Enhanced Methane Production Research Articles

Enhanced methane production kinetics by graphene oxide in fed-batch tests

The study aims to prove that the addition of graphene oxide (GO) improves anaerobic digestion (AD) kinetic performance. Classical batch tests were modified to a fed-batch strategy at four GO levels while using two substrates (glucose and microcrystalline cellulose (MCC)). First-order and modified Gompertz models were respectively applied to evaluate the kinetic performance. The results showed significantly (p < 0.05) improved kinetic from the third refeeding step for both substrates. 20 mg GO per g of volatile solids (VS) led to an increase of up to 210% for the first-order rate constant (k) and up to 120% for maximum biochemical methane potential (BMP) rate (RMAX) compared to control for glucose and MCC, respectively. The findings of this work suggest the implementation of GO in continuously operated systems to accelerate the AD process.

Impact of different pretreatments on the anaerobic digestion performance of cucumber vine

Copious amounts of cucumber vine (CV) derived from crop growing and harvesting are casually discarded in the field, posing severely negative impacts on public health and the ecological environment. Treating CV via anaerobic digestion (AD) could represent a promising approach while the recalcitrant lignocellulosic structure restricts its conversion efficiency, thus underscoring the importance of valid pretreatments. This study systematically investigated the effects of nine types of commonly applied chemical pretreatments involved H2SO4, HCl, H3PO4, NaOH, KOH, Ca(OH)2, CaO, H2O2, and alkaline hydrogen peroxide (AHP) pretreatments on methane production of CV. Results showed that alkaline and AHP pretreatments were beneficial to the methane production of CV and obtained the considerable cumulative methane yield and biodegradability of 194.3-241.5mL·gVS-1 and 47.59-59.15%, respectively, 36.83-70.07% higher than untreated. Analyses of lignocellulosic compositions and structural characterizations revealed that alkaline and AHP pretreatments well destroyed both hemicellulose and lignin, which commendably increased the accessibility of cellulose, facilitating the methane production. The findings of this study provide not only efficient pretreatment methods for the disposal and utilization of CV during AD process but also promising alternatives for enhancing methane production performance of similar vine residues, which would be greatly valuable for industrial applications in the future.

Two-step activated carbon cloth enhances microbial interactions and methane production during anaerobic digestion of municipal sludge

This study investigated the effects of two-step activated carbon cloth (CC) on the syntrophic microbial associations during anaerobic digestion (AD) of municipal sludge. A simple two-step activation, acid pretreatment (H2SO4/HNO3) followed by air calcination (550 °C), was used to convert commercial untreated CC (U-CC) into high performance activated CC (A-CC). Biochemical methane potential (BMP) assays conducted at different CC dosages indicated that A-CC, at a dose of 0.80 g A-CC {1.48 g A-CC/g-VS (volatile solids)substrate}, enhanced methane yield from by 3.7× and reduced the lag phase up to 15.6-fold, compared to non-CC Control within 3 days. Characterization of CC surfaces and kinetic modeling indicated indicated that A-CC pore size area increased by 435× a (Barrett, Joyner, and Halenda, BJH) with the potential to promote electron transfer and accelerate kinetic rates of methane production. Consistent with these results, microbial community composition profiles of CC surfaces indicated rapid adherence of methanogenic archaea and bacterial syntrophs to A-CC within 3 days. Multi-variate statistical analyses indicated that these populations were highly enriched on 0.80 g A-CC dosage compared to U-CC and Controls. Based on these results it can be concluded that A-CC provides a robust selective environment for syntrophic energy metabolism driving enhanced methane production from municipal sludge.

A parametric experimental validation of a biorefinery concept based on anaerobic digestion of fruit and vegetable waste

