Food Waste Treatment Research Articles

Combined Pre-Treatment Technologies for Cleaning Biogas before Its Upgrading to Biomethane: An Italian Full-Scale Anaerobic Digester Case Study

Biogas produced by anaerobic digestion contains different types of contaminants, and it is preferable to eliminate those contaminants before biogas’ energetic valorization or upgrading to biomethane as they are harmful to human health and detrimental to combustion engines. This study presents the biogas cleanup system optimized by an Italian full-scale anaerobic digester treating food waste (FW) and represented by micro-oxygenation, chemical scrubber, cooling, and activated carbon sections. The cleaned biogas is upgraded to biomethane using a membrane-based upgrading unit and injected into the natural gas network for transport sector use. H2S and volatile organic compound (VOC) concentration in raw biogas was reduced from an annual average value of 1207 ppmv and 895 mg/Nm3, respectively, to below 0.1 mg/Nm3 in the final biomethane. In the summer, the H2S average content in raw biogas was 833 ppmv due to a greater presence of low-sulfur-containing vegetables in FW, while in the winter it was an average of 1581 ppmv due to a larger portion of protein-containing FW. On the other hand, raw biogas VOC content in the winter was an average of 1149 mg/Nm3, with respect to 661 mg/Nm3 in the summer, due to the greater consumption of citrus fruits containing high amount of terpene compounds. The concentration of other trace contaminants, such as HCl, NH3, and siloxanes, was lowered from 17, 36, and 0.6 mg/Nm3 in raw biogas, respectively, to below 0.1 mg/Nm3 in the final biomethane. All the considerations and evaluations underlying the technological and plant engineering choices together with the individuation of the best operating conditions are discussed.

Nitrogen Metabolism during Anaerobic Fermentation of Actual Food Waste under Different pH Conditions

Acidogenic fermentation can convert food waste (FW) into small molecules of acids and alcohols, and the broth can be used as a carbon source of denitrification in wastewater treatment plants. However, the soluble nitrogen-containing substances generated in fermentation influence the quality of the carbon source, and microbial nitrogen transformation under different pH conditions has rarely been reported. In this study, four FW fermentation systems were operated continuously with a focus on nitrogen transformation, and metagenomic and metatranscriptomic analyses were used to reveal the metabolic pathways. The results showed that approximately 70% of nitrogen existed in solid organic matter, and the dissolution of solid proteins was limited at pH 4.0–5.0. The concentration of soluble nitrogen, encompassing both soluble organic nitrogen and ammonium, remained relatively stable across various pH conditions. However, high pH values promoted the conversion of soluble nitrogen-containing substances to ammonium, and its concentration increased by 122%, 180%, 202%, and 267% at pH 4.00, pH 4.27, pH 4.50, and pH 5.00. Lactobacillus played a crucial role in ammonium production via the arginine deiminase pathway at pH 4.0–4.5, and Prevotella was the key contributor with the assistance of glutamate dehydrogenase at pH 5.0. The findings provide insights into organic nitrogen transformation in acidogenic fermentation for optimizing FW treatment processes.

A novel approach for purifying food waste anaerobic digestate through bio-conditioning dewatering followed by activated sludge process: A case study

Although anaerobic digestion is the mainstream technology for treating food waste (FW), the high pollutant concentration in the resultant food waste anaerobic digestate (FWAD) often poses challenges for the subsequent biochemical treatment such as activated sludge process. In this study, taking a typical FW treatment plant as an example, we analyzed the reasons behind the difficulties in treating FWAD and tested a novel process called as bio-conditioning dewatering followed by activated sludge process (BDAS) to purify FWAD. Results showed that high concentrations of suspended solids (SS) (16439 ± 475 mg/L), chemical oxygen demand (COD) (24642 ± 1301 mg/L), and ammonium nitrogen (NH4+-N) (2641 ± 52 mg/L) were main factors affecting the purification efficiency of FWAD by the conventional activated sludge process. By implementing bio-conditioning dewatering for solid-liquid separation, near 100% of SS and total phosphorus (TP), 90% of COD, 38% of total nitrogen (TN), and 37% of NH4+-N in the digestate could be effectively removed or recovered, consequently generating the transparent filtrate with relatively low pollution load and dry sludge cake (<60% of moisture content). Furthermore, after ammonia stripping and biochemical treatment, the effluent met the relevant discharge standards regulated by China, with the concentrations of COD, TN, NH4+-N, and TP ranging from 151 to 405, 10–56, 0.9–31, and 0.4–0.8 mg/L, respectively. This proposed BDAS approach exhibited stable performance and low operating costs, offering a promising solution to purify FWAD in practical engineering and simultaneously realize resource recovery.

