Anaerobic Digestion Research Articles

Determination of the biochemical methane potential of swine hydrolyzate

Swine farming generates remains of births and animals that die during the process. Implementing a plan to eliminate these materials by hydrolysis process results in an animal by-product called swine hydrolyzate. The treatment of this by-product through its application in the anaerobic digestion process can also represent its conversion into a resource for energy production. Thus, the present study focuses on this by-product as a potential substrate for anaerobic digestion, evaluating the methane production potential. The results show biogas production with an average methane content of about 70 %. Theoretical biochemical methane potential was 967.95 ± 0.11 mL g VS−1, which represented a bioconversion efficiency of 59.97 ± 3.54 % and 62.26 ± 0.43 %, considering the experimental results of 580.47 ± 34.29 mL g VS−1 and 602.67 ± 4.16 mL g VS−1, respectively. By comparing the experimental biochemical methane potential with the predicted value using the modified Gompertz model, it was possible to conclude that the maximum methane production rate was 73.46 ± 0.36 mL g VS−1 day−1, with a digestion time of 18 days to obtain 90 % of the methane production potential.

Combining thermal model and kinetics: Implications in dynamic simulation of anaerobic digesters

In this study, ADM1-based kinetics were combined with a thermal model that accounts for various heat transfers inside and through the reactor’s boundaries. Computing the energy of bioreactions based on kinetic rates prevented an overestimation of approximately 20% in the heat demand of the heat exchanger, compared to calculations using feedstock degradation heat. This also improved the representation of the digester’s thermal and reactional inertia. Simulations across different climates demonstrated the necessity to tailor digester construction. In the North West United Kingdom, biogas auto-consumption was 23% higher than that of the same reactor in South West France. Enhancing the thermal insulation of the digester reduced heat losses by 37% in the United Kingdom. Therefore, coupling the kinetic and thermal models expands the insights that can be extracted from simulations, which can be valuable in optimizing the operation and design of biogas digesters.

Energy valorization of solid residue from steam distillation of aromatic shrubs

The interest for essential oils is increasing, alongside ongoing scientific research into distillation techniques. This process generates significant solid residue that could be revalorized as energy source. This study explores the energy recovery of the solid fraction produced during the distillation of three aromatic plants: Cistus ladanifer, Juniperus communis and Rosmarinus officinalis. Two conventional energy recovery technologies were considered and compared through an energy balance: solid biofuel production and biogas generation. In case of solid biofuels, the fractionation of biomass allowed for generation of three different qualities that meet the regulation standards of solid fuels, except for the dust fraction. According to the energy balance, the alternative use of these substrates for biogas production showed competitive production in case of Cistus ladanifer and Juniperus communis, while Rosmarinus officinalis biomass presented inhibition of the anaerobic digestion and null energy recovery.

Interaction of poly dimethyl diallyl ammonium chloride with sludge components: Anaerobic digestion performance and adaptive changes of anaerobic microbes

The wide utilization of poly dimethyl diallyl ammonium chloride (polyDADMAC) in industrial conditions leads to its accumulation in waste activated sludge (WAS), thereby affecting subsequent WAS treatment processes. This work investigated the interaction between polyDADMAC and WAS components from the perspective of anaerobic digestion (AD) performance and anaerobes adaptability variation. The results showed that polyDADMAC decreased the content of biodegradable organic substrates (i.e., soluble protein and carbohydrate) by binding with the functional groups and then settling to the solid phase, thus impeding the subsequent utilization. Higher concentrations of polyDADMAC prompted an initial protective response of excreting organic substrates into extracellular environment, but its toxicity to archaea was irreversible. Consequently, polyDADMAC inhibited the processes of AD and induced a 30 % reduction in methane production with 0.05 g polyDADMAC/g total suspended solid (TSS) addition. Changes in microbial community structure indicated that archaea involved in methane production (e.g., Anaerolineaceae sp. and Methanosaeta sp.) were inhibited when exposed to polyDADMAC. However, several adaptive bacteria with the ability of utilizing complex organics and participating in nitrogen cycle (e.g., Aminicenantales sp. and Ellin6067 sp.) were enriched with the above dosage. Specifically, the decreased abundance of genes relevant to methane metabolism pathway (i.e., mer and cdh) and increased abundance of genes involved in metabolism of cofactors and vitamins (e.g., nad and thi) indicated the toxicity of polyDADMAC and the irritant response of microflora. Moreover, polyDADMAC underwent degradation in AD system, resulting in a 12 % reduction in 15 days, accompanied by an increase in the -NO2 functional group. In general, this study provided a thorough understanding of the interaction between polyDADMAC and WAS components, raising concerns regarding the elimination of endogenous pollutants during AD.

