Electricity generation using eight amino acids by air–cathode microbial fuel cells

Eight kinds of amino acids including L-Serine (Ser), L-Asparagine (Asn), L-Asparticacid (Asp), L-Glutamicacid (Glu), DL-Alanine (Ala), L-lysine (Lys), L-Histidine (His) and L-Arginine (Arg) are tested as substrates of single-chambered air–cathode microbial fuel cells (MFCs) with domestic wastewater as inoculation. Their total organic carbon (TOC) concentrations in solution are standardized as 720 mg L−1. Ser produces the highest power density of 768 mW m−2 and Ala produces the lowest of 556 mW m−2. The Coulombic efficiencies (CEs) vary from 13 ± 3% (obtained with Arg) to 30 ± 1% (obtained with Ala). The removal efficiencies of total nitrogen (TN) are from 55 ± 5% (Asn) to 94 ± 4% (Asp), which may be associated with CEs. Maximum voltage outputs and TOC concentrations of the substrates appear to satisfy the empirical Monod-type equation when the external resistance is 150 Ω. The performances of MFCs are considered to relate to the molecular weights and structures of eight amino acids.