Application of Waste Glycerin Liquid Produced from Bio-diesel Production to Methane Fermentation

Abstract

In bio-diesel production, waste glycerin liquid containing methanol and potassium is produced as a byproduct. At present, this waste liquid is treated by burning. In consideration of the effective use of degradable organic substances such as glycerin and methanol, the possibility of applying waste glycerin liquid to methane fermentation was studied. In the experiments for this study, the decomposition rate of COD_cr was more than 80% and fermentation obstruction did not occur. The methane gas production rate per 1 g of COD_cr decomposition was 0.51 Nl-dry. This rate nearly coincides with the theoretical rate. It is also necessary to keep nutrients such as nitrogen and phosphate and solids at suitable concentrations for successful methane fermentation. However, since waste glycerin liquid contains no solids and less nitrogen and phosphate, kitchen waste was mixed with waste glycerin liquid to compensate for the lack of nutrients and solids.