LAUSR

In MFCs that are used to generate electricity, the discharging of phosphate electrolyte is not economical and environmentally friendly. To address this issue, the concept of “zero-electrolyte-discharge” MFCs was developed. In this study, the performance of “zero-electrolyte-discharge” air-cathode MFCs were critically evaluated using different types of substrates (sugar, alcohol, fatty acid, and salt). A final power loss of 68% and 48% was observed for the glucose- and ethanol-fed MFCs, respectively. This power loss was found to be mainly due to the substantially increased internal resistances under decreased electrolyte pH that is induced by the fast production of acidic metabolites. Moreover, cathodic biofilm growth was found to cause a higher electrolyte pH at the cathodic catalyst layer, resulted in a lower open circuit voltage (OCV) and power density. Among the studied substrates, our results suggest that acetic acid is the most suitable candidate for the zero-electrolyte-discharge MFC system since it provides a stable electrolyte environment and least cathodic biofilm growth. The drawbacks of using sodium acetate as an MFC substrate have also been discussed and it is compared with acetic acid.