Inhibitory effect of ethanol on the experimental electrical charge and hydrogen production in microbial electrolysis cells (MECs)

Abstract

Fermentation effluents are exploited in microbial electrolysis cells (MECs) for hydrogen production, but they may include ethanol and other compounds that are detrimental to MEC performance. Ethanol can disrupt microbial viability, and lactate makes MEC feeding more complex. The present work aimed to assess the effects of lactate and ethanol on hydrogen and electric current production in MECs to determine the corresponding inhibitory concentrations. A two-chamber MEC was inoculated with compost leachate and fed with lactate-ethanol mixtures at four ratios (total 2.5g COD L−1), and a volatile fatty acid mixture was used as a base substrate to achieve anolyte at a final concentration of 3.5g COD L−1. The MEC operated at 1.0V for 21days, and its performance was evaluated for COD removal, cathodic and energy efficiency. The inhibitory ethanol concentration was 0.8g COD L−1 (0.38gL−1), and lactate reduced the current density lag phase. The start of hydrogen production required 218±35C in the MEC system utilized. This work shows that ethanol content exerts an inhibitory effect on current and hydrogen production; moreover, a relationship between accumulated charge and accumulated hydrogen volume was found suitable to characterize the process.