Methane emissions monitoring at wastewater treatment plants in Europe and Australia

Methane (CH₄) emissions from wastewater treatment plants (WWTPs) represent a significant greenhouse gas (GHG) source, challenging utilities aiming for net-zero carbon goals. The majority of the non-biogenic, direct (Scope 1) wastewater treatment plant emissions originate from i) nitrous oxide from the secondary wastewater treatment, and ii) CH 4 from the anaerobic degradation of wastewater and wastewater sludge. This study evaluates the effectiveness and suitability of various emissions measurement technologies and methodologies for quantifying methane emissions from wastewater treatment processes using data from monitoring trials conducted across treatment plants in Europe and Australia. The results provide a practical framework to guide utilities in selecting the most appropriate methods for monitoring and quantifying fugitive methane emissions from key sources such as open sludge storage, digesters, and sludge drying pans. . Findings across the 3 utilities indicate CH 4 losses of 5%-25% of total CH 4 production, with legacy assets like floating roof digesters contributing 245–2,200 tCO₂e/year. At Melbourne Water’s Eastern Treatment Plant (ETP), measurement campaigns found that the open sludge drying pans were a major source of emissions and a mobile survey mapping campaign measured site-wide emissions of 46,000–114,000 tCO₂e/year. Aarhus Vand’s Egå WWTP measured CH 4 losses at ∼7% of total CH 4 production, predominantly from vented sludge storage tanks. The study reviews advanced CH 4 measurement technologies, analysing emissions from WWTPs with sludge treatment centres. Normalised emissions key performance indicators are proposed, with discussions on limitations and mitigation strategies. Recommendations include tailored measurement methods, immediate leak detection and repair, and long-term investments in asset upgrades and alternative sludge treatment technologies.