AbstractThe goal of this paper was to assess the possibilities for one‐stage reactor anaerobic digestion processing of fruit and vegetable biomass within a biorefinery concept for optimum products. Co‐digestion was the simplest strategy to implement to increase product yield among the variables tested (pH, ultrasonification, and co‐digestion). Methane yields from co‐digestion of fruit and vegetable waste (FVW) and pig manure (PM) ranged from 318 to 434 NmL /g VS, with the highest yield (434 NmL /g VS) achieved at a co‐digestion ratio of FVW75:PM25, representing a 20% increase over the methane production from FVW alone. The pH value was determined to be the most effective variable for enhancing methane production, with pH = 8 producing the maximum cumulative methane yield of 497 NmL/g VS. There was no significant change in the composition of volatile fatty acids (VFA) with pH in terms of dominant product type; valeric acid was the predominant VFA synthesized at all starting pH values except pH = 12, where formic acid was the predominant acid formed. As a digestate post‐treatment procedure, hydrothermal carbonization was combined with anaerobic digestion. At 200 °C, the maximum hydrochar yield production was 58.2%, with a higher heating value of 10.75 MJ/kg. © 2022 The Authors. Biofuels, Bioproducts and Biorefining published by Society of Industrial Chemistry and John Wiley &amp; Sons Ltd.

Saponification with calcium enhanced methane yield in anaerobic digestion of fat, oil, and grease: The essential role of calcium

Though saponification between calcium and fat, oil, and grease (FOG) could reduce inhibition caused by long chain fatty acids (LCFAs) in anaerobic digestion of FOG, the role of calcium in methane recovery is not well understood. In this study, different calcium sources (CaSO4, Ca(OH)2 and CaCl2) and mole ratios of Ca2+/LCFAs (0.25, 0.5 and 1) were chosen to investigate the role of calcium in anaerobic digestion of FOG. Compared to CaCl2/CaSO4, Ca(OH)2 was the most suitable calcium source due to the highest fraction of saponification in the calcium soaps as well as the 22% increment of methane production. For the reactors using CaCl2/CaSO4 as calcium source, Ca2+/LCFAs = 0.25 is preferred to enhance methane production, and the adsorption of the released LCFAs from calcium soaps onto biomass might be the primary pattern of LCFA degradation. Regarding the reactors using Ca(OH)2 as calcium source, Ca2+/LCFAs = 0.5 is beneficial for the enhancement of methane yield, and the combination of bio-aggregation on calcium soap and adsorption of released LCFAs on biomass may be the explanation for the relatively high methane production. Different calcium source and Ca2+/LCFAs could primarily affect the composition of syntrophs and methanogens, leading to different methane recovery from anaerobic digestion of FOG.

Optimization of process parameters for enhanced methane production from banana peduncle by thermal pretreatment

Optimization of process parameters for enhanced methane production from banana peduncle by thermal pretreatment

Bioelectrochemical enhancement of methane production from exhausted vine shoot fermentation broth by integration of MEC with anaerobic digestion

A microbial electrolysis cell integrated in an anaerobic digestion system (MEC-AD) is an efficient configuration to produce methane from an exhausted vine shoot fermentation broth (EVS). The cell worked in a single-chamber two-electrode configuration at an applied potential of 1 V with a feeding ratio of 30/70 (30% EVS to 70% synthetic medium). In addition, an identical cell operated in an open circuit was used as a control reactor. Experimental results showed similar behavior in terms of carbon removal (70–76%), while the specific averaged methane production from cycle 7 was more stable and higher in the connected cell (MECAD) compared with the unpolarized one (OCAD) accounting for 403.7 ± 33.6 L CH4·kg VS−1 and 121.3 ± 49.7 L CH4·kg VS−1, respectively. In addition, electrochemical impedance spectroscopy revealed that the electrical capacitance of the bioanode in MECAD was twice the capacitance shown by OCAD. The bacterial community in both cells was similar but a clear adaptation of Methanosarcina Archaea was exhibited in MECAD, which could explain the increased yields in CH4 production. In summary, the results reported here confirm the advantages of integrating MEC-AD for the treatment of real organic liquid waste instead of traditional AD treatment.

Biogas production performance and system stability monitoring in thermophilic anaerobic co-digestion of lipids and food waste

A thermophilic anaerobic co-digestion system treating lipids and food waste was demonstrated by a long-term operation (over 600 days) with different lipid/TS ratios (from 10 % to 80 %). The lipids degradation efficiency achieved 90 % in the system when the lipid/TS ratio was less than 70 %. Addition of lipids significantly enhanced methane production, as the lipid/TS ratio increased from 10% to 70 %, the biogas production rate increased from 2.36 g/L/d to 3.42 g/L/d with 59.7 % to 67.7 % of methane. From the view of system stability, the increase of lipid/TS ratio reduced the alkalinity of the system and eventually caused the system collapse. In order to avoid losses due to overload, the results suggested that the ratio of total ammonia nitrogen to alklinity-6.5 could be used as a monitoring indicator. And the system could maintain efficient operation when the indicator was less than 0.6.

