Anaerobic digestion of coconut copra: methane generation potential

Abstract

Pacific Island countries rely heavily on imported, expensive and unsustainable fossil fuels as their primary source for energy production. Establishing an alternative energy source from local resources would have considerable benefits; thus, the purpose of this research was to investigate the biogas generation potential of coconut copra during anaerobic digestion. Both batch and semi-continuous stirred tank reactors (SCSTRs) were investigated to optimise methane (CH4) production and increase overall conversion efficiency. The results suggest that coconut copra is amenable to anaerobic digestion with high theoretical methane yields available from the substrate’s high lipid content. However, the optimal organic loading (OL) was limited to within a narrow range of 3·6–6·0 g volatile solids (VS) (2·4–4·0 g VS/L reactor) for the batch reactors. A maximum of 0·420 L CH4/g VS was achieved at an OL of 3·6 g VS. High average methane yields of 0·708 L CH4/g VS·day were also successfully achieved for the SCSTRs, whereas increased mixing improved methane production.