Anode potential regulates gas composition and microbiome in anaerobic electrochemical digestion

Anaerobic electrochemical digestion (AED) is an effective system for recovering biogas from organic wastes. However, the effects of different anode potentials on anaerobic activated sludge remain unclear. This study confirmed that biofilms exhibited the best electroactivity at −0.2 V (vs. Ag/AgCl) compared to −0.4 V and 0 V. Gas was further regulated, with the highest hydrogen content (47 ± 7 %) observed at −0.2 V. The 0 V system produced the largest amount of methane (70 ± 8 %) and exhibited the greatest presence of hydrogen-utilizing microorganisms. The gas yield at −0.4 V was the lowest, with no hydrogen detected. Excess bioelectrohydrogen at −0.2 V and 0 V caused the co-enrichment of Methanobacterium and Acetoanaerobium, establishing a thermodynamically feasible current-acetate-hydrogen electron cycle to improve electrogenesis. These results provide insights into the regulatory strategies of MEC technology during anaerobic digestion, which play a decisive role in determining the composition of biogas.

Impact of lowering nitrogen content in pig manure through low crude protein diets on anaerobic digestion process stability, biogas yields, and digestate composition

Lowering crude protein in pig diets can reduce nitrogen (N) excretion and alter manure characteristics. Anaerobic digestion (AD) offers potential for converting pig manure into biogas and bio-based fertilizers (i.e., digestate). However, limited research exists on the effects of N content in pig manure on AD when pigs are fed diets with varying crude protein levels. This study investigated how lowering N content in pig manure through low crude protein diets may affect AD process stability, biogas generation, and digestate properties. Manures from different dietary treatments, named as control (CON), low N (LN), and very low N (VLN), with Total Kjeldahl Nitrogen concentrations of 5.87, 5.42, and 5.15 g/L, respectively, were investigated. Daily biogas production, composition (CH4, CO2, and H2S), and digestate properties were monitored over 13 fed-batch cycles (25 ± 4 days per cycle). The experiment was conducted at 20 ± 1 °C, a condition suited for milder climate regions, using six single-stage digesters operated in sequencing fed-batch mode. Data were analyzed by ANOVA using PROC MIXED with repeated measures. Results showed that the differences in N content in pig manure due to the three dietary treatments had a limited impact on biogas generation, with specific methane yields remaining similar over time. CH4 concentrations remained stable between 60 and 65 %, ensuring high-quality biogas despite dietary variations. Differences between treatments became more pronounced with increased organic loading rates (OLRs) due to variations in the amount of volatile solids fed. AD also remained stable (Total Volatile Fatty Acids/Total Alkalinity <0.25) even at an OLR of 2.15 g of chemical oxygen demand L−1 day−1, highlighting AD's robustness at lower temperatures. Digestate samples contained essential minerals beneficial for plant growth. More research is needed to explore varied manure compositions and feeding strategies to better understand the interactions of animal nutrition with AD.