Thiopseudomonas acetoxidans sp. nov., an aerobic acetic and butyric acids oxidizer isolated from anaerobic fermentation liquid of food waste.

A Gram-stain-negative, oxidase-negative, rod-shaped, motile, facultatively anaerobic bacterial strain, designated as CY1220T, was isolated from an anaerobic fermentation liquid of food waste treatment plant. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the strain CY1220T belongs to the genus Thiopseudomonas, with the highest sequence similarity to Thiopseudomonas alkaliphila B4199T (95.91%), followed by Thiopseudomonas denitrificans X2T (95.56%). The genomic DNA G + C content of strain CY1220T was 48.6mol%. The average nucleotide identity values and digital DNA-DNA hybridization values between strain CY1220T and the type species of T. alkaliphila and T. denitrificans were in the range of 70.8-71.6% and 19.2-20.0%, respectively, below the thresholds for species delineation. The strain was able to grow utilizing acetic acid and butyric acid (AABA) as the sole carbon source in aerobic conditions. Genomic analysis predicted that the strain could synthesize vitamin B12 and ectoine. The predominant cellular fatty acids were C18:1 ω7c and/or C18:1 ω6c, C16:0, C16:1 ω7c and/or C16:1 ω6c and C12:0. The polar lipids comprised diphosphatidylglycerol, unknown polar lipid, phosphatidylethanolamine, phosphatidylglycerol, and phospholipid. Q-8 (2.1%) and Q-9 (97.9%) were detected as the respiratory quinones. Based on its phenotypic, genotypic and genomic characteristics, strain CY1220T represents a novel species in the genus Thiopseudomonas, for which the name Thiopseudomonas acetoxidans sp. nov. is proposed. The type strain is CY1220T (= GDMCC 1.3503T = JCM 35747T).

Re-evaluating the impact of feeding shock on anaerobic co-digestion of food waste and waste activated sludge: Trade-off between efficiency and stability

To optimize the feeding strategy of anaerobic digestion (AD) treating food waste and waste activated sludge, the impact of relative feeding shock (RFS) on the trade-off between efficiency and stability was re-evaluated at six feeding conditions from 1/96 (approximate continuous feeding) to 1. The results showed that increasing the RFS from 1/96 to 1/3 increased the CH4 yield from 293.23 mL CH4/g-total solid (TS) to the maximum value of 345.11 mL CH4/g-TS, which was due to the highest specific microbial growth rates (μmax) of acetate (1.05d-1) and propionate (0.48d-1) and a balanced reaction rate between acidogenesis and methanogenesis. However, when the RFS increased to 1, the total volatile fatty acids (TVFA) concentration increased from 0.51 to 5.90 g-COD/L, with the predominant VFAs changing from acetate to propionate, limiting methanogenesis. Meanwhile, the stability coefficient decreased to 0.37, leading to decreased CH4 yield and μmax. In addition, the high hydrogen partial pressure caused by high RFS increased the Gibbs free energy by 17 %, aggravating the thermodynamic disadvantages. The abundant methanogens shifted from Methanosaeta to Methanosarcina, which cooperated with a syntrophic partner-Syntrophomonas to ensure the smooth VFAs degradation at RFS of 1/3. These findings provide prima facie insights into the optimization of operational conditions for AD treating organic wastes.

Switching from wet to dry anaerobic digestion of food waste with different dilution times under no mechanical mixing condition

Previous research on anaerobic digestion of food waste has primarily focused on either wet or dry anaerobic digestion (AD), typically accompanied by continuous mechanical mixing. However, the necessary dilution rates and the extent of mixing required have yet to be addressed. In this study, we investigated switching from wet to dry AD of food waste without mechanical mixing, employing different dilution rates. Lab-scale anaerobic reactors were operated with dilution rates of 10, 5, and 2 times during Phases I (0–56 days), II (57–121 days), and III (122–209 days), respectively. The methane production rates were not significantly different (p > 0.05) across the dilution rates decreased from 10 to 2 times. Remarkably, the methane production in the anaerobic reactors exhibited fluctuations due to variations in feeding, with the methane production rate ranging from 2.0 to 2.7 g CH4-COD/(L d), without mechanical mixing, as the solids content transitioned from wet to near-dry digestion conditions (15 %, food waste). The distribution of sludge volatile solids concentrations remained uniform in the reactor, even at high solids concentrations of up to 15 %. A dynamic microbial community response to changes in dilution rates, with a shift from aceticlastic to hydrogenotrophic methanogenesis pathways. Syntrophic acetate oxidization bacteria (the genus Syner-01 (4.2–8.9 %) and f_Synergistaceae (3.6–4.2 %)) were highly enriched as switching from wet AD to dry AD. The study's findings provide crucial operational insights for anaerobic food waste treatment, potentially resulting in decreased water usage and operational costs, particularly in scenarios with low dilution rates and without mechanical mixing.

