Investigating the Processing Potential of Ethiopian Agricultural Residue Enset/Ensete ventricosum for Biobutanol Production

The Enset plant is a potential food source for about 20 million Ethiopians. A massive amount of residual byproduct is discarded from traditional Ethiopian Enset food processing. This study shows a compositional analysis of Enset biomass and its use for biobutanol production. The Enset biomass was pretreated with 2% (w/v) NaOH or 2% (v/v) H2SO4 and subjected to enzymatic hydrolysis. The enzymatic hydrolysates were then fermented anaerobically by C. saccharoperbutylacetonicum DSM 14923. The majority of Enset biomass waste samples contained 36–67% cellulose, 16–20% hemicelluloses, and less than 6.8% lignin. In all alkali-pretreated Enset biomass samples, the enzyme converted 80–90% of the biomass to glucose within 24 h, while it took 60 h to convert 48–80% of the acid-pretreated Enset biomass. In addition, the alkali pretreatment method released more glucose than the acid pretreatment in all Enset biomass samples. After 72 h of ABE fermentation, 2.8 g/L acetone, 9.9 g/L butanol, and 1.6 g/L ethanol were produced from mixed Enset waste hydrolysate pretreated with alkali, achieving an ABE yield of 0.32 g/g and productivity of 0.2 g × L$^{−1}$ × h$^{−1}$, showing the first value of butanol produced from Enset biomass in the literature.