Food waste treatment by anaerobic co-digestion with saline sludge and its implications for energy recovery in Hong Kong

Evaluating the role of salinity in enhanced biogas production from two-stage anaerobic digestion of food waste by zero-valent iron

Salts including NaCl are the most common food flavoring agents so they are often accumulated in food waste (FW) and have potential impact on anaerobic digestion (AD) of FW. In this study, the enhanced biogas production from two-stage anaerobic digestion (TSAD) of FW by microscale zero-valent iron (ZVI) under different salinity (3, 6, 9, and 15 g NaCl/L) was evaluated. Under salinity stress, ZVI becomes a continue-release electron donor due to the enhanced corrosion and dissolution effect and the slow-down surface passivation, further improving the performance of TSAD. Experimental results revealed that the biogas production including H2 and CH4 from TSAD with 10 g/L ZVI addition was promoted under salinity stress. The maximum H2 and CH4 yield (303.38 mL H2/g-VS and 253.84 mL CH4/g-VS) were observed at the salinity 9 g NaCl/L. Compared with that of zero salinity, they increased by 40.94% and 318.46%, respectively. Additionally, Sedimentibacter, an exoelectrogen that can participate in the direct interspecies electron transfer, also exhibited the highest relative abundance (34.96%) at the salinity 9 g NaCl/L. These findings obtained in this study might be of great importance for understanding the influence of salinity on the enhanced AD by ZVI.

Recovery of metagenome-assembled microbial genomes from a full-scale biogas plant of food waste by pacific biosciences high-fidelity sequencing

Background

Anaerobic digestion (AD) is important in treating of food waste, and thousands of metagenome-assembled genomes (MAGs) have been constructed for the microbiome in AD. However, due to the limitations of the short-read sequencing and assembly technologies, most of these MAGs are grouped from hundreds of short contigs by binning algorithms, and the errors are easily introduced.

Results

In this study, we constructed a total of 60 non-redundant microbial genomes from 64.5 Gb of PacBio high-fidelity (HiFi) long reads, generated from the digestate samples of a full-scale biogas plant fed with food waste. Of the 60 microbial genomes, all genomes have at least one copy of rRNA operons (16S, 23S, and 5S rRNA), 54 have ≥18 types of standard tRNA genes, and 39 are circular complete genomes. In comparison with the published short-read derived MAGs for AD, we found 23 genomes with average nucleotide identity less than 95% to any known MAGs. Besides, our HiFi-derived genomes have much higher average contig N50 size, slightly higher average genome size and lower contamination. GTDB-Tk classification of these genomes revealed two genomes belonging to novel genus and four genomes belonging to novel species, since their 16S rRNA genes have identities lower than 95 and 97% to any known 16S rRNA genes, respectively. Microbial community analysis based on the these assembled genomes reveals the most predominant phylum was Thermotogae (70.5%), followed by Euryarchaeota (6.1%), and Bacteroidetes (4.7%), and the most predominant bacterial and archaeal genera were Defluviitoga (69.1%) and Methanothrix (5.4%), respectively. Analysis of the full-length 16S rRNA genes identified from the HiFi reads gave similar microbial compositions to that derived from the 60 assembled genomes.

Conclusion

High-fidelity sequencing not only generated microbial genomes with obviously improved quality but also recovered a substantial portion of novel genomes missed in previous short-read based studies, and the novel genomes will deepen our understanding of the microbial composition in AD of food waste.

Rhodotorula sp.-based biorefinery: a source of valuable biomolecules

The development of an effective, realistic, and sustainable microbial biorefinery depends on several factors, including as one of the key aspects an adequate selection of microbial strain. The oleaginous red yeast Rhodotorula sp. has been studied as one powerful source for a plethora of high added-value biomolecules, such as carotenoids, lipids, and enzymes. Although known for over a century, the use of Rhodotorula sp. as resource for valuable products has not yet commercialized. Current interests for Rhodotorula sp. yeast have sparked from its high nutritional versatility and ability to convert agro-food residues into added-value biomolecules, two attractive characteristics for designing new biorefineries. In addition, as for other yeast-based bioprocesses, the overall process sustainability can be maximized by a proper integration with subsequent downstream processing stages, for example, by using eco-friendly solvents for the recovery of intracellular products from yeast biomass. This review intends to reflect on the current state of the art of microbial bioprocesses using Rhodotorula species. Therefore, we will provide an analysis of bioproduction performance with some insights regarding downstream separation steps for the extraction of high added-value biomolecules (specifically using efficient and sustainable platforms), providing information regarding the potential applications of biomolecules produced by Rhodotorula sp, as well as detailing the strengths and limitations of yeast-based biorefinery approaches. Novel genetic engineering technologies are further discussed, indicating some directions on their possible use for maximizing the potential of Rhodotorula sp. as cell factories. KEY POINTS: • Rhodotorula sp. are valuable source of high value-added compounds. • Potential of employing Rhodotorula sp. in a multiple product biorefinery. • Future perspectives in the biorefining of Rhodotorula sp. were discussed.

