Enhanced Biogas Production Research Articles

Enhancing Biogas Production: An Assessment of Pasteurization Effects on Poultry, Swine, Bovine Manure and Food Waste Substrates

Within the evolving regulatory landscape of the European Union concerning animal by-product (ABP) management within the circular economy framework, this study explores the concurrent objectives of safeguarding public health and environmental integrity and maximizing final product value. Anaerobic digestion (AD) emerges as a holistic solution for ABP management, addressing sanitation concerns while enhancing end-product quality. Through laboratory-scale experimentation, the AD process applied to four substrates—poultry manure, swine manure, cattle manure, and food waste—is scrutinized. Prior to AD, pasteurization at 70 °C for 60 min ensures microbial safety. Subsequently, four experimental AD cycles compare pasteurized and unpasteurized substrates. Results highlight the efficacy of pasteurization in sanitizing final products across all substrates, emphasizing its pivotal role in product safety. However, pasteurization’s impact on system performance varies. While enhancing biogas yield from animal waste notably, its influence on food waste biogas production is less pronounced, indicating substrate-specific dynamics. This study offers insights into optimizing ABP management strategies, emphasizing the interplay between pasteurization, substrate characteristics, and AD performance. Such insights are crucial for advancing sustainable practices in the circular economy paradigm, balancing environmental stewardship with economic viability.

Integrating microbial electrochemical cell in anaerobic digestion of vegetable wastes to enhance biogas production

Anaerobic digestion is a highly promising approach to manage agricultural/food wastes that reduces pollution and produces energy effectively. In this study, we investigate the incorporation of a microbial electrolysis cell (MEC) in anaerobic digestion process with the introduction of two graphite felts to enhance biogas production with minimal electrical energy input. The high amount of biogas (1890 ± 113.1 mL) was produced from the 1:2 v/v mixture of vegetable wastes in water and 0.8 V supplemented at 27 °C. Biogas could also be effectively produced in MEC at 18 °C (632 ± 14.8 mL), which is more than double in comparison with biogas produced without voltage (303 ± 27.5 mL). Maximum COD reduction was found in MEC (70.84 ± 5.54 %) than in control (20.35 ± 4.53 %). Three Bacillus strains and one Exiguobacterium strain were isolated from the MEC sludge. Electricity supplemented anaerobic digestion can produce higher amount of biogas and improve waste degradation by transforming waste into energy.

Enhanced Biogas Production Using Anaerobic Co-digestion of Animal Waste and Food Waste: A Review

The current review is based on various reports that utilize a variety of kitchen waste & cafeteria leftovers like banana peels, orange peels, onion residues, and kiwi peels and their procedure of methane production under varied conditions. This review also covers the anaerobic digestion [AD] process which is reported to enhance biogas production under enhanced nitrogen supply such as ammonium chloride. We also covered an analysis of biogas production utilizing a mixture of cow dung slurry and kitchen refuse at various environmental conditions. Combining food waste and cow manure through anaerobic co-digestion can generate renewable biogas, reduce environmental impact and improve methane quality, making it a viable method for enhancing biogas production efficiency. Biogas derived from fruit waste and cow manure through anaerobic co-digestion shows increased production compared to processing fruit waste alone. Some factors affecting biogas production include temperature, pH levels and microbial activity. The study explores the dual functionality of fruit waste as an energy source and organic fertilizer. Combining fruit waste and cow manure under mesophilic conditions enhances biogas production. The study suggests that biogas production can improve agricultural practices, reduce environmental impact and serve as an alternative to traditional fuels like firewood.

