Evolution of organic matter during the mesophilic composting of lignocellulosic winery wastes

Insights into the management of food waste in developing countries: with special reference to India

Up to one third of the food that is purposely grown for human sustenance is wasted and never consumed, with adverse consequences for the environment and socio-economic aspects. In India, managing food waste is a significant environmental concern. Food waste output is increasing in Indian cities and towns as a result of the country's urban expansion, modernization, and population growth. Poor management of food waste can have negative consequences for the environment and pose a risk to the public's health issues. This review focuses on the current challenges, management strategies, and future perspectives of food waste management in India. The efficient management of food waste involves a comprehensive study regarding the characterization of food waste and improved waste management methods. In addition, the government policies and rules for managing food waste that is in effect in India are covered in this review.

Spectroscopic and microscopic characterization of humic acids from composts made by co-composting of green waste, spent coffee and OMWW sludge

Due to its important role in the formation of humic acids (HA), improving lignin degradation during composting has usually been considered a challenge. One practice that could stimulate the biodegradation of this recalcitrant molecule is inoculation with exogenous lignolytic fungal strains. Two composts (C1) and (C2) from piles (H1) and (H2) were evaluated. H1 was the control pile and H2 was inoculated at maturity with Trametes trogii, resulting in a 35% increase in lignin degradation rate compared to H1. The aim of this study was to show the main effects of this increase on the humification process in the co-composting of green waste, coffee grounds and olive mill wastewater sludge (OMWWs). Microstructure of HA1 and HA2 extracted from C1 and C2, respectively, was also investigated by scanning electron microscopy (SEM) and SEM coupled with energy-dispersive X-ray spectroscopy (X-EDS). The results showed that there were several similarities between the compost samples tested. These included the mineral content, the degree of polymerization (PD)> 1 and the compact and rigid surface of the extracted HA. However, C2 was characterized by a higher humic content (HC), degree of polymerization (PD), humification index (HI) and percentage of humic acids (PHA) than C1. Carbon-13 nuclear magnetic resonance (13C-NMR) and Fourier transmission-infrared spectroscopy (FTIR) analysis showed that aliphatic groups such as hydroxyls, alcohols and carboxyls were predominant in both composts. SEM analysis in conjunction with X-EDS analysis of HA2 showed a higher proportion of carbon and potassium (18 and 7.93%) than in HA1 (14 and 0.95%).

Bacillus licheniformis inoculation promoted humification process for kitchen waste composting: Organic components transformation and bacterial metabolic mechanism

Kitchen waste (KW) composting always has trouble with slow humification process and low humification degree. The objective of this study was to develop potentially efficient solutions to improve the humification of KW composting, accelerate the humus synthesis and produce HS with a high polymerization degree. The impact of Bacillus licheniformis inoculation on the transformation of organic components, humus synthesis, and bacterial metabolic pathways in kitchen waste composting, was investigated. Results revealed that microbial inoculation promoted the degradation of organic constituents, especially readily degradable carbohydrates during the heating phase and lignocellulose fractions during the cooling phase. Inoculation facilitated the production and conversion of polyphenol, reducing sugar, and amino acids, leading to an increase of 20% in the content of humic acid compared to the control. High-throughput sequencing and network analysis indicated inoculation enriched the presence of Bacillus, Lactobacillus, and Streptomyces during the heating phase, while suppressing the abundance of Pseudomonas and Oceanobacillus, enhancing positive microbial interactions. PICRUSt2 analysis suggested inoculation enhanced the metabolism of carbohydrates and amino acids, promoting the polyphenol humification pathway and facilitating the formation of humus. These findings provide insights for optimizing the humification process of kitchen waste composting by microbial inoculation.

Oxygen uptake rate versus CO2 based respiration rate for assessment of the biological stability of peat, plant fibers and woody materials with high C:N ratio versus composts

The biological stability of organic materials predicts their performance when used as either a soil improver or as an ingredient in growing media. CO₂ release in a static measurement and O₂ consumption rate (OUR) were compared for seven groups of growing media components. The ratio between CO₂ release and OUR was matrix-specific. This ratio was highest for plant fibers high in C:N and with a high risk of N immobilization, intermediate for wood fiber and woody composts, and lowest for peat and other compost types. The effect of variable test conditions in the OUR setup was assessed for plant fibers, where addition of mineral N and/or nitrification inhibitor had no effect on the OUR measurements. Testing at 30 °C instead of 20 °C resulted in higher OUR values as expected, but did not change the effect of mineral N dose. A strong increase in the CO₂ flux was measured when plant fibers were mixed with mineral fertilizer; in contrast, addition of mineral N or fertilizer before or during the OUR test had no effect. The present experimental setup did not allow for differentiation between a higher CO₂ release as a result of increased microbial respiration after adding mineral N versus an underestimation of stability due to N limitation in the dynamic OUR setup. Results indicate that type of material, C:N ratio and risk of N immobilization all appear to affect the OUR results. The OUR criteria may therefore require clear differentiation based on the different materials used in horticultural substrates.

Interval aeration improves degradation and humification by enhancing microbial interactions in the composting process

Five full-scale food waste composts were conducted under different aeration frequencies (no aeration, aeration at different intervals, and continuous aeration) to reveal the optimal strategy and its microbial mechanisms. The highest degradation rate (77.2%) and humus content (29.3%) were observed in Treatment D with interval aeration (aeration 20 min, pause 10 min). Aeration influenced the degradation and humification rate by regulating microbial interactions. The microbial interactions peaked in Treatment D, with a 1.30-fold increase. In terms of the microbial community, Thermobifida was a key genus for improving positive cohesion, fulfilling three criteria (high abundance, high occurrence frequency, and significant differences between treatments). The aeration strategy employed in Treatment D not only increased relative abundance of Thermobifida (1.2 times higher) but also strengthened interaction between it and functional genera (34 nodes). Overall, interval aeration, featured by 20 min aeration and 10 min pause, could increase microbial interactions and improve composting efficiency.

Pretreatment of rice straw by newly isolated fungal consortium enhanced lignocellulose degradation and humification during composting

The slow decomposition rate of the reluctant structure of lignocellulose in agricultural waste is the great limitation of composting processes, which can be averted by pretreatment-strategies. This study focused on the impacts of pretreating rice straw using a consortium of newly isolated fungal species on lignocellulose degradation and humic substances during composting. Fungal pretreatment had a significant impact on lignocellulose degradation (84%) of rice straw by producing higher lignocellulytic enzymes than chemical pretreatments (79%) or the control (61%). The compost with fungal pretreated rice straw (FPT) showed significantly high composting temperature in the late mesophilic stage, which enhanced the degradation of lignocellulose. The fluorescence excitation emission spectroscopy revealed that significantly more humic acid-like compounds were formed in FPT. These findings suggest that fungal pretreatment is a feasible method to accelerate straw degradation and humification.