Valorization of food waste by anaerobic digestion: A bibliometric and systematic review focusing on optimization

As food waste gets acknowledged as a global potential source of biomass, its valorization through anaerobic digestion becomes an attractive strategy. This work describes the state-of-the-art on the valorization of food waste by anaerobic digestion and the optimization of the process. The methodology used was a bibliometric and systematic review of the optimization of the process from 66 articles selected. Bibliometric mapping allowed us to identify that, until now, most studies have been focused on the: i) anaerobic co-digestion strategy in order to stabilize the process, ii) interest in the generation of biofuels to replace non-renewable fuels, iii) study of metabolic processes for a better understanding of the system iv) reactor design optimization and others facilities to increase process efficiency. The systematic analysis showed that the operational parameters has been extensively studied to optimize the process. Therefore, co-digestion has been the main strategy to improve the process. In this sense, knowledge of the substrate and co-substrate is extremely important to operate the reactors. For methane production, the ideal operating conditions indicated were: pH of 7, solids content between 4.0 and 15%, C/N ratio of 25, hydraulic retention time from 25 to 40 days and alkalinity from 2850 to 2970.5mgCaCO₃/L. In addition, the ideal OLR will vary mainly according to operating temperature, number of reactor stages, and raw material characteristics. This review indicates trends and knowledge gaps that are important to guide new research on the anaerobic digestion of food waste, pointing out the potential advantages, optimization strategies, by-products of interest and challenges of the process. The results were used for the development of references of ideal operating conditions for energy production, being able to guide the design and operation of reactors.

Salinity impact on the metabolic and taxonomic profiles of acid and alkali treated inoculum for hydrogen production from food waste

This study evaluated the combined impact of salinity (2.5, 13, and 19.3 g NaCl/L) and inoculum pretreatment (acid/alkali) on the genomic and metabolic profiles of mesophilic fermentative bacteria for hydrogen (H₂) production from food waste. Experimental results revealed that acid-treated inoculum showed the highest H₂ yield (201.12 ± 13.84 mL H₂/g of volatile solids added) under medium salinity levels compared to other experimental conditions. A 7-56% increase in H₂ yield was observed for pretreated inoculum than untreated inoculum. Genomic analysis and metabolic pattern revealed that the H₂ production was mainly through Clostridial-type fermentation under medium to high salinity levels, whereas Enterococcus-type fermentation under low salinity levels. Further, the genomic analysis uncovered that phyla Firmicutes (69.71-96.81%) and genus Clostridium sensu stricto 1 (33.28-94.04%) dominated during the exponential gas production phase. Overall, this study showed the significance of inoculum pretreatment for the bioconversion of food waste at different salinity levels.

Impact of total solids content on biochar amended co-digestion of food waste and sludge: Microbial community dynamics, methane production and digestate quality assessment

This study evaluates the impact of biochar addition on the performance of anaerobic co-digestion of food waste (FW) and sewage sludge at different total solids (TS) contents (2.5 %, 5.0 %, and 7.5 %). Biochar co-digestion improved hydrolysis and acidogenesis by neutralizing volatile fatty acids (VFAs) reducing its inhibitions (2.6-fold removal), which elevated the soluble chemical oxygen demand (sCOD) degradation by 2.5 folds leading to a higher cumulative methane production compared to the control. This increase corresponded to an improvement of methane yields by ∼21 %-33 % (242-340 mL/gVS_add) at different TS contents. The biochar surface area offered substantial support for direct interspecies electron transfer (DIET) activity, and biofilm-mediated growth of methanogens i.e., Methanosarcina, Methanosata, and Methanobrevibacter. The biochar-enriched digestate improved the seed germination index, and bioavailability of plant nutrients such as N, P, K, and NH₄^+-N. This study reports an improved biochar-mediated anaerobic co-digestion for efficient and sustainable FW valorization.

