In this study, the pretreatment process adopted was Changhae ethanol multiexplosion (CHEMEX), which was developed by Changhae Ethanol Co., Ltd. (Korea). The pretreatment facility was designed to handle 70–100 kg/day of lignocellulosic biomass and can be operated 2–3 times per day. In order to operate under various conditions such as hot water, acid, alkali, steam, and explosion, the pretreatment reactor was made from STS316L, a substance that is highly resistant to acid or alkali corrosion and can resist maximums of 300 °C and 50 kg f/cm2.
EFB weighing 50 kg were pretreated with 2.9 M sodium hydroxide at 130 °C and 3.5 kg f/cm2 for 20 min. A solid-to-liquid ratio of 1:5 was applied. This optimal pretreatment condition was taken from a previous study [13]. Pretreated biomass was collected into a buffer tank through a cyclone and was washed using a belt presser.