Mechanisms of biochar-mediated reduction of antibiotic-resistant bacteria and biogas production enhancement in anaerobic digesters

This study examined the impact of different biochar (BC) as an anaerobic digestion (AD) additive on antibiotic-resistant bacteria (ARB) survival and AD performance using dairy cow manure. Bamboo BC and Olive BC with different particle sizes were added into the mesophilic AD at 15 g/L and 30 g/L dosages (Bamboo-15, Bamboo-30, Olive-15, and Olive-30). The study provides a detailed analysis of biogas production, organic metabolism, and ARB and microbial dynamics, elucidating the mechanisms by which BC influences AD. Findings reveal significant reductions in CEZ-resistant bacteria (CEZ-r) across all reactors, ranging from 12.88 % to 76.47 %. Both Bamboo and Olive BC increased CEZ-r removal by 3.08–5.94 times compared to the control. Additionally, BC supplementation prevented the rise in CEZ-r percentage within the total bacteria count observed in the control reactor. Bamboo BC outperformed Olive BC in enhancing biogas yield, with Bamboo-15 and Bamboo-30 showing significant increases of 43.2 % and 48.0 %, respectively, compared to the control. Adding BC in AD regulates ARB by decreasing potential ARG hosts and impeding the transmission of resistance. It also enhances biogas production by improving the efficiency of methanogenic bacteria and optimizing the methanogenic pathway. This research provides insights into how BC can be used to enhance AD performance and mitigate ARB proliferation, offering a sustainable approach to waste management and energy production.

Anaerobic co-digestion of cow manure and microalgae to increase biogas production: A sustainable bioenergy source

The biogas production from microalgae has gained attention due to fast depleting of fossil fuels and oil reserves. This study evaluated the anaerobic co-digestion of microalgae in various concentrations with cow manure to enhance biogas production. The biogas production of each experiment was measured using the water displacement method. The results indicated that the addition of microalgae significantly enhanced biogas production. Particularly, high methane yield of Anabaena sp. 50 %, Chlorella sp. 50 %, control was 345 ± 2.88 mL CH4/g VS, 297.96 ± 0.49 mL CH4/g VS, 138.32 ± 0.50 CH4/g VS respectively. The slurry produced by 50 % Anabaena sp. biogas plant exhibited the greatest level of seed germination. The current study demonstrated that Sorgham bicolor had the highest seed germination rate (94.2 %) root and shoot length of all crops. Therefore, it is possible to employ Anabaena sp. (50 %) and Chlorella sp. (50 %) in the rapid production of biogas. Moreover, agricultural output would be increased by using biogas slurry.

The Potential Significance of Microwave-Assisted Catalytic Pyrolysis for Valuable Bio-Products Driven from Albizia Tree

The objective of this study is to investigate the feasibility of Na2CO3 and ZSM-5 as catalysts in the microwave pyrolysis of Albizia branches. An evaluation was conducted to determine the influence of power applied, experimental time, particle size, and catalysis type and ratio on the quality and quantity of pyrolysis products. Established methods such as GC-MS, FTIR, HHV, SEM, EDX, and BET were used to characterize the properties of bio-oil and biochar produced. The results demonstrated that using both catalyst types led to a substantial enhancement in biogas production. The improvement ranged from 5% to 41% with Na2CO3 and reached 45% with ZSM-5. At a lower power level of 300 W, the bio-oil yield augmented from 28% to 40% and 53% when using ZSM-5 and Na2CO3, respectively. The GC-MS analysis revealed that the utilizing of catalysts enhanced the levels of aromatic compounds, esters, and alcohols in bio-oil, along with an increase in the higher heating value (HHV) from 19.5 MJ/kg to 22 MJ/kg and 24.2 MJ/kg using Na2CO3 and ZSM-5, respectively. Moreover, the biochar's surface area and pore volume experienced a considerable rise, going from 0.5512 m2/g and 0.00011 cm3/g to a higher value of 115.2073 m2/g and 0.0774 cm3/g when treated with Na2CO3. The data indicated that both catalyst types enhanced the generation of CH4, and CO2 was lower with ZSM-5. The utilization of catalysts improves the quality of the biofuel produced and promotes the efficiency of the process in terms of energy consumption and processing time.

