Biochar’s Electrochemical Properties Impact on Methanogenesis: Ruminal vs. Soil Processes

The chemical composition of biochar and the pyrolysis temperature, under which biochar was produced, determine its electrochemical properties. Electrical conductivity, pseudo-capacitance, and double layer capacitance are the three main electrochemical properties of biochar. Due to the electrical conductivity biochar is able to interfere with the electrons flow and play a dual role of an electron donor or an electron acceptor. The average conductivity of biochar is 229.20 S/m. Pseudocapacitance of biochar lets it serve as a hydrogen sink, taking up the hydrogen produced by protozoa and preventing it from participating in methane-producing reactions in the rumen environment. The average value of biochar’s pseudocapacitance is 228 F·g-1. Positive and negative charges get stored due to the absorption of ions onto the carbon surface, which happens because of the existence of double layer capacitance as one of biochar’s electrochemical properties. Biochar’s double layer capacitance values can reach the point of 110.8 F·g-1. The electrochemical properties of biochar are directly co-dependent with its redox potential and pH. Electrical conductivity, pseudocapacitance, and double layer capacitance can significantly influence biochemical processes in the rumen and, thus, need to be studied practically.

Chemical Oxidation Effects on Anion Exchange and Nitrate Sorption Capacity of Biochar for Ruminal Methanogenesis Inhibition

The chemical composition of biochar is determined by the chemical profile of the material the by-product is made of and the pyrolysis conditions. Analysis of commercial biochar detected similarities to the chemical profile of hardwood, which was used as an object of pyrolysis for biochar production and showed the presence of bridge-forming cations, such as manganese, iron, and sodium. Despite frequently being reported in existing literature, the current study showed that the redox potential of biochar is not associated with biochar’s ability to recover certain anions. No association was detected between biochar’s redox potential and the material nitrate sorption capacity. In fact, higher redox potential values were associated with lower nitrate absorption. In the case of the anion exchange capacity of biochar, a direct association between this electrochemical property of the by-product and its redox potential was observed. However, redox potential’s impact on anion exchange capacity can be inhibited by the presence of organic compounds in biochar’s chemical profile. The chemical oxidation of biochar is a complex process and is a research priority for a potential role to mitigate enteric methanogenesis in livestock.

The integration of methanogenesis with denitrification and anaerobic ammonium oxidation in an expanded granular sludge bed reactor

The integration of methanogenesis with denitrification and anaerobic ammonium oxidation(ANAMMOX) was studied in an expanded granular sludge bed(EGSB) reactor in this work. Experimental results from the continuous treatment of wastewater with nitrite and ammonium, which lasted for 107 days, demonstrated that wastewater with high nitrite and ammonium could be anaerobically treated in an expanded granular sludge bed reactor. More than 91% to 97% of COD were removed at up to about 3.9 g COD/(L·d) of COD volumetric loading rate. More than 97% to 100% of nitrite was denitrified at up to about 0.8 g NO -_2-N/(L·d), which is 16 times higher than that in a conventional activated sludge system with nitrification/denitrification(0.05 gN/(L·d)). No dissimilatory reduction of nitrite to ammonium occurred in the process. However, maximum of about 40% ammonium was found to be lost. Batch tests of 15 days with sludge from the reactor showed that 100% of nitrite was denitrified completely, and about 3% of ammonium was removed when only ammonium (34.3 mg/L) and nitrite(34.3 mg/L) were added into the sludge suspension medium. Furthermore, about 15% of ammonium amounts were lost with organic COD addition. It suggested that the methanogenesis in the system could enhance ANAMMOX because of intermediate hydrogen produced during methanogenesis.

