Enhancing hydrogen production in a two-chamber microbial electrolysis cell fed with food waste: Influence of dark fermentation and filtration

Microbial electrolysis cell (MEC) is a technology for producing hydrogen from organic waste using electrically active microorganisms. The two-chamber type MEC, which is divided into a biotic (anode) chamber and abiotic (cathode) chamber based on the ion exchange membrane, is capable of producing high-purity hydrogen, and many studies are being conducted. Although the use of real wastewater is essential for the actual process of MEC, electroactive microorganisms, which are the main microorganisms in the MEC reaction, can only use organic carbon sources with a relatively simple structure, so MEC applied to actual wastewater is less efficient than synthetic wastewater. . Therefore, in order to enhance MEC performance, it is advantageous to inject wastewater after pre-fermentation rather than directly using wastewater as a substrate, and studies in which wastewater from pre-fermentation is injected as a substrate have already been reported. For practical use and scale-up of MEC, the work of filtering actual wastewater to remove solids should be considered, but research related to this is insufficient. Therefore, in this study, fermented products were produced by pre-fermentation of food waste without pH adjustment or input of other chemicals. Raw material, raw material filtrate product, fermentation product, and fermentation filtrate product were each introduced as substrates for bi-type MEC to compare substrate availability in MEC between raw material and fermentation product, and to compare each raw material and filtrate product for practical use. The need for wastewater filtration was investigated. As a result of operating the MEC reactor under each condition, high hydrogen yield (1.1 L H2/g COD) and organic matter removal rate (85.3% COD removal) were observed in the fermentation filtrate. The results of this study are an eco-friendly treatment of food waste (5.16 million tons/year, as of 2020), which is generated in large quantities in Korea, and at the same time produce hydrogen energy, which is an alternative technology to existing treatment methods (e.g., feed conversion, composting, etc.). expected to be usable.