(602d) Biochar Enhanced Alcohol Production from Syngas By Clostridium Carboxidivorans

Biological production of ethanol and butanol from syngas is an alternative route to traditional ABE (acetone-butanol-ethanol) fermentation. Ethanol and butanol can be mixed with gasoline. Butanol can be converted to jet fuel via a hydrogenation process. Biochar made by gasification and pyrolysis is a carbon-rich material with high surface area, pH buffer capacity and cation exchange capacity (CEC). Biochar use in biofuel production has not been extensively reported. This study examined the properties of biochar made from switchgrass (SGBC), forage sorghum (FSBC), red cedar (RCBC) and poultry litter (PLBC), and their effects as a medium additive on ethanol and butanol production by Clostridium carboxidivorans. Experiments were performed in 250 mL bottle reactors with a 50 mL working volume at 37 °C for 360 h. Syngas mixture containing CO:H₂:CO₂ (40:30:30, by volume) was fed every 24 h. Results showed that PLBC and SGBC enhanced ethanol production by 90% and 73%, respectively, and butanol production by fourfold compared to standard rich yeast extract medium without biochar (control). FSBC and RCBC also enhanced ethanol and butanol production but lower than PLBC and SGBC. Total CO and H₂ utilization was also enhanced in biochar media compared to control medium. PLBC had the highest concentrations of Na, K, Ca, Mg, P and Mn, pH buffering capacity and CEC compared to other biochars tested, which possibly contributed to its highest enhancement of ethanol and butanol production. This study showed the potential for biochar use as a medium substitute for expensive nutrients to enhance biofuel production via syngas fermentation, which increases the feasibility of the process.