Biodiesel production from spent coffee ground by in-situ transesterification with solvo-thermal effect of chlorine-containing organic co-solvent

Abstract

This study aimed to recycle the spent coffee ground, which is an underutilized municipal waste although it has a high lipid content. Wet spent coffee ground was used to make the biodiesel without energy-intensive drying process and use of an external catalyst by in-situ transesterification and solvo-thermal effect of 1,2-dichloroethane. Response surface methodology was applied to demonstrate the optimal condition and effects of process variables such as water content, reaction temperature on the biodiesel yield were investigated. A trade-off between water inhibition and hydrolysis of chlorine-containing co-solvent was found and 11.8wt.% fatty acid alkyl ester based on the dry mass of spent coffee ground was yielded at the optimal ($196.8^\cir C$, 3.36 mL EtOH/g dried SCG, 3.16ml DCE/g dried SCG). Solvo-thermal in-situ transesterification leaded the physical and chemical change of spent coffee ground to a favorable structure for extraction and conversion by disrupting particles, increasing surface area to volume ratio due to the size reduction and decomposing cellulose.