermicompost produced from SS under different C/N ratios. SS was mixed with pelletized wheat straw (PWS) at various proportions to produce C/N ratios of 6:1, 18:1, 28:1, and 38:1, then pre-composted for 14 days followed by vermicomposting using the earthworm Eisenia andrei for 120 days. Agrochemical properties were measured at 0, 30, 60, 90, and 120 days. Results revealed significantly higher levels of agrochemicals in vermicompost compared to compost, including total potassium (37-88%) and magnesium (4.3-12%), nitrate nitrogen (71-98%), available potassium (53-88%), available phosphorus (79%), available magnesium (54-453%), available boron (48-303%), and available copper (2.5-82%). However, lower levels of ammonium nitrogen by (59-85%), available iron (2.3-51.3%), available manganese (29.7-52.2%), available zinc (10.5-29.8%), total carbon (0.75-4.5%), and total nitrogen (1.6-22.2%) were measured. Comparison of the various C/N ratios, showed that vermicompost with an 18:1 C/N ratio outperformed compost and demonstrated the highest earthworm population (165 pieces/kg). Thus, vermicomposting SS at an 18:1 C/N ratio is strongly recommended as a sustainable technology for producing high-quality vermicompost from SS.

Evaluation of different composting systems on an industrial scale as a contribution to the circular economy and its impact on human health

Due to the production of volatile organic compounds (VOCs), large-scale composting can cause air pollution and occupational health issues. Due to this, it is necessary to determine if the amount generated poses a health risk to plant workers, which can be a starting point for those in charge of composting plant facilities. As a result, the goal of this work is to conduct a thorough analysis of both the physicochemical features and the VOC generation of three large-scale systems. For ten weeks, the three different composting plants were monitored weekly, and VOC identification and quantification were performed using GC-MS gas chromatography. It has been observed that the biggest risk related with VOC formation occurs between the fourth and fifth weeks, when microbial activity is at its peak. Similarly, it has been demonstrated that xylenes and toluene are the ones that are produced in the greatest quantity. Finally, after ten weeks of processing, it was discovered that the material obtained complies with the regulations for the sale of an amendment.Implications: The evaluation and monitoring of the composting processes at an industrial scale is very important, due to the implications they bring. VOCs are produced by the operation of composting facilities with substantial amounts of solid waste, such as the companies in this study. These may pose a health risk to those working in the plants; thus, it is critical to understand where the VOCs occur in the process in order to maintain workers' occupational health measures. This form of evaluation is rare or nonexistent in Colombia, which is why conducting this type of study is critical, as it will provide crucial input into determining when the highest levels of VOC generation occur. These are the ones that may pose a risk at some point, but with proper occupational safety planning, said risk may be avoided. This work has evaluated three composting systems, with different types of waste and mixtures. According to reports, while composting systems continue to produce VOCs and their generation is unavoidable, the potential risk exists only within the plant. These findings can pave the way for the implementation of public policies that will improve the design and operation of composting plants. There is no specific legislation in Colombia for the design and execution of this sort of technology, which allows the use of organic waste.

Investigation of underlying links between nitrogen transformation and microorganisms' network modularity in the novel static aerobic composting of dairy manure by "stepwise verification interaction analysis"

Conventional composting is a viable method treating agricultural solid waste, and microorganisms and nitrogen transformation are the two major components of this proces. Unfortunately, conventional composting is time-consuming and laborious, and limited efforts have been made to mitigate these problems. Herein, a novel static aerobic composting technology (NSACT) was developed and employed for the composting of cow manure and rice straw mixtures. During the composting process, physicochemical parameters were analyzed to evaluate the quality of compost products, and microbial abundance dynamics were determined using high-throughput sequencing technique. The results showed that NSACT achieved compost maturity within 17 days as the thermophilic stage (≥55 °C) lasted for 11 days. GI, pH, and C/N were 98.71 %, 8.38, and 19.67 in the top layer, 92.32 %, 8.24, and 22.38 in the middle layer, 102.08 %, 8.33, and 19.95 in the bottom layer. These observations indicate compost products maturated and met the requirements of current legislation. Compared with fungi, bacterial communities dominated NSACT composting system. Based on the stepwise verification interaction analysis (SVIA), the novel combination utilization of multiple statistical analyses (Spearman, RDA/CCA, Network modularity, and Path analyses), bacterial genera Norank Anaerolineaceae (-0.9279*), norank Gemmatimonadetes (1.1959*), norank Acidobacteria (0.6137**) and unclassified Proteobacteria (-0.7998*), and fungi genera Myriococcum thermophilum (-0.0445), unclassified Sordariales (-0.0828*), unclassified Lasiosphaeriaceae (-0.4174**), and Coprinopsis calospora (-0.3453*) were the identified key microbial taxa affecting NH₄⁺-N, NO₃^--N, TKN and C/N transformation in the NSACT composting matrix respectively. This work revealed that NSACT successfully managed cow manure-rice straw wastes and significantly shorten the composting period. Interestingly, most microorganisms observed in this composting matrix acted in a synergistic manner, promoting nitrogen transformation.

