Biogas production’s yield through anaerobic digestion (AD) of coffee production firm

Coffee is one of the most cultivated plant and the one of the most produced beverage in the world. The wastes derived from its production as Coffee Seed Skin (CSS), Send Refuse (SR) and Coffee Product Refuse (CPR) present a high content of organic matter. AD represents the best technology to treat these wastes in order to obtain a stabilized sludge and, mainly, a biogas rich in methane. This work concerns on the experimental tests on coffee production refuses. They were crushed and mixed with tap water till to obtain the dispersion with a Total Solids (TS) concentration of about 10% w/w. The mixture was carried out in 45 L anaerobic reactor working in continuous mode and in mesophilic condition (38 °C) with a hydraulic retention time (HRT) of about 40 days. A biogas production of 0.7 L/L•day with a methane percentage of 65% v/v was obtained. It corresponds to a specific methane production of 820 L CH4/ kg ΔVS.