Eubacteria and Archaea community of simultaneous methanogenesis and denitrification granular sludge

Based on the successful performance of a lab-scale upflow anaerobic sludge blanket （UASB） reactor with the capacity of simultaneous methanogenesis and denitrification （SMD）, the specific phylogenetic groups and community structure of microbes in the SMD granule in the UASB reactor were investigated by the construction of the Eubacteria and Archaea 16S rDNA clone libraries, fragment length polymorphism, and sequence blast. Real time quantitative-polymerase chain reaction （RTQ-PCR） technique was used to quantify the contents of Eubacteria and Archaea in the SMD granule. The contents of some special predominant methanogens were also investigated. The results indicated that the Methanosaeta and Methanobacteria were the predominant methanogens in all Archaea in the SMD granule, with contents of 71.59% and 22.73% in all 88 random Archaea clones, respectively. The diversity of Eubacteria was much more complex than that of Archaea. The low GC positive gram bacteria and ε-Protebacteria were the main predominant Eubacteria species in SMD granule, their contents were 49.62% and 12.03% in all 133 random Eubacteria clones respectively. The results of RTQ-PCR indicated that the content of Archaea was less than Eubacteria, the Archaea content in total microorganisms in SMD granule was about 27.6%.

Methanogenesis acceleration of fresh landfilled waste by micro-aeration

When municipal solid waste(MSW) with high content of food waste is landfilled, the rapid hydrolysis of food waste results in the imbalance of anaerobic metabolism in the landfill layer, indicated by accumulation of volatile fatty acids(VFA) and decrease of pH value. This occurrence could lead to long lag time before the initiation of methanogenesis and to the production of strong leachate. Simulated landfill columns with forced aeration, with natural ventilation, and with no aeration, were monitored regarding their organics degradation rate with leachate recirculation. Hydrolysis reactions produced strong leachate in the column with no aeration. With forced aeration, the produced VFA could be effectively degraded, leading to the reduction in COD of the leachate effluent since the week 3. The CH_4 in the landfill gas from the column with aeration rate of 0.39 m3/(m3·d) and frequency of twice/d, leachate recirculation rate of 12.2 mm/d and frequency of twice/d, could amount to 40%(v/v) after only 20 weeks. This amount had increased up to 50% afterward even with no aeration. Most of COD in the recirculated leachate was removed. Using natural ventilation, CH_4 could also be produced and the COD of the leachate effluent be reduced after 10 weeks of operation. However, the persistent existence of oxygen in the landfill layer yielded instability in methanogenesis process.

Biogeochemistry of methanogenesis with a specific emphasis on the mineral-facilitating effects

The Earth surface contains various oxic and anoxic environments. The later include natural wetlands,river and lake sediments, paddy field soils and landfills. In the last few decades, the biogeochemical cycle of carbon in anoxic environments, which leads to the production and emission of methane, a potent greenhouse gas in the atmosphere, has drawn great attentions from both scientific and public sectors. New organisms and mechanisms involved in methanogenesis and carbon cycling have been uncovered. Interspecies electron transfer is considered as a crucial step in methanogenesis in anoxic environments.Electron-carrying mediators, like H_2 and formate, are known to play the key role in electron transfer. Recently, it has been found that in addition to the conventional electron transfer via chemical mediators, direct interspecies electron transfer(DIET) can occur. In this Review, we describe the ecology and biogeochemistry of methanogenesis and highlight the effect of microbe-mineral interaction on microbial syntrophy. Recent advances in the study of DIET may pave the way towards a mechanistic understanding of methanogenesis and the influence of microbe-mineral interaction on this process.