Effect of calcium peroxide assisted microwave irradiation pretreatment on humus formation and microbial community in straw and dairy manure composting

In this study, the effects of four pretreatment methods on the crystallinity of maize straw were compared, and the CaO₂ assisted microwave pretreatment was selected for straw and dairy manure composting. The humification and microbial community were investigated. Results showed that the pretreatment increased the initial water-soluble carbon, which favored the microbial activity, and the CO₂ release increased by 15.71%. Pretreatment promoted the lignocellulose degradation, with total degradation ratio of 37.06%. The final humic acid content was 11.39 g/kg higher than the control. Spearman correlation analysis indicated that polyphenols and amino acids were significantly related to humus formation. In addition, pretreatment rendered the Firmicutes the most dominant phylum, and increased the metabolic intensity of reducing sugar metabolism, aromatic amino acid biosynthesis and carbon fixation pathways. Redundancy analysis revealed that the dominant genus of Firmicutes was significantly positively correlated with humus, while that of Actinobacteriota was correlated with CO₂ release.

Reactive oxygen species accelerate humification process during iron mineral-amended sludge composting

The production of hydroxyl radicals (OH) has been documented during composting. However, the effect of OH on composting efficiency remains unclear. Here, iron mineral supplemented thermophilic composting (imTC) is proposed and demonstrated for enhancing OH production and accelerating the maturation of composting. The results indicated that the maximum OH production of imTC was 1922.74 μmol·kg^-1, which increased by 1.39 times than that of ordinary thermophilic composting (oTC). Importantly, the increase of OH could greatly enhance organic matter degradation and humic substances formation during imTC, resulting in shorting the maturity time by 25 %. Enrichment of laccase-producing bacteria resulted in higher laccase activity (31.85 U·g^-1) in imTC compared with oTC (23.82 U·g^-1), which may have contributed to the higher level of humification in imTC treatment. This work, for the first time, proposes a feasible strategy for improving composting efficiency through the regulation of OH production during aerobic composting.

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.

Humification evaluation and carbon recalcitrance of a rapid thermochemical digestate fertiliser from degradable solid waste for climate change mitigation in the tropics

Indiscriminate, unhygienic and unscientific disposal of solid wastes poses significant risks leading to soil, water and air pollution. Abiotic and nonenzymatic rapid thermochemical processing technology provides a solution for the management of degradable solid waste at the source, converting it to organic digestate fertiliser within a day, thus overcoming the main drawback of the long time span required for composting. A study was performed to evaluate the maturity parameters and the extent of humification of the thermochemical digestate fertiliser and the raw biowaste substrate. We made an objective assessment of the recalcitrance efficiency of the added thermochemical digestate fertiliser on tropical Ultisol soil grown with two cycles of tomato and amaranthus crop sequences. Unlike the raw biowaste substrate, the thermochemical digestate complied with the threshold standards of compost maturity parameters and humification indices. Soil application of the thermochemical digestate fertiliser brought significant additions to the labile, microbial biomass and recalcitrant fractions of soil organic carbon within a year after four cycles of crop growth, as revealed by principal component analysis. Linear regression analysis revealed a strong and significant fit of the labile and microbial biomass carbon fractions with the total dry biomass of amaranthus and tomato. The thermochemical digestate fertiliser imparted a recalcitrance index of 85.57 % and enhanced the soil carbon stock by 4.81 % over the compost-based treatments with a superior soil carbon sequestration rate. The study confirmed that thermochemical digestate fertiliser is a fairly humified, high-resource organic fertiliser input with enhanced agronomic biomass production and recalcitrance efficiency, favouring soil carbon sequestration in Ultisol soils of the tropics.

Nutrient recovery and changes in enzyme activity during vermicomposting of hydrolysed chicken feather residue

Chicken feathers are hazardous to the environment because of their poor digestibility and potential as a source of environmental contaminants. However, this waste contains valuable plant nutrients that can be recovered and used to improve soil fertility and agricultural productivity. The objectives of this study were to evaluate how effective vermicomposting is at recovering nutrients and changes in enzymatic activity during vermicomposting of hydrolysed chicken feather residues (HCFR). The study included four treatments with three replications at different HCFR and pelletized wheat straw (PWS) mixing proportions: (T1) 25% HCFR+75% PWS with earthworms, (T2) 25% HCFR+75% PWS without earthworms, (T3) 50% HCFR+50% PWS with earthworms, and (T4) 50% HCFR+50% PWS (w/w) without earthworms. Eisenia andrei was used in the experiment for 120 days. Earthworm treatments recovered more available plant nutrients than non-earthworm treatments by 14% N - NO 3 - (T1); 50% K (T3); 47% Mg (T3); 75% P (T3); 55% B (T3); 34% Cu (T3); 40% Fe (T1); 46% Mn (T3); 11% Zn (T1). However, N - NH 4 + was significantly reduced by -80% (T1). Acid phosphatase, arylsulphatase, alanine aminopeptidase, and leucine aminopeptidase were more active in the treatments with earthworms and positively correlated with P and C: N ratio. Alanine aminopeptidase (3752 µmol AMCA.g-1.h-1) and leucine aminopeptidase (4252 µmol AMCL.g-1.h-1) had higher activities in T3 on day 60 of vermicomposting. As a result, the earthworm treatment recovers more plant nutrients than the non-earthworm treatments, and it can be recommended as a better vermicomposting approach for nutrient recovery from HCFR.