Microbial interaction promote the degradation rate of organic matter in thermophilic period

Composting is an efficient, microbe-driven method for the biodegradation of solid organic substrates. In such a complex engineering ecosystem, microbial interaction is more important to function than relative abundance and alpha diversity. However, microbial interaction and its driving force in the composting process has been rarely reported. Thus, we combined network analysis and positive cohesion to analyze the relationship between cooperation among bacteria taxa and the degradation of organic matter in ten industrial-scale food waste composting piles. The results showed that although the complexity of network and microbial diversity were inhibited by high temperature, microbial cooperation was stimulated in the thermophilic period. The positive cohesion, which reflected the degree of microbial cooperation, tended to be positively correlated with the degradation rate of organic matter, functional genera, and genes associated with organic matter degradation. Thus, microbial cooperation was a key factor in the promotion of the degradation of organic matter. From the insight microbial community, Thermobifida was the genera with high abundance, high occurrence frequency, and high contributions to microbial structure. Additionally, it was not only highly associated with the degree of cooperation but was also highly linked with the functional genera in the composting, implying that it might play an important role in regulating cooperation to promote the functional genera. Our research provides a deep understanding of the interaction among bacteria taxa during the composting process. Focusing on the abundance of Thermobifida might be an efficient way to improve composting quality by enhancing the cooperation of microbes.

Effect of different soil amendments on soil buffering capacity

The buffering capacity of the soil is a very important property of the soil, which determines the ability of the soil to resist external influences, especially changes in pH and thus create good living conditions for plants and microorganisms in the soil. The buffering capacity thus significantly contributes to maintaining the health and quality of the soil. Buffering capacity is an important indicator of soil quality, because it is related to the overall condition of the soil ecosystem and other soil properties. The goal of this paper is to determine the effect of applying different soil amendments on the soils, 10 years after application. We compared the effect of 6 different treatments in closed plots: Natural conditions (N = control); Bare soil (B); Straw mulching (S); Pine mulch (P); TerraCottem hydroabsorbent polymers (H); Prescribed burn (F); and Sewage sludge (M). Our results have shown that the application of different amedments leads to an effect on the plowing capacity of the soil. While in the case of the control variant (Natural conditions, N) the buffering capacity of the soil was measured at 144.93 ± 0.25, the addition of different amendments decreased the buffering capacity in the following order: Bare soil (B) 142.73±0.21 > TerraCotem hydroaborbent polymer (H) 142.23±.15 > Pine mulch (P) 140.40±0.30, Prescribed burn (F) 138.20±0.30, Sludge (S) 127.47±0.15. In the case of all variants, these are statistically significant differences (p ≤ 0.05). Thus, soil amendments have been shown to have a statistically significant effect on soil buffering capacity.

Cellulolytic bacteria joined with deproteinized whey decrease carbon to nitrogen ratio and improve stability of compost from wine production chain by-products

Composting residues from wine and dairy chains would contribute to increase the environmental sustainability of the production. The aim of this study was to evaluate the effects of deproteinized whey combined with bioactivators on the composting process. Bacillus velezensis and Kocuria rhizophila, bacteria with cellulolytic activity, were isolated from raw materials and inoculated in the organic mass to be composted. Piles moistened with deproteinized whey showed the highest reduction of total and dissolved organic carbon due to the stimulation of bacterial activity by nitrogen compounds held within deproteinized whey. Such findings were also confirmed by the speed up of the microbial carbon mineralization. Bioactivators and deproteinized whey speeded up the composting process and returned compost characterized by high stability and quality. The addition of available N is crucial to improve the composting process and can act even better if combined with cellulolytic bacteria.

Influence of microbial inoculants on co-composting of lignocellulosic crop residues with farm animal manure: A review

The rapidly developing agro-industry generates huge amounts of lignocellulosic crop residues and animal manure worldwide. Although co-composting represents a promising and cost-effective method to treat various agricultural wastes simultaneously, poor composting efficiency prolongs total completion time and deteriorates the quality of the final product. However, supplementation of the feedstock with beneficial microorganisms can mitigate these negative effects by facilitating the decomposition of recalcitrant materials, enhancing microbial enzyme activity, and promoting maturation and humus formation during the composting process. Nevertheless, the influence of microbial inoculation may vary greatly depending on certain factors, such as start-up parameters, structure of the feedstock, time of inoculation, and composition of the microbial cultures used. The purpose of this contribution is to review recent developments in co-composting procedures involving different lignocellulosic crop residues and farm animal manure combined with microbial inoculation strategies. To evaluate the effectiveness of microbial additives, the results reported in a large number of peer-reviewed articles were compared in terms of composting process parameters (i.e., temperature, microbial activity, total organic carbon and nitrogen contents, decomposition rate of lignocellulose fractions, etc.) and compost characteristics (humification, C/N ratio, macronutrient content, and germination index). Most studies confirmed that the use of microbial amendments in the co-composting process is an efficient way to facilitate biodegradation and improve the sustainable management of agricultural wastes. Overall, this review paper provides insights into various inoculation techniques, identifies the limitations and current challenges of co-composting, especially with microbial inoculation, and recommends areas for further research in this field.

Additional strains acting as key microbes promoted composting process

Microbial inoculums (MIs) were the widely used biofortification strategy in composting. However, lack of efficient MIs and unclear strengthening mechanisms might impaired the efficiency of MIs. Here, three experimental group (precise strains, commercial MI, Inoculum HJ) and one control group (untreated) were investigated to close these gaps. Adding MIs could significantly prolong the duration of thermophilic period (1.5-2.8 times), but the difference in GI, pH value, EC value and moisture content were marginal. Furthermore, it could be observed that adding Inoculum HJ could improve the degradation rate of lignocellulose and organic matters for 1.22-1.25 times. The high-throughput sequencing results showed that adding Inoculum HJ made additional genus dominant, with their relative abundance raised from 2.58 to 3.39 times. Results of network analysis showed that microbial interaction could be strengthened by adding MIs, and significantly improved composting quality. The most intensive interaction was observed in the pile with Inoculum HJ, which was 1.20 times higher than other piles. To explore how Inoculum HJ strengthened microbial interaction, module based connectivity analysis was used to distinguish key hubs. Results showed that twelve hkey OTUs in the thermophilic period were similar to additional strains' full-length 16S rRNA gene. These results showed that additional strains behaved like the key hubs to strengthen microbial interaction in the thermophilic period. This research indicated that additional strains from the most efficient inoculum could behave as key hubs to increase the network complexity and had the potential to strengthen microbial interaction.

Hydrogen peroxide plus ascorbic acid enhanced organic matter deconstructions and composting performances via changing microbial communities

This work aims to investigate the influence of hydrogen peroxide (H₂O₂) and ascorbic acid (ASCA) on the physicochemical characteristics, organic matter (OM) deconstructions, humification degree and succession of bacterial communities for co-composting of bagasse pith and dairy manure. The results indicated that H₂O₂ and ASCA accelerated the degradation of lignocellulose, improved the transformation of dissolved organic matter (DOM), and enhanced the content of humic substance (HS) and the degree of its aromatization. The bacterial communities were significantly changed in the presence of additives, in which the relative abundances of Firmicutes and Actinobacteria significantly increased. Redundancy analysis (RDA) indicated that the degradation of OM and lignocellulose more influenced the bacterial community compositions. Conclusively, adding H₂O₂ and ASCA accelerated lignocellulose degradation efficiency, and improved the composting process, which provided an optimized method to dispose of lignocellulose wastes and livestock manure.

