Cellulosic butanol production from alkali-pretreated switchgrass (Panicum virgatum) and phragmites (Phragmites australis)

A potential dedicated energy crop (switchgrass) and an invasive (North America) plant species (phragmites) were compared as potential substrates for acetone butanol ethanol (ABE) fermentation. Both biomass were pretreated with 1% (w/v) NaOH and subjected to enzymatic hydrolysis. Total reducing sugar yields were 365 and 385 g kg−1 raw biomass for switchgrass and phragmites. Fermentation of the hydrolysates resulted in overall ABE yields of 146 and 150 g kg−1 (per kg dry plant material), with a theoretical maximum of 189 and 208 g kg−1, respectively. Though similar overall solvent yields were obtained from both crops, the largest carbon loss in the case of switchgrass occurred during pretreatment, while the largest loss in the case of phragmites occurred to enzymatic hydrolysis. These findings suggest that higher overall yields are achievable and that both crops are suitable feedstocks for butanol fermentation.