Study of wet in situ transesterification of spent coffee grounds with supercritical fluid for the production of biodiesel

Abstract

Conventional biodiesel production processes inevitably require catalysts and pre-drying of the feedstock due to the hindrance effects of water. This study produces biodiesel from wet spent coffee grounds (SCGs) with supercritical fluids without any catalyst or initial drying process. Supercritical methanol and subcritical water effectively produced biodiesel via in situ transesterification by inducing mesoporous SCG particles, resulting in the enhancement of lipid extraction and conversion efficiency. Space loading, initial moisture content and methanol to wet SCG ratio were the critical factors for biodiesel production. A maximum biodiesel yield of 10.17 wt.% of dry SCG (86.33 w/w % of saponifiable lipid) was acquired at conditions of 270 oC, 90 bars, methanol to wet SCG ratio 5:1, space loading 58.4 ml/g and 20 min. Direct use of extracted coffee waste as feedstock for biodiesel production reduces environmental problems generated by landfill accumulation.