Composting of fish waste and its phytotoxicity effects

This work aimed to evaluate the composting of the mixture of residues from fish filleting, using sawdust as a structuring material as an alternative for stabilization, through physical-chemical analysis and phytotoxicity. The experiment was carried out in a composter 1.10 m long, 1.50 m wide, and 1.20 m high and presenting 2.50 m in total height, which received the mixture of fish filleting wastes and sawdust in a5:3 ratio, respectively. The results demonstrated that composting in cells is an efficient alternative for the decomposition of the mixture of fish filleting and sawdust residues. The rapid decomposition of fish waste and the low C/N ratio harms the development of thermophilic microorganisms during the composting of the mixture of fish filleting and sawdust residues. The compaction of the sawdust layers and the absence of stirring in the composting method in cells collaborate for the compost to need a time greater than 60 days to be recommended as simple organic fertilizer. The biomass stirring is necessary so that sawdust can be considered a good structuring agent. The phytotoxicity test should be taken into account by the Normative Instruction n° 25/2009 as an indicator of compost maturity.

Influence of reusable polypropylene packing on ammonia and greenhouse gas emissions during sewage sludge composting-a lab-scale investigation

Bulking agents are particularly important for sewage sludge composting. In this study, reusable polypropylene packing (RPP) was mixed with sawdust to improve composting. The effect of the mix ratio of sawdust and RPP on the physicochemical characteristics, nitrogen transformation, and emissions of greenhouse gas (GHG) as well as differences in the germination index values was detected in a lab-scale composting experiment. The results showed that the unique use of RPP as a bulking agent increased the moisture content over 70%, which resulted in poorer porosity and a less efficient O₂ utilization environment and thus suppressed the degradation of organic matter. The highest CH₄ 9275.8 mg and lowest CO₂ 202.6 g emissions were detected after 25 days of composting in the treatment with RPP used as a bulking agent. When the mixing ratio of sawdust and RPP was 1:1, the temperature, oxygen supply, and dissolved organic carbon degradation were improved. The NH₃, N₂O, and CH₄ emissions were reduced by 32.2, 18.3, and 90.7% compared with a treatment with RPP as a unique bulking agent. The RPP had no effect on conserving nitrogen during sludge composting; the total nitrogen loss was reduced from 29.3 to 18.2% when sawdust was mixed with RPP in a ratio of 1:1. Therefore, mixing RPP and sawdust in the dry weight ratio of 1:1 (sawdust: RPP) can be potentially used for reducing composting cost and improving the sewage sludge composting by reducing the amount of sawdust mixed and mitigating GHG and NH₃ emissions.

Effects of different additives on the chemical composition and microbial diversity during composting of Camellia oleifera shell

The influence of three additives including Camellia oleifera meal, C. oleifera seed cake and goat dung during the C. oleifera shell composting was evaluated. The result of physic-chemical parameters indicated that compost of C. oleifera shell with one of additives could achieve the effect of maturity.16S rDNA sequencing suggested that Proteobacteria, Bacteroidetes, Firmicutes, Actinobacteria, Chloroflexi, Tenericutes, Deinococcus-Thermus, Patescibacteria, Fibrobacteres and Acidobacteria were the dominant microorganisms in all compost piles, and their abundances varied with compost additive and composting phase. Goat dung significantly increased the microbial diversity at the mesophilic phase. The microbial composition was most diverse at the end of composting for all piles. No pathogens were detected in the compost products of all three groups, and thus were safe for utilization in plant cultivation. This work considered that compost was best way to address the contamination problem of C. oleifera shell, where goat dung was best additive for compost.

Effects of Clonostachys rosea f. catenula Inoculum on the Composting of Cabbage Wastes and the Endophytic Activities of the Composted Material on Tomatoes and Red Spider Mite Infestation

Globally, fungal inocula are being explored as agents for the optimization of composting processes. This research primarily evaluates the effects of inoculating organic vegetable heaps with the entomopathogenic fungus Clonostachys rosea f. catenula (Hypocreales) on the biophysicochemical properties of the end-product of composting. Six heaps of fresh cabbage (Brassica oleracea var. capitata) waste were inoculated with C. rosea f. catenula conidia and another six were not exposed to the fungus. The composted materials from the fungus- and control-treated heaps were subsequently used as a medium to cultivate tomatoes (Solanum lycopersicum). The biophysicochemical characteristics of the composted materials were also assessed after composting. In addition, the protective effect of the fungal inoculum against red spider mite (Tetranychus urticae) infestations in the tomatoes was evaluated through the determination of conidial colonization of the plant tissue and the number of plants infested by the insect. Furthermore, phytotoxicity tests were carried out post experiment. There were few significant variations (p < 0.05) in heap temperature or moisture level between treatments based on the weekly data. We found no significant differences in the levels of compost macronutrient and micronutrient constituents. Remarkably, the composted materials, when incorporated into a growth medium from fungus-treated heaps, induced a 100% endophytic tissue colonization in cultivated tomato plants. While fewer red spider mite infestations were observed in tomato plants grown in composted materials from fungus-treated heaps, the difference was not significant (χ² = 0.96 and p = 0.32). The fungal treatment yielded composted materials that significantly (p < 0.05) enhanced tomato seed germination, and based on the phytotoxicity test, the composted samples from the heaps exposed to the C. rosea f. catenula inoculum were not toxic to tomato seeds and seedlings. In conclusion, this study showed that C. rosea f. catenula improved the quality of composted materials in terms of fungal endophytism and seed germination.

Fungal community succession contributes to product maturity during the co-composting of chicken manure and crop residues

The succession of the fungal community during the co-composting of chicken manure and crop residues and its role in relation to compost maturity was deciphered using Illumina sequencing and FUNGuild (Fungi + Functional + Guild) tool. In the maturation phase of composting, the relative abundance of pathogenic and symbiotrophic fungi decreased by 68%-85% and 145%-622%, respectively, as compared to the initial phase, which showed 574%-720% increase in the saprotrophic guild. The pathogenic and saprotrophic fungi abundance was correlated to compost maturity represented by germination index and humic spectroscopic ratio (p < 0.05). Random forest analysis and structural equation modeling elucidated the positive effects of the aforementioned fungal taxa on compost maturity, and these effects were mediated by the micro-environmental variables, such as temperature, NH₄⁺-N/NO₃^--N ratio and total organic carbon content. Our study outlines the importance of fungal community succession for improving composting performance and efficiency.

