Investigating the effect of anaerobic co-digestion of fecal sludge and cooked food waste for biogas production

Abstract

Fecal sludge management (FSM) in Uganda is inadequately implemented because of inaccessibility to sanitation facilities and high FS emptying costs, among other factors. Equally, food waste from markets and restaurants contributes to solid waste management challenges especially in urban congested settlements. This study focused on investigating the synergetic effect of co-digestion of fecal sludge and cooked food waste under mesophilic temperatures to generate biogas for energy production and nutrient-rich bio-slurry for agricultural purposes. The experiment investigated three co-digestion ratios of 1FW:1FS, 1FW:3FS and 100% FS based on total solids percentage in each substrate using 30 L batch reactors (28 L working volume). The AD process took 40 days. Process stability and performance were investigated by monitoring pH, biogas volume and methane content. The final digestate quality was investigated through analysis of pH, nutrient content (N, P, and K). The findings reveal average methane percentage for the compositions 1FW:1FS, 1FW:3FS and 100% FS as 54.8%, 20% and 27.6% respectively. Remarkably, the 1FW:3FS mixture gave the highest biogas volume, exceeding or equaling 0.5 liter per day. The digestate had a pH range of 4.99 to 6.4 across the mixtures, along with nutrient compositions in the range 0.346% to 2.325%N, 0.073% to 1.375% P,0.824% to 1.16% for K.