Metagenomics analysis revealed the coupling of lignin degradation with humus formation mediated via shell powder during composting

This study was the first to explore the effect of shell powder (SP) on lignin degradation and humus (HS) formation during composting. The results showed that the treatment group (T) with SP consumed more polyphenols, reducing sugar and amino acids than the control group (CK), especially the rate of reducing sugar consumption in T (50.61 %) was significantly higher than CK (28.40 %). SP greatly enhanced the efficiency of lignin degradation (T:45.47 %; CK:24.63 %) and HS formation (T:34.93 %; CK:20.16 %). The content of HA in T was 12.94 mg/g while CK was 12.06 mg/g. SP maintained a continuous increase in the relative abundance of AA1, AA3 after cooling phase. Meanwhile, T (48.98 %) significantly increased the abundance of Actinobacteria compared with CK (37.19 %). Actinobacteria, AA1 and AA3 were identified as the main factors promoting lignin degradation and HS formation by correlation analysis. Therefore, adding SP could be a novel strategy to improve compost quality.

Influence of thermally activated peroxodisulfate pretreatment on gaseous emission, dissolved organic matter and maturity evolution during spiramycin fermentation residue composting

Aerobic composting combined with appropriate pretreatment is promising to achieve the utilization of antibiotics fermentation residues (AFRs). This research studied the effect of thermally activated peroxodisulfate (TAP) pretreatment on greenhouse gas (GHGs) emission, dissolved organic matter (DOM) and maturity evaluation during spiramycin fermentation residue (SFR) composting. Three treatments were conducted from co-composting of SFR and wheat straw, while 90% and 99.9% residual spirmycin removal pretreatment SFR by TAP were provided and compared with raw SFR. The cumulative CO₂ and NH₃ emissions increased by 17.2% and 30.8% after TAP pretreatment removed 99.9% residual spiramycin in SFR, while the cumulative CH₄ and N₂O emission decreased by 34.0% and 5.27%, respectively. The DOM, humic acid (HA)/fulvic acid (FA) and NH₄⁺/NO₃^- analysis confirmed that the composting maturity was improved with the increasing of HA and NO₃^- content by TAP pretreatment.

Combined use of olive mill waste compost and sprinkler irrigation to decrease the risk of As and Cd accumulation in rice grain

Sprinkler irrigation has been successfully introduced in rice production as an alternative to the traditional flooding system, allowing water savings and the reduction of As accumulation in the grain. However, the same conditions can increase Cd mobility and grain accumulation, an effect that needs to be countered. A 3-year field experiment was set-up in a Mediterranean region (Extremadura, Spain), to evaluate how the application of compost from olive mill waste (single application, 80 t ha^-1), influences the accumulation of As and Cd in the grain under different irrigation regimes. Accumulation of As in the grain was always lower in the sprinkler irrigation when compared with the flooding irrigation, reaching a 5-fold difference in the third year. Compost application did not evidence a clear effect on the As accumulation in the rice grain, but highly significant negative correlations (p < 0.001) were obtained between As content in the grain (total, inorganic, and organic) and the humification parameters in the soil, evidencing the importance of using a mature and stable organic amendment to avoid As accumulation in the grain. Cadmium accumulation in the rice grain decreased in each treatment where compost was applied, relatively to the non-treated counterpart (e.g., from 0.080 to <0.010 mg kg^-1, in direct seeding with sprinkler irrigation, in the third year). There were no significant differences in the total inorganic As between treatments with or without compost application, but it was possible to observe an increase in the predominance of the organic As over the more toxic inorganic As, when compost was applied, allowing a decrease in the risk associated to As accumulation. Therefore, the aerobic cultivation of rice, with the simultaneous application of an adequate source of organic matter, can be considered a good solution to cope with the risk of accumulation of As and Cd in the rice grain.

Mechanism associated with the positive effect of nanocellulose on nitrogen retention in a manure composting system

Additives can play important roles in effectively inhibiting nitrogen losses during livestock manure composting due to the activities of microbes. This study investigated the effects of adding nanocellulose at 300 mg/kg, 600 mg/kg, and 900 mg/kg (NC900) on nitrogen conversion, nitrogen conversion functional genes, and related microorganisms during composting. The results showed that compared with the control, nanocellulose hindered the ammoniation reaction. In addition, NC900 promoted nitrification, interfered with the denitrification process, and reduced the abundance of the nirK gene, thereby increasing the nitrate nitrogen content and decreasing ammonia spillover. NC900 promoted nitrogen fixation by increasing the abundance of members of Rhizobiales, which play important roles in nitrogen fixation. In general, compared with the control, NC900 improved the retention of nitrogen by controlling ammonia emissions. The results obtained in this study demonstrate that nanocellulose can be applied in the treatment of organic solid waste and agricultural production.

Compost preparation, chemical analyses and users' perception in the utilization of water hyacinth, Ethiopia

Lake Tana is the largest freshwater body in Ethiopia. Currently, the lake has been facing alarming environmental degradation and loss of biodiversity due to the invasion of water hyacinth. Although the weed is invasive, it can be converted into various benefits. Hence, this study was conducted in North Eastern Lake Tana, Sheha Gomengie Kebele. The main objective is compost preparation in terms of its drying periods, analyses, and user perception. Physicochemical and nutrient analyses were performed according to the standard procedures. Acid digestion was used for heavy metal analyses. From the result, the pH measurements ranged from 7.619 ± 0.195 to 7.719 ± 0.261, and the moisture content ranged from 38.712 ± 0.680 to 49.60 ± 9.06%. The mean electrical conductivity (EC) values of all treatments of matured compost ranged from 2.780 ± 0.542 to 3.51 ± 0.971 ds/m. The TN values of the matured compost ranged from 0.420 ± 0.379 to 0.754 ± 0.194 on a dry weight basis. The overall mean values of the C:N ratio for all the treatments were 11.60 which is within an acceptable range. A high amount of available P concentrations was observed in all compost treatments which ranged from 2.740 ± 0.190 to 2.940 ± 1.410 g/kg. Moreover, the concentrations of heavy metals in all treatments were below the permissible limit of different agencies and there was also no significant difference in the mean values of analysis of variance at (P < 0.05). Therefore, the prepared compost can be recommended for better agricultural purposes. Considering users' understanding of compost preparation as an opportunity, converting WH into compost is promising in terms of its rich supply and the possibility of preparing in the dry season where labor is abundant. Therefore, it can be one way of sustainably reducing WH adverse effects on the Lakeshore.