Bioreactor-scale production of rhamnolipids from food waste digestate and its recirculation into anaerobic digestion for enhanced process performance: Creating closed-loop integrated biorefinery framework

Reaching industrially relevant productivities in bioprocesses and their efficient integration in the existing industrial infrastructure remain as important challenges in the circular economy to create closed loop sustainability framework. Using anaerobic digestion (AD) biorefinery as a model, the present work addressed these problems via integration of next-generation rhamnolipids production with AD. A high rhamnolipids concentration of 10.25 ± 1.34 g/L was obtained by fed-batch fermentation using food waste digestate as medium. Digestate-derived rhamnolipids contained Rha-C₁₀-C₁₀ and Rha-Rha-C₁₀-C₁₀ as the predominant congeners. These were used back in single-phase AD to demonstrate their effect on sludge solubilization and digestion efficiency. A dosage of 0.02 g rhamnolipids/g total suspended solids was found to be optimal which enhanced the hydrolysis-acidogenesis reactions to up to 27% over control. It however retarded methane production which could be overcome by the prolongation of digestion time. Finally, the value chain appreciation by the proposed process was demonstrated by a feasibility analysis.

Recent advances in conductive materials amended anaerobic co-digestion of food waste and municipal organic solid waste: Roles, mechanisms, and potential application

Recently, conductive materials (i.e., carbon-based and iron-based materials) as a feasible and attractive approach have been introduced to anaerobic co-digestion (ACoD) system for promoting its performance and stability through direct interspecies electron transfer. Owing to the key roles of conductive materials in ACoD process, it is imperative to gain a profound understanding of their specific functions and mechanisms. Here, this review critically examined the state of the art of conductive materials assisted ACoD of food waste and common municipal organic solid waste. Then, the fundamental roles of conductive materials on ACoD enhancement and the relevant mechanisms were discussed. Last, the perspectives for co-digestate treatment, reutilization, and disposal were summarized. Moreover, the main challenges to conductive materials amended ACoD in on-site application were proposed and the future remarks were put forward. Collectively, this review poses a scientific basis for the potential application of conductive materials in ACoD process in the future.

Going beyond conventional wastewater treatment plants within circular bioeconomy concept - a sustainability assessment study

Wastewater treatment plants (WWTP) have extensive energy processes that undermine their economic and environmental performance. In this context, the integration of wastewater treatment with other biochemical processes such as co-digestion of sludge with organic wastes, and production of value-added products at their downstream processes will shift conventional WWTPs into biorefinery platforms with better sustainability performance. The sustainability of such a biorefinery platform has been investigated herein using an economic and life cycle assessment approach. This WWTP-based biorefinery treats wastewater from Copenhagen municipality, co-digests the source-sorted organic fraction of municipal solid waste and sludge, and upgrades biogas into biomethane using a hydrogen-assisted upgrading method. Apart from bioenergy, this biorefinery also produces microbial protein (MP) using recovered nutrients from WWTP's reject water. The net environmental savings achieved in two damage categories, i.e., -1.07 × 10^-2 species.yr/FU in ecosystem quality and -1.68 × 10⁶ USD/FU in resource scarcity damage categories along with high potential windows for the further environmental profile improvements make this biorefinery platform so encouraging. Despite being promising in terms of environmental performance, the high capital expenditure and low gross profit have undermined the economic performance of the proposed biorefinery. Technological improvements, process optimization, and encouraging incentives/subsidies are still needed to make this platform economically feasible.

Effect of low salinity on nitrogen removal from municipal wastewater via a double-anammox process coupled with nitritation and denitratation: Performance and microbial structure

Saline wastewater present in municipal pipe networks poses challenges to biological nitrogen removal due to its inhibition on microorganisms. This study focuses on the effects of low salinity (0.0%, 0.4%, 0.7% and 1.0%) on a system featuring a combination of nitritation/anammox in oxic stage and denitratation/anammox in anoxic stage (double-anammox) in a step-feed SBR for municipal wastewater over a period of 130 days. The results showed that a maximum nitrogen removal efficiency of 81.2% was achieved at a salinity of 1.0% with anammox contribution of 76.5%. Analysis of anammox contribution and sludge activities discovered that low salinity promoted both nitritation and denitratation, further enhancing the coupling with anammox. Further, microbial analysis confirmed that Ca. Brocadia was enriched on biofilms from 0.21% to 0.51% and Nitrosomonas was enriched in flocs from 0.50% to 1.04%. Overall, the double-anammox process appears to be a promising method for the treatment of saline wastewater.

