FIG. 6.

Current and potential produced in a glucose (3 g/liter) fuel cell when anaerobic sewage sludge was used as the catalyst and NR (100 μM) was used as the electronophore. The arrows indicate when the circuit was converted from an open circuit to a closed circuit with 2.2 kΩ of resistance (arrow 1), when 3 g of glucose per liter was added (arrow 2), when the circuit was converted from a closed circuit to an open circuit (arrow 3), and when the circuit was converted from an open circuit to a closed circuit without external resistance (arrow 4).