Enhanced ethanol production by Clostridium ragsdalei from syngas by incorporating biochar in the fermentation medium

- Biochar provides nutrients and buffering capacity for enhanced syngas fermentation.
- PLBC biochar Medium enhanced ethanol production by 58.9% compared to YE medium.
- RCBC biochar Medium enhanced ethanol production by 16.3% compared to YE medium.
- Ethanol/acetic acid molar ratios were 4.5 and 7.9 in PLBC and RCBC media.
- Acetic acid enhances release of Ca, Mg, Fe, and Mn from PLBC.

Biochar contains minerals and metals that can serve as nutrients for acetogens to produce ethanol via syngas fermentation. In this study, four fermentation media containing biochar from switchgrass (SGBC), forage sorghum (FSBC), red cedar (RCBC) and poultry litter (PLBC) were compared with standard yeast extract (YE) medium for syngas fermentation using Clostridium ragsdalei. Fermentations were performed in 250 mL bottle reactors at 150 rpm and 37 °C with syngas containing CO:H2:CO2 (40:30:30) by volume. Results showed that media containing RCBC and PLBC improved ethanol production by 16.3% and 58.9%, respectively, compared to YE medium. C. ragsdalei consumed 69% more H2 and 40% more CO in PLBC medium compared to YE medium. However, no enhancement of ethanol production was observed in SGBC and FSBC media. The highest release of Na, K, Ca, Mg, S and P was from PLBC, which was considered to contribute in enhancement of ethanol production.