Bioelectrochemically assisting anaerobic digestion enhanced methane production under low-temperature

Bioelectrochemical systems (BES) with carbon brush electrode were developed to improve methanogenic performance of low-temperature (15 °C) anaerobic digestion (AD) in this study. It turned out that the BES system (1.0 V) could significantly improve the CH4 yield, and during the reaction process, propionic acid (∼618.73 mg/L) had a serious accumulation. Metatranscriptomic analysis revealed that methane was mainly produced by acetoclastic methanogenic pathway, and application of voltage could promote its improvement. On carbon brush electrodes, the enhancement of the acetoclastic pathway mainly depended on acetate kinase (Pta) and phosphate acetyltransferase (Ack) to convert acetate to acetyl-CoA. While it was mainly regulated by the acetate-CoA ligase (Acs) in fluid activated sludge. The activity of methanogenesis-related enzymes on the cathode was generally higher than that on the anode, while the enzyme activity on the fluid sludge anode was mostly inhibited. In addition, BES system significantly increased the abundance of methanogens and electrogens, and enhanced the activity of electron transfer related enzymes, which greatly promoted the direct interspecies electron transfer (DIET) of species. Therefore, the BES system could be an attractive alternative strategy to improve the performance of AD when treating low-temperature wastewater.

Enhanced methane production by using phytoremediated Halogeton glomeratus as substrate via anaerobic digestion

The phytoremediated plant contains rich carbon resources, but the anaerobic digestion (AD) process can be inhibited due to high Heavy metals (HMs). In this study, the phytoremediated Halogeton glomeratus (H. glomeratus) was utilized in AD. Results showed that suitable HMs improved the AD efficiency, and the HMs were positively correlated to methane production and microbiota. Compared to CK (without HMs contaminated), H. glomeratus containing HMs (TG) enhanced methane production (increased 85.5%). Also, the highest VS removal rate of 66.5% were achieved. Furthermore, the increased of hydrolytic and acidogenic Acinetbacter and Hydrogenophaga improved substrates degradation. Besides, the methanogenic Methanosarcina increased from 6.5 to 89.5%, and the methanogenic pathway shifted from hydrogenotrophic methanogenesis to aceticlastic methanogenesis. Thus, substrates conversion to methane was improved. Finally, the HMs in digestion slurry were successfully removed and decreased its secondary pollution. This study provided a potential for the resourceful utilization of the phytoremediated plants with suitable HMs concentration.

Anthropocene Geochemical and Technological Signatures of an Experimental Landfill Bioreactor in the Central Valley of California

The geochemical signatures of a 12-year-old experimental bioreactor at a California landfill are used to identify elemental concentrations and ratios that characterize the landfill and relate it to the age and state of technology of the deposited waste. The bioreactor was constructed and sealed with a synthetic liner during 2001–2002 and operated and monitored as an anaerobic digester to enhance methane production. In 2013, the bioreactor was sampled and trace element concentrations of the extracted fine fractions were determined. The concentrations normalized to a regional soil composition, reveal systematic peaks for transition metals, alkali metals, heavy metals, and various metalloids and non-metals. A group of potential solder elements (Cu, Zn, Cd, In, Sn, Pb, Bi, and Sb) shows moderate to strong co-variations and is largely attributed to household electronic components and other similar products, while elements that correlated well with rare-earth and other elements are related to the diluting effect of a soil component used as cover. Batteries show modest to little effects on the overall concentrations. Circulating fluids (recycled leachate) in the controlled reactor did not completely redistribute and homogenize the elemental signatures within the time frame of the bioreactor. It is concluded that the present experimental landfill defines an Anthropocene marker identifiable by building material (plaster), PVC plastic, and household electronic components (Pb–Sn solder). These marker elements and ratios are variably diluted by soil components identified by alkali metals, rare-earths, and high field-strength elements (Hf, Zr, Nb, and Ta).

