Sorption of Iodine on Biochar Derived from the Processing of Urban Sludge and Garden Waste at Different Pyrolysis Temperatures.

The United Nations proposed the Sustainable Development Goals with the aim to make human settlements in cities resilient and sustainable. The excessive discharge of urban waste including sludge and garden waste can pollute groundwater and lead to the emission of greenhouse gases (e.g., CH4). The proper recycling of urban waste is essential for responsible consumption and production, reducing environmental pollution and addressing climate change issues. This study aimed to prepare biochar with high adsorption amounts of iodine using urban sludge and peach wood from garden waste. The study was conducted to examine the variations in the mass ratio between urban sludge and peach wood (2/1, 1/1, and 1/2) as well as pyrolysis temperatures (300 °C, 500 °C, and 700 °C) on the carbon yield and adsorption capacities of biochar. Scanning electron microscopy, Brunauer-Emmett-Teller analysis, Fourier transform infrared spectrometry, powder X-ray diffraction, and elemental analysis were used to characterize the biochar produced at different pyrolysis temperatures and mass ratios. The results indicate that the carbon yield of biochar was found to be the highest (>60%) at a pyrolysis temperature of 300 °C across different pyrolysis temperatures. The absorbed amounts of iodine in the aqueous solution ranged from 86 to 223 mg g-1 at a mass ratio of 1:1 between urban sludge and peach wood, which were comparably higher than those observed in other mass ratios. This study advances water treatment by offering a cost-effective method by using biochar derived from the processing of urban sludge and garden waste.

Granular activated carbon enhances volatile fatty acid production in the anaerobic fermentation of garden wastes.

Garden waste, one type of lignocellulosic biomass, holds significant potential for the production of volatile fatty acids (VFAs) through anaerobic fermentation. However, the hydrolysis efficiency of garden waste is limited by the inherent recalcitrance, which further influences VFA production. Granular activated carbon (GAC) could promote hydrolysis and acidogenesis efficiency during anaerobic fermentation. This study developed a strategy to use GAC to enhance the anaerobic fermentation of garden waste without any complex pretreatments and extra enzymes. The results showed that GAC addition could improve VFA production, especially acetate, and reach the maximum total VFA yield of 191.55 mg/g VSadded, which increased by 27.35% compared to the control group. The highest VFA/sCOD value of 70.01% was attained in the GAC-amended group, whereas the control group only reached 49.35%, indicating a better hydrolysis and acidogenesis capacity attributed to the addition of GAC. Microbial community results revealed that GAC addition promoted the enrichment of Caproiciproducens and Clostridium, which are crucial for anaerobic VFA production. In addition, only the GAC-amended group showed the presence of Sphaerochaeta and Oscillibacter genera, which are associated with electron transfer processes. Metagenomics analysis indicated that GAC addition improved the abundance of glycoside hydrolases (GHs) and key functional enzymes related to hydrolysis and acidogenesis. Furthermore, the assessment of major genera influencing functional genes in both groups indicated that Sphaerochaeta, Clostridium, and Caproicibacter were the primary contributors to upregulated genes. These findings underscored the significance of employing GAC to enhance the anaerobic fermentation of garden waste, offering a promising approach for sustainable biomass conversion and VFA production.

Composition and selected properties of bio-waste collected in towns from single- and multi-family housing and in rural areas.

The progress of civilisation contributes, among other things, to an increase in the mass of waste produced in households. A significant part of it is bio-waste (about 31% in Poland). It is generally agreed that bio-waste is a suitable substrate for valorisation through fermentation with biogas production. Designing new and optimising existing facilities, however, requires precise data on the composition of bio-waste and its properties, which is challenging due to seasonal variability, place of origin (single- or multi-family housing, urban or rural) and collection method. This paper presents the method adopted for conducting the study and the results of an annual, monthly analysis of the morphological composition and selected properties of bio-waste from source-segregated households from 4 rural municipalities and 4 cities, from neighbourhoods with single-family and multi-family housing in Poland. In household bio-waste, the proportion of food waste content ranges from 36.7 to 47.6% (annual average values). The proportion of edible food waste in relation to the total weight of food waste is 5 to 7 times lower. The yearly percentage of garden waste varied from 35.8 to 52.8%. A considerable amount of impurities (such as plastics, glass, and stones) is present in the bio-waste stream. The waste collected in containers in urban areas with multi-family houses is the most polluted (16.6%). The proportion of pollutants in bio-waste collected in bags (rural areas and cities with single-family housing) does not exceed 10%.