Bioaugmentation mechanism on humic acid formation during composting of food waste

In this study, microbes were added to food waste compost in order to investigate the bioaugmentation mechanism of Humic acid (HA) formation. Thermogravimetric analysis, structural equation model, Fourier transform infrared spectroscopy and statistical analysis were utilized to explain the bioaugmentation mechanism. The results showed that bioaugmentation increased humification rate and degree. Bioaugmentation not only promoted the formation of aromatic structures and CC bonds but also brought different change orders of functional groups in HA. The HA obtained in bioaugmentation group (BA, 7.51 g/kg) was significantly higher compared to the control group (CK, 2.37 g/kg). Similarly, the HA/FA of BA (1.90) was also higher than that of CK (0.62), and peaked at 2.34 on day 40. The polyphenol humification pathway played a major role regardless of the addition of inoculant. However, the exogenous microbes promoted protein and carbohydrate degradation in the initial stage, and the abundance of precursors (amino acids and reducing sugars) enhanced both Maillard and polyphenol humification pathways. When polyphenol was insufficient in later stage, bioaugmentation mainly embodied in the strengthening of Maillard humification pathway. This finding benefited the practice of directional humification process of food waste composting.

Study on dynamic changes of microbial community and lignocellulose transformation mechanism during green waste composting

There are few reports on the material transformation and dominant microorganisms in the process of greening waste (GW) composting. In this study, the target microbial community succession and material transformation were studied in GW composting by using MiSeq sequencing and PICRUSt tools. The results showed that the composting process could be divided into four phases. Each phase of the composting appeared in turn and was unable to jump. In the calefactive phase, microorganisms decompose small molecular organics such as FA to accelerate the arrival of the thermophilic phase. In the thermophilic phase, thermophilic microorganisms decompose HA and lignocellulose to produce FA. While in the cooling phase, microorganisms degrade HA and FA for growth and reproduction. In the maturation phase, microorganisms synthesize humus using FA, amino acid and lignin nuclei as precursors. In the four phases of the composting, different representative genera of bacteria and fungi were detected. Streptomyces, Myceliophthora and Aspergillus, maintained high abundance in all phases of the compost. Correlation analysis indicated that bacteria, actinomycetes and fungi had synergistic effect on the degradation of lignocellulose. Therefore, it can accelerate the compost process by maintaining the thermophilic phase and adding a certain amount of FA in the maturation phase.

Frass derived from black soldier fly larvae treatment of biodegradable wastes. A critical review and future perspectives

Inadequately treated biodegradable waste is considered an environmental, social and economic threat worldwide, which call for great attention. Waste treatment with larvae of the black soldier fly (BSF, Hermetia illucens) complies with the concepts of circular economy, as it enables the transformation of these wastes into marketable products, closing loops and promoting circularity. The processing residues of the treatment (frass) is constantly generated in waste management facilities in large volumes, and this product can be used as an organic fertilizer in agriculture, stimulating a transition to a circular economy. However, many aspects related to frass are still unknown, such as its varying composition of nutrients, microorganisms and bioactive compounds, its post-processing requirements for improved biological stabilization, its behavior in the soil and action in the plants' metabolism, among other aspects. In this review article, we highlight the potential of frass from BSF larvae treatment of biodegradable waste in the world market regarding its possible use as a fertilizer, summarize recent results with this novel product and point towards future research perspectives.

Investigation of the aerobic biochemical treatment of food waste: A case study in Zhejiang and Jiangsu provinces in China

Food waste production is increasing rapidly and becoming a global concern. In areas with small production volumes and scattered production sources, the use of biochemical processors can be a beneficial supplement to the centralized treatment method for the in-situ treatment of wastes to effectively improve the efficiency of resource utilization. China is an important case study for this global issue; however, the implementation and outcomes of this process are not clear in China. In this study, field investigation and laboratory analysis were carried out on 14 biochemical processors in four representative regions of the Jiangsu and Zhejiang Provinces. The results showed that biochemical processors mostly used high-temperature aerobic fermentation, accounting for more than 80% of the commonly used procedures. The fermentation period was relatively short and ranged from 48 h to 10 days. Only 21.4% of devices were equipped with relatively complete secondary pollution-control units, which introduced the risk of secondary pollution during operation. The fermentation products exhibited common characteristics of acidity, high salt levels, and low maturity, rendering them unsuitable for agricultural use directly prior to an additional secondary fermentation process. Therefore, it is necessary to unify the design standards of biochemical processors and develop acid-resistant thermophilic microbial inoculants to increase fermentation efficiency. Thus, this study has significant implications in regulating food waste and serves as a theoretical and practical reference point to promote its in-situ treatment.

