The effect of pH adjustment together with different substrate to inoculum ratios on biogas production from sugar beet wastes in an anaerobic digester

Abstract

The effect of pH adjustment together with substrate to inoculum ratio on biogas production from sugar beet wastes, which are chopped parts of the sugar beet that do not go through the sugar extraction process, was investigated in a lab-scale batch reactor. The pH was set on 7, 8, and 9 for the first 4 days and 0.5:1, 1.5:1, and 2.5:1 substrate to inoculum ratios were used at the same time. There was one sample without pH adjustment for each substrate to inoculum ratio. The results showed that sugar beet wastes have good potential for biogas production. Whilst there was no biogas production in 2.5:1 substrate to inoculum ratio, pH adjustment made it possible to generate biogas. pH adjustment on 7 lead to approximately 1.87 and 10.48 times higher specific biogas production in 0.5:1 and 1.5:1 substrate to inoculum ratios, respectively. Methane content from anaerobic digestion of sugar beet wastes slightly increased with substrate to inoculum ratio increasing. The highest specific biogas production was recorded at a 0.5:1 substrate to inoculum ratio and pH adjustment on 7.