Biochar reinforced the populations of cbbL-containing autotrophic microbes and humic substance formation via sequestrating CO2 in composting process

The quality of compost is drastically reduced due to the loss of carbon, which negatively impacts the environment. Carbon emission reduction and carbon dioxide (CO₂) fixation have attracted much attention in composting research. In this study, the relationship between CO₂ emission, humic substances (HS) formation and cbbL-containing autotrophic microbes (CCAM) was analyzed by adding biochar during cow manure composting. The results showed that biochar can facilitate the degradation of organic matter (OM) and formation of HS, as well as reinforce the diversity and abundance of CCAM community, thereby promoting CO₂ fixation and reducing carbon loss during composting. High-throughput sequencing analysis revealed significant increase in Actinobacteriota and Proteobacteria abundance by 30.97 % and 10.48 %, respectively, thus increasing carbon fixation by 32.07 %. Additionally, Alpha diversity index increased significantly during thermophilic phase, while Shannon index increased by 143.12 % and Sobs index increased by 51.62 %. Redundancy analysis (RDA) indicated that CO₂ was positively correlated with C/N, temperature, HS and dissolved organic matter (DOM), while the abundance of Paeniclostridium, Corynebacterium, Bifidobacterium, Clostridium, Turicibacter and Romboutsia were positively correlated with temperature, CO₂, C/N and E₂/E₄ (p <  0.01).

Implementation of strategies to optimize the co-composting of green waste and food waste in developing countries. A case study: Colombia

Green waste (GW) management is a key issue due to its high production rate and its variety of physical properties and chemical composition. Composting is a promising alternative for GW treatment and valorization. However, the presence of recalcitrant components such as lignin and cellulose increase the processing time. Strategies such as addition of co-substrates and operative modifications have improved the processing time and compost quality. Therefore, in this study, three strategies have been implemented (i) addition of unprocessed food (UF) and processed foods (PF) as co-substrates for GW to improve the nutrients composition of the substrates at the beginning of the process, (ii) addition of phosphate rock (PR) to improve product quality, and (iii) the use of two-stage composting (TSC) to accelerate the degradation. For this purpose, three treatments with the same mixture (48% GW + 21% UF + 18% PF + 13% sawdust (SW)) were conducted: (i) TA (TSC + 15% PR), (ii) TB (traditional composting +15% PR), and (iii) TC (traditional composting). TSC did not show significant differences compared with TC regarding the process and compost quality, while the addition of PR increased the phosphorus content of the product. However, TC produced the compost with the highest quality according to the Colombian legislation for soil amendment.

Energy Utilization of Torrefied Residue from Wine Production

A significant amount of waste is generated in the food industry, which is both an environmental and an economic problem. The recycling of this waste has become an important area of research. The processing of grapes produces 20-30% of the waste in the form of grape pomace and stalks. This article assesses the fuel values of these materials before and after torrefaction. The input materials were grape pomace samples from the varieties Riesling (Vitis vinifera "Welschriesling") and Cabernet Sauvignon (Vitis vinifera "Cabernet Sauvignon") from the South Moravia region and stalks from the variety Welschriesling. The torrefaction process was performed using a LECO TGA 701 thermogravimetric analyzer under nitrogen atmosphere at set temperatures of 225 °C, 250 °C, and 275 °C. The residence time was 30 min. Elemental analysis, calorific value, and gross calorific value were determined for all samples. The analyses show a positive effect of torrefaction on fuel properties in the samples. Between temperatures 250 °C and 275 °C, the carbon content increased by 4.29 wt.%, and the calorific value increased with the increase in temperature reaching a value of 25.84 MJ·kg^-1 at a peak temperature of 275 °C in the sample grape pomace from blue grapevine.

Composting of winery waste and characteristics of the final compost according to Brazilian legislation

The waste generated in the production of wine and grape juice is characterized by a high concentration of organic matter, when properly treated, can serve as sustainable strategies for its use and destination, and among these, the production of biocompost. Thus, the objective of this study was to evaluate the process of composting grape marc, sheep manure, and mango leaves, evaluating in the biocompost its physical-chemical, nutritional and microbiological characteristics for use in agriculture. The composting pile assembly followed the proportion of 30% of sheep manure as nitrogenous material and 70% of carbon-rich material (divided into 50% of grape marc and 20% of hose leaves), the initial C/N ratio was 33:1, and the process lasted 120 days according to legislation. When evaluating the results, the process occurred in an accelerated manner, where at 30 days the biocompost was already stabilized, and at the end of the process (120 days) it presented a C/N ratio of 5.85, as well as acceptable levels for the macronutrients K and P, and without risk of phytotoxicity, and could be used as organic fertilizer or as soil conditioner, reducing environmentally inadequate destination and generating savings with their reinsertion in the production chain.

The degradation of organic matter coupled with the functional characteristics of microbial community during composting with different surfactants

The purpose of this study was to investigate the effects of anionic and cationic surfactants on the physico-chemical properties, organic matter (OM) degradation, bacterial community structure and metabolic function during composting of dairy manure and sugarcane bagasse. The results showed that the surfactant could optimize the composting conditions to promote the degradation of OM. The most OM degradation and humic substances (HS) synthesis were observed in SAS. Firmicutes and Proteobacteria were more abundant in SAS and CTAC, and Actinobacteria in CK. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) showed that SAS and CTAC are more abundant than CK in genes related to metabolism, environmental and genetic information processing. The correlation analysis showed that the dominant bacteria had more significant correlation with environmental factors. In general, the anionic surfactant could better promote the degradation of OM, change the structure of microbial community, and improve the quality of compost.

Streptomyces griseorubens JSD-1 promotes rice straw composting efficiency in industrial-scale fermenter: Evaluation of change in physicochemical properties and microbial community

The influence of Streptomyces griseorubens JSD-1 on microbial community succession during rice straw composting in an industrial-scale fermenter was assessed by high-throughput sequencing technology. Compared to uninoculated control, JSD-1 inoculation effectively raised composting temperature and improved other maturation indices. JSD-1 inoculation increased the relative abundance of Actinobacteria in thermophilic phase and Firmicutes in cooling and maturation phases. At the genus level, JSD-1 inoculation increased the abundance of organic matter degrading bacteria (Virgibacillus) and lignocellulose degrading fungi (Chaetomium and Melanocarpus); while it decreased the abundance of pathogenic fungi (Geosmithia and Acremonium). Moreover, JSD-1 changed microbes that differed significantly and altered the key connecting nodes of microbial community. Organic matter and temperature were the most significant indices that had mutual influences on bacterial and fungal communities, respectively. This study demonstrated that JSD-1 was an effective inoculant on rice straw fast composting in the industrial-scale fermenter.

