Ethanol Production through Optimized Alkaline Pretreated Elaeis guineensis Frond Waste from Krabi Province, Thailand

Abstract

Oil palm frond as an abundant and inexpensive lignocellulosic waste was used to optimize alkaline pretreatment for ethanol production. The studied lignocellulosic waste is one of the largest biomasses (47%) in oil palm waste. Oil palm frond fibers were processed by steam explosion, hot water extraction, and alkaline extraction pretreatment, followed by simultaneous saccharification and fermentation (SSF), for ethanol production as an alternative energy resource. To optimize alkaline extraction for oil palm frond, a Taguchi method with a three-factor design constituted a concentration of NaOH (15%, 20%, and 25%), time (30, 60, and 90 min), and temperature (70, 80, and 90 °C). An optimum alkaline extraction condition of 15% NaOH at 90 °C for 60 min gave the highest percentage of α-cellulose (80.74%) and the lowest percentages of lignin (15.99%), ash (1.05%), and pentosan (2.09%). In addition, the optimized pretreatment condition significantly improved α-cellulose to 52.65% and removed lignin up to 51.78%. Simultaneous saccharification and fermentation (SSF) was carried out with 10% (dry weight) alkaline pretreated OPF fibers, Celluclast 1.5 L (15 FU/gram substrate), Novozyme 188 (15 IU/gram substrate), and Saccharomyces cerevisiae SC90 at 40 and 45 °C. The highest ethanol concentration, theoretical ethanol yield, and ethanol productivity observed at 40 °C were 33.15 g/L, 72.54%, and 0.55 g/L/h, respectively. The results suggest that an optimized alkaline pretreatment process using palm frond as a lignocellulosic waste is a sustainable approach to produce efficient ethanol production.