Lovastatin as a supplement to mitigate rumen methanogenesis:an overview

Methane from enteric fermentation is the gas with the greatest environmental impact emitted by ruminants.Lovastatin(Lv)addition to feedstocks could be a strategy to mitigate rumen methane emissions via decreasing the population of methanogenic archaea(MA).Thus,this paper provides the first overview of the effects of Lv supplementation,focusing on the inhibition of methane production,rumen microbiota,and ruminal fermentation.Results indicated that Lv treatment had a strong anti-methanogenic effect on pure strains of MA.However,there are uncertainties from in vitro rumen fermentation trials with complex substrates and rumen inoculum.Solid-state fermentation(SSF)has emerged as a cost-effective option to produce Lv.In this way,SSF of agricultural residues as an Lv-carrier supplement in sheep and goats demonstrated a consistent decrease in ruminal methane emissions.The experimental evidence for in vitro conditions showed that Lv did not affect the volatile fatty acids(VFA).However,in vivo experiments demonstrated that the production of VFA was decreased.Lv did not negatively affect the digestibility of dry matter during in vitro and in vivo methods,and there is even evidence that it can induce an increase in digestibility.Regarding the rumen microbiota,populations of MA were reduced,and no differences were detected in alpha and beta diversity associated with Lv treatment.However,some changes in the relative abundance of the microbiota were induced.Further studies are recommended on:(i)Lv biodegradation products and stability,as well as its adsorption onto the solid matter in the rumen,to gain more insight on the“available”or effective Lv concentration;and(ii)to determine whether the effect of Lv on ruminal fermentation also depends on the feed composition and different ruminants.

Electrical stress and acid orange 7 synergistically clear the blockage of electron flow in the methanogenesis of low-strength wastewater

Energy recovery from low-strength wastewater through anaerobic methanogenesis is constrained by limited substrate availability.The development of efficient methanogenic communities is critical but challenging.Here we develop a strategy to acclimate methanogenic communities using conductive carrier(CC),electrical stress(ES),and Acid Orange 7(AO7)in a modified biofilter.The synergistic integration of CC,ES,and AO7 precipitated a remarkable 72-fold surge in methane production rate compared to the baseline.This increase was attributed to an altered methanogenic community function,independent of the continuous presence of AO7 and ES.AO7 acted as an external electron acceptor,accelerating acetogenesis from fermentation intermediates,restructuring the bacterial community,and enriching electroactive bacteria(EAB).Meanwhile,CC and ES orchestrated the assembly of the archaeal community and promoted electrotrophic methanogens,enhancing acetotrophic methanogenesis electron flow via a mechanism distinct from direct electrochemical interactions.The collective application of CC,ES,and AO7 effectively mitigated electron flow impediments in low-strength wastewater methanogenesis,achieving an additional 34%electron recovery from the substrate.This study proposes a new method of amending anaerobic digestion systems with conductive materials to advance wastewater treatment,sustainability,and energy self-sufficiency.

Anti-methanogenic potential of seaweeds and seaweed-derived compounds in ruminant feed:current perspectives,risks and future prospects

With methane emissions from ruminant agriculture contributing 17%of total methane emissions worldwide,there is increasing urgency to develop strategies to reduce greenhouse gas emissions in this sector.One of the proposed strategies is ruminant feed intervention studies focused on the inclusion of anti-methanogenic compounds which are those capable of interacting with the rumen microbiome,reducing the capacity of ruminal microorganisms to produce methane.Recently,seaweeds have been investigated for their ability to reduce methane in ruminants in vitro and in vivo,with the greatest methane abatement reported when using the red seaweed Asparagopsis taxiformis(attributed to the bromoform content of this species).From the literature analysis in this study,levels of up to 99%reduction in ruminant methane emissions have been reported from inclusion of this seaweed in animal feed,although further in vivo and microbiome studies are required to confirm these results as other reports showed no effect on methane emission resulting from the inclusion of seaweed to basal feed.This review explores the current state of research aiming to integrate seaweeds as anti-methanogenic feed additives,as well as examining the specific bioactive compounds within seaweeds that are likely to be related to these effects.The effects of the inclusion of seaweeds on the ruminal microbiome are also reviewed,as well as the future challenges when considering the largescale inclusion of seaweeds into ruminant diets as anti-methanogenic agents.

