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Coconut husk (CCH) as an abundant agricultural waste in Indonesia has the potential to be utilized for sugar production, which is the intermediate product of biofuel. In this study, subcritical water (SCW) assisted by nitrogen (N2) was developed to enhance the enzymatic hydrolysis of CCH. SCW process was optimized by varying the operation condition: the pressure of 60-100 bar, the temperature of 150-190 °C, and the time of 20-60 min. The SCW-treated solid was subsequently hydrolyzed by utilizing a mixture of commercial cellulase and xylanase enzymes. The result shows that the optimum total sugar yield was obtained under the mild condition of SCW treatment, resulting in the sugar of 15.67 % and 10.31 % gained after SCW and enzymatic hydrolysis process, respectively. SEM and FTIR analysis of SCW-treated solid exhibited the deformation of lignin and solubilization of cellulose and hemicellulose, while XRD and TGA revealed an increase of the amount of crystalline part in the solid residue. The use of N2 in SCW treatment combined with enzymatic hydrolysis in this study suggested that the method can be considered economically for biofuel production from CCH waste in commercial scale. Copyright © 2020 BCREC Group. All rights reserved

In this study, the optimization of microwave-assisted alkaline (MAA) pretreatment is performed to attain the optimal operating parameters for the delignification of cocoa pod husk (CPH). The MAA performance was examined by heating the CPH solid with different particle sizes (60–120 mesh) and NaOH solution with a different sample to a solvent (SS) ratio (0.02–0.05 g/L), for short irradiation time (1–4 min). Box-Behnken Design (BBD) was utilized to optimize the percentage of lignocellulose composition changes. The results show that by enlarging particle size, the content of lignin and cellulose decreased while hemicellulose increased. By prolong irradiation time, the content of lignin and hemicellulose decreased while cellulose elevated. On the other hand, increasing the SS ratio was not significant for hemicellulose content changes. From FTIR and SEM characterization, the MAA drove the removal of lignin and hemicellulose of CPH and increased cellulose slightly. Supported by kinetic study which conducted in this work, it was exhibited that MAA pretreatment technology is an effective delignification method of CPH which can tackle the bottleneck of its commercial biofuel production. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA   License (https://creativecommons.org/licenses/by-sa/4.0).

Coconut husk hydrolysis using subcritical water (SCW) with N2 as pressurizing gas was carried out in a batch reactor at temperature of 150 °C-190 °C, at pressure of 60-100 bar and the reaction time from 20-60 min. The effect of SCW pretreatment could reduce lignin and produced reducing sugars. The highest TRS (total reducing sugar) yield was 0,4904 at 170 °C, 80 bar, and the reaction time of 20 min. Reducing sugars concentration increased when temperatures rised from 150 to 170 °C. However, reducing sugar concentration decreased at temperature above 170 °C. The decrease of reducing sugar was due to degradation of reducing sugars into its degradation products. A first-order reaction model was determined to describe the reaction rate constant of the formation of reducing sugar and its degradation products. Kinetic parameters were obtained by fitting the proposed equation with the experimental data. The reaction rate constant increased when temperature increased from 150 to 170 °C, but then decreased when the temperature increased above 170 °C. Activation energy was also determined based on the Arrhenius equation.