Producing Bio-electricity and Bio-heat from Urban Sewage Sludge in Turkey Using a Two-Stage Process

This study investigates the bio-electricity and bio-heat production potential of an urban wastewater treatment plant using biogas-engine powered cogeneration system and fluidized bed sewage sludge incineration system operating data. The facilities of the Gaziantep Metropolitan Municipality Central Wastewater Treatment Plant were used as case studies. The operating data of the plants was analyzed to perform thermodynamically qualitative and quantitative assessments of the energy recovery potential. Wastewater treatment plant digests 68.26 kg of sludge with a dry matter content of 8.0% for each 1 m(3) of biogas. The annual production of the cogeneration plant is 8.760 GWh, which corresponds to an annual biogas consumption of 3,400,000 m(3). For each 1 kWh of electricity produced in the biogas-engine, 0.387 m(3) of biogas with a methane content of 60% is consumed. The average energy produced in the fluidized bed sludge incineration plant is 10,240,000 kcal/hour in the winter and 7,700,000 kcal/hour in the summer. On the other hand, the average energy consumed in the incineration plant 4,900,000 kcal/hour in the winter and 4,800,000 kcal/hour in the summer.