Improvement of sewage sludge anaerobic digestion through synergistic effect combined trace elements enhancer with enzyme pretreatment and microbial community response

In this study, a double E strategy (enzymes and enhancer) characterized by high efficiency for enhancing sewage sludge anaerobic digestion (AD) is proposed. This strategy combines addition of trace elements (TEs) enhancer and enzyme pretreatment, inducing a synergistic effect on AD, and it is more effective and economical compared with TEs addition or enzyme pretreatment in isolation. When adding 400 U/g cocktail enzymes and 1.24% trance elements enhancers, the cumulative methane production and the maximum daily methane increased yield by 45.29% and 84.7%, respectively. According to microbial community analysis, the double E strategy significantly motivate the growth of acetogens and protein fermenting bacterium. The relative abundance of Fermentimonas and Lutispora increased by 6.15% and 5.4%, respectively. Archaeal community analysis and changes in the mcrA gene abundance demonstrate enrichment of hydrogenotrophic methanogens, with the methanogens exhibiting high vitalities and stress resistance. The double E strategy could be a promising way to improve industrial sewage sludge AD efficiency.

Food waste and sewage sludge co-digestion amended with different biochars: VFA kinetics, methane yield and digestate quality assessment

This work investigated the impact of the addition of different biochar types on mitigation of volatile fatty acid (VFA) accumulation, methane recovery and digestate quality in mesophilic food waste-sludge co-digestion. Four biochars derived from agricultural and sludge residues under different pyrolysis temperatures were compared. Specific biochar properties such as pH, surface area, chemical properties and presence of surface functional groups likely influenced biochar reactions during digestion, thereby resulting in a varying performance of different biochars. Miscanthus straw biochar addition led to the highest specific methane yield of 307 ± 0.3 mL CH₄/g VS_added versus 241.87 ± 5.9 mL CH₄/g VS_added from control with no biochar addition over 30 days of the co-digestion period. Biochar supplementation led to enhanced process stability which likely resulted from improved syntrophic VFA oxidation facilitated by specific biochar properties. Overall, a 21.4% increase in the overall methane production was obtained with biochar addition as compared to control. The resulting digestate quality was also investigated. Biochar-amended digester generated a digestate rich in macro- and micro-nutrients including K, Mg, Ca, Fe making biochar-amended digestate a potential replacement of agricultural lime fertilizer. This work demonstrated that the addition of specific biochars with desirable properties alleviated VFA accumulation and facilitated enhanced methane recovery, thereby providing a means to achieve process stability even under high organic loading conditions in co-digestions. Moreover, the availability of biochar-enriched digestate with superior characteristics than biochar-free digestate adds further merit to this process.

Integrated Approach for Wastewater Treatment and Biofuel Production in Microalgae Biorefineries

The increasing world population generates huge amounts of wastewater as well as large energy demand. Additionally, fossil fuel’s combustion for energy production causes the emission of greenhouse gases (GHG) and other pollutants. Therefore, there is a strong need to find alternative green approaches for wastewater treatment and energy production. Microalgae biorefineries could represent an effective strategy to mitigate the above problems. Microalgae biorefineries are a sustainable alternative to conventional wastewater treatment processes, as they potentially allow wastewater to be treated at lower costs and with lower energy consumption. Furthermore, they provide an effective means to recover valuable compounds for biofuel production or other applications. This review focuses on the current scenario and future prospects of microalgae biorefineries aimed at combining wastewater treatment with biofuel production. First, the different microalgal cultivation systems are examined, and their main characteristics and limitations are discussed. Then, the technologies available for converting the biomass produced during wastewater treatment into biofuel are critically analyzed. Finally, current challenges and research directions for biofuel production and wastewater treatment through this approach are outlined.

Food waste valorization: Energy production using novel integrated systems

Management of food waste (FW) is a global challenge due to increasing population and economic activities. Presently, landfill and incineration are the keyways of FW management, while economical and environmental sustainability have been an issue. Therefore, the biological processes have been investigated for resource and energy recovery from FW. However, these biological approaches have certain drawbacks and cannot be a complete solution for FW management. Therefore, this review aims to offer a detailed and complete analysis of current available technologies to achieve environmental and economical sustainability. In this context, zero solid waste discharge for resource and energy recovery has been put into view. Corresponding to which several innovative technologies using integrated biological methods for resource and energy recovery from FW have been elucidated.

