Biogas Production from Sugar Beet Wastes in an Overload Bioreactor with pH Adjustment

Considering the importance of environmental protection and necessity of using new energy sources and innovative fuels, in this study, biogas production from sugar beet wastes using a batch lab-scale bioreactor was investigated experimentally.

All experiments were done at constant temperature of 37±1 oC with using water bath. Four reactors with the same feed concentration and condition put in a circulated water bath. pH was adjusted in the reactors for the first 4 days on 7, 8 and 9. Substrate to inoculum (S/I) ratio in the reactors was constant and equal to 6:1.

In the over load mono-digester system with high S/I ratio, due to the sharp drop in pH, biogas couldn’t be produced. By adjusting the pH, even for such a system, biogas production can be achieved, although the efficiency of the process is low. 

The results revealed that, whilst biogas was not produced in the reactor with high S/I ratio, pH adjustment made it possible to generate biogas. Mole fraction of methane in biogas produced in the reactors with pH adjustment were 35-50%. Biogas production occurred with long time delay, so that after 14 days, very little or no biogas was produced. Maximum volume of biogas was produced in reactor with pH=8. Whilst in the reactor with pH=9, biogas produced with high methane purity.