Butanol production from hydrothermolysis-pretreated switchgrass: Quantification of inhibitors and detoxification of hydrolyzate

•pH adjustment and CaCO3 addition to switchgrass hydrolyzate improved ABE production.•Switchgrass hydrolyzate contained both furanic and phenolic inhibitors.•Activated carbon detoxification removed detected inhibitors except cinnamaldehyde.•Detoxification of switchgrass hydrolyzate increased butanol titer from 1 to 11 g/L.•17 g/L total ABE was produced with detoxified hydrolyzate.

The present study evaluated butanol production from switchgrass based on hydrothermolysis pretreatment. The inhibitors present in the hydrolyzates were measured. Results showed poor butanol production (1 g/L) with non-detoxified hydrolyzate. However, adjusting the pH of the non-detoxified hydrolyzate to 6 and adding 4 g/L CaCO3 increased butanol formation to about 6 g/L. There was about 1 g/L soluble lignin content (SLC), and various levels of furanic and phenolic compounds found in the non-detoxified hydrolyzate. Detoxification of hydrolyzates with activated carbon increased the butanol titer to 11 g/L with a total acetone, butanol and ethanol (ABE) concentration of 17 g/L. These results show the potential of butanol production from hydrothermolysis pretreated switchgrass.