Calorific Characterization of Faecal Sludge and its use as a Fuel

Using faecal sludge (FS) as a fuel to provide energy for industry processes could help to solve both the sanitation challenge and reliance on unsustainable or expensive fossil fuels. This research aimed at testing the viability of using FS as a solid fuel - an end use that could unlock an environmentally and financially beneficial replacement for costly, disposal-oriented FS management solutions. To determine the average calorific value of FS, samples were collected from sanitation systems in Kampala, Uganda and were tested for calorific value, total solids, total volatile solids, moisture content, ash content, biochemical oxygen demand (BOD) and chemical oxygen demand (COD). Calorific value of FS was 17.2 MJ/kg dry solids (DS), which compares well with other commonly used fuels such as rice husks at 15.6 MJ/kg DS, forest residues at 19.5 MJ/kg DS, coffee husks at 19.8 MJ/kg DS, and sawdust at 20.9 MJ/kg DS. For industries to derive net energy from FS at 17.2 MJ/kg DS, the sludge must be dried to 27% dry solids. The TS of FS from drying beds in Kampala was above 30% of wet weight after two weeks, indicating that additional energy for drying the FS can be harnessed.