Nitrogen transformation and its microbial mechanism under co-composting of biogas slurry with garden waste.

Large amount of garden waste is consecutively produced in China every year. The composting with urea and microbial inoculum makes it possible to dispose garden waste in large quantities. However, composting accompanies with serious nitrogen loss and environmental problems. The biogas slurry contains considerable nitrogen nutrients and microorganisms, which theoretically could be used as alternative to urea and bacteria to reduce nitrogen loss, respectively. We set up three treatments of biogas slurry + garden waste (GB), biogas slurry + garden waste + urea (GBU), and biogas slurry + garden waste + urea + microbial inoculum (GBUM) to investigate the decomposition, nitrogen conversion and nitrogen loss in the co-composting process. The results showed that the high tempe-rature period of GB treatment was longer and more stable compared to that of GBU and GBUM treatments. The pH and EC value of GB treatment would benefit composting process and generated products with the highest germination index (GI) (221.8%). In addition, NH3 and N2O emission rates in the GB treatment were 2.59 mg·kg-1·d-1 and 3.65 µg·kg-1·d-1, respectively, being 99.0% and 50.0% lower than that in the GBU treatment and 99.4% and 40.7% lower than that in the GBUM treatment. The results of δ18O vs. δ15NSP dual isotopocule plots approach analysis showed that the GB and GBU treatments were dominated by denitrification, and that the contribution of denitrification was higher in the GB treatment. In contrast, the GBUM treatment was dominated by nitrification. The degree of N2O reduction in GB treatment (83.7%) was higher than the other two treatments. It was clear that GB treatment had the best maturity and lowest nitrogen loss in all treatments by enhancing the N2O reduction process during denitrification to reduce N2O emission. In conclusion, the biogas slurry and garden wastes could be directly co-composted without the limitation of C/N and microbial addition. The co-composting method could protect the environment and save resources leading to the recycling of waste in actual production.

Metagenomic characterization of the enhanced performance of multicomponent synergistic thermophilic anaerobic co-digestion of food waste utilizing kitchen waste or garden waste as co-substrate.

Food waste (FW) single-substrate anaerobic digestion usually suffers from rapid acidification and inhibition of oil and salt. To overcome these problems and improve the process efficiency, supplementing other substrates has been used in FW anaerobic digestion. This study investigated the biogas production potential through co-digestion of FW with kitchen waste (KW) or garden waste (GW) in different ratios under thermophilic conditions. The results showed that the optimal ratios were FW:KW=60:40 and FW:GW=80:20 which biogas production improved 73.33% and 68.45% compared with single FW digestion, respectively. The organic matter removal rate of co-digestion was 84.46% for FW+KW group (RFK) and 65.64% for FW+GW group (RFG). Co-digestion increased the abundance of the dominant hydrolytic bacteria Defluviitoga and Hydrogenispora and hydrogenotrophic methanogen Methanoculleus. Furthermore, glycoside hydrolases (GHs), vital carbohydrate-active enzymes (CAZymes), were improved by co-digestion. Co-digestion could also effectively promote the function of cellulase and hemicellulose. This strategy for utilizing different organic wastes together as co-substrate provides a new avenue for bioenergy production.

Nitrate-Nitrogen Adsorption Characteristics and Mechanisms of Various Garden Waste Biochars.

