Disruption of Oil Palm Empty Fruit Bunches by Microwave-assisted Oxalic Acid Pretreatment

Abstract

Abstract. Developing an effective pretreatment for the conversion of lignocellulosic biomass to ethanol is an important effort in reducing the cost of this process. Microwave-assisted pretreatment is considered a green technology that can effectively break down lignocellulosic structures. The objective of this study was to investigate the most effective temperature for microwave-assisted oxalic acid pretreatment regarding the structural characteristic changes of oil palm empty fruit bunches (OPEFB) fibers. The fibers were subjected to microwave-assisted oxalic acid pretreatment at 160-200 °C with 2.5 minutes heating time and a liquid to solid ratio of 10. The effectiveness of the pretreatment was determined based on its delignification selectivity, morphological characteristics, and functional group changes. Microwave irradiation of OPEFB fibers at 180 ºC was effective in increasing the cellulose content by 24%. This pretreatment resulted in 1.82 delignification selectivity. More than 50% of the hemicellulose of the OPEFB was removed after this treatment, which was confirmed by a decrease of the absorption bands of functional groups at 1732 cm -1 . The increase of pretreatment temperature disrupted the morphological structure of the OPEFB and removed its hemicellulose but did not change its functional groups and lignin content.

Pretreatment of Oil Palm Empty Fruit Bunch (OPEFB) at Bench-Scale High Temperature-Pressure Steam Reactor for Enhancement of Enzymatic Saccharification

“…These compounds have similar structures and behaviours with extractives (de Carvalho et al, 2015). This phenomenon was also reported in acid pretreatment of OPEFB (Solihat et al, 2017), and hydrothermal pretreatment of eucalyptus (de Carvalho et al, 2015). The number of inorganic compounds in OPEFB is presented as ash content.…”

“…An effective pretreatment is indicated from the ability to remove lignin and preserve cellulose during pretreatment. Therefore, higher DS values indicate more effective pretreatment process while a low DS value means a relatively high loss of cellulose occurred during pretreatment compared to lignin (Fatriasari et al, 2014;Solihat et al, 2017). Table 2 also shows that the higher the temperature, the lower the DS value.…”

“…where t is the reaction time (min), T is the temperature (°C), 100 is the reference temperature, and 14.75 is the fitted value of the arbitrary constant. The ratio of lignin loss to cellulose loss during pretreatment was calculated to determine the delignification selectivity (DS) (Fatriasari et al, 2014;Solihat et al, 2017). The component loss was calculated following Eq.…”

Optimization of Xylose Production from Sugarcane Trash by Microwave-Maleic Acid Hydrolysis

“…The experiments at those points were conducted in duplicates. The ranges of acid concentration (0.5-2%), temperature (170-200 °C), and heating time (2-8 min) for the optimization were selected based on our previous experiments on microwave-maleic acid pretreatemnt of some biomass, such as sugarcane bagasse, oil palm empty fruit bunch, and sugarcane trash (Sari et al, 2016, Solihat et al, 2017, Fatriasari et al, 2018, Anita et al, 2019. The quadratic second order polynomial model was fitted to the data by multiple regression análysis as follows.…”

“…Microwave heating has been proved more efficient than conventional heating, because the heating process using microwave is direct, uniform, and faster (Tsubaki et al, 2013, Ohashi andWatanabe, 2018). The use of organic acids, such as maleic or oxalic acid, in the fractionation of lignocellulosic biomass has been reported by Kootstra et al, 2009;Jung et al, 2014Jung et al, , 2015Barisik et al, 2016;Kundu and Lee, 2015;Solihat et al, 2017;Fatriasari et al, 2018;Anita et al, 2019). However, they mostly focused on the effects of the pretreatment on the enzyme susceptibility of the solid residues resulted from pretreatment.…”