Carbonization of excess sewage sludge using superheated water vapor to produce fuel

Excess sewage from activated sludge treatment of municipal wastewater is considered one of the most severe solid waste problems. The excess sewage sludge with 64% moisture content was converted to valuable material throughout the superheated water vapor carbonization process. The superheated water vapor carbonized the excess sewage sludge using a bench-scale Rotary Kiln setup to make fuel at 200°C, 250°C, 300°C, 350°C and 400°C. The effect of carbonization with superheated water vapor on the yield and heating value of fuel was studied. In 1 h treatment, organic waste lost about 70% of its original weight due to volatile release during carbonization. The yield of carbonization decreased when the temperature of carbonization increased. A carbon, hydrogen, nitrogen, and sulfur (CHNS) analyzer was used to measure the elemental composition of the carbonized product. The heating value (LHV) of the fuel carbonized at 250°C was 15.0 MJ/kg, determined by a bomb calorimeter. Thus, this study has shown that instead of the landfill, excess sewage sludge can be utilized using superheated water vapor for conversion to fuel