Nitrate-nitrogen (NO3--N) removal and garden waste disposal are critical concerns in urban environmental protection. In this study, biochars were produced by pyrolyzing various garden waste materials, including grass clippings (GC), Rosa chinensis Jacq. branches (RC), Prunus persica branches (PP), Armeniaca vulgaris Lam. branches (AV), Morus alba Linn. sp. branches (MA), Platycladus orientalis (L.) Franco branches (PO), Pinus tabuliformis Carrière branches (PT), and Sophorajaponica Linn. branches (SL) at three different temperatures (300 °C, 500 °C, and 700 °C). These biochars, labeled as GC300, GC500, GC700, and so on., were then used to adsorb NO3--N under various conditions, such as initial pH value, contact time, initial NO3--N concentration, and biochar dosage. Kinetic data were analyzed by pseudo-first-order and pseudo-second-order kinetic models. The equilibrium adsorption data were evaluated by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models. The results revealed that the biochar yields varied between 14.43% (PT700) and 47.09% (AV300) and were significantly influenced by the type of garden waste and decreased with increasing pyrolysis temperature, while the pH and ash content showed an opposite trend (p < 0.05). The efficiency of NO3--N removal was significantly influenced by the type of feedstock, preparation process, and adsorption conditions. Higher pH values had a negative influence on NO3--N adsorption, while longer contact time, higher initial concentration of NO3--N, and increased biochar dosage positively affected NO3--N adsorption. Most of the kinetic data were better fitted to the pseudo-second-order kinetic model (0.998 > R2 > 0.927). Positive b values obtained from the Temkin model indicated an exothermic process of NO3--N adsorption. The Langmuir model provided better fits for more equilibrium adsorption data than the Freundlich model, with the maximum NO3--N removal efficiency (62.11%) and adsorption capacity (1.339 mg·g-1) in PO700 under the conditions of pH = 2, biochar dosage = 50 mg·L-1, and a reaction time of 24 h. The outcomes of this study contribute valuable insights into garden waste disposal and NO3--N removal from wastewater, providing a theoretical basis for sustainable environmental management practices.

Characteristics of denitrification activity, functional genes, and denitrifying community composition in the composting process of kitchen and garden waste.

N2O can be easily produced during the co-composting of kitchen waste (KW) and garden waste (GW). This study investigated the effects of the co-composting of KW and GW at different ratios (1:2, 1:1.5, 1:1, and 1.5:1) on the denitrifying activities, functional genes, and community composition of denitrifiers. The results showed that the denitrification activity of KW and GW at a 1:2 ratio was the lowest. The gene abundances of nirS, nirK, nosZI, and nosZII were high on days 12 and 28 under the four different ratios. Network analysis demonstrated that nosZ-type denitrifiers could construct a complex and reciprocal bacterial network to promote the reduction of N2O to N2. Mantel test results revealed that nirS-, nirK-, nosZI-, and nosZII-type denitrifiers were significantly positively correlated with pH, C/N, and moisture content. These findings demonstrated that composting with appropriate proportions of KW and GW could reduce N2O emissions caused by denitrification.

Dynamic composting actuated by a Caldibacillus thermoamylovorans isolate enables biodecomposability and reusability of Cinnamomum camphora garden wastes.

The ecotoxic substances in Cinnamomum camphora garden wastes (CGW) often restrain microbe-driven composting process. Here, a dynamic CGW-Kitchen waste composting system actuated by a wild-type Caldibacillus thermoamylovorans isolate (MB12B) with distinctive CGW-decomposable and lignocellulose-degradative activities was reported. An initial inoculation of MB12B optimized for temperature promotion with reduced emission of CH4 and NH3 by 61.9% and 37.6%, respectively, increased germination index and humus content by 18.0% and 44.1%, respectively, and reduced moisture and electrical conductivity, and all were further reinforced by reinoculation of MB12B during the cooling stage of composting. High-throughput sequencing showed varied bacterial community structure and abundance following MB12B inoculation, with temperature-relative Caldibacillus, Bacillus, and Ureibacillus, and humus-forming Sphingobacterium emerging to dominate abundance, which strongly contrasted with Lactobacillus (acidogens related to CH4 emission). Finally, the ryegrass pot experiments showed significant growth-promoting effectiveness of the composted product that successfully demonstrated the decomposability and reuse of CGW.