Aerobic Composting of Sugar Pressmud with Stabilized Spentwash and selected Microbial Consortium

India is the world’s largest producer of sugar, with an annual production capacity of 29 million tonnes. Each crushing season, this intern produces over 10 million tonnes of pressmud, which is difficult to dispose of due to its inherent properties. The present study is part of larger investigation for treatment and disposal of pressmud and spentwash. Further, scope of this research article is confined to utilization of pressmud for aerobic composting of pressmud along with selected microbial consortium and stabilized spentwash. Composting was carried out in an open area with 50 kg of pressmud and 1% (w/w) dosage of microbial consortium. Stabilized spentwash was used at concentrations of 25, 50, 100, 150 and 200% (v/w) and applied at predetermined time intervals. The entire study lasted for 50 days and the results were compared to those recommended by the Fertilizer Control Order (FCO), Ministry of Agriculture, Government of India (1). In an organic compost, the FCO recommends a minimum concentration of 12%, 0.80%, 0.40%, and 0.40% in TOC, TKN, phosphorous and potassium, with a maximum C/N ratio of 20. During composting, the addition of 150% (CH5) stabilized spentwash resulted in a maximum nutrient concentration in the majority of the parameters analysed. CH5 showed that the concentration of TOC, TKN, C/N, phosphorous and potassium were 25.92±2.19%, 2.16±0.29%, 12.28±0.66, 6.55±0.11% and 15.90±1.37% respectively. Hence, it can be concluded that selected microbial consortium is capable of decomposing the organic matter found in pressmud. Additionally, the application of stabilized spentwash enhanced the nutritional content of end product.

Evolution of physicochemical properties and bacterial community in aerobic composting of swine manure based on a patent compost tray

The objective of this study was to explore the changes in physicochemical properties and bacterial community during swine manure composting with a new compost tray (CT). The results showed that the organic matter (OM), moisture content (MC), and C/N decreased. The total Kjeldahl nitrogen (TKN), P₂O₅, K₂O and humic acids (HAs) contents of the compost increased. The properties of the final compost product comply with the requirements of regulation except for the moisture according to NY/T 525-2012. Firmicutes, Actinobacteria, Proteobacteria and Bacteroidetes were the major phyla during the composting. Genus Terrisporobacter played a key role in degrading organic (OM). The content of K₂O was main factors driving the succession of bacterial communities. These findings shed some novel lights into the dynamic changes of physicochemical propertied and their impact on bacterial community in a composting process.

Effect of biochar combined with a biotrickling filter on deodorization, nitrogen retention, and microbial community succession during chicken manure composting

The high-nitrogen content and dense structure of poultry manure compost cause volatilization of N to ammonia (NH₃). This study evaluated the combined application of biochar and biotrickling filtration (BTF) to remove of odor in chicken manure mixed straw compost (w/w, 2.5:1). Adding of 10% biochar reduced NH₃, hydrogen sulfide (H₂S), and total volatile organic compounds (TVOCs) contents by 20.04%, 16.18%, and 17.55% respectively, and decreased the N loss rate by 8.27%, compared with those observed in control. The organic matter content decreased by 28.11% and germination index reached 97.36% in the experimental group. Meanwhile, the N-cycling microorganisms such as Pusillimonas and Pseudomonas became more active, and the relative abundance of sulfur-cycling microorganisms Hydrogenispora decreased in the experimental group. Following BTF application, the NH₃, H₂S, and TVOCs removal rates reached 95%, 97%, and 53%, respectively.

The addition of sawdust reduced the emission of nitrous oxide in pig manure composting by altering the bacterial community structure and functions

Although composting, a measure to dispose agricultural waste, is widely accepted and applied, specific knowledge of microbially driven effects on nitrous oxide (N₂O) emissions during composting remains limited. Here, we monitored the impact of sawdust on N₂O emissions during pig manure composting. The results suggested that adding sawdust to the compost improved the compost temperature and reduced N₂O emissions. The addition of sawdust significantly altered the bacterial community structure and enhanced community turnover during the composting process. The addition of sawdust significantly reduced the relative abundance of denitrification and ureolysis, while increasing the relative abundance of nitrogen fixation. Specifically, adding sawdust may reduce N₂O emissions by reducing the relative abundance of Salinithrix, Truepera, Azomonas, Iamia, Silanimonas, Phycisphaera, and Gp21 during the thermophilic and mature phases of the composting period.

The Use of Phosphate Washing Sludge to Recover by Composting the Leachate from the Controlled Landfill

The percolation of rainwater and runoff water through household waste in the dumpsite generally leads to an overabundance of leachate in Moroccan landfills, which is a source of soil, surface water and groundwater contamination. In order to ecologically solve the problem posed by the leachate in the dump site, to safeguard the environment and to contribute to sustainable development, we have carried out this study which aims to study the possibility of composting leachate with green waste and phosphate washing sludge. Various combinations with five substrates (leachate, green waste, sugar lime sludge, phosphate washing sludge and olive mill wastewater) in different proportions were used to build five windrows. A 24 h contact between the phosphate sludge or sugar lime sludge and the leachate took place prior to the addition of the green waste for the construction of the different windrows. This contact time ensured the absorption of a significant portion of the leachate and the disappearance of bad odor. A significant reduction was obtained with streptococci and mesophilic flora after 24 h of contact. The monitoring of the physicochemical parameters throughout the composting process showed that the temperature of the different windrows followed a good pace presenting all composting phases. Moisture, pH, C/N ratio and the percentage of degradation of the organic matter conformed to the quality standards of the compost. The combinations of the alkaline treatment and the composting process allowed a significant hygienization of the leachate. The results of the humification parameters and the E4/E6 ratio suggest that the composts obtained with phosphate sludge were the most stable and mature and can be used in the agricultural field or green space.

