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

Authors

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 oC, 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.