Synergistic integration of hydrothermal pretreatment and co-digestion for enhanced biogas production from empty fruit bunches in high solids anaerobic digestion

This study investigates the co-digestion of hydrothermally pretreated empty fruit bunches (EFB) at 190 °C for 5 min (HTP190-EFB) with decanter cake (DC) to improve biogas production in high solid anaerobic digestion (HSAD). The HTP190-EFB exhibited a 67.98 % reduction in total solids, along with the production of 0.89 g/L of sugar, 2.39 g/L of VFA, and 0.56 g/L of furfural in the liquid fraction. Co-digestion of HTP190-EFB with DC at mixing ratios of 5, 10, and 15 %w/v demonstrated improved methane yields and process stability compared to mono-digestion of HTP190-EFB. The highest methane yield of 372.69 mL CH4/g-VS was achieved in the co-digestion with 5 %w/v DC, representing a 15 % increase compared to digestion of HTP190-EFB (324.30 mL CH4/g-VS) alone. Synergistic effects were quantified, with the highest synergistic methane yield of 77.65 mL CH4/g-VS observed in the co-digestion with 5 %w/v DC. Microbial community analysis revealed that co-digestion of hydrothermally pretreated EFB with decanter cake promoted the growth of Clostridium sp., Lactobacillus sp., Fibrobacter sp., Methanoculleus sp., and Methanosarcina sp., contributing to enhanced biogas production compared to mono-digestion of pretreated EFB. Energy balance analysis revealed that co-digestion of HTP190-EFB with DC resulted in a total net energy of 599.95 kW, 52 % higher than mono-digestion of HTP190-EFB (394.62 kW). Economic analysis showed a shorter return on investment for the co-digestion system (0.86 years) compared to the mono-digestion of HTP190-EFB (1.02 years) and raw EFB (2.69 years). The co-digestion of HTP190-EFB with 5 %w/v DC offers a promising approach to optimize methane yield, process stability, and economic feasibility, supporting the palm oil industry for producing renewable energy and sustainable waste management.

Towards carbon neutrality and circular economy: an innovative combination of enhanced biogas production and nutrient recovery from sludge dewatering liquor at a municipal wastewater treatment plant in Germany.

An innovative circular economy (CE) system was implemented at the wastewater treatment plant (WWTP) in Brunswick. The performance of the CE system was evaluated for 4 years: the thermal pressure hydrolysis enhanced the methane production by 18% and increased the digestate dewaterability by 14%. Refractory COD formed in thermal hydrolysis and increased the COD concentration in the WWTP effluent by 4 mg L-1 while still complying with the legal threshold. Struvite production reached high phosphorus recovery rates of >80% with a Mg:P molar ratio ≥0.8. Nitrogen was successfully recovered as ammonium sulfate with high recovery rates of 85-97%. The chemical analyses of secondary fertilizers showed a low pollutant content, posing low risks to soil and groundwater ecosystems. The total carbon footprint of the WWTP decreased due to enhanced biogas production, the recovery of renewable fertilizers and a further reduction of nitrous oxide emissions. Using green energy will be crucial to reach carbon neutrality for the entire WWTP.

Study on biogas production from pig manure wastewater by microbial electrosynthesis at sub-psychrophilic conditions

In colder regions, relatively low temperatures results in low microbial activity and low biogas production in anaerobic digestion. This study investigated if microbial electrosynthesis system (MES) can enhance biogas production from pig manure wastewater under sub-psychrophilic conditions (20 °C). Results showed that the applied voltage of MES (0.4 V and 0.8 V) significantly increased the biogas production and COD removal rate. Biogas production and COD removal rate increased most when the voltage reached 0.8 V (34.77 %, 26.67 %), and decreased when the voltage was 1.2 V. Low voltage (≤ 0.8 V) did not significantly alter the microbial structure, but higher voltage (1.2 V) resulted in a significant decrease in Clostridium and Methanosarcina. Coenzyme F420, NADH, as indicators for methanogenic efficiency, showed the highest fluorescence intensity at 0.8 V and decreased at 1.2 V. Results indicated that the improvement of gas production was mainly due to the improvement of key enzymes rather than the shift of microbial structure. The information provided will be useful to improve the efficiency of biogas production.