Anaerobic Treatment of Food Waste with Biogas Recirculation under Psychrophilic Temperature

Food waste has emerged as a pressing concern, and thus advanced techniques to valorize food waste into nutrition rich materials as well as renewable energy are highly important. The exceptional biodegradability of food waste renders it a highly suitable substrate for anaerobic treatment. This leads to energy production and a reduction in the carbon footprint. Nevertheless, in frigid territories like Canada, the conventional mesophilic anaerobic digestion at 30–40 °C can require substantial amounts of energy. Consequently, this study introduces a new approach to treat food waste at psychrophilic temperatures (1–20 °C). Lower temperatures can negatively impact cellular processes during anaerobic treatment, rendering substrates less accessible to microscopic organisms. To address this challenge associated with lower temperatures, the study introduces an innovative biogas recirculation strategy. The primary objectives of this study are to assess the viability of anaerobic treatment for food waste at psychrophilic temperatures and to investigate the effectiveness of reintroduction of the produced biogas to the anaerobic system in enhancing biomethane generation and stability of the system. Batch experiments were conducted on food waste in various assessments, both with and without biogas recirculation. The outcomes revealed a methane concentration ranging from 68% to 93% when biogas recirculation was employed, whereas without this technique, methane concentration varied between 10% and 45%. Moreover, with biogas recirculation, the reduction in volatile solids reached a maximum of 92%, and there was an 82% decrease in chemical oxygen demand. In conclusion, the utilization of the recirculation of biogas at the psychrophilic temperature range enhanced biomethane production and reduction of volatile solids and chemical oxygen demand. This study underscores the potential of employing anaerobic treatment with reintroduction of produced biogas into the system in cold regions as an economically viable and sustainable choice for treating food waste with nominal energy consumption.

Impact of chick mash, rice bran, and wheat bran as starter feeds on the performance of black soldier fly larvae in food waste treatment

ABSTRACT Inadequate management of food waste (FW) has contributed to environmental degradation. Bioconversion of FW using black soldier fly larvae has proven to be a safe and cost-effective method for FW management. However, limited studies exist on the influence of starter feeds. The impact of rice bran, wheat bran, and chick mash as starter feeds was evaluated by investigating the optimal larval weight, substrate reduction, feed conversion ratio (FCR), and bioconversion rate (BCR) of the larvae after initial treatment in rice bran (T1), wheat bran (T2), chick mash (T3), and control (T4). The highest mean larval weight observed was 0.22 g in T3 followed by 0.18, 0.16, and 0.13 g in T2, T4, and T1, respectively. A similar trend was observed for substrate reduction and BCR. Nevertheless, the obtained substrate reduction range of 75.5–82.8% was comparable with the published ranges. The best performance in T3 may be attributed to high protein and nitrogen content in chick mash, while the lowest performance is attributed to high ash content in rice bran, which negatively affected the BCR. It can be concluded that the physico-chemical properties of the starter feeds strongly determine the growth and development of larvae.

Multi-scale assessment of global warming mitigation potential of anaerobic digestion for food waste management in the United States: A comparison of Life Cycle Assessment approaches

This study provides a holistic Life Cycle Assessment (LCA) for evaluating the decarbonization potential of using Anaerobic Digestion (AD) in food waste treatment. The LCA is based on the development of a new flexible tool that allows the integration of the LCA at the process level with geospatial data and therefore includes a wide range of factors such as multiple feedstocks, technologies for end-use applications, and facility locations. This tool estimates a potential for reducing 21.8 MMtons CO2eq/y (345 gCO2eq/kgwaste) and generating 161 TBTU/y of renewable natural gas for the whole United States by managing food waste based on waste-hierarchy. This study also identifies those states with a more efficient AD implementation potential regarding CO2eq avoidance. It highlights the importance of including region-specific conditions since feedstock diversion depends on the state and is the main contributor to the decarbonization potential, up to 60 % of the avoided emissions.