Anaerobic digestates in agricultural soils: A systematic review of their effects on antibiotic resistance genes

Tackling the dissemination of antibiotic resistance is one of the main global challenges. Manures from animal production are a recognized source of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) requiring appropriate treatment methods. One of the main approaches for manure treatment is anaerobic digestion (AD). Meta-analyses have demonstrated that AD can significantly reduce the load of ARGs. However, antibiotics, ARGs and MGEs still remain in the final product (digestate). A sustainable agricultural use of digestates under the One Health framework requires wide assessments of their effects in the soil resistome. The objective of this review was to present the state of the art of digestate effects on ARGs of agricultural soils, focusing exclusively on digestates from animal manures. A systematic review was conducted. The examination of the resulting literature indicated that although temporal decays are observed for a variety of ARGs in single-application and repeated-applications experiments, for certain ARGs the pre-treatment or control levels are not restored. However, the low number of studies and the heterogeneous experimental conditions preclude a clear understanding of the fate of ARGs in soil and their risk for agroecosystems. The inclusion of multiple MGEs and the assessment of the long-term influence of digestates on soil properties and microbial communities could be keystones for a better understanding of the risks associated with digestate-induced changes in the soil resistome.

A cyclic shift-temperature operation method to train microbial communities of mesophilic anaerobic digestion

Temperature is the critical factor affecting the efficiency and cost of anaerobic digestion (AD). The current work develops a shift-temperature AD (STAD) between 35 °C and 55 °C, intending to optimise microbial community and promote substrate conversion. The experimental results showed that severe inhibition of biogas production occurred when the temperature was firstly increased stepwise from 35 °C to 50 °C, whereas no inhibition was observed at the second warming cycle. When the organic load rate was increased to 6.37 g VS/L/d, the biogas yield of the STAD reached about 400 mL/g VS, nearly double that of the constant-temperature AD (CTAD). STAD promoted the proliferation of Methanosarcina (up to 57.32 %), while severely suppressed hydrogenophilic methanogens. However, when the temperature was shifted to 35 °C, most suppressed species recovered quickly and the excess propionic acid was quickly consumed. Metagenomic analysis showed that STAD also promoted gene enrichment related to pathways metabolism, membrane functions, and methyl-based methanogenesis.

Influence of Molasses and Caesalpinia spinosa Meal Inoculums on Biogas Production from Cattle Manure

The management of organic waste through anaerobic digestion is an alternative to energy recovery. This research focused on evaluating the production of biogas with different inoculums. For this purpose, two types of systems were implemented—one used a heating system controlled by an STC-1000 thermostat, while the other used a solar heating system under a polycarbonate parabolic trough. The experiment was carried out at laboratory level with 3 L PET bottle biodigesters and the biogas produced was collected with the water displacement technique in 3 L bottles, calibrated every 50 mL, over 43 days. Inoculums of the following manure concentrations were used: water (1:5, 1:2, 1:3) mixed with Caesalpinia spinosa meal and molasses. The results determined that the thermostat-controlled heating system generated 69.6 mL/day of biogas while the other system produced 610.9 mL/day. On the other hand, the T1 treatment with a manure:water ratio of 1:5 and molasses and Caesalpinia spinosa meal inoculums in both systems had a higher average biogas volume. In terms of methane (CH₄), the highest value of 76.9% was obtained through the T1 treatment under the controlled heating system. This allows the production of biogas with a high concentration of methane, which in future applications can be utilized for residential or industrial purposes, promoting economic, social and environmental development. Since the main challenge in the production of biogas is to reduce the digestion time, which is influenced by the temperature of the site, two types of inoculums with a low cost and easy access were used.

