In 2020, STW committed to going operational net zero by 2030. Research has shown that one of the biggest individual challenges for us, is to mitigate the methane emissions from our bioresources plant; the greatest source of which being our post digestion sludge storage tanks. Since making this commitment, we have been developing a combination of monitoring techniques to better understand the rate of emissions from these tanks to inform some of the solutions we need to both characterise our process and guide our capital investment. The study examines methane emissions from sludge stored in secondary tanks at wastewater treatment plants using three types of treatment: conventional anaerobic digestion (AD), acid phase digestion (APD), and thermal hydrolysis process (THP). It combines laboratory tests (Residual Biogas Potential, RBP) and on-site methane flux monitoring to determine how much methane remains in the sludge and is emitted during storage. The goal is to develop specific emission factors for each treatment type. These factors can help estimate emissions at other facilities without direct measurements and guide emission reduction strategies throughout Bioresources.

To be presented in the 'Methane Emissions' session.