Effect of traditional Chinese medicine compounds on rumen fermentation, methanogenesis and microbial flora in vitro

This study was conducted to investigate the effects of traditional Chinese medicine compounds(TCMC)on rumen fermentation, methane emission and populations of ruminal microbes using an in vitro gas production technique. Cablin patchouli herb(CPH), Atractylodes rhizome(AR), Amur Cork-tree(AC) and Cypsum were mixed with the weight ratios of 1:1:1:0.5 and 1:1:1:1 to make up TCMC1 and TCMC2,respectively. Both TCMC were added at level of 25 g/kg of substrate dry matter. In vitro gas production was recorded and methane concentration was determined at 12 and 24 h of incubation. After 24 h, the incubation was terminated and the inoculants were measured for pH, ammonia nitrogen, volatile fatty acids(VFA). Total deoxyribonucleic acid of ruminal microbes was extracted from the inocula, and populations were determined by a real-time quantitative polymerase chain reaction. Populations of total rumen methanogens, protozoa, total fungi, Ruminococcus albus, Fibrobacter succinogenes and Ruminococcus flavefaciens were expressed as a proportion of total rumen bacterial 16 S ribosomal deoxyribonucleic acid. Compared with the control, the 2 TCMC decreased(P < 0.05) total VFA concentration,acetate molar proportion, acetate to propionate ratio, gas and methane productions at 12 and 24 h,hydrogen(H) produced and consumed, and methanogens and total fungi populations, while the 2 TCMC increased(P < 0.05) propionate molar proportion. Traditional Chinese medicine compound 1 also decreased(P ≤ 0.05) R. flavefaciens population. From the present study, it is inferred that there is an effect of the TCMC in suppressing methanogenesis, probably mediated via indirect mode by channeling H2 utilized for methanogenesis to synthesis of propionate and direct action against the rumen microbes involved in methane formation. In addition, the relative methane reduction potential(RMRP) of TCMC2 was superior to that of TCMC1.

Developing“precise-acting”strategies for improving anaerobic methanogenesis of organic waste:Insights from the electron transfer system of syntrophic partners

Methanogenesis is the last step in anaerobic digestion,which is usually a rate-limiting step in the biological treatment of organic waste.The low methanogenesis efficiency(low methane production rate,low methane yield,low methane content)substantially limits the development of anaerobic digestion technology.Traditional pretreatment methods and bio-stimulation strategies have impacts on the entire anaerobic system and cannot directly enhance methanogenesis in a targeted manner,which was defined as“broad-acting”strategies in this perspective.Further,we discussed our opinion of methanogenesis process with insights from the electron transfer system of syntrophic partners and provided potential targeted enhancing strategy for high-efficiency electron transfer system.These“precise-acting”strategies are expected to achieve an efficient methanogenesis process and enhance the bio-energy recovery of organic waste.

Methanogenic community structure in simultaneous methanogenesis and denitrification granular sludge

A laboratory scale up-flow anaerobic sludge bed （UASB） bioreactor ted with synthetic wastewater was operated with simultaneous methanogenesis and denitrification （SMD） granules for 235 days with a gradient decrease of C/N. Molecular cloning, qRT-PCR and T-RFLP were applied to study tile methanogenic community structures in SMD granules and their changes in response to changing influent C/N. The results indicate that when C/N was 20：1, the methane production rate was tastest, and Methanosaetaceae and Methanobacteriaceae were the primary methanogens within tile Archaea. The richness and evenness of methanogenic bacteria was best with the highest T-RFLP diversity index of 1.627 in the six granular sludge samples. When C/N was reduced from 20：1 to 5：1, tbe methanogenic activity of SMD granules decreased gradually, and the relative quantities of methanogens decreased from 36.5% to 10.9%. The abundance of Methanosaetaceae in Archaea increased from 64.5% to 84.2%, while that of Methanobacteriaceae decreased from 18.6% to 11.8%, and the richness and evenness of methanogens decreased along with the T-RFLP diversity index to 1.155, suggesting that the community structure reflected the succession to an unstable condition represented by high nitrate concentrations.