Effect of salinity and pH on dark fermentation with thermophilic bacteria pretreated swine wastewater

The utilization of swine wastewater is affected by salinity and pH owing to the extensive use with seawater instead of domestic water as swine farm flushing water in coastal city. Therefore, swine wastewater pretreated with thermophilic bacteria was used as fermentation substrate in this work, the effects of salinity and pH on dark fermentation under mesophilic condition were investigated. The research showed that 1.5% salinity and pH 6.0 were the optimal conditions for hydrogen production with swine wastewater. The activity of hydrogenogen was inhibited at 3.5% salinity and pH 5.0. Soluble organic matter in substrate was accumulated under high salinity and alkaline conditions. The utilization of carbohydrate during dark fermentation was up to 61.1% at 1.5% salinity and 51.5% at pH 9.0. Enhancing of salinity and pH had an advantage in accumulation of total soluble metabolites. Acetate was the main metabolite during dark fermentation, and 1.5% salinity contributed to the formation of butyrate.

Enhanced volatile fatty acid degradation and methane production efficiency by biochar addition in food waste-sludge co-digestion: A step towards increased organic loading efficiency in co-digestion

This work investigated the effect of biochar addition to mitigate VFA accumulation and enhance methane production in mesophilic food waste/sludge co-digestion. Different types of biochar derived from agricultural and forestry residues at two pyrolysis temperatures were tested. Results showed that wheat straw biochar 550 °C supported the highest specific methane yield of 381.9 LCH₄/kg VS_added and VS removal efficiency of 41.62% among all treatments. Degradation of propionic acid and long-chain fatty acids such as valeric, caproic and isovaleric acids was observed. This also corresponded to an increase in methanogenic favorable substrates including acetic acid (>40%) and butyric acid (~20%) over the control. Consequently, a 24% increase in overall methane production was obtained as compared to control. This demonstrated that biochar addition had positive effects on VFA degradation and methane production which could be a useful strategy to increase the organic loading in co-digestions without the fear of process failure.

An integrated anaerobic system for on-site treatment of wastewater from food waste disposer

In this study, an integrated system of siphon-driven self-agitated anaerobic reactor (SDSAR) and anaerobic fixed bed reactor (AFBR) was conducted for the treatment of wastewater from food waste disposer (FWD), and the effect of influent total solids (TS) concentration on the process performance was evaluated. When the influent TS concentration increased from 7.04 to 15.5 g/L, the methane gas production rate increased from 0.45 to 0.92 L-CH₄/L/day. However, with the influent TS concentration of food waste (FW) further increased to 23.5 g/L, a large amount of scum formed and accumulated in the SDSAR. According to the result of chemical oxygen demand (COD) recovery, the proportion of COD remained in the effluent at different TS concentrations was only around 2%. On the other hand, with an increase in TS concentration, the proportion of COD remained in the reactors increased significantly. Our results demonstrated that effluent from the integrated system can meet the water quality requirements recommended by Japan Sewage Works Association (JSWA) for wastewater from FWD. In addition, to enhance the process stability, the influent TS concentration should be maintained below 15.5 g/L.

Impact of low-thermal pretreatment on physicochemical properties of saline waste activated sludge, hydrolysis of organics and methane yield in anaerobic digestion

This work studied the influence of low-thermal pretreatment (60-120 °C) on anaerobic digestion of saline waste activated sludge. The findings showed higher temperature and longer pretreatment time considerably improve organics hydrolysis (soluble chemical oxygen demand increased by 4.2-11.9 times) and volatile solid reduction (maximum 24.6%). Carbohydrate and proteins solubilization accelerated by 5.6-43.8 times and 8.9-35.9 times, respectively by temperature rose from 60 to 120 °C. Low temperature (60 °C) promotes faster release of ammonia and phosphate. Thermal treatment had positive effect on biogas production because methane yield was enhanced by 13.7, 27.0, 29.0 and 29.6% when pretreated at 60, 80, 100 and 120 °C, respectively. Significant positive relationships observed between pretreatment temperature/duration and sludge properties. Energy and economic assessment displayed anaerobic digestion of 80 °C pretreated sludge is more economically feasible. Thus, low-thermal pretreatment technology could be useful for improvement of methane yield in anaerobic digestion.

