In this paper, the effect of root oxygen loss on energy recovery of the plant microbial fuel cell (PMFC) is described. In this manner, advanced understanding of competing processes within the rhizosphere-anode interface was provided. A microscopic model was developed on the basis of exudation, oxygen loss, biological oxidation, and biological current generation. The model was successfully validated by comparison to oxygen concentration profiles, volatile fatty acid profiles, and chemical oxygen demand profiles measured in the anode compartment. The model predicted oxic zones around roots in the anode of the plant microbial fuel cell. Results show no direct link between current generation and photosynthesis. This was consistent with the model which predicted that current was generated via hydrolysis of root-derived organic compounds. This result means that to optimize energy recovery of a PMFC, the plant selection should focus on high root biomass production combined with low oxygen loss. (c) 2011 Elsevier Ltd. All rights reserved.