Contrasting effects of food waste and its biochar on soil properties and lettuce growth in a microplastic-contaminated soil

The incorporation of organic amendments, such as food waste (FW) and biochar, into soil is an established agronomic practice known for enhancing soil fertility and improving overall soil health. However, the individual and combined effects of FW and biochar on soil properties in microplastic (MP)-contaminated soil–plant systems remain poorly understood. To address this knowledge gap, we conducted a field experiment to investigate the individual and combined effects of polystyrene MPs, FW, and FW-derived biochar on soil properties and lettuce growth. Soil chemical properties were unaffected by the addition of MPs. However, the application of FW and biochar increased the soil pH, with the highest pH (8.2) observed in the combined treatment of biochar and MPs. Despite the presence of MPs, FW application resulted in notable increases in soil electrical conductivity (EC; 2.04 dS m−1), available nitrogen (NO3−–N: 325.5 mg kg−1, NH4+–N: 105.2 mg kg−1), available phosphorus (88.4 mg kg−1), and total exchangeable cations (18.6 cmol(+) kg−1). However, these values decreased after lettuce cultivation. In soil cultivated with lettuce, the coexistence of MPs and biochar reduced soil Fluorescein diacetate hydrolase enzyme activity by 46.2% and urease activity by 94.0%. FW addition doubled acid phosphatase activity, whereas FW and its coexistence with MPs decreased alpha diversity. The relative abundance of Actinobacteria decreased with MP application, whereas that of Acidobacteria and Actinobacteria decreased with FW treatment. Gemmatimonadetes and Nitrospirae decreased in soil treated with FW and biochar. The highest relative abundances of Firmicutes and Proteobacteria were observed in the FW-added soils, and Planctomycetes were the highest in the biochar-added soils. FW application negatively affected lettuce growth. Overall, the coexistence of MPs with FW or biochar had limited effects on soil properties and lettuce growth, with FW and biochar serving as the primary factors in modifying soil–plant systems. Future studies should investigate the effects of different MPs and their interactions with organic soil amendments on soil properties and crop growth under different management practices.Graphical

Simulating Rumen Conditions Using an Anaerobic Dynamic Membrane Bioreactor to Enhance Hydrolysis of Lignocellulosic Biomass.

An anaerobic dynamic membrane bioreactor (AnDMBR) mimicking rumen conditions was developed to enhance the hydrolysis of lignocellulosic materials and the production of volatile fatty acids (VFAs) when treating food waste. The AnDMBR was inoculated with cow rumen content and operated at a 0.5 day hydraulic retention time, 2-4 day solids retention time, a temperature of 39 °C, and a pH of 6.3, characteristics similar to those of a rumen. Removal rates of neutral detergent fiber and acid detergent fiber of 58.9 ± 8.4 and 69.0 ± 8.6%, respectively, and a VFA yield of 0.55 ± 0.12 g VFA as chemical oxygen demand g volatile solids (VS)fed-1 were observed at an organic loading rate of 18 ± 2 kg VS m-3 day-1. The composition and activity of the microbial community remained consistent after biofilm disruption, bioreactor upset, and reinoculation. Up to 66.7 ± 5.7% of the active microbial populations and 51.0 ± 7.0% of the total microbial populations present in the rumen-mimicking AnDMBR originated from the inoculum. This study offers a strategy to leverage the features of a rumen; the AnDMBR achieved high hydrolysis and fermentation rates even when treating substrates different from those fed to ruminants.

Biogas production prediction model of food waste anaerobic digestion for energy optimization using mixup data augmentation-based global attention mechanism.

Achieving rapid, efficient, and cost-effective anaerobic digestion (AD) of food waste is a key means to improve the efficiency of food waste treatment. However, in view of the shortage of historical anaerobic digestion data, the limitation of general neural networks in predicting biogas production, and its sensitivity to abnormal variation points, achieving accurate prediction of biogas production is not easy. This paper proposes a novel biogas production prediction model of food waste AD for energy optimization based on the mixup data augmentation integrating an improved global attention mechanism long short-term memory (LSTM). Taking the AD data of the actual factory as samples, the mixup data augmentation is introduced to generate virtual samples with the similar distribution as original samples. Then original samples and generated virtual samples are used as the input of the global attention mechanism LSTM to establish the food waste AD biogas production prediction model. Finally, the proposed method is applied in the biogas production prediction of actual food waste treatment plants. Compared with other industrial modeling models, the experimental results show that the proposed method has the highest prediction accuracy of 0.988, which performs well in predicting biogas production and can effectively guide and timely adjust feed configuration of AD plants.

