BIOMASS CONVERSION AND BIOREFINERY, vol.13, no.3, pp.2449-2458, 2023 (SCI-Expanded)
Thermal energy content of sewage sludge offers opportunities in terms of energy production. Incineration is extensively used for energy conversion of sludge. Dewatered sludge needs to be dried prior to incineration or supplementary fuel should be supplied to the incinerator. Energy production rate is exaggerated when dryer energy is neglected. Net energy production rate depends on dryer energy consumption. The effect of the dryer energy consumption on the net energy production is not emphasized. Energy consumption data of the sludge management process is collected from wastewater management utilities. Thermal and electrical energy conversion of sludge is studied within a scenario analysis. Energy consumption of the examining drying plants (11000-3900 kJ/kg water) is higher than literature (4320-3000 kJ/kg water) data. In order for the dewatered sludge to be burned and dried with its own energy (90% solid), the ratio of its lower calorific value to the specific energy consumption of drying should be 2.8. Net energy production with fully dried sludge is only possible in Plant 4. In the case of auto-thermal combustion, with partially dried (50% solid) sludge, net energy production is possible in 3 of the 4 plants examined. Twenty-five to seventy-five percent of the energy consumption of the wastewater treatment plant can be met by electricity generated using biogas and sludge.