Effects of Low Moisture Anhydrous Ammonia (LMAA) Pretreatment at Controlled Ammoniation Temperatures on Enzymatic Hydrolysis of Corn Stover

Abstract

Corn stover was treated using low-moisture anhydrous ammonia (LMAA) at controlled ammoniation temperature. Moisturized corn stover (50 % moisture) was contacted with anhydrous ammonia (0.1 g NH3/g-biomass) in a batch reactor at various temperatures (ambient to 150 degrees C). After ammoniation at elevated and controlled temperature, ammoniated corn stover was pretreated at various temperatures (60-150 degrees C) for 72-144 h. Change in composition was marginal at low pretreatment temperature but was relatively severe with pretreatment at high temperature (130-150 degrees C). The latter resulted in low enzymatic digestibility. It was also observed that extreme levels (either high or low) of residual ammonia affected enzymatic digestibility, while residual ammonia improved by 1.0-1.5 %. The LMAA method enhanced enzymatic digestibility compared to untreated corn stover (29.8 %). The highest glucan and xylan digestibility (84.1 and 73.6 %, respectively) was obtained under the optimal LMAA conditions (i. e., ammoniation at 70 degrees C for 20 min, followed by pretreatment at 90 degrees C for 48 h).