Real-world assessment of a decentralized food waste anaerobic digestion system: A test-bedding case study application

Addressing the global challenge of food waste, this research delves into the assessment of an on-site food waste treatment solution through a full-scale decentralized anaerobic digester (AD) system, specifically deployed at a Singapore hawker centre. Demonstrating efficiency in Singapore's tropical climate (29 °C) without external heating, the 10.8 m³ digester exhibited resilience over 234 days, navigating through real-world fluctuations in average organic loading rates ranging from 0.07 ± 0.02 to 0.81 ± 0.38 kgVS/(m3d). The normalized specific biogas production averaged 0.70 ± 0.48 m3/kgVS, accompanied by a methane concentration of 56.9 ± 2.9%. During peak performance, with an organic loading rate of 1.1 kgVS/(m3d), the system achieved an impressive volumetric biogas production rate of 1.18 m3biogas/m3reactor, equivalent to 1.1 m3/kgVS of specific biogas production per day. The energy assessment revealed consumption rates of 0.57–0.97 m3/kWh, positioning it comparably with commercialized biogas technologies in China and Taiwan. In the realm of microbiome composition, the prevalence of hydrogenotrophic methanogens, including Methanomicrobia, Thermoplasmata, and Nanoarchaeia, is notable. These methanogens showcase a remarkable tolerance to acetate, surpassing common aceticlastic methanogens by 11 times, thereby playing a pivotal role in enhancing the stability of the AD system over extended periods. On the economic front, the present AD system yielded losses ranging from SG$552,434 to SG$742,919, primarily due to a low payback period and substantial investment costs. Profitability becomes a possibility if there are significant reductions in capital costs and operator salaries. The challenges encountered during the operation of this decentralized system, along with the corresponding mitigation measures, are thoroughly discussed. Positioned as a promising test-bedding model, this application underscores its technical feasibility potential for sustainable food waste management through AD technology in Singapore. It stands as a replicable prototype, contributing to closing the food waste loop and advancing the bioeconomy.

An Integrated Bipolar Picture Fuzzy Decision Driven System to Scrutinize Food Waste Treatment Technology through Assorted Factor Analysis

An Integrated Bipolar Picture Fuzzy Decision Driven System to Scrutinize Food Waste Treatment Technology through Assorted Factor Analysis

A Study on the Biogasification Facility for Combined Treatment of Food Waste and Livestock Manure

A Study on the Biogasification Facility for Combined Treatment of Food Waste and Livestock Manure

Comparative analysis of food waste laws in Singapore and Japan: an examination of legal frameworks in hope of achieving Singapore’s zero-waste vision

This article compares food waste laws in Singapore and Japan and analyses similarities and differences in their legal approaches to minimizing food waste across the food supply chain. The research undertaken demonstrates that although there is broad alignment in many aspects of the two countries’ food waste recycling laws, the specific requirements differ significantly due to each country’s unique circumstances. This has given rise to implementation issues that hamper large-scale food waste recycling in Singapore. These issues encompass, inter alia, the law’s limited applicability to food-related establishments and the lack of clarity regarding acceptable output from food waste treatment processes. Moreover, Singapore does not have a separate law targeted at avoiding food loss, a potentially more effective approach that is aligned with the food waste hierarchy. However, Japan’s experience demonstrates that, even with a law in place, success in food waste prevention typically relies on voluntary efforts and strong public engagement. Based on these findings, the article concludes that Singapore’s existing food waste law can contribute to a certain extent the achievement of its ‘zero-waste’ vision.

Food waste collection versus food waste disposers: A case study of a Portuguese city

The European Union (EU) prioritises sustainable development and aims to achieve climate neutrality by 2050 through investments in green technologies and a legislative climate framework. Waste collection and treatment systems, including biowaste like food waste, protect natural capital and citizens' well-being. Directive 2008/98/EC defines biowaste and sets the stage for exploring alternative solutions. This study focuses on the city of Guarda (Portugal) and analyses the use of disposers for food waste treatment. By comparing storage/collection systems with disposers regarding environmental and economic costs and benefits, the study aims to determine the most effective solution for collecting food waste. The analysis utilises a simulator provided by the Portuguese Fundo Ambiental®. The results show that while operating costs are higher for food waste collection systems, disposers require a more significant initial investment. Nevertheless, the cost-benefit ratio favours disposers, while the net present value analysis suggests that the food waste collection system is more favourable. Additionally, food waste collection systems contribute to higher greenhouse gas (GHG) emissions per tonne of food waste compared to using disposers.