Comprehensive evaluation of spent mushroom substrate-chicken manure co-composting by garden waste improvement: physicochemical properties, humification process, and the spectral characteristics of dissolved organic matter.

The performance of garden waste on spent mushroom substrate (SMS) and chicken manure (CM) co-composting efficiency and humification is unclear. Therefore, this study investigated the impact of garden waste addition on SMS-CM co-composting physicochemical properties, humification process, and the spectral characteristics of dissolved organic matter (DOM). The results showed that garden waste improved the physicochemical properties of SMS-CM co-compost, the thermophilic period was advanced 2 days, the seed germination index increased by 30.2%, and the total organic carbon and total nitrogen content increased by 8.80% and 15.0%, respectively. In addition, garden waste increased humic substances (HS) and humic acid (HA) contents by 10.62% and 34.52%, respectively; the HI, PHA and DP increased by 31.53%, 43.19% and 55.53%, respectively; and the SUVA254 and SUVA280 of DOM also increased by 6.39% and 4.39%, respectively. In particular, HA content and DOM humification increase rapidly in the first 10 days. The increase of HA accounted for 52% of the total increase during composting. Fourier-transform infrared and two-dimensional correlation analysis further confirmed that garden waste could facilitate the degradation of organic molecules, including amino acids, polysaccharides, carboxyl groups, phenols, and alcohol, and contributed to the preferential utilization of carboxyl groups and polysaccharides and thus enhanced humification.

Anaerobic co-digestion of kitchen waste with hyperthermophilically pretreated grass for biohydrogen and biomethane production.

Anaerobic digestion of kitchen waste with grass after hyperthermophilic pretreatment was performed in semi-continuously operated reactors. The greatest methane yield of 293 NmlCH4/gVS (volatile solids) was reported for the mixture of both substrates at 55 °C with a solids retention time of 30 d and the corresponding organic lading rate of 1.72 kgVS/m3/d. In contrast, pretreated grass subjected to thermophilic digestion produced only 131 NmlCH4/gVS. However, when mesophilic conditions were applied, the digestion process turned into dark fermentation, especially visible for the mixture. Metagenomic analysis revealed the dominance Ruminococcaceae, Atopobiaceae and Lactobacillaceae at a family level in mesophilic processes, whereas Petrotogaceae, Synergistaceae, Hungateiclostridiaceae, Planococcaceae and two methanogens Methanosarcinaceae and Methanothermobacteriaceae were the most frequent microbes of thermophilic digestion. Kitchen waste can successfully be co-digested with hyperthermophilically pretreated grass at high loading rates, however the digesters must be operated at thermophilic temperatures.

Succession of Microbial Community during the Co-Composting of Food Waste Digestate and Garden Waste.

Microorganisms are of critical importance during the composting process. The aim of this study was to reveal the bacterial and fungal compositions of a composting pile of food waste digestate and garden waste, where the succession of the microbial communities was monitored using Illumina MiSeq sequencing. We explored the efficiency of composting of different microorganisms to judge whether the composting system was running successfully. The results showed that the composting process significantly changed the bacterial and fungal structure. Firmicutes, Proteobacteria, and Bacteroidota were the dominant phyla of the bacterial communities, while Ascomycota was the dominant phylum of the fungal communities. Moreover, the highest bacterial and fungal biodiversity occurred in the thermophilic stage. The physical and chemical properties of the final compost products conformed to the national standards of fertilizers. The efficient composting functional microbes, including Cladosporium, Bacillus and Saccharomonospora, emerged to be an important sign of a successfully operating composting system.

Comparison between cold plasma, ultrasonication, and alkaline hydrogen peroxide pretreatments of garden waste to enhance humification in subsequent composting with kitchen waste: Performance and mechanisms.

