Anaerobic Co-Digestion of Fats, Oils and Grease (FOG) with Waste Activated-Sludge

Two mesophilic batch digestion runs were set-up in which a FOG is co-digested with waste activated sludge. FOG loadings range from 0 to 50% of the VS. This co-digestion of FOG and activated sludge successfully increased the biogas production up to 400% when the FOG loading consisted around 50% of the VS. An inhibition effect was observed in one of the tests when the FOG loading was over 25% of the VS, apparent from a drop in methane yield per VS. Additionally, a beneficial co-digestion effect was observed at FOG loading of 25% of the VS when the measured biogas production was compared to the maximum predicted biogas production. This indicates a possible enhancing effect on the sludge degradation.