A biorefinery process typically uses about 4-10 times more water than the amount of biofuel generated. The wastewater produced in a biorefinery process contains residual sugars, 5-furfural, phenolics, and other pretreatment and fermentation byproducts. Treatment of the wastewater can reduce the need for fresh water and potentially add to the environmental benefits of the process. Use of microbial fuel cells (MFCs) for conversion of the complete range of phenolic compounds and furan aldehyde derivatives present in a postfermentation biorefinery stream is reported here. The consortium was capable of removing the molecules simultaneously with sugars, which were present at 2 orders of magnitude higher concentrations. Organic loading in a fed-batch MFC affected Coulombic efficiency, which decreased from 40% at 0.66 g/L loading to 1.8% at 66.4 g/L loading. Power density increased with loading reaching 1180 mW/m(2) at 5.3 g/L (8% dilution), but decreased thereafter. Excessive loading leads to poor electrogenic performance; therefore, operation of an MFC at an intermediate loading using dilution and recirculation of the process stream can enable effective treatment with bioenergy recovery.