The aim of this work was to investigate the feasibility of using oxalate at the anode in a continuous reactor. Complete oxalate removal was observed, albeit at a maximum coulombic efficiency of 33.9 +/- 0.4%. At the cathode side, there was an increase in pH from 8 to 11 showing production of caustic. Analysis of the microbial community demonstrated a clear shift during reactor start-up, resulting in enrichment of microorganisms belonging to Bacteroidetes, Firmicutes, Mollicutes, and beta and gamma-Proteobacteria. Methane was produced throughout the experiment; Archaea belonging to the Methanosarcinacea, Methanomicrobiaceae and Methanosaetaceae were identified as key representatives. (C) 2013 Elsevier Ltd. All rights reserved.