This study compared the performance and mechanisms of cold plasma, ultrasonication, and alkali-assisted hydrogen peroxide for garden waste pretreatment to advance humification in composting with kitchen waste. High-throughput sequencing integrated with Functional Annotation of Prokaryotic Taxa was used to relate bacterial dynamics to humification. Results show that all pretreatment techniques accelerated humification by 37.5% - 45.7% during composting in comparison to the control treatment. Ultrasonication and alkalization preferred to decompose lignocellulose to produce humus precursors in garden waste, thereby facilitating humus formation at the beginning of composting. By contrast, cold plasma was much faster and simpler than other pretreatment techniques to effectively disrupt the surface structure and reduce the crystallinity of garden waste to enrich functional bacteria for aerobic chemoheterotrophy, xylanolysis, cellulolysis, and ligninolysis during composting. As such, a more robust bacterial community was developed after cold plasma pretreatment to advance humification at the mature stage of composting.

Fallen leaves are superior to tree pruning as bulking agents in aerobic composting disposing kitchen waste.

Though aerobic composting has been frequently applied to kitchen waste disposal, appropriate bulking agents are essential to acquire a promising performance. Fallen leaves and tree pruning in urbans face huge disposal demands and have great potentials as bulking agents of aerobic composting while have been seldom examined yet. This study comparably explored the performance of fallen leaves bulked and tree pruning bulked aerobic composting disposing kitchen waste. Results indicated that though both reactors were effective in degrading kitchen waste, leaf bulked composting was superior to tree pruning bulked composting in terms of longer thermophilic period and higher maximum temperature, higher organics degradation efficiency, higher humification and less odorous gas emission. Bacterial community was a driving mechanism for above results. This study shows that fallen leaves bulked aerobic composting has great potentials for kitchen waste disposal.

Removal of Cr (VI) by Biochar Derived from Six Kinds of Garden Wastes: Isotherms and Kinetics.

Garden waste is one of the main components of urban solid waste which affects the urban environment. In this study, garden waste of Morus alba L. (SS), Ulmus pumila L. (BY), Salix matsudana Koidz (LS), Populus tomentosa (YS), Sophora japonica Linn (GH) and Platycladus orientalis (L.) Franco (CB) was pyrolyzed at 300 °C, 500 °C, 700 °C to obtain different types of biochar, coded as SSB300, SSB500, SSB700, BYB300, etc., which were tested for their Cr (VI) adsorption capacity. The results demonstrated that the removal efficiency of Cr by biochar pyrolyzed from multiple raw materials at different temperatures was variable, and the pH had a great influence on the adsorption capacity and removal efficiency. GHB700 had the best removal efficiency (89.44%) at a pH of 2 of the solution containing Cr (VI). The pseudo second-order kinetics model showed that Cr (VI) adsorption by biochar was chemisorption. The Langmuir model showed that the adsorption capacity of SSB300 was the largest (51.39 mg·g-1), BYB500 was 40.91 mg·g-1, GHB700, CBB700, LSB700, YSB700 were 36.85 mg·g-1, 36.54 mg·g-1, 34.53 mg·g-1 and 32.66 mg·g-1, respectively. This research, for the first time, used a variety of garden wastes to prepare biochar, and explored the corresponding raw material and pyrolysis temperature for the treatment of Cr (VI). It is hoped to provide a theoretical basis for the research and utilization of garden wastes and the production and application of biochar.

Safety and efficiency of sewage sludge and garden waste compost as a soil amendment based on the field application in woodland.