A new integrated single-chamber air-cathode microbial fuel cell - Anaerobic membrane bioreactor system for improving methane production and membrane fouling mitigation

A novel integrated single-chamber air-cathode microbial fuel cell - anaerobic membrane bioreactor (ScMFC-AnMBR) system was designed. It involved an anaerobic membrane bioreactor (AnMBR) and a single-chamber air-cathode microbial fuel cell (ScMFC) being constructed in a common reaction chamber to enhance methane production and reduce membrane fouling in the AnMBR. Results indicated that ScMFC-AnMBR delivered a stable micro-bioelectric field environment with a voltage output of 95 ± 4 mV. Compared with conventional AnMBR (C-AnMBR), methane production using this system increased by 35.89%. Soluble microbial product (SMP) and extracellular polymeric substances (EPS) dropped by 65.3% and 43.1%, respectively. Particularly, the transmembrane pressure (TMP) in the operating cycle was in a slow growth status with the maximum value of only 18.5 kPa. The bioelectric field helped aceticlastic methanogens (Methanosaeta) replace hydrogenotrophic methanogens (Methanobacterium) as the dominant methanogens via electron transfer under a closed-circuit scenario. As syntrophic bacteria of methanogens (Syntrophobacter, Smithella and Syner-01) and exoelectrogens of Desulfovibrio were selected by the bioelectric field and gained a stable foothold, bio-foulant (Megasphaera) was significantly reduced. The complex microbial synergism in ScMFC-AnMBR greatly improved the methanogenic performance, thus effectively alleviated membrane fouling and prolonged the operation cycle of the system. Demonstrated here is the feasibility of practical application.

Enhancing biogas production from livestock manure in solid-state anaerobic digestion by sorghum-vinegar residues

This study investigated the performance of sorghum vinegar residue to enhance methane production from livestock manures during solid-state anaerobic digestion. Sorghum vinegar residue was co-digested with cattle, sheep, and pig manure, respectively. Results show that co-digesting vinegar residue with livestock manures effectively diluted inhibitory substances (e.g. ammonium, sodium ion, and potassium ion) to alleviate the accumulation of volatile fatty acids and amend microbial composition to enhance digester stability and thus methane production by 10.1 – 58.2%. The highest increase was observed for cattle manure, possibly due to its low inhibitory substances to induce effective synergistic effects with vinegar residue in co-digestion. Modified Gompertz model well fitted the experimental methane yield and exhibited an increase in the maximum methane production rate of livestock manures by 35.2 –58.0% to corroborate their enhanced methanogenesis kinetics with the addition of vinegar residue. Further microbial analyses also indicated that co-digesting vinegar residue with livestock manures enriched hydrolytic bacteria (e.g. the genus vadinBC27_wastewater-sludge_group ), acetogenic bacteria (e.g. the genera Syntrophomonas and Petrimonas ) and aceticlastic methanogens (e.g. the genera Methanosarcina and Methanosaeta ) to promote substrate biodegradation and secure methane production. • Sorghum vinegar residue was co-digested with livestock manures at solid state. • Digester stability and methane production were enhanced in anaerobic co-digestion. • Modified Gompertz model corroborated enhanced methanogenesis kinetics in co-digestion. • Vinegar residue addition enriched functional microbes to sustain methane production.

Propionate-cultured sludge bioaugmentation to enhance methane production and micropollutant degradation in landfill leachate treatment

This research investigates the use of propionate-cultured sludge to enhance methane (CH4) production and micropollutant biodegradation in biochemical methane potential (BMP) experiment treating landfill leachate. The experiments were carried out using non-acclimatized and acclimatized seed sludge with variable food to microorganism ratios of 1:1 and 1:2. Under the propionate-cultured sludge bioaugmentation, the concentrations of propionate-cultured sludge were varied between 10, 20, and 30 % (v/v). The acclimatized seed sludge exhibited high microbial abundance and diversity which promoted the CH4 production and micropollutant biodegradation. The modified Gompertz model indicated that the optimal condition was the acclimatized seed sludge with 30% (v/v) propionate-cultured sludge, achieving the lag time (λ), maximum CH4 production rate (Rmax), and maximum CH4 potential yield (Pmax) of 0.57 day, 17.35 NmL/h, and 140.58 NmL/g COD. The research novelty lies in the use of propionate-cultured sludge bioaugmentation in landfill leachate treatment to enhance CH4 production and micropollutant biodegradation.