Alkali lignin and sodium lignosulfonate additives promote the formation of humic substances during paper mill sludge composting

Alkali lignin (AL) and sodium lignosulfonate (SLS) are by-products of the papermaking industry and could influence composting processes due to their rich aromatic structures. In this study, the roles of AL and SLS additives in the formation of humic substances (HS) during paper mill sludge composting were investigated. Results showed that HS content and degree of polymerization of the final products in AL (44.42 mg·g^-1 and 0.70, respectively) and SLS (45.87 mg·g^-1 and 1.14, respectively) treatments were appreciably higher than those of the control sample (34.36 mg·g^-1 and 0.67). Excitation-emission matrix-parallel factor coupled with two-dimensional FT-IR correlation spectroscopy analysis suggested that AL and SLS additives could speed the transformation of quinone-like substances by increasing the amounts of low molecular weight lignin depolymerized products, which led to higher HS concentrations. This work provided a way of promoting HS formation and the comprehensive utilization of papermaking wastes.

Molecular mechanisms underlying lignocellulose degradation and antibiotic resistance genes removal revealed via metagenomics analysis during different agricultural wastes composting

In this study, the differences on the physico-chemical parameters, lignocellulose degradation, dynamic succession of microbial community, gene expression of carbohydrate-active enzymes and antibiotics resistance genes were compared during composting systems of bagasse pith/pig manure (BP) and manioc waste/pig manure (MW). The results revealed that biodegradation rates of organic matter, cellulose, hemicellulose and lignin (29.14%, 17.53%,45.36% and 36.48%) in BP were higher than those (15.59%, 16.74%, 41.23% and 29.77%) in MW. In addition, the relative abundance of Bacillus, Luteimonas, Clostridium, Pseudomonas, Streptomyces and expression of genes encoding carbohydrate- active enzymes in BP were higher than those in MW based on metagenomics sequencing. During composting, antibiotics and antibiotic resistance genes were substantially reduced, but the removal efficiency was divergent in the both samples. Taken together, metagenomics analysis was a potential method for evaluating lignocellulose's biodegradation process and determining the elimination of antibiotic and antibiotic resistance genes from different composting sources of biomass.

Effectiveness of vermicomposting for bioconversion of grape marc derived from red winemaking into a value-added product

Grape marc, the main solid by-product of the wine industry, can be used as a nutrient-rich organic amendment if treated appropriately before its application into soil. In this study, we evaluated the potential of vermicomposting to process grape marc derived from the red winemaking of Mencía grapes in order to yield a high-quality, polyphenol-free organic vermicompost that could be used as an environmentally friendly fertiliser. We observed that the grape marc from this cultivar appears to be an optimum substrate for feeding earthworms providing optimum conditions for growth and reproduction, and sufficient energy to sustain large populations. Moreover, earthworm activity favoured the stabilisation of the grape marc resulting in a final vermicompost characterised by a higher concentration of macro- and micro-nutrients and a reduced polyphenol content after 112 days of vermicomposting. Lower values of microbial activity, indicative of stabilised materials, were recorded at the end of the process. These findings highlight vermicomposting as an environmentally sound management system for processing grape marc that could easily be scaled up for industrial application.

Role of the proportion of cattle manure and biogas residue on the degradation of lignocellulose and humification during composting

The effects of different proportions of cattle manure (CM) and biogas residue (BR) on the degradation of lignocellulose and humification during composting were investigated. The results showed that increasing the CM content prolonged the thermophilic period duration, thus promoting organic matter degradation and enhancing the humification degree during composting. Compared with the initial compost, the cellulose content decreased 3.90%-22.81%. The addition of CM increased humic acid content by 17.21%-26.02% compared with the control. The excitation-emission matrix (EEM) fluorescence spectroscopy analysis indicated that a higher CM content was conducive to the formation of protein-like substances, but a disadvantage for humic substances. The cell viability decreased as CM content increased. The redundancy analysis (RDA) demonstrated that proportions of CM and BR were positively correlated with cellulose content and negatively correlated with cell viability and the content of lignin. The results suggest that adding 6.7% CM was optimal for BR composting.

Temporal Dynamics of Bacterial Communities in a Pilot-Scale Vermireactor Fed with Distilled Grape Marc

Vermicomposting has been found as a profitable approach to dispose of and treat large quantities of raw grape marc. However, less information is available with regard to its efficiency for treating distillery winery byproducts, even though distillation has been widely used as a way to economically valorize grape marc. As such, we sought to characterize the compositional and functional changes in bacterial communities during vermicomposting of distilled grape marc by using 16S rRNA high-throughput sequencing. Samples were collected at the initiation of vermicomposting and at days 14, 21, 28, 35 and 42. There were significant changes (p < 0.0001) in the bacterial community composition of distilled grape marc after 14 days of vermicomposting that were accompanied by twofold increases in bacterial richness and diversity from a taxonomic and phylogenetic perspective. This was followed by significant increases in functional diversity of the bacterial community, including metabolic capacity, lignin and cellulose metabolism, and salicylic acid synthesis. These findings indicate that the most striking compositional and functional bacterial community changes took place during the active phase of the process. They also pinpoint functional attributes that may be related to the potential beneficial effects of distilled grape marc vermicompost when applied on soil and plants.

Utilization and re-use of solid and liquid waste generated from the natural indigo dye production process - A zero waste approach

The main aim of this work is focused towards possible reuse of both solid and liquid waste generated from the natural indigo dye production process. The solid waste (C/N:15.01) was utilized to produce stable compost with possible re-use in Indigofera cultivation. Among seven compost combinations (C1-C7) using jeevamrutha (JA) and cow-dung (CD) as inoculum, C4 with 8% JA showed higher biomass degradation (51%) and plant growth potential (GI > 125%). Whereas the undiluted liquid waste was treated using algal consortia, bacteria, and indigenous microbial population, achieved a maximum removal of 90% ammonia, 82% nitrate, and 88% phosphorus for its re-use in the dye production process. Hence, incorporation of suitable waste management strategies in natural indigo dye production could help to achieve a zero waste sustainable process.

A new liquid-phase method and its comparison to two solid-phase microbial respiration activity methods to assess organic waste stability

Goal of the work was to compare the respiration activities, as measured via oxygen consumption with three different organic waste stability methods so that to propose the optimal one. The novelty of the work is that there exists no comparison of solid-phase with liquid-phase stability assessment techniques in the literature. The respiration activities were assessed using two solid-phase methods and a manometric liquid-phase method (MANLIQ) performed on twenty-seven organic substrates. The methods rely on measuring oxygen consumption (uptake) via pressure drops (liquid-phase test, static solid-phase test) or via direct O₂ measurements on the gaseous phases at the inlet and outlet of the respirometer (solid-phase dynamic test). A positive statistically significant correlation was calculated between the MANLIQ and the static solid-phase indices. The maximum rate MANLIQ index for the raw substrates was 2900 mg O₂ kg^-1 VS h^-1, while most of the processed substrates had cumulative MANLIQ indices below 160 g O₂ kg^-1 VS. The ratio of the liquid indices to the static solid-phase indices ranged from 1.6 to 2.7 and the ratio of the liquid indices to the dynamic solid-phase indices ranged from 0.2 to 0.4. The MANLIQ method failed to result in a good correlation of the processing time with the respiration indices. On the other hand, a correlation was more visible in the two solid-phase tests, despite the large variability of the types and sources of the substrates. Therefore, the solid-phase methods should be preferred over the liquid-phase method to assess stability for various organic substrates.