Anaerobic co‑digestion of bovine ruminal waste and brewery spent grain: Effects of inoculum to substrate ratio, mixing ratio, process stability, organic matter removal, and methane yield

The technological potential of co-digesting bovine rumen waste (BRW) with brewery spent grain (BSG) is significant, offering enhanced biogas production and effective waste management. This study's findings demonstrate that the anaerobic digestion process becomes significantly more efficient when difficult to degrade BRW is combined with easily degradable BSG. The highest methane yield obtained in the mono-digestion of BRW was 127.11 NmLCH4 gVS−1 with biodegradability of 33.89 % in inoculum to substrate ratio (ISR) 2, and for de BSG obtained was 304.18 NmLCH4 gVS−1 with biodegradability of 68.26 % in ISR 4. The overall average obtained in co-digestion for volatile solids (VS) removal was 26.28 %, and the concentration of methane present in the biogas was 57.18 %. The VS removal efficiency and the increase in biogas and methane yield were directly proportional to the rise in ISR and the proportion of BSG in the mixture. Specifically, the ideal mix of 25 % BRW with 75 % BSG at ISR 4 resulted in a notable methane yield of 255.30 NmLCH4 gVS−1. This process stabilizes digestion and significantly improves solids removal and methane concentration, making it a highly efficient solution for sustainable energy production and industrial waste management.

Biostimulation of styrene-containing wastewater in carrier-supported anaerobic bioreactor towards enhancing biogas production and styrene degradation

Biological treatment of styrene-containing petrochemical wastewater usually suffers from styrene volatility and its toxicity to microorganisms. The main aim of the present study was to enhance the treatment performance of synthetic petrochemical wastewater using carrier-supported anaerobic bioreactor, in terms of biogas production and styrene degradation. For this purpose, three types of carrier, including magnetic granular activated carbon (MGAC), cuttlefish bone (CFB) and pumice, were used. A control reactor and the three carrier-supported reactors were operated under three styrene concentrations of 20 (cycle 1), 50 (cycle 2), and 100 (cycle 3) mg/L. Ethanol was used as a co-solvent and the total chemical oxygen demand (COD) was 500 mg/L in each cycle. According to the results, under all examined styrene concentrations, all the carrier-supported reactors exhibited higher styrene removal efficiency and gas production than the control reactor. Among carrier-containing rectors, the reactor supplemented with MGAC showed the best performance with styrene removal of 85.4 %–91.4 % and gas production of 368–890 mL/g COD added. The corresponding values for the control reactor were 72.3–79.2 % and 174–358 mL/g COD added. In addition, Carrier-containing reactors showed 31.2–67.2 % less styrene volatilization than the control reactor. The process performance was also affected by the styrene concentration so that the highest and the lowest gas productions were achieved for styrene contents of 50 and 100 mg/L, orderly. Using modified Gompertz model, it was found that the carriers shortened the lag phase and increased the maximum methane production rate, proving the establishment of stable conditions in carrier-supported reactors for the treatment of styrene-containing wastewater.

Optimizing Biogas Production: Comparative Analysis Of Organic Substrates For Enhanced Gas Yield

