Co-digestion of food waste and algae biomass for biogas production.

Completely-mixed, research scale mesophilic anaerobic dirters were fed food-waste or food-waste co-digested with algae at organic loading rates (OLR) of 2 to 5 gVS L(-1)d(-1) and co-substrate fractions of 10% to 25%. Digesters fed food waste alone yielded biogas production rates of 1.1 to 2.5 LL(-1)d(-1), with biogas yields of 245 to 1,127 mL gVS(-1). Digesters fed food-waste with algae yielded biogas production rates of 1.2 to 2.7 L(-1)d(-1), with biogas yields of 240 to 947 mL gVS(-1). Digesters fed food alone at an OLR of 2.5 gVS L(-1)d(-1) or lower were stable while digesters fed a combination of algae and food-waste remained stable at loading rates up to 4 gVS L(-1)d(-1) as evidenced by digester volatile fatty acid concentrations. It was found that adding algal biomass to food waste can improve digester stability, but it does so at the expense of reduced specific gas yields.