Compost supplementation with nitrogen loss and greenhouse gas emissions during pig manure composting

This research investigated the influence of biochar (B) and bean dregs (BD) amendments on carbon and nitrogen losses through greenhouse gas (GHG) emissions during pig manure (PM) composting. The treatments included 15% BD, 10% B and 15% BD+10% B (w/w dry basis of PM) amendments in the compost, whereas the CK (control) lacked any additives. The NH₄⁺-N, C/N and germination index (GI) of the end products ensured compost maturity. Compared with the CK, the 15% BD amendment increased the total nitrogen content (TKN) of the final product by 8.05% but also increased NH₃ (54.98%) and GHG emissions (40.35%) as well as nitrogen loss (25.62%). Furthermore, the combined treatment of 15% BD+10% B improved the TKN (2.83%) of the end product and controlled NH₃ emissions (33.71%), GHG emissions (29.56%) and nitrogen loss (24.26%) while increasing CO₂ only with the 15% BD amendment. Therefore, the combination of BD+B was recommended.

Recalcitrant carbon for composting of fibrous aquatic waste: Degradation kinetics, spectroscopic study and effect on physico-chemical and nutritional properties

Biochar, a recalcitrant carbon, is known to enhance organic matter degradation and improve physical properties. The objective of the study is to examine the probable effect of biochar addition during composting of a fibrous aquatic waste, i.e., water hyacinth though degradation kinetics and spectroscopic (FTIR and PXRD) analysis. Four dosages of biochar (0, 2.5, 5, and 10% w/w) were mixed to a mixture of water hyacinth, cow-dung and saw-dust comprising a total weight of 150 kg and composted using rotary drum composter for 20 days in batch mode. The study outcomes indicated that the amendment of biochar prolonged the duration of the thermophilic temperatures, reduced salinity, and promoted nutritional quality of compost. Moreover, biochar amendment enhanced the organic matter degradation with a rate constant of 0.029 day^-1 and increased the total Kjeldahl nitrogen content up to 1.75% from an initial value of 1.10% in the reactor with 2.5% biochar amendment. Concurrently, biochar amendment aided in reducing Cu and Cr in the final product inferring 2.5% biochar is best suited for composting of water hyacinth. However, future studies are encouraged to decipher the microbial shifts and bioavailability of metals due to biochar dosage during composting for mitigating and managing the menace of such fibrous waste like water hyacinth by converting it to a soil conditioner.

A compost-derived thermophilic microbial consortium enhances the humification process and alters the microbial diversity during composting

This work was conducted to assess the influence of a compost-born multifunctional thermophilic microbial consortium (CTMC) on the physico-chemical parameters, organic matter (OM) transformation and dynamic succession of microbial communities in dairy manure-sugarcane leaves co-composting. The results revealed that CTMC inoculation not only improved the bio-degradation of OM and lignocellulose but also distinctly enhanced the aromaticity and stability degrees of dissolved organic matter and humic substance (HS). Additionally, the complexity and diversity of bacterial and fungal community increased after inoculation. Redundancy analysis indicated that the microbial communities compositions and the physico-chemical parameters interacted with each other in humification process. The dominated bacterial and fungal species related to lignocellulose degradation and humification process were also detected. Accordingly, this research could put forward a possible optimized inoculation strategy to enhance the mineralization of organic carbon, accelerate the lignocellulose degradation and promote the humification process in solid organic waste composting.

Bacterial succession and functional diversity during vermicomposting of the white grape marc Vitis vinifera v. Albariño

Winemaking produces millions of tons of grape marc, a byproduct of grape pressing, each year. Grape marc is made up of the skins, stalks, and seeds remaining after pressing. Raw grape marc can be hazardous to the environment due to its low pH and high polyphenol content, but previous work has shown that grape marc can be stabilized via vermicomposting to produce organic fertilizer. Here, we utilize 16S rRNA high-throughput sequencing to characterize the bacterial community composition, diversity and metabolic function during vermicomposting of the white grape marc Vitis vinifera v. Albariño for 91 days. Large, significant changes in the bacterial community composition of grape marc vermicompost were observed by day 7 of vermicomposting and throughout the duration of the experiment until day 91. Similarly, taxonomic and phylogenetic α-diversity increased throughout the experiment and estimates of β-diversity differed significantly between time points. Functional diversity also changed during vermicomposting, including increases in cellulose metabolism, plant hormone synthesis, and antibiotic synthesis. Thus, vermicomposting of white grape marc resulted in a rich, stable bacterial community with functional properties that may aid plant growth. These results support the use of grape marc vermicompost for sustainable agricultural practices in the wine industry.

Strategies for recycling and valorization of grape marc

Grapes are one of the most cultivated fruit crops worldwide. Either for wine or juice production, grape processing generates a large amount of residues that must be treated, disposed of or reused properly to reduce their pollution load before being applied to the soil. In this review, a special focus is given to the treatment and valorization of the winemaking by-product like grape marc via anaerobic digestion, composting and vermicomposting at laboratory, pilot, and industrial scales. The impact of the final products (digestates, composts, and vermicomposts) on soil properties is briefly addressed. Moreover, the role of grape marc and seeds as a valuable source of natural phytochemicals that include polyphenols and other bioactive compounds of interest for pharmaceutical, cosmetic, and food industries is also discussed. This is of paramount importance given the fact that sustainability requires the use of management and valorization strategies that allow the recovery of valuable compounds (e.g. antioxidants) with minimum disposal of waste streams.

Influence of sugar beet pulp and paper waste as bulking agents on physical, chemical, and microbial properties during green waste composting

Composting is considered to be a natural, sustainable, and highly beneficial method for solid waste disposal. The objective of this study was to investigate the two-stage composting of green waste (GW) as affected by the addition of sugar beet pulp (SBP; at 0, 25, and 35%) and/or paper waste (PW; at 0, 5, and 10%) as bulking agents. The combination of SBP and PW greatly improved the composting conditions and the final compost quality in terms of composting temperature; pH; emissions of ammonia, nitrite nitrogen, and carbon dioxide; lignocellulose degradation; microbial abundance; enzyme activities; particle-size distribution; the ratio of water-soluble organic carbon to organic nitrogen; and phytotoxicity. The optimal two-stage composting process of GW and the highest quality compost product were obtained with the combination of 25% SBP and 10% PW. This optimal combination of bulking agents produced a mature and stable final compost product in only 20 days.