Sewage sludge (SS) and garden waste (GW) compost can be used as soil amendments to improve the soil environment. Studies done till date have been focused on the changes of harmful substances during sludge composting, but the safety and efficacy of SS and GW composting on woodland soil environment are still unclear. In the study, a field experiment was performed using to investigate the safety and efficacy of SS and GW compost as a soil amendment on woodland soil. Soil nutrients (such as nitrogen, phosphorus and potassium), organic matter and electrical conductivity were significantly increased after the addition of the SS and GW compost, while there were no significant changes in soil heavy metals content and soil enzyme activities. From these soil properties, it was found that SS and GW compost was safe and efficacious in improving the soil environment. The application of SS and GW compost had no significant effect on microbial diversity. Co-occurrence network analysis revealed that SS and GW compost efficaciously enhanced the interaction between bacterial communities, which proved that it was safe and efficacious. Furthermore, SS and GW compost enhanced ABC transporters and carbohydrate metabolism of bacterial community, while reduced the pathotroph action (such as the plant pathogen) and wood saprotrophs. Overall, these results proved the safety and efficacy of SS and GW compost as soil amendments after being added to the soil. This study contributes to the use of harmless treatments and reutilization processes of SS and GW.

Relating bacterial dynamics and functions to gaseous emissions during composting of kitchen and garden wastes.

This study aims to relate bacterial dynamics to gaseous emissions during the composting of kitchen and garden wastes. High-throughput sequencing and Functional Annotation of Prokaryotic Taxa (FAPROTAX) were used to analyse the bacterial community and potential functions during composting, respectively. Results show that the addition of garden waste up to 15% of the total wet weight of composting materials notably mitigated gaseous emissions and improved maturity during kitchen waste composting. Ammonium nitrogen, temperature, oxygen content, and electrical conductivity were identified as critical factors to impact gaseous emissions. The bacterial community analysis indicated that the proliferation of anaerobes during the storage of kitchen waste induced the dramatic emission of methane (CH4) and nitrous oxide (N2O) at the beginning of composting. Adding garden waste could effectively amend the physiochemical properties of composting materials to reduce the relative abundance of microbes (e.g. Desulfotomaculum and Caldicoprobacter) that contributed to gaseous emissions, but enrich those (e.g. Bacillus and Pseudoxanthomonas) for organic biodegradation. Further analysis by FAPROTAX corroborated that adding garden waste could effectively inhibit relevant microbial metabolisms (e.g. fermentation, nitrite/nitrate respiration and sulphate respiration) and thus alleviate the emission of greenhouse gases and odours during kitchen waste composting.

Synergy of municipal solid waste co-processing with lignocellulosic waste for improved biobutanol production.

Co-processing of lignocellulosic wastes, e.g., garden and paper wastes, and the organic matters fraction of municipal solid waste (OMSW) in an integrated bioprocess is a possible approach to realize the potential of wastes for biobutanol production. Dilute acid pretreatment is a multi-functional stage for breaking the recalcitrant lignocellulose's structure, hydrolyzing hemicellulose, and hydrolyzing/solubilizing starch, leading to a pretreated solid and a rich hydrolysate. In this study, dilute-acid pretreatment of the combination of wastepaper and OMSW, composite I, as well as garden waste and OMSW, composite II, at severe conditions resulted in "pretreatment hydrolysates" containing 33.7 and 19.4 g/L sugar along with 18.9 and 33.2 g/L soluble starch, respectively. In addition, the hydrolysis of solid remained after the pretreatment of composite I and II resulted in "enzymatic hydrolysates" comprising 19.4 and 33 g/L sugar, respectively. The fermentation of the pretreatment hydrolysates and enzymatic hydrolysates resulted in 3.5 and 6.4 g/L ABE from composite I and 15 and 5.2 g/L ABE from composite II, respectively. In this process, 148 and 173 g ABE (60 and 100 g gasoline equivalent/kg) was obtained from each kg composite I and composite II, respectively, where co-processing of OMSW with lignocellulosic wastes resulted in 10 and 49% higher ABE than that produced from the individual substrates.

Effect of biochemical composition on odor emission potential of biowaste during aerobic biodegradation.