Light alters microbiota and electron transport: Evidence for enhanced mesophilic digestion of municipal sludge

Light as an environmental factor can affect the process of anaerobic digestion, but there is no systematic study in municipal wastewater sludge mesophilic digestion. In this study, the effects of light on the performance of the anaerobic digestion system and photo-anaerobic microbiota (PAM) were evaluated in lighted anaerobic batch digesters (LABRs). The methane yield from the reactor under the dark condition (LABR0) was 179.2 mL CH4/g COD, which was lower than 305.4 mL CH4/g COD and 223.0 mL CH4/g COD (n = 3, p < 0.05) from reactors under the light intensity of 3600 lm (LABR1) and 7200 lm (LABR2), respectively. The dominant genera in the bacterial and archaeal communities were Bacillus and Methanosarcina under light conditions, Enterococcus and Methanobacterium under dark conditions. And these two bacteria acted as electroactive bacterial genera, indicating that light changes the combination of direct interspecies electron transfer (DIET) microbial partners and activates the DIET pathway for methane production. The electron conduction pathways analysis further suggests that biological DIET (bDIET) between microbial biomass, rather than DIET via conductive material (cDIET) between microbes and conductive materials, is promoted and behaves as the dominant factor enhancing methane production under light conditions. The morphology of microorganisms and the amount and properties of EPS corroborate these views. Our findings are guided to anaerobic digester constructions under the outdoor environment with light exposure.

Biochemical methane potential of Opuntia ficus-indica (L.) Mill. cladodes in co-digestion with cow manure

In recent years, Opuntia ficus-indica (L.) Mill. (OF) has emerged as a species that has a growing role in the area of agro-energy for their use as substrate in anaerobic digestion for the production of biogas and methane. In order to improve Biochemical Methane Potential (BMP), the objective of this study was to evaluate the influence of different feedstock ratios of cladodes in co-digestion with cow manure (CM) (OF:CM, 0:100 to 95:5) to determine the best co-digestion condition that improves BMP. Two co-digestion systems had BMP statistically significantly higher than the mono-digestion system, with improvements in the range of 80–92%. No statistical differences were found among the tested co-digestion treatments. These results demonstrate that the co-digestion of and CM biomass enhanced methane production through anaerobic digestion, with important implications for bioenergy production.

Preface

Due to recent pandemic, the 2021 International Conference on Energy Technology and Engineering Management (ETEM 2021) which was planned to be held in Harbin, China, was held virtually online during December 24-26, 2021. The decision to hold the virtual conference was made in compliance with many restrictions and regulations that were imposed by countries around the globe. Such restrictions were made to minimize the risk of people contracting or spreading the COVID-19 through physical contact. There were 100 individuals who attended this on-line conference, represented many countries including Japan, Algeria, Brazil and China.This conference aimed to boost development of the Greater Bay Area, expand channels of international academic exchange in science and technology, build a sharing platform of academic resources, promote scientific innovation on the global scale, improve academic cooperation between China and the outside world, enhance development of Energy Technology and Engineering Management. It also aimed to encourage exchange of information on research frontiers in different fields, connect the most advanced academic resources in China and abroad, turn research results into industrial solutions, bring together talents, technologies and capital to boost development.During the conference, the conference model was divided into three sessions, including oral presentations, keynote speeches, and online Q&A discussion. In the first part, some scholars, whose submissions were selected as the excellent papers, were given about 5-10 minutes to perform their oral presentations one by one. Then in the second part, keynote speakers were each allocated 30-45 minutes to hold their speeches. In the second part, we invited four professors as our keynote speakers. Assoc. Prof. Quanqing Yu, Harbin Institute of Technology, performed a speech: Fire safety issues and countermeasures for the battery system of new energy vehicles. And then we had Assoc. Prof. Yanling Yu , Harbin Institute of Technology. She made a wonderful speech: Heat generation and recovery from aerobic fermentation of corn stover. Associate Professor Alina Steblyanskya, School of Economics and Management, Harbin Engineering University, delivered a speech: GDP growth under environmental constraints: the case of Russia. Assoc. Prof. Zhaohan Zhang, from Harbin Institute of Technology. He presented a wonderful speech: Enhancing bioelectron transfer and methane production with nano-meidators and voltage in anaerobic wastewater treatment systems. Their insightful speeches had triggered heated discussion in the third session of the conference. Every participant praised this conference for disseminating useful and insightful knowledge.List of Committee member, Program Committees and Technical Program Committees are available in this pdf.