Sulfate in anaerobic co-digester accelerates methane production from food waste and waste activated sludge

The presence of sulfate in food waste (FW) and waste activated sludge (WAS) threatens the anaerobic co-digestion for methane production. In this study, methane production from the anaerobic co-digestion of FW and WAS at sulfate concentrations of 50, 100, and 400 mg S/L was not affected, but instead deteriorated at 200 and 300 mg S/L. However, a model-based kinetic analysis reveals that sulfate can significantly promote the conversion of rapidly biodegradable substrates by up to 93%. From a point of thermodynamic view, the presence of sulfate can stimulate sulfate-reducing bacteria acting as acetogens to convert propionate to acetate, providing an alternative metabolic pathway for methanogenesis. In the anaerobic co-digestion, regulation of sulfate can be a potential strategy to improve the efficiency of methane production. However, more research is needed to optimize the sulfate concentration and substrate types in the anaerobic co-digester.

Integrated food waste and sewage treatment - A better approach than conventional food waste-sludge co-digestion for higher energy recovery via anaerobic digestion

This work proposes a new treatment approach involving both food waste disposal and sewerage treatment called MOWFAST i.e. Municipal Organic Waste management by combined Food waste disposal and Sewerage Treatment. MOWFAST involves mixing of food waste directly with raw sewage instead of separate addition to sludge and their combined anaerobic digestion (AD). Compared to conventional sludge digestion, MOWFAST exhibited better digestion capability and allowed a greater degradation of organic material along with higher production of methanogenic-favourable products from the beginning of digestion. This resulted in producing higher specific methane yields (7.86 LCH₄/kg VS_added versus 0.95 LCH₄/kg VS_added) and 1.4-fold higher cumulative methane yield over sludge AD. Furthermore, compared with conventional food waste-sludge co-digestion, MOWFAST gave higher solubilization of organic material (0.82 g sCOD/g VS_added versus 0.23 g sCOD/g VS_added) and specific methane yields (7.86 LCH₄/kg VS_added versus 3.2 LCH₄/kg VS_added). This proves its feasibility for digestion and methane generation potential.

Organic matter rather than salinity as a predominant feature changes performance and microbiome in methanogenic sludge digesters

Due to low digestibility and long retention time of anaerobic sludge digestion, pre-treatment with alkaline/acid has been widely employed to enhance the rate and extent of sludge digestion. Nonetheless, effects of gradient concentrations of alkaline/acid pre-treatments and resulting salinity on digestion performance and sludge microbiome remain poorly understood. To elucidate these effects, both batch- and reactor-experiments were setup with varied feeding sludge. Significant digestion improvement and sludge microbiome changes were observed with alkaline/acid sludge pre-treatment, compared to non-pretreatment controls, e.g., ˜88% increase of carbon removal in sludge digesters. Surprisingly, with the same concentration of influent sludge, no notable change in digestion performance and sludge microbiome was observed in digesters when increasing alkaline/acid concentrations from 0.25 to 0.8 mol/L, and in batch serum bottles with or without NaCl amendment. Consequently, organic compounds dissolved in sludge pre-treatment could be a predominant selective pressure driving the performance and microbiome changes. By contrast, salinity as a consequence of the alkaline/acid pre-treatment could only enrich specific lineages, without altering the overall community profile and function. Together, this study provided insights into specific impacts of major factors on digester performance and sludge microbiome, and shed lights on optimization of sludge digestion.

Aerobic co-composting degradation of highly PCDD/F-contaminated field soil. A study of bacterial community

This study investigated bacterial communities during aerobic food waste co-composting degradation of highly PCDD/F-contaminated field soil. The total initial toxic equivalent quantity (TEQ) of the soil was 16,004 ng-TEQ kg^-1 dry weight. After 42-day composting and bioactivity-enhanced monitored natural attenuation (MNA), the final compost product's TEQ reduced to 1916 ng-TEQ kg^-1 dry weight (approximately 75% degradation) with a degradation rate of 136.33 ng-TEQ kg^-1 day^-1. Variations in bacterial communities and PCDD/F degraders were identified by next-generation sequencing (NGS). Thermophilic conditions of the co-composting process resulted in fewer observed bacteria and PCDD/F concentrations. Numerous organic compound degraders were identified by NGS, supporting the conclusion that PCDD/Fs were degraded during food waste co-composting. Bacterial communities of the composting process were defined by four phyla (Proteobacteria, Actinobacteria, Bacteroidetes and Firmicutes). At the genus level, Bacillus (Firmicutes) emerged as the most dominant phylotype. Further studies on specific roles of these bacterial strains are needed, especially for the thermophiles which contributed to the high degradation rate of the co-co-composting treatment's first 14 days.