Advanced Waste-to-Energy Technologies: A Review on Pathway to Sustainable Energy Recovery in a Circular Economy

In the face of the rapid rise in global waste production and the pressing need to shift towards sustainable energy options, advanced Waste-to-Energy (WtE) technologies have emerged as a highly promising solution. These innovative technologies effectively utilize waste as a valuable resource, presenting a viable pathway for sustainable energy recovery and making a substantial contribution to the principles of the circular economy paradigm. This review provides a comprehensive overview of advanced WtE technologies, including thermal, biological, and chemical methods, such as gasification, pyrolysis, plasma arc gasification, anaerobic digestion, fermentation, transesterification, and hydrothermal carbonization. The efficiency of these technologies is evaluated based on their energy recovery potential, environmental impact, and economic feasibility. Case studies on successful implementations of advanced WtE technologies are analyzed to highlight their practicality and effectiveness. Finally, the paper addresses technical, regulatory, and policy challenges in this field and provides future perspectives. The objective is to underscore the role of advanced WtE technologies in achieving a sustainable and resource-efficient circular economy.

Life Cycle Assessment as a Catalyst for Embedding Sustainability in Waste Management Practices

The establishment of sustainable campuses acts as a catalyst, fostering a Living Lab environment where active community engagement is crucial. Recognizing the pivotal role of waste management, university campuses prioritize detailed mapping and characterization of organic waste streams. This process paves the way for the identification of alternative scenarios that reduce and divert waste from landfills through valorization routes such as composting and anaerobic digestion. Acknowledging students' pivotal role in shaping sustainable solutions, their perceptions of solid waste separation assume significance. The effectiveness of the current separation system is critical, especially given the monitoring of bin contamination levels, revealing hindrances to organic waste valorization. Life Cycle Assessment (LCA) emerges as a valuable tool for identifying alternative scenarios for waste reduction and diversion, encompassing anaerobic digestion, composting, and waste-to-food strategies. This study centers on evaluating and reshaping student perspectives on organic waste separation and end-of-life waste management through LCA. A comprehensive survey was designed to elucidate current perspectives on the efficiency and communication of the existing waste management system. Student insights into waste separation practices revealed that the major barriers to effective waste management practices on campus include a lack of education and awareness regarding waste separation. The survey findings also underscore the significance of LCA not only in measuring carbon footprints but also in influencing perceptions and behaviors towards sustainable waste management practices. In conclusion, our study contributes to the discourse on embedding sustainability in educational settings, offering valuable insights for institutions aspiring to drive positive change through innovative waste management strategies.

Cascading valorization of defatted rice bran for lactic acid fermentation and biogas production

This study investigated the integrated valorization of defatted rice bran (DRB) by converting it into lactic acid (LA) and subsequently utilizing the residues from LA production for biomethane generation through anaerobic digestion (AD). Processing 480 kg of DRB resulted in the production of 70 L of pure LA and generated significant waste streams, primarily consisting of 572 kg of decanted hydrolysate pellet (Pellet DEC) and 220 kg of microfiltration retentate (Retentate MF). Exceptionally high methane yields of 374‒434 LN kgVS-1 were observed for residues from LA fermentation in biochemical methane potential tests, indicating their high potential for biogas production. During long-term semi-continuous AD, varying organic loading rates (OLRs) from 0.5‒2.5 kgVS m-3 d⁻¹ demonstrated feedstock- and OLR-dependent methane production. Reactor failure at higher OLRs was attributed to the accumulation of total ammoniacal nitrogen (TAN). The co-digestion of Pellet DEC and Retentate MF proved to be more resilient, with OLRs up to 2 kgVS m-3 d-1, mitigating TAN inhibition. Methane yields, ranging from 265‒334 LN kgVS-1 before reaching inhibitory OLR levels, were higher than those found in the literature. Process integration has emerged as a promising approach because the biogas generated from residues could effectively offset the energy demands of LA production. Supported by life cycle assessment, the integrated processes showed a 67% lower environmental impact at the midpoint and a 71% lower environmental impact at the endpoint, along with an 80% reduction in energy costs compared to the standalone LA production. Results proved a significant enhancement of the sustainability and economic viability of this integrated biorefinery approach.

