Electricity Production from Steam-Exploded Corn Stover Biomass

Electricity generation using microbial fuel cells (MFCs) was examined from corn stover waste biomass using samples prepared through either neutral or acid steam-exploded hydrolysis processes that convert the hemicellulose to soluble sugars. Maximum power densities in fed-batch tests using an air-cathode MFC were 371 ± 13 mW/m² and 367 ± 13 mW/m² for the neutral and acid hydrolysates (1000 mg-COD/L, 250 Ω). Power output exhibited saturation kinetics with respect to fuel concentration, with predicted maximum power densities of P_max = 475 mW/m² and half-saturation constants of K_s = 347 mg/L (neutral) and P_max = 422 mW/m² and K_s 170 mg/L (acid). Coulombic efficiencies (CEs) were comparable to that found using carbohydrates in this type of MFC, with values ranging from 20 to 30% for both hydrolysates. All sugars (monomeric or oligomeric) were completely utilized, with overall biochemical oxygen demand (BOD) removal efficiencies of 93 ± 2% (neutral) and 94 ± 1% (acid). Power output could be increased by using a cathode containing a diffusion layer, resulting in maximum power densities of 810 ± 3 mW/m² (neutral) and 861 ± 37 mW/m² (acid). Power was further increased by increasing solution conductivity to 20 mS/cm, resulting in 933 mW/m² (neutral) and 971 mW/m² (acid) for the two hydrolysates. Additional increases in solution conductivity lowered the anode potential and did not increase power. These results demonstrate the potential for a new method of renewable energy production based on conversion of biomass to electricity using MFCs.