Metagenomic analysis reveals enhanced biodiversity and composting efficiency of lignocellulosic waste by thermoacidophilic effective microorganism (tEM)

Converting kitchen waste into value-added fertilizer using thermophilic semi-continuous composting-biofiltration two-stage process with minimized NH3 emission

Thermophilic semi-continuous composting (TSC) is effective for kitchen waste (KW) treatment, but large amounts of NH3-rich odorous gas are generated. This study proposes a TSC-biofiltration (BF) two-stage process. Compost from the front-end TSC was used as the packing material in the BF to remove NH3 from the exhaust gas. The BF process was effective in removing up to 83.7 % of NH3, and the NH3 content was reduced to < 8 ppm. Seven days of BF improved the quality of the product from TSC by enhancing the germination index to 134.6 %, 36.5 % higher than that in the aerated-only group. Microbial community analysis revealed rapid proliferation and eventual dominance in the BF of members related to compost maturation and the nitrogen cycle from Actinobacteria, Proteobacteria, Chloroflexi, and Bacteroidetes. The results suggest that the TSC-BF two-stage process is effective in reducing NH3 emissions from TSC and improving compost quality.

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

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

Catalyzed Hydrothermal Pretreatment of Oat Husks for Integrated Production of Furfural and Lignocellulosic Residue

This study presents a novel approach for biorefining oat husks into furfural, leveraging a unique pilot-scale setup. Unlike conventional furfural manufacturing processes, which often result in substantial cellulose degradation and environmental concerns associated with sulfuric acid usage, our method utilizes phosphoric acid as a catalyst to achieve high furfural yield while minimizing cellulose destruction. Drawing on our research conducted in a distinctive pilot-scale environment, we successfully developed and implemented a tailored biorefining process for oat husks. Through meticulous experimentation, we attained a remarkable furfural yield of 11.84% from oven-dried mass, accompanied by a 2.64% yield of acetic acid. Importantly, our approach significantly mitigated cellulose degradation, preserving 88.31% of the cellulose content in oat husks. Existing catalytic (H2SO4) furfural manufacturing processes often lead to substantial cellulose degradation (40-50%) in lignocellulosic leftover during the pretreatment stage. As a result of the research, it was also possible to reduce the destruction of cellulose in the lignocellulose leftover to 11.69% of the output (initial) cellulose of oat husks. This research underscores the feasibility and sustainability of utilizing oat husks as a valuable feedstock for furfural production, highlighting the potential of phosphoric acid as a catalyst in biorefining processes. By showcasing our unique pilot-scale methodology, this study contributes to advancing the field of environmentally friendly biorefining technologies.

The co-inoculation of Trichoderma viridis and Bacillus subtilis improved the aerobic composting efficiency and degradation of lignocellulose

The aim of this study was to reveal the mechanism by which co-inoculation with both Trichoderma viridis and Bacillus subtilis improved the efficiency of composting and degradation of lignocellulose in agricultural waste. The results showed that co-inoculation with Trichoderma and Bacillus increased abundance of Bacteroidota to promote the maturation 7 days in advance. Galbibacter may be a potential marker of co-inoculation composting efficiency compost. The compost became dark brown, odorless, and had a carbon to nitrogen ratio of 16.40 and a pH of 8.2. Moreover, Actinobacteriota and Firmicutes still dominated the degradation of lignocellulose following inoculation with Trichoderma or Bacillus 35 days after composting. Bacterial function prediction analysis showed that carbohydrate metabolism was the primary metabolic pathway. In conclusion, co-inoculation with Trichoderma and Bacillus shortened the composting cycle and accelerated the degradation of lignocellulose. These findings provide new strategies for the efficient use of agricultural waste to produce organic fertilizers.