Evaluating energy balance and environmental footprint of sludge management in BRICS countries

Climate change is driving global endeavours to achieve carbon neutrality and renewable energy expansion. Sludge, a nutrient-rich waste, holds energy potential yet poses environmental challenges that need proper management. We conducted a comprehensive life cycle assessment to evaluate the energy balance and environmental footprint of the most commonly used sludge management scenarios in BRICS countries, namely Brazil, Russia, India, China, and South Africa. Technologies such as incineration and anaerobic digestion with energy recovery units (i.e., cogeneration unit) maximize energy balance and minimize the environmental footprint, with incineration showing a superior performance. Shifting sludge management scenarios from the worst to the best can boost energy production by 1.4–98.4 times and cut the environmental footprint by 1.5–21.4 times. In 2050, these improvements could lead to a 98-fold boost in energy generation and a 25-fold drop in carbon emissions, according to the Announced Pledges Scenarios. Optimizing parameters such as volatile solids and anaerobic digestion efficiency further boosts energy output and minimizes the environmental footprint. This study offers robust evidence to support sustainable sludge management and thus promote energy recovery and carbon neutrality goals, guide technological transitions, and inform policymaking for sustainable development.

Evaluating energy generation potential from municipal solid waste in an open dumping site of Khulna

The expanding global population, waste output, land scarcity, and environmental deterioration make waste-to-energy (WtE) technology a feasible option for managing MSW. This study explores the economic benefits of WtE in the Rajbandh open dumpsite in Khulna and the potential of generating energy from MSW. The electricity generation potential under alternative scenarios namely scenario 2 (landfill gas to electricity (LFGTE)), scenario 3 (mass-burn incineration), scenario 4 (hybrid LFGTE, mechanical–biological treated (MBT) anaerobic digestion (AD) and incineration), and scenario 5 (hybrid AD and refuse-derived fuel (RDF) incineration) is based on projected waste generation over the next 20 years, taking population growth into account. These four options are compared to Business as Usual (BAU). Scenario 3 has the highest electricity generation capacity at 207799.73 MWh/year, followed by hybrid RDF-incineration/MBT-AD (scenario 5), LFGTE, however, lowest generation at 30683.07 MWh/year. Net Present Value (NPV), Levelized Cost of Electricity (LCOE), and Payback Period define each scenario’s economic feasibility. Due to its greatest NPV of approximately 41.378 million USD, Scenario 3 is the most economically beneficial. Sensitivity analysis has been done selecting some sensitive parameters to evaluate the robustness of the output. Waste reduction model (WARM) estimates greenhouse gas (GHG) emissions and energy use for each scenario. However, scenario 3 has the lowest GHG emissions and energy use. In addition to reducing GHG emissions and energy usage, recycling waste increased NPV and economic benefits. This analysis reveals that scenario 3 is the best way to generate power, provide economic benefits, and reduce energy consumption for ecologically friendly waste management in Khulna City.

Optimizing aeration rates via bio-methane potential test for enhanced biodrying efficiency of refuse-derived fuel-3

Aeration forms a critical part of the biodrying of refuse-derived fuel-3 (RDF-3) and significantly affects the fuel’s energy potential. Understanding the organic content (OC) of RDF-3 is crucial for determining the optimal aeration strategy. In this study, we conducted a bio-methane potential (BMP) test to estimate the OC by observing the conversion of organic matter into methane (CH₄) and carbon dioxide (CO₂). The observation of BMP was conducted using anaerobic digestion approach where substrate and inoculum are important parameters considered for the success of this test. Various ratios substrate-to-inoculum (S/I) were explored to assess their impact on biogas production, our research involved testing four S/I ratios (0.25, 0.5, 1.0, and 1.5) focusing on identifying the optimal aeration strategy. Based on stoichiometric calculations, the sample’s biogas yield per gram volatile solid indicates RDF-3’s OC is 1.5%. This OC value played a role in establishing the appropriate aeration rate (AR) for the biodrying process, which was determined to be 0.6 m³/kg.day, indicating the action of effective microbial degradation processes. Ensuring the correct AR is vital for maximizing the energy potential of RDF-3. Implementing optimized aeration rates based on the BMP test in waste management practices can significantly improve RDF-3 biodrying efficiency. This approach enhances RDF quality, reduces moisture, increases calorific value, and minimizes greenhouse gas emissions, leading to more sustainable and efficient waste-to-energy conversion.

