Microbial electrolysis cells for electromethanogenesis: Materials, configurations and operations

Abstract

Anaerobic digestion is a traditional method of producing methane-containing biogas by utilizing the methanogenic conversion of organic matter like agricultural waste and animal excreta. Recently, the application of microbial electrolysis cell (MECs) technology to a traditional anaerobic digestion system has been extensively studied to find new opportunities in increasing wastewater treatability and methane yield and producing valuable chemicals. The finding that both anodic and cathodic bacteria can synthesize methane has led to the efforts of optimizing multiple aspects like microbial species, formation of biofilms, substrate sources and electrode surface for higher production of the combustible compound. MECs are very fascinating because of its ability to uptake a wide variety of raw materials including untreated wastewater (and its microbial content as biocatalysts). Extensive work in this field has established different systems of MECs for hydrogen production and biodegradation of organic compounds. This review is dedicated to explaining the operating principles and mechanism of the MECs for electromethanogenesis using different biochemical pathways. Emphasis on single- and double-chambered MECs along with reactor components is provided for a comprehensive description of the technology. Methane production using hydrogen evolution reaction and nanocatalysts has also been discussed.

Sustainable bioelectrochemical systems for bioenergy generation via waste treatment from petroleum industries

“…Additionally, it is a well-known fact that among all the fuels (46.4 MJ/kg for gasoline, 55.6 MJ/kg for CH 4 , 24.0 MJ/kg for ethanol), H 2 proves to be highly efficient (120 MJ/kg) in terms of energy densities [126]. In this regard, H 2 production through waste valorization has gained importance due to its clean, renewable, and sustainable approach [127][128][129].Yet currently, most of the H 2 (around 96 %) is generated from fossil fuel-based technologies such as steam reforming, thermochemical conversion (pyrolysis), and gasification (Table 2; Table 3) [130,131]. The generation of H 2 from carbon-neutral and biorefinery approaches to reduce environmental-related problems is highly prioritized to decrease energy demand.…”

Valorisation of CO2 into Value-Added Products via Microbial Electrosynthesis (MES) and Electro-Fermentation Technology

“…have been widely researched to explore the EET mechanisms. The initial DET occurs through membrane-bound ETC proteins, like Cytochrome c (Cyt c), while the other carries e − from the microbe to the surface of the electrode along conductive pili (also known as nanowires), which are attached to membrane-bound e − transport compounds [44][45][46].…”

“…Researchers have mainly focused on understanding the mechanism of the anode while information on the reverse processes like the flow of e − from electrodes to microorganisms was insubstantial. In 2004, cathodic DET flow was reported for the reduction of various forms of nitrogen (nitrate NO 3 − to nitrite NO 2 − ) from the cathode and assured at about −0.34 V vs. SHE, it further enriched the substances along with microbial species [18,46,49]. Several Desulfovibrio sp.…”

“…Similarly, hydrogen peroxide can be produced in BES via carbon cathode, which can later be used as a beneficial chemical. H 2 O 2 thus produced can further be used for oxidation reactions, bioproduction and bioremediation processes [36,39,46,[53][54][55], as well as in Fenton reaction [56]. Thus, microbial assisted electrosynthesis can efficiently be employed for the production of disinfectants or oxidants [39].…”

Solar Photovoltaic Industry in Korea: Current Status and Perspectives

“…머나먼 태양으 로부터 지구까지 전자기파인 태양 복사(solar radiation)의 형태 로 태양 에너지가 전달된다. 태양 복사는 다양한 파장으로 이뤄 진 전자기파로서, 지구에서는 빛과 열 에너지의 형태로 태양열 난방(solar heating), 태양광 발전(solar photovoltaics), 태양열 발전(solar thermal power generation), 용융염 발전(molten salt power generation) 및 인공 광합성 ( [46][47][48][49][50][51][52][53][54][55]…”