Low Temperature and Long Residence Time AFEX Pretreatment of Corn Stover

Low temperature and long residence time pretreatments have been proposed as an alternative to conventional pretreatments within a centralized biorefinery, allowing for a decentralized pretreatment without high energy costs. Ammonia fiber expansion (AFEX (TM)) pretreatment may be uniquely suitable for decentralized pretreatment, and this study considers the possibility of decreasing the temperature in AFEX pretreatment of corn stover. AFEX pretreatment at 40A degrees C and 8 h produced comparable sugar and ethanol yields as conventional AFEX pretreatment at high temperatures and short residence time during subsequent hydrolysis and fermentation. Increasing the ammonia loading at these temperatures tends to increase digestibility, although the moisture content of the reaction has little effect. This study suggests a greater flexibility in AFEX pretreatment conditions than previously thought, allowing for an alternative approach for decentralized facilities if the economic conditions are appropriate.