The Advantages of Soaking with Aqueous Ammonia Pre-treatment Process of Oil Palm Empty Fruit Bunches
Oil palm empty fruit bunches (OPEFB) as one of lignocellulosic biomass, consists of three main components: cellulose, lignin, and hemicelluloses. Cellulose may occur in a crystalline form in addition to amorphous form. Cellulose and hemicelluloses can be converted into fermentable sugar, i.e. glucose and xylose, by chemical or enzymatic hydrolysis. These sugar usually used as a feedstock of bio ethanol production. Lignin and high-crystallinity of cellulose are inhibits the performance of enzymatic hydrolysis process. Therefore pretreatment is necessary to remove lignin, decrease the crystallinity and improve the yield of enzymatic hydrolysis. One of the developed pre-treatment processes is soaking with aqueous ammonia solution or called by SAA process. In this study, the advantage of SAA pre-treatment process was investigated using ammonium solution prior to the enzymatic hydrolysis. The pre-treatments were carried out in various ammonium concentrations (5%, 7.5%, and 10%) at mild conditions (25 oC and 1 atm) for 24 hrs, and with or without a following additional diluted-acid pre-treatment (92 – 98 oC and 1 atm for 1 hour). The pre-treated materials were then enzymatic hydrolyzed by cellulose and β-glycosidase for 96 hrs and anaerobic digested by inoculums microbial. The changes in cellulose crystallinity were analyzed by FTIR Spectroscopy. The OPEFB pre-treated by 10% ammonium solution without a following dilute-acid pre-treatment shows low crystallinity with a crystallinity index (CI) of 0.80 compared to that of the untreated material (2.11). The method could increase the yield of hydrolyzed glucose to 79% compared with that of untreated material (13 g/g glucan added). The results also show increasing the methane production from 0.18 Nm3/g volatile solid to 0.35 Nm3/g volatile solid via anaerobic digestion.
ammonia pre-treatment; dilute-acid pre-treatment; crystallinity index; enzymatic hydrolysis; anaerobic digestion.
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Published by INSIGHT - Indonesian Society for Knowledge and Human Development