Study’s Novelty/Excerpt This study uniquely evaluates the biogas optimization potential of various locally sourced substrates, including cow dung, poultry dung, human, and pig manure, through a comparative analysis over a 15-day period using custom-made biodigesters. The research reveals that poultry dung yields the highest gas production, significantly outperforming other substrates with a gas production ratio of 0.20 on day 15, indicating its superior effectiveness. These findings contribute valuable insights into substrate efficiency for biogas production, suggesting poultry dung as a highly effective substrate and proposing co-digestion strategies to further enhance biogas yields. Full Abstract This research aimed to investigate the utilization of various locally sourced substrates in the biogas optimization process and compare the gas yield to determine the most efficient domestic substrate. The samples tested included cow dung, poultry dung, human, and pig manure. A comparative analysis of gas production over a 15-day period was carried out at 3-day intervals using four custom-made biodigesters with batch culture fermentation. The findings revealed that digester 4, utilizing poultry dung, exhibited the highest gas output. The gas production ratios for human, cow, pig, and poultry dung on day 15 were 0.10:0.11:0.12:0.20, equating to percentages of 18.86%, 20.78%, 22.64%, and 37.73% respectively. The notably higher percentage for poultry dung suggests its superior effectiveness as a substrate for biogas production. Alternatively, the co-digestion of cow and/or poultry dung could be considered as a strategy to enhance biogas production.

Valorization of fruit and vegetable waste in a novel three-stage hybrid anaerobic digester for enhanced biogas production: Performance study and microbial community analysis

The study proposes the performance of a three-stage hybrid mesophilic anaerobic digester comprising a suspended-growth hydrolytic reactor, a hybrid (suspended-growth + attached-growth) acidogenic down-flow reactor, and a hybrid methanogenic up-flow reactor, for enhanced biogas production. Commingled fruit and vegetable waste (FVW) – shredded to sizes 1 – 4 mm – plus 2.5 L of tap water served as the feedstock in 8 different batch combinations, where the weight of the waste was increased from 3.5 to 7 kg. Decoupling the three major anaerobic steps ensured desirable working pH ranges for the hydrolytic (4.02 – 6.79), the acidogenic (5.69 – 6.62), and the methanogenic stages (6.94 – 7.7). Triplicate studies of each batch type vis-à-vis all three stages were performed. The highest cumulative soluble chemical oxygen demand percentage removal of 96.3 % was noticed in the case of batch run 5. The maximum biogas yield of 781.8 ml/g CODremoved was corresponding to batch 7, with 6.5 kg FVW, whereas the lowest biogas yield, 735.8 ml/g CODremoved, was corresponding to batch 1. The produced biogas from the methanogenic digester was of high quality (≤ 0.01 % H2S) and constituted 58–62 % CH4 and 6–7 % H2. Microbial community analysis confirmed the presence of pertinent bacterial and archaeal groups, such as Firmicutes, Proteobacteria, Spirochaetes, and Methanothrix, including key homoacetogenic genera, such as Acetobacterium Woodii, Desulfotomaculum, and Desulfitobacterium.

Evaluation of Biogas Production from Swine Manure Using a UASB Reactor (Upflow Anaerobic Sludge Blanket) with Long-Term Operation

To meet Colombia’s energy needs by 2050, a total installed capacity of 42 MW across its power generation infrastructure is required. To achieve this, transitioning to cleaner energy sources, such as biomass—a non-conventional renewable energy—is necessary. Biomass is a promising renewable source for thermal and electrical energy production. This study researched the production of biogas from swine manure using a UASB reactor to valorize this waste. Swine manure was collected every 20 days from a pig farm with a capacity of 200 sows, located in Santa Rosa de Osos, Antioquia. The flow rate was increased three times (1.30 L d−1, 1.62 L d−1, and 2.08 L d−1) to reduce the hydraulic retention time (HRT) and enhance biogas production. The volatile and total solids, chemical oxygen demand (COD), alkalinity, and biogas composition were measured over one year. The proposed system achieved 87.40% COD remotion from the feed stream and generated a yield of 507 mLCH4 gVS−1, with an HRT of 19 days and an OLR of 4.27 gCOD L−1 d−1. The reactor produced biogas with a CH4 content of 67.7%, CO2 content of 18.1%, and H2S content of 1413 ppm. This study highlights the effectiveness of the UASB reactor for biogas production using swine manure as a substrate.