Effects of waste lime and Chinese medicinal herbal residue amendments on physical, chemical, and microbial properties during green waste composting

Traditional composting is time-consuming and often results in a low-quality product. The objective of this study was to determine the effects of waste lime (WL; at 0, 2.5, and 3.5%) and/or Chinese medicinal herbal residues (CMHRs; at 0, 10, and 20%) as amendments on the two-stage composting of green waste (GW). The combination of WL and CMHRs improved compost particle-size distribution and pH, decreased nitrogen loss, and increased cation exchange capacity (CEC), nutrient content, and microbial numbers. The combination of WL and CMHRs also accelerated organic matter humification and lignocellulose degradation and therefore increased the germination index of the final compost. Relative to the non-amended compost, the optimal amendment (2.5% WL and 20% CMHRs) increased the percentage of particles of ideal size from 23.8 to 66.9%, the pH from 6.69 to 7.17, the CEC from 52 to 169 cmol/kg, the humic acid to fulvic acid ratio from 1.32 to 2.49, the hemicellulose degradation rate from 42 to 87%, and the cellulose degradation rate from 20 to 61%. The treatment with addition of 2.5% WL and 20% CMHRs to GW required only 21 days to generate the highest quality compost product.

Evaluation of maifanite and silage as amendments for green waste composting

Composting is a popular method for recycling organic solid wastes including agricultural and forestry residues. However, traditional composting method is time consuming, generates foul smells, and produces an immature product. The effects of maifanite (MF; at 0%, 8.5%, and 13.5%) and/or silage (SG; at 0%, 25%, and 45%) as amendments on an innovative, two-stage method for composting green waste (GW) were investigated. The combined addition of MF and SG greatly improved composting conditions, reduced composting time, and enhanced compost quality in terms of composting temperature, bulk density, water-holding capacity, void ratio, pH, cation exchange capacity, ammonia nitrogen content, dissolved organic carbon content, crude fibre degradation, microbial numbers, enzyme activities, nutrient contents, and phytotoxicity. The two-stage composting of GW with 8.5% MF and 45% SG generated the highest quality and the most mature compost product and did so in only 21 days. With the optimized composting, the degradation rate of cellulose and hemicellulose reached 46.3 and 82.3%, respectively, and the germination index of Chinese cabbage and lucerne was 153 and 172%, respectively, which were all far higher than values obtained with the control. The combined effects of MF and SG on GW composting have not been previously explored, and this study therefore provided new and practical information. The comprehensive analyses of compost properties during and at the end of the process provided insight into underlying mechanisms. The optimized two-stage composting method may be a viable and sustainable alternative for GW management in that it converts the waste into a useful product.

Succession and diversity of microorganisms and their association with physicochemical properties during green waste thermophilic composting

A comprehensive characterization of the bacterial diversity associated to thermophilic stages of green waste composting was achieved. In this study, eight different treatments (T1-T8) and three replicated lab-scale green waste composting were carried out to compare the effect of the cellulase (i.e. 0, 2%), microbial inoculum (i.e. 0, 2 and 4%) and particle size (i.e. 2 and 5 mm) on bacterial community structure. Physicochemical properties and bacterial communities of T1-T8 composts were observed, and the bacterial structure and diversity were examined by high-throughput sequencing via a MiSeq platform. The results showed that the most abundant phyla among the treatments were the Firmicutes, Chloroflexi and Proteobacteria. The shannon index and non-metric multidimensional scaling (NMDS) showed higher bacterial abundance and diversity at the metaphase of composting. Comparing with 5-mm treatments, particle size of 2-mm had a richer diversity of bacterial communities. The addition of cellulase and a microbial inoculum could promote the fermentation temperature, reduce the compost pH and C/N ratio and result in higher GI index. The humic substance (HS) and humic acid (HA) contents for 2-mm particle size treatments were higher than those of 5-mm treatments. Canonical correspondence analysis suggested that differences in bacterial abundance and diversity significantly correlated with HA, E₄/E₆ and temperature, and the relationship between bacterial diversity and environmental parameters was affected by composting stages. Based on these results, the application of cellulase to promote green waste composting was feasible, and particle size was identified as a potential control of composting physicochemical properties and bacterial diversity.

Sustainable wineries through waste valorisation: A review of grape marc utilisation for value-added products

Grapes are one of the most cultivated fruits worldwide, with one third of total production used in winemaking. Both red and white winemaking processes result in substantial quantities of solid organic waste, such as grape marc (pomace) and stalks, which requires suitable disposal. Grape marc accounts for approximately 10-30% of the mass of grapes crushed and contains unfermented sugars, alcohol, polyphenols, tannins, pigments, and other valuable products. Being a natural plant product rich in lignocellulosic compounds, grape marc is also a promising feedstock for renewable energy production. However, despite grape marc having such potential, advanced technologies to exploit this have not been widely adopted in wineries and allied industries. This review covers opportunities beyond traditional composting and animal feed, and examines value-added uses via the extraction of useful components from grape marc, as well as thermochemical and biological treatments for energy recovery, fuel or beverage alcohol production, and specialty novel products and applications such as biosurfactants and environmental remediation. New advances in relevant technology for each of these processes are discussed, and future directions proposed at both individual producer and regional facility scales, including advanced processing techniques for integrated ethanol production followed by bioenergy generation from the spent marc.

Improvement of pig manure compost lignocellulose degradation, organic matter humification and compost quality with medical stone

The present study aimed to investigate the effect of different concentrations (0%, 2.5%, 5.0%, 7.5% and 10.0%) of medical stone (MS) on the lignocellulose degradation and organic matter humification during pig manure (PM) composting. The results indicated that the addition of MS drastically promoted the organic carbon and lignin degradation. Compared to the control, the decomposition rate of hemicellulose and cellulose was increased by 9.64-27.08% and 2.11-12.07% in MS added treatments. Meanwhile, MS amendment significantly improved the humification of composting process, and the humic acid contents in MS added treatments were 5.58-9.75% higher than control. The FTIR and synchronous fluorescence spectra indicated that the aromatization of final compost was promoted with increasing the MS amount. In addition, the application of MS blended composts could significantly improve the biomass and chlorophyll content of pachoi (Brassica chinensis L.). Due to the effective performance of MS, the 10.0% MS was suggested for PM composting.

Comparison of additives amendment for mitigation of greenhouse gases and ammonia emission during sewage sludge co-composting based on correlation analysis

In this study, the pilot scale co-composting of sewage sludge (SS)+wheat straw amended with 10% (dry weight ratio of basis) of three different additives (zeolite, Ca-bentonite and medical stone) was conducted for 56days to evaluate the greenhouse gases (GHGs) and nitrogen conservation efficacy and its correlation with analyzed physicochemical, gaseous and biological parameters. The results indicated that all of three additives could adequately buffer pH, considerably increase temperature, and enhance organic matter degradation as well as reduce ammonia and GHGs emission. Particularly, zeolite amended treatment showed the maximum reduction of CH₄ emission by 88.45% and less amount of nitrogen loss by 28.80%, meanwhile reduced the maturity period by 2weeks. In addition, the redundancy analysis was confirmed most significant relationship between biological, GHGs, bacterial community and nutrients concentration in 10% zeolite applied treatment than other treatments. The result suggested 10% zeolite could be a suitable additive to improve the quality of sewage sludge composting.