Effect of bamboo sphere amendment on the organic matter decomposition and humification of food waste composting

The aim of this study is to examine the effect of bamboo sphere on the organic matter decomposition and humification of food waste composting. Food waste composting were carried out on four treatments, namely control (CK), 3% (T1), 6% (T2) and 9% (T3) (w/w) bamboo sphere treatments. Results showed that adding bamboo sphere facilitated the organic matter decomposition and increased the seed germination index. The number of cells in T2 treatment was always the highest during the composting process. Furthermore, the final humic substances and humic acid contents increased by 41.08% and 68.3%, respectively, in 6% bamboo sphere treatment. Fourier transform infrared and excitation-emission matrix fluorescence spectroscopy analysis revealed that adding bamboo sphere accelerated the humification of composting with more aromatic structures and humic acid-like substances. GC-MS studies revealed that the compost products of 6% bamboo sphere treatment had more ring structures, and thus enhanced the humification.

Impacts of red mud on lignin depolymerization and humic substance formation mediated by laccase-producing bacterial community during composting

The aim of this study was to investigate the impacts of red mud on lignin degradation, humic substance formation and laccase-producing bacterial community in composting to better improve composting performances. The results indicated that the organic matter contents of final compost products in the treatment group with red mud (T) decreased by 25.74%, which was more than the control group without red mud (CK) (12.09%). The final lignin degradation ratio and humic substance concentration of the T were 18.67% and 22.80% higher than that of the CK, respectively. The final C/N values of compost in the CK and T were 11.32 and 10.66, respectively, which were both less than 15, suggesting that compost reached maturity. Redundancy analysis showed that temperature was the main factors driving the variation of laccase-producing bacterial community. Pearson analysis suggested that Pseudomonas, Phenylobacterium, and Caulobacter were the most significantly correlated with lignin degradation and humification in the T.

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

The aim of this study was to assess the maturity indicators of municipal solid waste compost (MSWC) enrichment with different byproduct of (sugar and fertilizer industry) sulphur (S). The concentration of total S (TS), water-soluble S (WSS), HCl extractable S and available S were significantly different in composts prepared through different byproduct of S with MSW. WSS varied from 4.6 to 5.9% of TS after 120 days of the composting period, whereas, available S varied from 14.5 - 8.6% of TS. S enriched MSW compost had lower C/N, C/S ratio and higher nitrification index as well as lower phyto-toxicity, demonstrating that composts are properly matured and stabilised. Highest compost quality index (0.97) was recorded with S1 compost. Arylsulphatase activity significantly increased with compost maturity. Results stated that all S enriched products maintained a superior amount of plant nutrients and quality indices, indicating that S enriched compost could be a possible substitute for expensive fertilizers.

Thermochemical digestate fertilizer from solid waste: Characterization, labile carbon dynamics, dehydrogenase activity, water holding capacity and biomass allocation in banana

Thermochemical digestion is a rapid technology of biowaste management resulting in the instant production of organic fertilizer. Characterization and assessment of its suitability as an organic fertilizer is essential for recommendation for crop application. Biowaste and the thermochemical digestate were subjected to physicochemical and biochemical characterization and the compost maturity parameters assessed. The product integrated with inorganic fertilizers was tested in an Ultisol grown with banana in comparison with farmyard manure based fertilizers. Temporal variation in soil reaction, water holding capacity, carbon dynamics, dehydrogenase activity and plant biomass were determined. The thermochemical digestate fertilizer had a bulk density (0.76 Mg m^-3), pH (neutral), C:N ratio (16.26), CEC (85.70 cmol₍₊₎ kg^-1), CEC/ TOC ratio (3.99), Fertilizing index (4.7) and a Clean index (5.0). Field evaluation revealed enhanced water holding capacity (38.75-83.17%). Total carbon increased with consistently high labile (R² = 0.9551) and non labile carbon fractions and the lowest average lability index (0.78). Dehydrogenase activity at harvest enhanced by 72.81%. An even biomass allocation resulted in 38.84% more biomass production in the fruit over farmyard manure based treatments. In addition to ensuring the safety of the environmental ecosystem, the thermochemical digestate conformed to be a quality resource favoring microbial proliferation and carbon sequestration, thereby restraining carbon dioxide emission. The thermochemical digestate fertilizer based nutrition serves the key deliverables of natural resource management, ecofriendly rapid disposal of biowaste and quality organic fertilizer for banana in Ultisols.

Thermal pretreatment enhances the degradation and humification of lignocellulose by stimulating thermophilic bacteria during dairy manure composting

This study investigated the effect of thermal pretreatment (TP) on the lignocellulose degradation and humification during dairy manure composting and the underlying microbial mechanism. The results showed that TP accelerated temperature rise and elevated composting temperature by increasing 26% initial content of simple organics. The degradation of cellulose, hemicellulose and lignin was 78, 10 and 109% higher in thermal pretreatment composting (TPC) than traditional composting (TC), respectively. Moreover, TP significantly improved the humification degree of composts, as indicated by 14 and 38% higher humus content and humification indexes in TPC, respectively. 16S rRNA sequencing showed that TP increased the relative abundance of thermophilic bacteria in TPC, of which Thermobifida, Planifilum, Truepera and Thermomonospora were potentially involved in lignocellulose biodegradation and humification. Canonical correspondence analysis revealed that TP changed the main factor determining the bacterial community evolution from dissolved organic carbon (DOC) in TC to temperature in TPC.

