An Experimental Study on the Effects of Oxygen in Bio-Gasification- Part 1

Abstract

An experimental study was carried out to understand the possible impacts of limited aeration in an anaerobic bio-gasification process. A number of anaerobic bioreactors were operated at 35 C, both under semi-continuous and batch feed modes, with different oxygenation loads. Two series of batch experiments clearly indicated an increasing methane yield in the range of oxygenation loads of 0 – 16 % (% O2 of COD input). In the semi continuous feed mode, four completely mixed bioreactors operated under oxygenation levels of 0, 1.3, 2.6 and 3.9 % produced biogas at approximately equal level and constant rates. The methane generation rate at the low oxygenation level of 1.3 % was higher than the strict anaerobic condition, while higher oxygenation levels induced increasingly negative impact on methane production. Accumulation of volatile fatty acids at the start up of the continuous feed reactors was lower for the aerated than the strict anaerobic reactor. The positive effect of oxygen on methane production has a much larger range in the batch feed mode compared to the semi-continuous feed mode. This suggests that methane production can be optimized by some limited aeration in the first of two or more stages of anaerobic digestion.