Addressing Facts and Gaps in the Phenolics Chemistry of Winery By-Products

Grape and wine phenolics display a noticeable structural diversity, encompassing distinct compounds ranging from simple molecules to oligomers, as well as polymers usually designated as tannins. Since these compounds contribute critically to the organoleptic properties of wines, their analysis and quantification are of primordial importance for winery industry operators. Besides, the occurrence of these compounds has been also extensively described in winery residues, which have been pointed as a valuable source of bioactive phytochemicals presenting potential for the development of new added value products that could fit the current market demands. Therefore, the cumulative knowledge generated during the last decades has allowed the identification of the most promising compounds displaying interesting biological functions, as well as the chemical features responsible for the observed bioactivities. In this regard, the present review explores the scope of the existing knowledge, concerning the compounds found in these winery by-products, as well as the chemical features presumably responsible for the biological functions already identified. Moreover, the present work will hopefully pave the way for further actions to develop new powerful applications to these materials, thus, contributing to more sustainable valorization procedures and the development of newly obtained compounds with enhanced biological properties.

Combining woody biomass for combustion with green waste composting: Effect of removal of woody biomass on compost quality

The question was tackled on how the green waste compost industry can optimally apply the available biomass resources for producing both bioenergy by combustion of the woody fraction, and high quality soil improvers as renewable sources of carbon and nutrients. Compost trials with removal of woody biomass before or after composting were run at 9 compost facilities during 3 seasons to include seasonal variability of feedstock. The project focused on the changes in feedstock and the effect on the end product characteristics (both compost and recovered woody biomass) of this woody biomass removal. The season of collection during the year clearly affected the biochemical and chemical characteristics of feedstock, woody biomass and compost. On one hand the effect of removal of the woody fraction before composting did not significantly affect compost quality when compared to the scenario where the woody biomass was sieved from the compost at the end of the composting process. On the other hand, quality of the woody biomass was not strongly affected by extraction before or after composting. The holocellulose:lignin ratio was used in this study as an indicator for (a) the decomposition potential of the feedstock mixture and (b) to assess the stability of the composts at the end of the process. Higher microbial activity in green waste composts (indicated by higher oxygen consumption) and thus a lower compost stability resulted in higher N immobilization in the compost. Removal of woody biomass from the green waste before composting did not negatively affect the compost quality when more intensive composting was applied. The effect of removal of the woody fraction on the characteristics of the green waste feedstock and the extracted woody biomass is depending on the season of collection.

Improving green waste composting by addition of sugarcane bagasse and exhausted grape marc

The composting of lignocellulosic waste into compost is a potential way of sustainably disposing of a waste while generating a useful product. The current study determined whether the addition of sugarcane bagasse (SCB) (at 0, 15, and 25%) and/or exhausted grape marc (EGM) (at 0, 10, and 20%) improved the two-stage composting of green waste (GW). The combined addition of SCB and EGM improved composting conditions and the quality of the compost product in terms of temperature, water-holding capacity, particle-size distribution, coarseness index, pH, electrical conductivity, water-extractable organic carbon and nitrogen, microbial numbers, enzymatic activities, polysaccharide and lignin content, nutrient content, respiration, and phytotoxicity. The optimal two-stage composting and the best quality compost were obtained with the combined addition of 15% SCB and 20% EGM. With the optimized two-stage composting method, the compost matured in only 21days rather than in the 90-270days required for traditional composting.

Chemical, Thermal and Spectroscopic Methods to Assess Biodegradation of Winery-Distillery Wastes during Composting

The objective of this work was to study the co-composting process of wastes from the winery and distillery industry with animal manures, using the classical chemical methods traditionally used in composting studies together with advanced instrumental methods (thermal analysis, FT-IR and CPMAS ¹³C NMR techniques), to evaluate the development of the process and the quality of the end-products obtained. For this, three piles were elaborated by the turning composting system, using as raw materials winery-distillery wastes (grape marc and exhausted grape marc) and animal manures (cattle manure and poultry manure). The classical analytical methods showed a suitable development of the process in all the piles, but these techniques were ineffective to study the humification process during the composting of this type of materials. However, their combination with the advanced instrumental techniques clearly provided more information regarding the turnover of the organic matter pools during the composting process of these materials. Thermal analysis allowed to estimate the degradability of the remaining material and to assess qualitatively the rate of OM stabilization and recalcitrant C in the compost samples, based on the energy required to achieve the same mass losses. FT-IR spectra mainly showed variations between piles and time of sampling in the bands associated to complex organic compounds (mainly at 1420 and 1540 cm^-1) and to nitrate and inorganic components (at 875 and 1384 cm^-1, respectively), indicating composted material stability and maturity; while CPMAS ¹³C NMR provided semi-quantitatively partition of C compounds and structures during the process, being especially interesting their variation to evaluate the biotransformation of each C pool, especially in the comparison of recalcitrant C vs labile C pools, such as Alkyl /O-Alkyl ratio.

Numerical simulation of organic waste aerobic biodegradation: a new way to correlate respiration kinetics and organic matter fractionation

Composting wastes permits the reuse of organic matter (OM) as agricultural amendments. The fate of OM during composting and the subsequent degradation of composts in soils largely depend on waste OM quality. The proposed study aimed at developing a model to predict the evolution in organic matter quality during the aerobic degradation of organic waste, based on the quantification of the various OM fractions contained in the wastes. The model was calibrated from data gathered during the monitoring of four organic wastes (two non-treated wastes and their digestates) exposed to respirometric tests. The model was successfully fitted for all four wastes and permitted to predict respiration kinetics, expressed as CO2 production rates, and the evolution of OM fractions. The calibrated model demonstrated that hydrolysis rates of OM fractions were similar for all four wastes whereas the parameters related to microbial activity (eg. growth and death rates) were specific to each substrate. These later parameters have been estimated by calibration on respirometric data, thus demonstrating that coupling analyses of OM fractions in initial wastes and respirometric tests permit the simulation of the biodegradation of various type of waste. The biodegradation model presented in this paper could thereafter be integrated in a composting model by implementing mass and heat balance equations.

Enhanced reductive dechlorination of polychlorinated biphenyl-contaminated soil by in-vessel anaerobic composting with zero-valent iron

Anaerobic dechlorination is an effective degradation pathway for higher chlorinated polychlorinated biphenyls (PCBs). The enhanced reductive dechlorination of PCB-contaminated soil by anaerobic composting with zero-valent iron (ZVI) was studied, and preliminary reasons for the enhanced reductive dechlorination with ZVI were investigated. The results show that the addition of nanoscale ZVI can enhance dechlorination during in-vessel anaerobic composting. After 140 days, the average number of removed Cl per biphenyl with 10 mg g(-1) of added nanoscale ZVI was 0.63, enhancing the dechlorination by 34 % and improving the initial dechlorination speed. The ZVI enhances dechlorination by providing a suitable acid base environment, reducing volatile fatty acid inhibition and stimulating the microorganisms. The C/N ratios for treatments with the highest rate of ZVI addition were smaller than for the control, indicating that ZVI addition can promote compost maturity.