Performance of biogas production from coffee pulp waste using semi-continuous anaerobic reactor

Abstract

The abundant coffee pulp waste can be used as a potential biogas feedstock due to its high cellulose and hemicellulose content. However, it contains lignin that difficult to be digested and caffeine and tannin that cause severe effects on microbial activity inside the digester. Therefore, alkaline hydrogen peroxide (AHP) followed by rumen fluid pretreatment had been performed to remove those compounds and improve digestibility of the substrate. Moreover, the study obtained to find the reaction kinetics in biogas production from coffee pulp waste using a semi-continuous anaerobic reactor with HRT 20, 25, 30 and 35 days and a working volume of 1.5 L operated at 37 °C. In this study, the AHP pretreatment resulted in 75% of lignin removal, 57.76% of caffeine removal and a decrease in tannin until 0.54%. The highest methane yield obtained in this study was 0.24 L CH4 g VS−1. The kinetic constants (k) obtained were; k1 (reaction’s kinetic constant): 0.2923 day−1; k2 (maximum rate of soluble organics production/degradation): 720.1309 mg SCOD L−1 day−1; k3 (saturation constant): 253.2091 mg SCOD L−1 day−1; k4 (maximum rate of TVA consumption): 1,426.0831 mg TVA-COD L−1 day−1; and k5 (saturation constant): 57,794.4025 mg TVA-COD L−1 day−1.