The increasing growth of palm oil industry results in an increase in the accumulation of waste generated from the industry, such as oil palm empty fruit bunches (OPEFB). OPEFB is a good source of renewable raw materials if a pretreatment process can overcome the recalcitrance of OPEFB and allows the fractionation of all carbohydrates and lignin. In this work, the effectiveness of organosolv pretreatment to deconstruct OPEFB and to recover high purity of lignin and glucan was studied. The pretreatment experiments were carried out at 210 °C for 90 minutes with a solid to liquid ratio of 1/10. Ethanol 50% (v/v) was used as solvent. The effect of H2SO4 0.07% (w/w) as catalyst was also studied. The results showed that organosolv pretreatment with the addition of acid increased the purity of glucan and lignin by 36 and 5%, respectively. A total of 65% lignin was recovered, which was 3.6 times higher than lignin from pretreatment without acid catalyst. After organosolv pretreatment with an acid catalyst, the crystallinity index (CRI) decreased by 54%, while the decrease in CRI was only 14.4% after pretreatment without an acid catalyst. The water retention value of the pretreated OPEFB with acid catalyst increased by 8%. It can be concluded that organosolv pretreatment using ethanol as a solvent with the addition of acid catalyst succeeded in fractionating OPEFB with high purity and reducing recalcitrant OPEFB.

The glucan-rich fraction, hemicellulosic compounds-rich fraction, and a mixture of both fractions obtained from organosolv pretreatment of oil palm empty fruit bunch (OPEFB) were used as substrates to produce volatile fatty acids (VFAs) in acidogenic fermentation. In this study, the effects of medium adjustment (carbon to nitrogen ratio and trace elements supplementation) and methanogenesis inhibition (through the addition of 2-bromoethanesulfonate or by heat shock) to enhance VFAs yield were investigated. The highest VFA yield was 0.50 ± 0.00 g VFAs/g volatile solid (VS), which was obtained when methanogens were inhibited by heat shock and cultivated in a mixture of glucan-rich and hemicellulosic compounds-rich fractions. Under these conditions, the fermentation produced acetic acid as the only VFA. Based on the results, the mass balance of the whole process (from pretreatment and fermentation) showed the possibility to obtain 30.4 kg acetic acid and 20.3 kg lignin with a 70% purity from 100 kg OPEFB. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.