This study aimed to identify the individual effect of biochemical composition on odor emission potential of biowaste during aerobic biodegradation. Three kinds of typical mixed wastes, including vegetable-fruit waste, garden waste, and protein-rich waste, were tested for emission quantity of seven common odorous families within 21 days of biodegradation under aerobic conditions. The cumulative odor yields (COY) were as follows: protein-rich waste (2408 µg g-1 DM) > vegetable-fruit waste (1169 µg g-1 DM) > garden waste (62 µg g-1 DM), and their cumulative odor intensity were 16,701, 1888, and 212 g-1 DM, respectively. The odor emission of vegetable-fruit waste mainly occurred in the first 3 days, accounting for 91.7% COY, and the predominant contributor to odor intensity (PCOI) were terpenes and sulfur compounds. With regard to garden waste, the odor emission rate was the highest on day 1 (22.4 µg g-1 DM d-1) and then rapidly decreased, and the PCOI were aldehydes. The odor emission rate of protein-rich waste increased gradually in the initial stage and reached the peak value on day 10 (661.9 µg g-1 DM d-1), and its PCOI were sulfur compounds. This study revealed for the first time the relationship between the odor emission potential of biowaste and its characteristic of biochemical composition, then proposed potential application for odor pollution control during aerobic composting.

Comparative study of vermicomposting of garden waste and cow dung using Eisenia fetida.

Vermicomposting is the process of composting using worms and is applied in waste management to produce high-quality organic fertilizer. Garden waste (GW) is often mixed with other raw materials for vermicomposting. In the present study, the feasibility of vermicomposting using only GW was investigated in comparison with cow dung (CD). The total nitrogen (TN), total phosphorus (TP), and total potassium (TK) contents and the electrical conductivity increased, while total organic carbon (TOC) and the C/N ratio decreased in both substrates after vermicomposting. The nutrient content (TN, TP, and TK) of the GW vermicompost was promoted less than that in CD. Scanning electron microscopy images and specific surface area analysis showed that the vermicompost was strongly disaggregated and became more compacted and fragmented compared with the raw substrates. No mortality of earthworms was observed in GW; however, the earthworms had a higher mean body weight and reproduction rate in CD than that in GW. There were higher bacterial community richness and diversity in the vermicompost than that in the raw materials, and the dominant phylum species were Proteobacteria, Actinobacteria, and Bacteroidetes. Redundancy analysis demonstrated that TN, C/N ratio, and TOC play an important role in bacterial community dynamics. These data indicate that vermicomposting is a robust process that is suitable for the management of GW.

Spent mushroom substrate and cattle manure amendments enhance the transformation of garden waste into vermicomposts using the earthworm Eisenia fetida.

Garden wastes (GW) having high lignin contents could hinder the growth of earthworms and microorganisms in vermicomposting. This study investigated the Eisenia fetida-based vermicomposting of GW mixed with cattle manure (CM) and/or spent mushroom substrate (SMS) at different ratios of GW alone (control), 3:1 GW:SMS, 1:1 GW:SMS, 3:1 GW:CM, 1:1 GW:CM and 2:1:1 GW:SMS:CM to promote earthworm growth and improve the final vermicompost quality. In general, treatments with the addition of SMS and/or CM increased the survival rate, biomass, cocoon and juvenile numbers of E. fetida compared to the control. The addition of SMS and/or CM also significantly increased the activities of dehydrogenase, cellulase, urease, and alkaline phosphatase compared to the control. Furthermore, the addition of SMS and/or CM facilitated the decomposition of organic matter, cellulose and lignin, increased nutrient (N, P and K) concentrations, and accelerated nitrification compared to the control. The addition of SMS and CM led to greater chemical changes of the substrate compared to control. Heavy metal concentrations were increased in the final vermicomposts comparatively to the initial materials, but none of them exceeded the permissible limits. The highest germination index of Chinese cabbage and tomato seeds were both observed in the treatment of 2:1:1 GW:SMS:CM which reached 146.9 and 148.1. Overall, the 2:1:1 GW:SMS:CM treatment had the highest growth and reproduction rates of E. fetida, higher percentage degradation of organic matter, cellulose and lignin, as well as the best quality of the final vermicompost.