Methane Dynamics in Northern Peatlands: A Review

Northern peatlands store a large amount of carbon and play a significant role in the global carbon cycle. Owing to the presence of waterlogged and anaerobic conditions, peatlands are typically a source of methane (CH4), a very potent greenhouse gas. This paper reviews the key mechanisms of peatland CH4 production, consumption and transport and the major environmental and biotic controls on peatland CH4 emissions. The advantages and disadvantages of micrometeorological and chamber methods in measuring CH4 fluxes from northern peatlands are also discussed. The magnitude of CH4 flux varies considerably among peatland types (bogs and fens) and microtopographic locations (hummocks and hollows). Some anthropogenic activities including forestry, peat harvesting and industrial emission of sulphur dioxide can cause a reduction in CH4 release from northern peatlands. Further research should be conducted to investigate the in fluence of plant growth forms on CH4 flux from northern peatlands, determine the water table threshold at which plant production in peatlands enhances CH4 release, and quantify peatland CH4 exchange at plant community level with a higher temporal resolution using automatic chambers.

Co-inhibition of methanogens for methane mitigation in biodegradable wastes

The inhibition effects and mechanisms of chlorinated methane and acetylene on methanogenesis in the anaerobic digestion process of the biodegradable wastes were investigated.It was found that both chloroform and acetylene could effectively inhibit methanogens while the biodegradability of the wastes was not affected.Acetylene inhibited the activity of methanogens,while chloroform inhibited metabolic process of methanogenesis.A central composite design（CCD） and response surface regression analysis（RSREG） were employed to determine the optimum conditions and interaction effects of chloroform and acetylene in terms of inhibition effciency,production of volatile fatty acids（VAF） and molar ratio of propionic acid to acetic acid.Chloroform had significant effect on enhancing the production of VFA（F = 121.3;p 〈 0.01）,and acetylene promoted the inhibition effciency（F = 99.15;p 〈 0.05） more effectively than chloroform（F = 9.72;p 〉 0.05）.In addition,a maximum molar ratio of propionic acid to acetic acid of 1.208 was estimated under the optimum conditions of chloroform concentration of 9.05 mg/kg and acetylene concentration of 3.6×10^-3（V/V）.Hence,methanogens in the wastes can be inhibited while the stabilization process of the biodegradable wastes can still work well,as propionic acid generated during the inhibition process could hardly be utilized by methanogens.

Influence of lactic acid on the two-phase anaerobic digestion of kitchen wastes

To evaluate the influence of lactic acid on the methanogenesis, anaerobic digestion of kitchen wastes was firstly conducted in a two-phase anaerobic digestion process, and performance of two digesters fed with lactic acid and glucose was subsequently compared. The results showed that the lactic acid was the main fermentation products of hydrolysis-acidification stage in the two-phase anaerobic digestion process for kitchen wastes. The lactic acid concentration constituted approximately 50% of the chemical oxygen demand （COD） concentration in the hydrolysis-acidification liquid. The maximum organic loading rate was lower in the digester fed with lactic acid than that fed with glucose. Volatile fatty acids （VFAs） and COD removal were deteriorated in the methanogenic reactor fed with lactic acid compared to that fed with glucose. The specific methanogenic activity （SMA） declined to 0.343 g COD/（gVSS-d） when the COD loading were designated as 18.8 g/（L-d） in the digester fed with lactic acid. The propionic acid accumulation occurred due to the high concentration of lactic acid fed. It could be concluded that avoiding the presence of the lactic acid is necessary in the hydrolysis-acidification process for the improvement of the two-phase anaerobic digestion process of kitchen wastes.

