Stimulation of methane yield rate from food waste by aerobic pre-treatment

Aerobic pre-treatment (AP) was applied to enhance methane yield from food waste through anaerobic digestion. Different AP durations (i.e. 2, 5 and 8 days) prior to anaerobic digestion were tested. The results indicated that AP of food waste led to no significant differences (p > 0.05) in methane yield potential (ca. 418 mL/g-VS). However, a suitable AP duration (5 days) increased methane yield rates (ca. 18 mL/d/g-VS; 22.0% higher than the control) by anticipating methane generation and shortening the methanogenic phase via volatile fatty acid reduction and pH increase. Although AP induced chemical oxygen demand loss to some extent (i.e. by 2.6%–9.9%) in the AP stage via aerobic degradation, the methane yield potential could be recovered by enhancing organic matter hydrolysis. Therefore, maximisation of hydrolysis should be used as a basis for determining a suitable AP duration for various types of organic matter.