Valorizing kitchen waste to produce value-added fertilizer by thermophilic semi-continuous composting followed by static stacking: Performance and bacterial community succession analysis

To explore an effective decentralized kitchen waste (KW) treatment system, the performance and bacterial community succession of thermophilic semi-continuous composting (TSC) of KW followed by static stacking (SS) was studied. A daily feeding ratio of 10% ensured stable performance of TSC using an integrated automatic reactor; the efficiencies of organic matter degradation and seed germination index (GI) reached 80.88% and 78.51%, respectively. SS for seven days further promoted the quality of the compost by improving the GI to 91.58%. Alpha- and beta-diversity analyses revealed significant differences between the bacterial communities of TSC and SS. Firmicutes, Actinobacteria, Chloroflexi, Gemmatimonadetes, and Myxococcota were dominant during the TSC of KW, whereas the members of Proteobacteria and Bacteroidetes responsible for product maturity rapidly proliferated during the subsequent SS and ultimately dominated the compost with Firmicutes and Actinobacteria. These results provide new perspectives for decentralized KW treatment using TSC for practical applications.

Combined use of biochar and microbial agent can promote lignocellulose degradation and humic acid formation during sewage sludge-reed straw composting

This study investigated the effects of corn straw biochar (CSB) and effective microorganisms (EM) added individually or combinedly on lignocellulose degradation, compost humification, and microbial communities during sewage sludge-reed straw composting process. All the additive practices were found to significantly elevate the humification degree of compost products. The degradation rates of cellulose, hemicellulose, and lignin in different additive treatments were 20.8-31.2 %, 36.2-44.8 %, and 19.9-25.7 %, respectively, which were greatly higher than those of the control. Compared with the single uses of CSB or EM, the combined use of CSB and EM generated greater promotions in lignin and hemicellulose degradations and increase in humic acid content. By comparing the differences in microbial communities among different treatments, the CSB-EM demonstrated greater increases in activity and diversity of lignocellulose degradation-related microbes, especially for fungus. Lastly, the combined use of CSB and EM was highly recommended as a high-efficient improvement strategy for organic compost production.

Impacts of composting duration on physicochemical properties and microbial communities during short-term composting for the substrate for oyster mushrooms

A short-term composting process to prepare substrate is an effective way to cultivate oyster mushrooms (Pleurotus spp.), which can increase the yield of mushrooms and lower the rate of contamination in non-industrialized cultivation. Moreover, it is different from the traditional composting processes for fertilizers and lacks systematic study, such as microbial succession and compost quality. In this study, a series of different tests of composting duration (0, 2, 4 and 5 d) were performed. A composting duration of 4-5 d over 58 °C was suitable for mushroom cultivation based on the biological efficiency (BE) range of 69.76-73.41 % and the contamination rate of 0 %. The content of total carbon (TC) continuously decreased during composting, while the content of total nitrogen (TN) reacted in an opposite matter. The final TN and C/N ratios were 1.89 % and 28/1, respectively, which fell well within the optimal range of nutritional requirements for oyster mushroom cultivation. The composting bacteria were more diverse than the fungal species. Caldibacillus, Thermobispora, Thermopolyspora, Thermobacillus and Ureibacillus were the predominant bacterial genera during the thermophilic stage. Co-occurrence patterns of microbial communities and physicochemical properties were performed using a network analysis, which indicated that bacteria can play more efficient roles than fungi in the degradation of organic matter. The structural equation model showed that composting duration significantly affected bacterial diversity, lignocellulose degradation rates, and BE. The correlations between bioinformatics parameters with composting characters and agronomic traits were determined by the Mantel test and showed that the induction of bacterial diversity over time rapidly activated carbon metabolism during short-term composting. This study provides a new idea of agro-waste composting for mushroom cultivation.

Application of Additives in Platycladus orientalis (L.) Franco Tending Shreds Compost in Forest