Comparison between controlled landfill reactor and conditioned landfill bioreactor

Bioreactor landfills allow a more active landfill management that recognizes the biological, chemical and physical processes involved in a landfill environment. The laboratory-scale simulators of landfill reactors treating municipal solid wastes were studied, the effect of solid waste size, leachate recirculation, nutrient balance, pH value, moisture content and temperature on the rate of municipal solid waste(MSW) biodegradation were determined, and it indicated the optimum pH value, moisture content and temperature decomposing MSW. The results of waste biodegradation were compared with that of the leachate-recirculated landfill simulator and conservative sanitary landfill simulator. In the control experiment the antitheses of a decreasing trend of the organic load, measured as biological oxygen demand and chemical oxygen demand, was shown. An obvious enhancement of effective disposal from conservative sanitary landfill(CSL) simulator, to the leachate-recirculated landfill(LRL) simulator and to the conditioned bioreactor landfill(CBL) simulator would be noted, through displaying the compared results of solid waste settlement, heavy metal concentration in leachate, methane production rate, biogas composition, BOD and COD as well as their ratio.

Anaerobic digestion of kitchen wastes in a single-phased anaerobic sequencing batch reactor(ASBR) with gas-phased absorb of CO_2

The performance of the single-stage anaerobic digestion of kitchen wastes was investigated in an anaerobic sequencing batch reactor(ASBR) with gas-phased absorb of CO 2. The ASBR was operated at four chemical oxygen demand(COD) loading rates, 2.8, 5.1, 6.2 and 8.4 g/(L·d) respectively. The COD loading rate was increased with the TS concentration and HRT changing. At maximum COD loading rate of 8.4 g/(L·d), the COD, total solid(TS) removal rate and methane gas yield were 69%, 68% and 2.5 L/(L·d) respectively. The operation of the reactor with gas-phased absorb of CO 2 was stable in spite of the low pH(2.6—3.9) and high concentration of TS(142 g/L) of input mixture. The output volatile fatty acid(VFA) concentration was between 2.7—4.7 g/L and had no inhibition on the methanogenic microorganism. The reactor without gas-phased absorb of CO 2 became acidified when the total COD loading rate was increased to 5.1 g/(L·d). Stoichiometry of the methanogenesis for kitchen wastes showed a considerable amount of alkaline will be required to keep pH in the appropriate range for the methanogenic microorganism based on theoretical calculation. Gas-phased absorb of CO 2 effectively reduced the alkaline consumption, hence avoided excessive cation into the reactor.

Aquatic Macrophytes Detritus Quality and Sulfate Availability Shape the Methane Production Pattern in a Dystrophic Coastal Lagoon

Aquatic macrophytes usually show high productivity rate, especially in shallow environments, and may constitute the main source of organic matter to these ecosystems. The coastal lagoons are shallow environments that typically present a broad colonization by aquatic macrophytes. The organic matter derived from aquatic macrophytes consists of detritus and root exudates, from live plants. Methanogens are microorganisms that use labile organic matter (e.g. acetate) in the metabolism, releasing methane (CH4) as an end product. Assessing the influence of aquatic macrophytes on methanogenesis is fundamental to understanding the carbon cycle in shallow environments, such as coastal lagoons. A peculiarity of coastal lagoons that may also influence the methanogenesis is its proximity to the sea, providing the entrance of sulfate in the environment. The methanogenesis can be inhibited by the sulfate reduction when there is sulfate availability sulfate. In this context, we aimed to analyze the methane production in an aquatic macrophyte stand and in the limnetic region of a coastal lagoon, assessing the influence of quantity and quality of organic carbon and sulfate availability on methane production in the sediment profile. We observe that the presence of aquatic macrophytes benefits the methanogenesis, not only by detritus accumulation, but particularly by the release of root exudates from the living plants. The variation in quantity and quality of organic carbon is the main factor that controls the range and shape of the methane production curves. The availability of sulfate presents probably a secondary role, being important when the organic matter is not sufficient for the occurrence of methanogenesis and sulfate reduction simultaneously.

