Investigating the sustainability of biogas recovery systems in wastewater treatment plants- A circular bioeconomy approach

Abstract

Advanced wastewater treatment options offer a unique opportunity to recover valuable resources such as energy (biogas), nutrients, and minerals embedded in the wastewater streams. However, considerable challenges remain when designing and planning sustainable wastewater treatment systems. This study aims to evaluate the sustainability of waste-to-energy (WtE) recovery in the form of biogas in a wastewater treatment plant (WWTP). The study investigates the performance of a biogas recovery system in different scenarios and applications from 2018 to 2040, considering the city of Tbilisi in Georgia. The study results reveal a significant biogas production potential, with an average annual energy (heat and power) generation of 137 GWh when biogas is recovered from the wastewater (WW) and sewage sludge (SS). The WWTP-based WtE systems can avoid up to 38,500 tCO2eq emissions every year. The combined recovery (from WW and SS) scenario is financially feasible with a net present value of 14.88 million EUR and a levelized cost of biogas of 0.08 EUR/m³. Recovered biogas can help avoid the usage of 172.34 million m³ of natural gas worth 42.4 million EUR. Sensitivity analysis shows that the quality of wastewater, price of energy, and capital cost of the anaerobic digestion plant are the key factors in determining the economics of WtE recovery systems. This research also demonstrates the interlinkages between sustainable development goals and various benefits of resource recovery systems. This study could be helpful for decision-makers involved in planning and deploying resource recovery systems in a circular bioeconomy approach in WWTPs globally.