This study aimed to explore the effects of different additives on tending shreds of Platycladus orientalis (L.) Franco. Two different additives (priming 0.2% and common compost 0.2%) combined with C, N, and P adjustment of raw material treatments were tested on the temperature, moisture, EC, pH, lignocellulose degradation rate, nutrient content, and toxicity of compost. Priming made the compost temperature rise rapidly, and the peak temperature of the composting group with priming reached 51 ℃. At the end of composting, the moisture in each treatment from high to low was in the order: common compost > priming > C/N, C/P adjustment only > control group. The increase of EC in the treatments with additives was great, and the peak value of EC in the treatment of priming was 1.30 ms·cm−1, which was 3.9 times higher than that of the control group. At the end of composting, the decomposition rate of cellulose in priming compost was 1.7 times higher than that in the control group, and the hemicellulose decomposition rate in the common compost group was 3.2 times higher than that in the control group. By the end of composting, the pH value of the composts in additive treatments was above 7.0, and the pH value of the priming treatment was the highest (7.5). The highest content of organic matter was found in the priming treatment, which was 52%, 1.7 times higher than that in the control group. The total nutrient content (TN + K2O + P2O5) of additive treatments was higher than 5.0%, and the priming treatment was 2.7% higher than that of the control group. By the end of composting, the germination rate and germination index ranged from 88% to 91% and 60% to 81%. Except for the control group, the C/N ratio of other treatments decreased to below 25. Additives can accelerate the decomposition of raw materials, shorten the composting cycle, and improve the quality of composts, and the effect of adding priming is the most significant.

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.

Carbohydrate degradation contributes to the main bioheat generation during kitchen waste biodrying process: A pilot study

Biodrying is a promising method for processing kitchen waste (KW) with high moisture content into reusable solid recovered fuels (SRFs). During biodrying, a large amount of bioheat generated from biodegradation of biochemical components results in KW dehydration. However, the degradation rules of these components and their contribution to the bioheat in KW biodrying have not been systematically clarified. Here, a pilot experiment was performed to investigate the variations in biochemical components, hydrolase activities, and bioheat generation during three successive cycles of biodrying processes. Results showed that KW could be rapidly converted into SRFs with low calorific values of 6705-7062 kJ/kg and moisture content of 31.26%-35.21%. Analyses of hydrolase activities and mean fluorescence intensity suggested that the biodrying process pioneered the degradation of lipids and proteins in the warming stages, while carbohydrates (i.e. amylum, celluloses, etc.) underwent rapid decomposition in a large extent in the high-temperature and cooling stages. Carbohydrates with minimal difficulty in degradation, contributed 73.37%-89.92% to the total degradation mass and 59.23%-60.80% to the bioheat source during the three-cycle biodrying process. The generated bioheat was 4.32-4.56 times the amount of the theoretical heat used for water removal, indicating that internal bioheat could significantly enhance water evaporation and was sufficient for the expected water removal mass. Therefore, the evaluation of the main components to bioheat generation and its utilization efficiency makes a prominent contribution that can greatly clarify the conversion of KW biodrying into SRFs in order to efficiently promote renewable bioenergy and support the bioeconomy.

Microbe assisted depolymerization of lignin rich waste and its conversion to gaseous biofuel

Biomethanation potential of lignin rich residue (LRR) obtained from lignocellulosic ethanol fermentation was evaluated after subjecting to microbe assisted pretreatment using selectively enriched lignin depolymerizing consortia (LDC). The efficiency of LDC in lignin depolymerization was established using alkali and dealkali lignins (AL and DL) along with LRR as feedstocks. Microbial growth on media having lignin as sole carbon source, activity of lignin depolymerizing enzymes, viz., lignin peroxidase and laccase, ability of culture to decolorize the lignin mimicking dyes like methylene blue and ramezol brilliant blue, were considered to confirm the efficiency of enriched mixed culture. Microbial treatment using LDC showed significant positive impact on lignin breakdown irrespective of the substrate (LRR, 46.33%; AL, 31.37%; DL, 34.20%). The hydrolysate of LRR obtained from microbial pretreatment showed higher biogas yield (424 ml/g VS) owing to the efficiency of lignin depolymerization and availability of readily available biodegradable components in residual lignin from previous processing. Depolymerization of commercial lignins also produced a good amount of biogas (302-324 ml/g VS) after pretreatment with LDC. Overall, an additional energy conversion efficiency of about 11.75 kJ/g VS was obtained by valorizing the residual lignin through integrating biomethanation technology to ethanol fermentation. Outcome of this study indicated the feasibility of using lignin rich residue generated from the second generation cellulosic bioethanol plants as a potential feedstock to meet the current gaseous fuel demands. This integration also helps in closing the biomass based biorefinery loop and also promotes the circular economy.

