AFEX™ Pretreatment-Based Biorefinery Technologies

Ammonia fiber expansion (AFEX™) pretreatment is a novel thermochemical pretreatment using ammonia as catalyst. AFEX-pretreated lignocellulosic biomass features high enzymatic digestibility, high fermentability, and low toxicity. Extractive ammonia (EA) pretreatment is developed based on AFEX. EA converts native cellulose I to more reactive cellulose III and removes lignin to further improve enzymatic digestibility. Rapid bioconversion with integrated recycle technology (RaBIT) is invented to resolve high enzyme loading and low ethanol productivity issues encountered using traditional process for conversion of pretreated biomass to ethanol. RaBIT shortens enzymatic hydrolysis time, recycles enzymes using unhydrolyzed solids, and accelerates fermentation using high-cell-density microbial cells with cell recycle after fermentation. RaBIT reduces enzyme loading by around 40% and improves ethanol productivity by twofold. This chapter covers the development of AFEX-related biorefinery technologies in recent years.