Evolution of Cu and Zn speciation in agricultural soil amended by digested sludge over time and repeated crop growth

Metals such as Zn and Cu present in sewage sludge applied to agricultural land can accumulate in soils and potentially mobilise into crops. Sequential extractions and X-ray absorption spectroscopy results are presented that show the speciation changes of Cu and Zn sorbed to anaerobic digestion sludge after mixing with soils over three consecutive 6-week cropping cycles, with and without spring barley (Hordeum vulgare). Cu and Zn in digested sewage sludge are primarily in metal sulphide phases formed during anaerobic digestion. When Cu and Zn spiked sludge was mixed with the soil, about 40% of Cu(I)-S phases and all Zn(II)-S phases in the amended sludge were converted to other phases (mainly Cu(I)-O and outer sphere Zn(II)-O phases). Further transformations occurred over time, and with crop growth. After 18 weeks of crop growth, about 60% of Cu added as Cu(I)-S phases was converted to other phases, with an increase in organo-Cu(II) phases. As a result, Cu and Zn extractability in the sludge-amended soil decreased with time and crop growth. Over 18 weeks, the proportions of Cu and Zn in the exchangeable fraction decreased from 36% and 70%, respectively, in freshly amended soil, to 28% and 59% without crop growth, and to 24% and 53% with crop growth. Overall, while sewage sludge application to land will probably increase the overall metal concentrations, metal bioavailability tends to reduce over time. Therefore, safety assessments for sludge application in agriculture should be based on both metal concentrations present and their specific binding strength within the amended soil.

Assessment of the Biochemical Methane Potential of Wastewater and Sludge Cake from a Poultry Slaughterhouse

Objectives : This study evaluates the potential for resource recovery through anaerobic digestion of organic waste generated in a poultry slaughterhouse, specifically focusing on poultry slaughterhouse wastewater and sludge cake obtained from in-house wastewater treatment.Methods : Basic characteristics (total solids, alkalinity, etc.), total nitrogen/ammonia nitrogen, and elemental analysis (macro and trace elements) were performed to determine the properties of the samples and calculate theoretical methane potential. Experimental methane potential was determined through BMP tests, with parameters such as lag period (λ) and maximum methane production rate (CH 4 mL/g VS/d) obtained using the modified Gompertz equation.Results and Discussion : The wastewater exhibited low organic matter concentration (1.79 g VS/kg; 3.74 g COD/L), while the sludge cake showed high total solids content (TS 170.8 g/kg) and organic matter concentration (131.5 g VS/kg; 220 g COD/L). Elemental analysis revealed that the C/N ratio was 9.17 for the sludge cake and 8.24 for the wastewater, indicating high nitrogen content. Methane production modeling using the modified Gompertz equation revealed a lag period of 7.5 days and T80 (time to produce 80% of total methane) of 21 days for wastewater, and a lag period of 2.4 days and T80 of 14 days for sludge cake.Conclusion : Wastewater and sludge cake from poultry slaughterhouses show significant potential as substrates for anaerobic digestion. However, the wastewater has low organic matter content, and the sludge cake, while high in organic matter, has low moisture and high ammonia levels. Therefore, it may be appropriate to co-digest these two substrates, or to co-digest the sludge cake with other substrates that have low nitrogen content and high water content. These findings provide fundamental data for the anaerobic digestion of slaughterhouse waste and highlight the need for further research on co-digestion and continuous processes.