Valorization and optimization of agro-industrial orange waste for the production of enzyme by halophilic Streptomyces sp

This study underlines the biotechnical valorization of the accumulated and unusable remains of agro-industrial orange fruit peel waste to produce α-amylase under submerged conditions by Streptomyces sp. KP314280 (20r). The response surface methodology based on central composite design (RSM-CCD) and artificial neural network coupled with a genetic algorithm (ANN-GA) were used to model and optimize the conditions for the α-amylase production. Four independent variables were evaluated for α-amylase activity including substrate concentration, inoculum size, sodium chloride powder (NaCl), and pH. A ten-fold cross-validation indicated that the ANN has a greater ability than the RSM to predict the α-amylase activity (R²_ANN = 0.884 and R²_RSM = 0.725). The analysis of variance indicated that the aforementioned four factors significantly affected the α-amylase activity. Additionally, the α-amylase production experiments were conducted according to the optimal conditions generated by the GA. The results indicated that the amylase yield increased by 4-fold. Moreover, the α-amylase production (12.19 U/mL) in the optimized medium was compatible with the predicted conditions outlined by the ANN-GA model (12.62 U/mL). As such, the ANN and GA combination is optimizable for α-amylase production and exhibits an accurate prediction which provides an alternative to other biological applications.

Integrated eco-strategies towards sustainable carbon and nitrogen cycling in agriculture

To meet the ever-growing human demands for food, fuel, and fiber, agricultural activities have dramatically altered the global carbon (C) and nitrogen (N) cycles. These biogeochemical cycles along with water, phosphorus, and sulfur cycles are fundamental features of life on Earth. Human alteration of the global N cycle has had both positive and negative outcomes. To efficiently feed a growing population, crop-livestock production systems have been developed, however, these systems also contribute significantly to environmental pollution and global climate change. Management of agricultural waste (AW) and the application of N fertilizers are central to the issues of greenhouse gas (GHG) emissions and nutrient runoff that contributes to the eutrophication of water bodies. If managed properly, AW can provide nutrients for plants and contribute to the conservation of soil health. In order to achieve the long-term conservation of agricultural production systems, it is important to promote the proper recycling of AW in agroecosystems and to minimize the reliance on chemical N fertilizers. Composting is one of the sustainable and effective approaches for recycling AW in agriculture. However, the conventional composting process is dilatory and produces compost with low N content compared to chemical N fertilizers. For this reason, comprehensive research is required to improve the composting process and the N content of the soil organic amendments. This work aims to explore the beneficial effects of the integrated application of biochar and specific C and N cycling microorganisms to the composting process and the quality of the composted products. In pursuit of replacing chemical N fertilizers with bio/organic fertilizers, we further discussed the power of the combined application of compost, biochar, and N-fixing bacteria in agricultural production systems. The knowledge of smart integration of AW and microorganisms in agriculture could solve the main agricultural and environmental problems associated with human-induced flows of C and N. Building upon the knowledge disseminated in review to further extensive research will pave the way for better management of agricultural production systems and sustainable C and N cycling in agriculture.

Effect of excess sludge and food waste feeding ratio on the nutrient fractions, and bacterial and fungal community during aerobic co-composting

The effect of excess sludge and food waste feeding ratio on the co-composting process was explored using 5% bagasse biochar as an additive and conditioner. Results showed that when the mass ratio was 1:1, nitrogen fixation ability was the strongest and ammonia nitrogen increment in the pile reached 2.31 mg/g. The increase in excess sludge content/food waste ratio during composting was conducive to the accumulation of H₂O-P, BD-P, HCl-P, NaOH-P and NaOH₈₅-P. When the ratio of excess sludge to food waste mass was 1:1, the relative abundance of Firmicutes was the largest in the compost, which corresponded to 72.77% at the phylum level. Food waste mass was more beneficial to the growth and reproduction of microorganisms and to the metabolic activities related to membrane transport. Considering the fungal content, Ascomycota and Basidiomycota were maximum, with relative abundance of 69.53% and 20.91%, respectively, at the mass ratio of 1:1.