Transiting from the inhibited steady-state to the steady-state through the ammonium bicarbonate mediation in the anaerobic digestion of low-C/N-ratio food wastes

The current study aimed to determine the effects of NH4+ on anaerobic digestion (AD) metabolism and the feasibility of using NH4HCO3 to improve methane production in an AD system when treating a low-C/N-ratio food waste (FW). Increasing the ammonium concentration (500–1000 mg NH4Cl-N/L) added into the AD system did not limit the methane production but caused the volatile fatty acid (VFA) accumulation, forming an “inhibited steady-state” system. The addition of 200 mg NH4HCO3-N/L increased methane yield by 20% by aiding the microbial oxidation of VFAs. The high acetate content (65–85%) and abundance of acetoclastic methanogens (Methanosaeta and Methanosarcina) indicated an efficient acetoclastic methanogenesis process, which was facilitated by NH4HCO3. The long-term operation of the AD system demonstrated that NH4HCO3, at a concentration of 200 mg N/L, was capable of forming an active buffer system with NH4+ and VFAs, enhancing methane production (221 ± 86 mL/g VS).

The role of biomass gasification in the future flexible power system – BECCS or CCU?

In this work we study if biomass gasification for production of advanced biofuels can also play a role in managing variability in the electricity system. The idea is a CCU/power-to-gas concept to enhance methane production from biomass gasification. The suggested process is flexible in that CO2 not used for methane production can be stored through a BECCS concept that implies negative GHG emissions. For this purpose, rigorous models of three different gasification process configurations were simplified through surrogate modeling and integrated into a dynamic optimization model of regional electricity systems. The results show the diverse advantages of flexible operation between CCU and BECCS and that it is economically beneficial for the system to invest in gasification at the investigated levels of CO2 charge. The gasification option also provides value for low-priced electricity and thus stimulate increased investments in renewable electricity generation, which indicates the importance of considering geographical diversities in the assessment and highlights the importance of studying this type of concept with a time-resolved model. It is clear that the BECCS option is the most used, however, the limited quantities of CO2 used for the CCU option has a large impact on the investments made in the electricity system.

An operative laboratory investigation of bioconversion route from waste coal to natural energy

PurposeIn the present research, the potential of reactivated consortium for the methane production consuming waste coal as a carbon source (1% w/v) in the modified media at mesophilic temperature (37 °C) was determined.MethodsMedia modification was conducted for the enhancement of methane production by selecting three different components from the two media, i.e., Methanosprillium sp. producing media (MSP) and methane-producing bacteria media (MPB). From MSP medium, C2H2NaO2 (sodium acetate), KH2PO4 (potassium dihydrogen the phosphate), and NaHCO3 (sodium bicarbonate) whereas from MPB medium; yeast extract, peptone, and NH4Cl (ammonium chloride) were selected in the range of 0.5–2.5 (g/l). Analytical assay, i.e., Fourier transform infrared spectroscopy (FTIR), gas chromatography mass spectrophotometry (GCMS), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) were conducted. Further, compatibility study and pathogenicity was performed.ResultsIn the present study, reactivated consortia was used therefore key components of the media were modified. In case of MPB medium, 2 g/l of yeast extract, 2 g/l peptone, and 1 g/l NH4Cl showed the promising results; whereas for MSP medium, 1 g/l of KH2PO4, 0.5 g/l of NaHCO3, and 1.5 g/l of C2H2NaO2 were noted to be the suitable range for methane production. Analytical studies confirmed the presences of -OH and aliphatic groups which majorly belongs to alkane, alkene, and phenol derivative compounds whereas SEM and EDX studies delineated the active interaction of bacteria with coal particles and presences of carbon (C) as a major peak in untreated coal and absence of C peak in microbial treated coal. In addition, a compatibility study was performed and their successful results aid in the future approach of field implementation. Further, pathogenicity data indicated the non-virulent and non-toxic nature of the consortia.ConclusionsThe production of waste coal is one of the most problematic and common activities of the mining industry. They release toxic substances into the environment (water, air, and soil) and damage the local biodiversity. Therefore, the generation of biogenic methane from waste coal is an environmentally friendly approach to overcome this problem.