Steam explosion pretreatment improved the biomethanization of coffee husks.

Abstract

This study evaluated the potential of energy generation using a combined heat and power co-generation system (CHP) from biogas produced during the anaerobic digestion of coffee husks (CH) pretreated with steam explosion. Pretreatment conditions assessed were time (1, 5, 15 and 60 min) and temperature (120, 180 and 210 °C). Polysaccharides solubilisation and biogas production were not correlated. While pretreatment with severities higher than 4 resulted in a highest solubilisation of cellulose, hemicelluloses and lignin; however, furans concentration in those cases hindered biomass biodegradation. Considering a CHP, all pretreatment conditions were worthwhile when compared to non-pretreated CH. The best condition was 120 °C for 60 min, in which a 2.37 severity showed the highest methane yield (144.96 NmL CH4 g COD−1) and electricity production (0.59 kWh kg CH−1). However, even better results could be achieved using 120 °C for only 5 min, which would lead to a larger amount of CH daily processed.