Effect of the addition of residual glycerol in anaerobic digestion of starch and abbatoir effluents

Abstract

Anaerobic co-digestion consists in the mixture of two or more substrates with complementary features, with the advantage of higher methane yield rates and high removal of organic matter. Current assay quantifies and monitors the behavior of methane production and the removal of volatile solids by anaerobic co-digestion of starch and of the effluent of the red line of bovine laying down with residual glycerol of biodiesel production. The 1.6 L reactors were operated in batches with hydraulic retention time (TRH) of 21 days. A gasometer based on volume displacement of a NaOH solution by gas was employed to quantify methane production. High methane productivity and SV removal efficiency were obtained by anaerobic co-digestion of starch+glycerol with 0.17 ± 0.11 L methane L-1 reactor d-1 and 68 ± 1%, respectively. In the case of anaerobic digestion of the effluent of the red line + glycerol, methane productivity was 55% higher than control (without addition of glycerol), although the treatment had the lowest removal efficiency rate among all the assays. Residual glycerol as co-substrate increased the methane production rate and made possible cost decrease in the production of the biofuel and mitigation of environmental impacts.