Coffee extract residue for production of ethanol and activated carbons

Abstract

Biomass as a waste product in the form coffee extract residue (CER) has been shown to have potential for the dual purpose of ethanol production and preparation of activated carbons. A straightforward method of direct hydrolysis and fermentation (DHF) is considered as the main option utilized in this study for the generation of fuel ethanol from the biomass waste. Factors such as loadings of saccharomyces cerevisiae, temperatures (21 and 30 °C) and substrate content were investigated to maximize the yield of ethanol. Ethanol production rates between 1.1 g and 0.70 g h−1 kg−1 without pretreatment and 2.7 and 2.3 g h−1 kg−1 dry substance with mild treatment were obtained, respectively. The CER was also used to prepare activated carbons using both chemical and physical activation methods. The effects of process parameters such as temperatures and concentrations of acid were varied and determined as to the yield, BET-surface areas and porosities of the final product. H3PO4 treatment at 600 °C and steam treatment at 700 °C show maximum surface area of >640 m2 g−1 with increased total pore and micropore volumes.