Techno-Economic Assessment of Biochar Production from Sewage Sludge as a Climate Change Mitigation Strategy

Municipal sewage plants generate sewage sludge as a by-product resulting in the sludge accumulation and potential waste management challenges. Sewage sludge has the potential to generate greenhouse gases such as methane and carbon dioxide, which can potentially contribute to climate change. This study focused on the techno-economic evaluation of the production of biochar from sewage sludge as means of both waste valorization and mitigation of climate change. The sewage sludge contained 24–26 wt. % of total solids and carbonization to biochar was done at an optimum temperature 500 °C resulting in a biochar with a moisture content of 13.7%, fixed carbon content of 8.8%, and particle size of 1.5 mm. A process for the production of biochar from waste sewage sludge was then proposed with a biochar yield of 74.5%. Preliminary cost estimation for a plant which can process 9600 kg/day of sewage sludge to produce 2.8 tons/day of biochar indicated that the process is economically viable with a 41.2% return on investment and a payback period of 2.4 years.