Optimising the production of energy from coblended food waste and biosolids using batch reactor studies

Energy production from a coblended mixture of biosolids and food waste was optimised for hydrogen and methane production. Four different blends were prepared by varying the carbohydrate:protein (carb:pro) ratios. The biosolids contained a low carbohydrate fraction and so was not suitable for hydrogen production when used alone. However coblending this waste with a carbohydrate-enriched food waste produced a greater hydrogen yield, making this option viable. Batch studies showed that the optimised mix had a biosolids concentration of 25.7% (w/w). The largest hydrogen yield of 198.5mL/gVSremoved was observed when the carb:pro was 2.78, and this was threefold higher than the other carb:pro ratios evaluated in this study. The digestate recovered after hydrogen recovery had a C:N of 17.5, which is in the ideal range for methane production. The biochemical methane potential test showed a methane yield of 239mL/gVSremoved, and the total volatile solids destruction following two-phase hydrogen and methane production was 93%.