Earthworm intervened nutrient recovery and greener production of vermicompost from Ipomoea staphylina - An invasive weed with emerging environmental challenges

The invasive weed, Ipomoea staphylina (IS) with cow dung (CD) and mushroom spent straw (MS) in four different combinations (IS:CD:MS), V1 (1:1:0), V2 (2:1:1), V3 (1:0:1) and V4 (1:1:1) were pre-decomposed for 21 days followed by 50 days vermicomposting using Eudrilus eugeniae in triplicates in order to alleviate and to utilize the weed biomass in an environment-friendly manner. The contents of organic matter, organic carbon, cellulose, lignin, C/N and C/P ratios showed a decrease, while electrical conductivity, total NPK, calcium, sodium, and nitrate-nitrogen showed a significant increase in vermicompost over control. Water-soluble organic carbon to organic nitrogen ratio and C/N ratio in V1 (0.52 and 17.55) and V4 (0.43 and 16.56), respectively, were in conformity with the maturity of vermicomposts. Scanning electron micrographs of the end products clearly showed more fragmented, fine, and porous particles in vermicompost. Copper, chromium, cadmium, lead, and zinc in vermicomposts were below the permissible limits. Dehydrogenase, acid phosphatase, alkaline phosphatase, cellulase, and protease activities were significantly higher in V4 than other treatments, implying the role of MS and CD addition during vermicomposting. Though V3 combination supported worm biomass, V4 combination was found to favor the fecundity of Eudrilus eugeniae. Results reveal that 1:1:1 combination of SI + CD + MS (V4) is suitable for utilizing the weed biomass for vermicompost production and nutrient recovery. From the biomass of environmentally problematic weed, Ipomoea staphylina, nutrient-rich vermicompost can be produced through vermitechnology for sustainable environmental management and agriculture.

Recycling of Organic Wastes through Composting: Process Performance and Compost Application in Agriculture

Composting has become a preferable option to treat organic wastes to obtain a final stable sanitized product that can be used as an organic amendment. From home composting to big municipal waste treatment plants, composting is one of the few technologies that can be practically implemented at any scale. This review explores some of the essential issues in the field of composting/compost research: on one hand, the main parameters related to composting performance are compiled, with especial emphasis on the maturity and stability of compost; on the other hand, the main rules of applying compost on crops and other applications are explored in detail, including all the effects that compost can have on agricultural land. Especial attention is paid to aspects such as the improvement of the fertility of soils once compost is applied, the suppressor effect of compost and some negative experiences of massive compost application.

Gasification filter cake reduces the emissions of ammonia and enriches the concentration of phosphorous in Caragana microphylla residue compost

Nutrient loss is a major problem during agricultural waste composting. This study investigated the impact of gasification filter cake (GFC) addition on gaseous emissions and nutrient loss during composting of chicken manure mixed with Caraganna microphylla straw. The GFC was added to the composting mix at dry weight rates of 0% (GFC₀), 6.25% (GFC_6.25), 12.5% (GFC_12.5), 25% (GFC₂₅) and 50% (GFC₅₀). Overall, GFC_12.5 and GFC₂₅ efficiently enhanced organic matter decomposition, reduced N loss and enriched P and K concentrations during composting, as compared to GFC₀. However, GFC_6.25 did not show a significant effect on organic matter decomposition, while GF_C50 had no effect on N loss. As a result, an overall enhancement of nutrient contents was observed in the final composts of GFC_12.5 and GFC₂₅. These results suggest that the addition of GFC at moderate-rates (i.e. 12.5% and 25%) can enhance nutrient retention and thereby result in a nutrient-rich compost.

Vermiproductivity, maturation and microbiological changes derived from the use of liquid anaerobic digestate during the vermicomposting of market waste

Recently, it has been suggested that the liquid fraction of anaerobic digestate, derived from the treatment of wastewater and solid wastes, could be used in vermicomposting as a solution to its disposal, and even for its valorization. Nevertheless, the literature does not provide enough information about its impact on the process of vermicomposting itself and on the final quality of the end-product. In this study, the effect of different doses of digestate in the vermicomposting process treating market waste is assessed measuring earthworm population dynamics, the bacterial community succession present in the vermibeds, as well as maturation and the end-quality of the vermicompost. Our results show that the addition of liquid digestate to the vermibeds increased the earthworms biomass, i.e. 71%, 94% and 168% in control, and vermibeds with 30% and 60% digestate, respectively. Further, the increase in the amount of N in the vermicompost decreased as the digestate addition increased, i.e. 75%, 8%, 3%. The maturity achieved was high in all treatments as shown by the C/N ratio, 7.98, 7.40 and 10.20, and the high seed germination rate, above 90%. Finally, the succession of the microbial community was not disturbed and compositional stabilization was reached after 92 days.