Dual roles in interspecies electron transfer of carbon-based materials for accelerating anaerobic digestion of food waste

Food waste is tremendously generated and leads to serious environmental pollution if it is improperly disposed. Anaerobic digestion is recognized as an effective biotechnology to treat food waste. In order to improve the conversion efficiency, the effect of carbon-based materials on anaerobic digestion of food waste was investigated, and the microbial communities and electron transport pathways were also analyzed. The results showed that adding biochar improved the performance of anaerobic digestion of food waste, but adding graphite had no significant effect. The maximum daily methane yield of 67.79 ± 6.37 and 72.78 ± 6.17 mL/g VS·d were obtained with 1.250 (BC10) and 1.875 (BC15) g biochar/g VS raw material added, increased by 13.27% and 21.61% in comparison with the control system. Meanwhile, the systems reached 80% of cumulative methane yield on day 10, and the increase of 13.50% (423.66 ± 13.74 mL/g VS) and 13.57% (423.96 ± 20.33 mL/g VS) were obtained for the methane yield. Adding biochar selectively increased the relative abundance of Syntrophomonas, Clostridium sensu stricto, Petrimonas, Clostridium XlVb, Comamonas, Acinetobacter, Methanothrix and Methanobacterium. The interaction between Methanobacterium and Syntrophomonas was also promoted due to biochar acted as an electron carrier. Therefore, biochar had complex regulation on electron transport pathway of anaerobic digestion and promoted the conversion efficiency of food waste.

Enhancement of anaerobic digestion from food waste via inert substances based on metagenomic analysis: Oxidative phosphorylation and metabolism

The application of anaerobic digestion (AD) in the treatment of food waste (FW) has become widespread. However, the presence of inert substances, such as bones, ceramics, and shells, within FW introduces a degree of uncertainty into the AD process. To clarify this intricate issue, this study conducted an in-depth investigation into the influence of inert substances on AD. The results revealed that when inert substances were present at a concentration of 0.08 g/g VSS, methane productivity in the AD process was significantly augmented by 86%. Subsequent investigations suggested that this positive effect was primarily evident in various biochemical processes, including solubilization, hydrolysis acidification, methanogenesis, and the accumulation of extracellular polymeric substances. Metagenomic analysis showed that inert substances enhance the relative abundance of hydrolytic bacteria and have a pronounced impact on the relative abundance of hydrogenotrophic methanogens (Methanosarcina) and acetotrophic methanogens (Methanobacterium). Additionally, inert substances significantly increased the relative abundance of functional genes in oxidative phosphorylation, a pivotal pathway for ATP synthesis. Furthermore, inert substances had a substantial effect on the functional genes related to the metabolic pathways associated with methanogenesis (both hydrogenotrophic and acetotrophic). This comprehensive study shed light on the substantial impact of inert substances on the AD of food waste, contributing to an enhanced understanding of the underlying mechanisms of anaerobic fermentation.

Evaluating the potential of different bioaugmented strains to enhance methane production during thermophilic anaerobic digestion of food waste

Bioaugmentation technology for improving the performance of thermophilic anaerobic digestion (TAD) of food waste (FW) treatment is gaining more attention. In this study, four thermophilic strains (Ureibacillus suwonensis E11, Clostridium thermopalmarium HK1, Bacillus thermoamylovorans Y25 and Caldibacillus thermoamylovorans QK5) were inoculated in the TAD of FW system, and the biochemical methane potential (BMP) batch study was conducted to assess the potential of different bioaugmented strains to enhance methane production. The results showed that the cumulative methane production in groups inoculated with E11, HK1, Y25 and QK5 improved by 2.05%, 14.54%, 19.79% and 9.17%, respectively, compared with the control group with no inoculation. Moreover, microbial community composition analysis indicated that the relative abundance of the main hydrolytic bacteria and/or methanogenic archaea was increased after bioaugmentation, and the four strains successfully became representative bacterial biomarkers in each group. The four strains enhanced methane production by strengthening starch, sucrose, galactose, pyruvate and methane metabolism functions. Further, the correlation networks demonstrated that the representative bacterial genera had positive correlations with the differential metabolic functions in each bioaugmentation group. This study provides new insights into the TAD of FW with bioaugmented strains.