Preparation of graphite granules
Eight setups were operated without plants to develop elec- trochemically active biofilms on the graphite granules. The anode was inoculated with 5 ml of anolyte from an MFC running on acetate (Dekker et al. 2009),andtheanolytewas extracted with a syringe. The setups were operated in batch mode. As nutrient solution 1/2 Hoagland Medium (Taiz and Zeiger 2006)bufferedwithan8-mMpotassiumphosphate buffer solution (pH 6.8) was used. The electron donor was supplied by adding 10 mM potassium acetate to the nutrient solution of setups 1 through 4 and 10 mM glucose to the nutrient solution of 5 through 8. After 40 days, the acetate-fed setups generated a current density of 0.248±0.004 Am−2, and the glucose fed setups generated a current density of 0.151± 0.02 Am−2. Current densities are expressed per square meter of cross-sectional area of the PMFC (0.00096 m2) throughout the document.