Material conversion, microbial community composition and metabolic functional succession during green soybean hull composting

In this study, green soybean hulls and maize straw were used for composting to explore the dynamics of material conversion, bacterial and fungal communities and metabolic functions. The results showed that bacterial and fungal communities had different temporal successions during composting. The bacterium Streptosporangiaceae was a biomarker in the thermophilic stage of composting, and the fungus Chaetomiaceae was a biomarker in the thermophilic stage and cooling stage. In the bacterial network, the germination index (GI) had a time-delayed association with Truepera, Pseudomonas and Methylococcaceae, which represented the key physicochemical characteristics that affect the community. In the fungal community, the GI, pH, fulvic acid (FA) and temperature etc. had a joint effect. Carbohydrate metabolism and amino acid metabolism were the main metabolic pathways, and saprotrophs represented the dominant fungal trophic mode in the composting process. These results provide a reference from screening specific and efficient agents to accelerate natural vegetable composting.

Succession of the bacterial community structure and functional prediction in two composting systems viewed through metatranscriptomics

In this work, Illumina MiSeq sequencing of cDNA from metatranscriptomics RNA reverse transcription were employed in combination with phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) to estimate the dynamic variations of bacterial community structures and metabolic functions in a bioreactor and traditional composting process. Results showed that the change of bacterial α-diversity in the first three stages exhibit opposite trends in the two composting systems. The four most abundant phyla were the same in both systems (Firmicutes, Proteobacteria, Bacteroidetes and Actinobacteria), but the most abundant genera were different. The five most abundant genus-level groups in the bioreactor were Psychrobacter, Galbibacter, Pseudomonas, Staphylococcus and Flavobacterium. Within the same phase, the functional bacteria were dramatically different in the two composting processes. In the bioreactor system both bacterial community structure and metabolism function were greatly affected by available phosphorus.

Phytotoxicity indexes and removal of color, COD, phenols and ISA from pulp and paper mill wastewater post-treated by UV/H2O2 and photo-Fenton

Pulp and paper mill wastewater (PPMWW) contains high concentrations of recalcitrant compounds that cause toxicity to organisms. Advanced oxidation processes (AOPs) have the ability to degrade these compounds and reduce overall toxicity. Physicochemical characterization and Lactuca sativa toxicity test were conducted to compare the effectiveness of two post-treatments: UV/H₂O₂ and photo-Fenton. A comparison of four phytotoxicity indexes was carried out. PPMWW from a Brazilian treatment plant was characterized by high values of phenols, color, integrated spectral area (ISA), and chemical oxygen demand (COD), and caused significant inhibition to seedling development. The use of both post-treatments allowed the removal of over 75% of phenols, color, ISA, and COD. Although UV/H₂O₂ was more effective in removing phenols and ISA, photo-Fenton better reduced phytotoxicity. The most sensitive phytotoxicity indexes were RGIC_0.8 and GIC_80%, whereas SGC₀, REC_-0.25 and REC_-0.50 better showed the effectiveness of the post-treatments. We suggest the combined use of two phytotoxicity indexes: one that evaluates the effects on seed germination and, another, on root elongation, e.g., SGC₀ and RGIC_0.8. Additionally, we recommend the use of ISA for monitoring programs of wastewater treatments because it is a cost-effective approach that allows narrowing down the search and identification of compounds present in complex mixtures.

The contribution of water extractable forms of plant nutrients to evaluate MSW compost maturity: a case study

The object of the experiment was to evaluate municipal solid waste (MSW) compost. Composting was carried out in a pile under aerobic conditions. Total content as well as water-extractable forms of macro and microelements were analysed during composting. Nutrient solubility indices were calculated for samples taken at various stages of maturity. The soluble forms of C, P, K, Ca and Mg decreased relatively to their total forms following maturation phases. For all micronutrients tested, a significant reduction in the proportion of soluble forms in relation to their total content was observed with an increase in composting time. In mature compost, low solubility were found for nitrogen, potassium, sodium and magnesium, which may indicate that the final product is a good source of these nutrients. The solubility index (percentage share of water-extractable forms of macro- and micronutrients in the total content) for iron indicates that the composting process does not affect its degree of solubility. Solubility index instead of the content of water-extractable forms of chosen macro- and microelements could be taken into account in determining the degree of MSW compost maturity.

Insight to key diazotrophic community during composting of dairy manure with biochar and its role in nitrogen transformation

Analyzing diazotrophic community may help to understand nitrogen transformation in composting and improves the final compost quality. In this study, diazotrophic community dynamics were investigated in terms of nifH gene during dairy manure and corn straw composting with biochar addition using high-throughput sequencing. Biochar decreased the diversity of diazotrophic community and altered diazotroph community structure during composting. At phylum level, Proteobacteria, Actinobacteria and Firmicutes were dominant diazotrophic communities throughout composting process. Biochar addition registered higher correlation coefficient (R) between physicochemical factors (temperature, ammonium (NH₄⁺-N) and nitrate (NO₃^--N)) and diazotroph community composition. Rhodopseudomonas and Pseudoxanthomonas was the key diazotrophic communities influencing NH₄⁺-N transformation in control (CK) and biochar compost (BC), respectively, while for NO₃^--N transformation Clostridium and Bradyrhizobium in CK, Azospira and Methylocystis in BC served as predominant factors. These results indicated that addition of biochar altered the key diazotroph communities influencing nitrogen transformation. Furthermore, some diazotrophs (e.g. Rhodopseudomonas, Bradyrhizobium and Azospira) affecting NH₄⁺-N and NO₃^--N transformation were also observed to be mediating total nitrogen (TN). Interestingly, interactions between diazotrophic communities were observed and these interactions could also influence nitrogen transformation.