Impact of tannery wastes on anaerobic co-digestion: enhancing biogas production and process efficiency

The study investigates the potential of anaerobic co-digestion (AcoD) as a sustainable solution for managing putrescible organic waste generated by leather processing. Three experiments were conducted to assess the impact of various tannery wastes, pretreatment methods, and waste combinations on methane production. Experiment 1 demonstrated that co-digesting tannery wastewater primary sludge (TWPS) and fleshings significantly increased methane yield compared to digesting TWPS alone, though the addition of chromium- and vegetable-tanned leather wastes decreased yield. Experiment 2 explored TWPS pretreatment methods and found that ultrasonic pretreatment increased soluble chemical oxygen demand (SCOD) but did not significantly improve methane yield, suggesting that pretreatment may not be necessary. Experiment 3 revealed that increasing the proportion of fleshings to TWPS resulted in higher methane yield, ranging from 226.52 mL/gVS with 6% fleshings to 395.71 mL/gVS and 538.34 mL/gVS with 12% and 20% of fleshings, respectively. Additionally, this increase in fleshings also led to a reduction in digester volume. These findings highlight the importance of AcoD in addressing both environmental and economic challenges in the leather industry.Graphical

Enhancing the efficiency of high solid anaerobic digestion of empty fruit bunches under thermophilic conditions by particle size reduction and co-digestion with palm oil mill effluent

This study investigates the impact of thermophilic high solid anaerobic digestion (HS-AD) on biogas production from empty fruit bunches (EFB), focusing on the effects of total solids (TS) loading (5–40 %), particle size reduction (0.5, 3.25, and 6 cm), and co-digestion with palm oil mill effluent (POME) (10–30 % VS basis). The HS-AD at a 15–20 % TS loading has a methane yield of 103.4–105.3 mL CH4/g-VS with 24.6–25.1 % biodegradability. Particle size reduction to 0.5 cm enhanced methane yield by 54–61 % and improved hydrolysis rates by 45 % compared to the untreated EFB (6 cm) at a 15–20 % TS loading. Co-digestion of EFB with POME at a ratio of 31:1 based on VS basis led to a synergistic effect of 17.77 mL CH4/g-VS, increasing methane yield by 24–46.5 % and improving process stability, as evidenced by a 22.8–38.1 % reduction in volatile fatty acids (VFAs) accumulation. Microbial community analysis showed a 2-fold increase in the relative abundance of hydrogenotrophic methanogens (Methanothermobacter sp. and Methanoculleus sp.) during co-digestion, while the abundance of key cellulolytic bacteria (Clostridium sp. and Fibrobacter sp.) increased by 1.5-fold. The optimized HS-AD process achieved a maximum methane yield of 287.77 mL CH4/g-VS and a biodegradability of 61.2 % under thermophilic conditions, with a 20 % POME co-digestion addition (31:1 VS ratio) and 0.5 cm particle size. These findings demonstrate the potential of thermophilic HS-AD for the sustainable management of EFB and highlight the importance of process optimization and co-digestion strategies for enhanced biogas production from EFB.

Construction of a Synthetic Microbial Community for Enzymatic Pretreatment of Wheat Straw for Biogas Production via Anaerobic Digestion.

Biological pretreatment is a viable method for enhancing biogas production from straw crops, with the improvement in lignocellulose degradation efficiency being a crucial factor in this process. Herein, a metagenomic approach was used to screen core microorganisms (Bacillus subtilis, Acinetobacter johnsonii, Trichoderma viride, and Aspergillus niger) possessing lignocellulose-degrading abilities among samples from three environments: pile retting wheat straw (WS), WS returned to soil, and forest soil. Subsequently, synthetic microbial communities were constructed for fermentation-enzyme production. The crude enzyme solution obtained was used to pretreat WS and was compared with two commercial enzymes. The synthetic microbial community enzyme-producing pretreatment (SMCEP) yielded the highest enzymatic digestion efficacy for WS, yielding cellulose, hemicellulose, and lignin degradation rates of 39.85, 36.99, and 19.21%, respectively. Furthermore, pretreatment of WS with an enzyme solution, followed by anaerobic digestion achieved satisfactory results. SMCEP displayed the highest cumulative biogas production at 801.16 mL/g TS, which was 38.79% higher than that observed for WS, 22.15% higher than that of solid-state commercial enzyme pretreatment and 25.41% higher than that of liquid commercial enzyme pretreatment. These results indicate that enzyme-pretreated WS can significantly enhance biogas production. This study represents a solution to the environmental burden and energy use of crop residues.

