Environmental and techno-economic analysis of the integration of biogas and solar power systems into urban wastewater treatment plants

Abstract

This study analyses the environmental and economic benefits of integrating renewable energy sources (RES), biogas and solar energy into urban wastewater treatment plants (WWTPs). The energy intensity (kWh/m3) of the selected 456 WWTPs in Turkey was evaluated according to type and treatment process. The energy intensity of primary WWTPs (0.066–0.335 kWh/m3) is lower than that of secondary (0.075–1.361 kWh/m3) and advanced WWTPs (0.147–0.988 kWh/m3). RES integration is investigated using energy system optimization software for a sample of 25 WWTPs. Six scenarios were developed based on different CO2 emission penalties (0 and 16 USD/ton) and prices for selling electricity to the grid (0.000, 0.050, and 0.133 USD/kWh) to demonstrate the impact of market-based instruments. RES integration is cost-effective for secondary and advanced WWTPs with a flow capacity above 1 million m3/y. Market-based instruments are found to significantly influence the decision to integrate, generate and use renewable electricity at WWTPs. The RES integration can meet up to 88% of the annual energy demand of the WWTPs at an electricity selling price of 0.133 USD/kWh. When no market-based instruments are implemented, RES generation can reach up to 23% of the WWTPs' annual energy demand while reducing CO2 emissions by 15%.