Synergistic enhancement of the secondary peak in methane production from anaerobic digestion of corn stover: The combined effects of polydopamine thermally modified tourmaline and magnetic field

This study explored the impact of using polydopamine thermally modified tourmaline (PTMT) in combination with various structured magnetic fields on methane production during the anaerobic digestion (AD) of corn stover. Results show that PTMT, when used with a spatial magnetic field, significantly enhances the secondary peak of methane production. Specifically, coupling PTMT at a concentration of 3.0 g/L with an 11.4 mT spatial magnetic field increased cumulative methane yield by 34.5 %, from 261 mL/g VS to 351 mL/g VS. Microbial diversity analysis indicated that the ST group (PTMT with a spatial magnetic field) was predominantly composed of Halobacterota (37.8 %), much higher than the control group's (C) Halobacterota (15.6 %). The energy conversion efficiency of corn stover in the ST group reached 31.3 %, with substrate carbon flow to CH4 at 0.156 mol, representing increases of 34.1 % and 33.3 %, respectively, compared to the C group. Economic analysis revealed that the net profit of the ST group was 13.2 % higher than that of the C group. This novel approach of combining PTMT with a spatial magnetic field offers a promising strategy for the efficient conversion of corn stover to methane.

Co-digestion of Sewage Sludge and Biowaste for Biogas Production, GHG Avoided Emissions, and Profitable Carbon Credit Development

In Estonia, where biowaste comprises a significant portion of municipal waste, efficient waste management strategies are essential. Co-digestion presents a promising avenue to enhance biogas yield and reduce greenhouse gas emissions. This study explores the potential of co-digesting sewage sludge and biowaste for biogas production, emphasizing carbon credit calculation and offset project development. Sewage sludge was effectively utilized as a co-feedstock for the co-digestion process, contributing to increased biogas production. In Narva City, 20,401.08037 m3 /year of biogas was produced in 2012, facilitating the generation of electricity from renewable sources and thus reducing GHG emissions, which facilitates the calculation of carbon credits. We developed a robust carbon offset project based on the biogas volume, meeting additionality criteria and demonstrating long-term benefits. The revenue potential from carbon credits ranged from 118 EUR to 41300 EUR, depending on market prices and project attributes. Moreover, the offset project and calculated carbon credits offer tangible benefits to sustainable waste management and the implementation of the circular economy. By valorizing sewage sludge and biowaste through anaerobic digestion, the project contributes to waste diversion from landfills, reduces methane emissions, and promotes renewable energy generation. This integrated approach aligns with principles of sustainable waste management and supports the transition towards a circular economy model. Our findings provide valuable insights for policymakers and stakeholders interested in leveraging anaerobic digestion for renewable energy production and carbon mitigation.

CuMgAl-layered double hydroxide activating peroxydisulfate for efficient degradation of norfloxacin in sludge anaerobic digestion liquor

Norfloxacin (NOFX) in the sludge anaerobic digestion liquor (ADL) should be removed before returning to the mainstream wastewater biological treatment system. In this study, CuMgAl-layered double hydroxide (LDH) activating peroxydisulfate (PDS) for NOFX degradation was conducted. Research results indicated that reaction temperature, CuMgAl-LDH dosage and inorganic anions content in the wastewater all showed significant influences on NOFX degradation. Mechanisms analysis confirmed that Cu(I)-Cu(II) redox cycle led to PDS activation, and SO4−, OH as well as 1O2 made primary contribution to NOFX degradation. CuMgAl-LDH stability and reusability as well as possible degradation pathway of NOFX were systematically investigated. In view of ADL characteristic, the optimal condition for NOFX degradation was determined as initial pH of 7, 35 °C, 0.5 g/L CuMgAl-LDH, 0.5 mmol/L PDS and removing carbonate and phosphate from ADL, which could achieve 67 % of degradation rate within 10 h. What's more, the ecotoxicity of NOFX and its main degradation products was assessed by ECOSAR prediction. This study provided primary guideline of copper-based LDH/PDS system for antibiotics removal in real wastewater matrixes.