In recent years, the concerns about non-renewable resources depletion and environmental concerns resulting from fossil fuels overconsumption have led the researcher’s interest in producing biofuels from inexpensive, renewable, sustainable resources (e.g., lignocellulosic wastes). In this study, orange waste was used as a feedstock for acetone, butanol, and ethanol (ABE) production. Two different pretreatments, i.e., hot water and dilute acid (1% w/w), were performed before hydrolysis. The solid phases were then enzymatically hydrolyzed, while liquid phases were detoxified by overliming. The untreated substrate’s total sugars amount and glucose yield was 14.5 g/L and 254.0 g glucose per each Kg of untreated substrate after the enzymatic hydrolysis. In this regard, the highest produced sugars after enzymatic hydrolysis was 25.6 and 31.2 g/L for hot water (140 ? for 120 min) and dilute acid (140 ? for 60 min) pretreatments, respectively. Furthermore, the hydrolysate (enzymatic hydrolysis of solid phase), liquid phase, and detoxified liquids were fermented to ABE by Clostridium acetobutylicum. The produced ABE from the untreated substrate was 42.7 g per Kg substrate. Accordingly, the highest produced ABE per Kg of orange waste was 78.7 and 95.5 g for hot water and dilute acid pretreated substrate, respectively. It is noteworthy that the harsh conditions of pretreatment (i.e., high temperature and duration) caused a considerable reduction in hydrolysis yield and ABE production. According to the results, orange waste could be suggested as a suitable feedstock for biobutanol production.