Bulking agent in dry anaerobic digestion as a key factor for the enhancement of biogas production

Dry anaerobic digestion (dry-AD) is an attractive process for solid wastes such as agri-food waste. However, some limitations mainly associated to lack of effective mixing, can hinder the methane production capacity of the systems. Bulking agent (BA) has been proposed as a solution to the compaction issues in systems without mechanical agitation, such as leaching bed reactors. However, effects of BA are still not clear, and, thus, the factors to consider for its dose has not been optimized yet. This work studies the effect of BA in dry-AD. Two substrates with different characteristics were proposed as models, bean peel as a lignocellulosic substrate and a mixture of food waste as a readily biodegradable substrate. Inert plastic rings were used as BA at different BA:S ratios. Assessed BA:S ratio did not affect the performance of methane production for the lignocellulosic waste, but it did significantly affect to the easily biodegradable substrate, showing up to a 28% of methane production increase. This result could be due to the presence of lignocellulosic compounds in the bean peel, behaving like a natural BA. In assays with an increased bed height, the compaction of the system was more severe, resulting in the rapid acidification of the processes. At these conditions, the positive effect of BA addition was more marked, allowing methane production and no acidification of the system. Thus, the addition of BA is a suitable strategy for improving methane production or stability in dry-AD systems without requiring the stirring of the systems.

High-efficiency anaerobic digestion of soybean curb residue with simultaneous phosphorus recovery by Mg[sbnd]Fe layered double hydroxides addition

Anaerobic digestion of food waste faces several technical problems, such as process failure caused by over-acidification, low heating value of biogas, and high treatment cost of liquid digestate. Layered double hydroxides (LDH) are expected to simultaneously enhance biogas production and quality and immobilize soluble phosphorus in AD due to their excellent anion exchange capability. This study first verified the above hypothesis, indicated by a dramatically enhanced methane yield of 17 folds under a high substrate load and a high quality of generated biogas with 89 % methane content and 90 % lowered hydrogen sulfide. Meanwhile, the soluble phosphorus was efficiently reduced to 3 mg/L after AD. Moreover, the calcined product of LDH showed comparable performance, indicating the possibility of reusing LDH in the AD process. The above results implied the great potential of LDH as a multifunctional material for enhancing the efficiency of waste treatment and energy/resource conversion in the AD process.

Magnetic iron oxide nanoparticle enhanced microwave pretreatment for anaerobic digestion of meat industry sludge

Our study investigates the effects of iron oxide (Fe3O4) nanoparticles combined microwave pretreatment on the anaerobic digestibility and soluble chemical oxygen demand (SCOD) of meat industry sludge. One of our main objectives was to see whether the different microwave-based pretreatment procedures can enhance biogas production by improving the biological availability of organic compounds. Results demonstrated that combining microwave irradiation with magnetic iron oxide nanoparticles considerably increased SCOD (enhancement ratio was above 1.5), the rate of specific biogas production, and the total cumulative specific biogas volume (more than a threefold increment), while having no negative effect on the biomethane content. Furthermore, the assessment of the sludge samples’ dielectric properties (dielectric constant and loss factor measured at the frequency of 500 MHz) showed a strong correlation with SCOD changes (r = 0.9942, R2 = 0.99), offering a novel method to evaluate pretreatment efficiency.