Aqueous pretreatment of triticale straw for integrated production of hemicellulosic methane and cellulosic butanol

Abstract

Despite its advantages, lignocellulosic butanol cannot become a real alternative without processes for obtaining credits from non-cellulosic fraction of lignocellulose. In this study, the process of “cellulosic butanol” was integrated with “hemicellulosic methane” process, i.e., anaerobic digestion (AD), for higher energy return on investment (EROI). Aqueous pretreatment was evaluated as a connecting chain between the processes. The alkaline (1% NaOH), acidic (1% H2SO4), and neutral (autohydrolysis) pretreatments were utilized at 140, 160, and 180 °C for bioenergy recovery from triticale straw. Enzymatic hydrolysis of the straw pretreated by alkaline (180 °C), dilute acid (140 °C), and autohydrolysis (180 °C) and fermentation of the hydrolysates by Clostridium acetobutylicum led to 13.6, 8.5, and 10.2 g/L acetone-butanol-ethanol (ABE), respectively. AD of the liquors remained after pretreatment by alkaline, dilute acid, and autohydrolysis led to 83–121, 240–247, and 380–430 mL/g VSS methane leading to more than 60% increase in EROI.