A large epeiric methanogenic Bambuí sea in the core of Gondwana supercontinent?

Carbon isotope compositions of both sedimentary carbonate and organic matter can be used as key proxies of the global carbon cycle and of its evolution through time,as long as they are acquired from waters where the dissolved inorganic carbon(DIC)is in isotope equilibrium with the atmospheric CO2.However,in shallow water platforms and epeiric settings,the influence of local to regional parameters on carbon cycling may lead to DIG isotope variations unrelated to the global carbon cycle.This may be especially true for the terminal Neoproterozoic,when Gondwana assembly isolated waters masses from the global ocean,and extreme positive and negative carbon isotope excursions are recorded,potentially decoupled from global signals.To improve our understanding on the type of information recorded by these excursions,we investigate the pairedδ^13Ccarb andδ^13Corg evolution for an increasingly restricted late Ediacaran-Cambrian foreland system in the West Gondwana interior:the basal Bambui Group.This succession represents a 1~(st)-order sedimentary sequence and records two majorδ^13Ccarb excursions in its two lowermost lower-rank sequences.The basal cap carbonate interval at the base of the first sequence,deposited when the basin was connected to the ocean,hosts antithetical negative and positive excursions forδ^13Ccarb andδ^13Corg,respectively,resulting inΔ^13C values lower than 25‰.From the top of the basal sequence upwards,an extremely positiveδ^13Ccarb excursion is coupled toδ^13Corg,reaching values of+14‰and-14‰,respectively.This positive excursion represents a remarkable basin-wide carbon isotope feature of the Bambui Group that occurs with only minor changes inΔ^13C values,suggesting change in the DIC isotope composition.We argue that this regional isotopic excursion is related to a disconnection between the intrabasinal and the global carbon cycles.This extreme carbon isotope excursion may have been a product of a disequilibria between the basin DIC and atmospheric CO2 induced by an active methanogenesis,favored by the basin restriction.The drawdown of sulfate reservoir by microbial sulfate reduction in a poorly ventilated and dominantly anoxic basin would have triggered methanogenesis and ultimately methane escape to the atmosphere,resulting in a^13C-enriched DIC influenced by methanogenic CO2.Isolated basins in the interior of the Gondwana supercontinent may have represented a significant source of methane inputs to the atmosphere,potentially affecting both the global carbon cycle and the climate.

Suppression of Methane Gas Emissions and Analysis of the Electrode Microbial Community in a Sediment-Based Bio-Electrochemical System

The effects of bioelectrochemical systems (BESs) for the suppression of methane gas emissions from sediment were examined using a laboratory-scale reactor system. Methane gas emissions from acetate were suppressed by approximately 36% from control based on the installation of a BES in which carbon-graphite electrodes were buried in sediment and arbitrarily set at certain oxidative potentials (+300 mV vs Ag/AgCl) using a potentiostat. Meanwhile, methane gas emissions increased in the BES reactor where the electrode potential was set at -200 mV. Results obtained from pyrotag sequencing analysis of the microbial community on the surface of the buried electrodes targeting 16S rRNA genes demonstrated that the genusGeobacterhad drastically propagated in a sample from the reactor where the electrodes were buried. Quantitative analysis of 16S rRNA genes of archaea also revealed that the archaeal population had decreased to approximately 1/6 of its original level on the electrode of the BES set at +300 mV. This implied that the oxidation-reduction potential (ORP) in the sediment was raised to the inhibition level for methanogenesis in the vicinity of the buried electrode. Analysis of electron flux in the experiment revealed that electrons intrinsically used for methanogenesis were recovered via current generation in the sediment where a potential of +300 mV was set for the electrode, although most electrons donated from acetate were captured by oxygen respiration and other electron-accepting reactions. These results imply that BES technology is suitable for use as a tool for controlling re-dox-dependent reactions in natural environments, and that it also brought about changes in the microbial population structure and methanogenic activity in sediment.