A recently published study, led by Sahar H. El Abbadi, reveals some startling conclusions regarding greenhouse gas emissions from U.S. wastewater treatment plants. The full research published in the interdisciplinary journal Nature Water. Dunn, who is co-chair of the McCormick School of Engineering’s Department of Civil and Environmental Engineering at Northwestern University, directs the Center for Engineering Sustainability and Resilience. He stresses that understanding the opposite—how wastewater treatment contributes to and can mitigate climate change—is crucial in informing and guiding effective decarbonization efforts.
That first-of-its-kind study shows that U.S. wastewater treatment plants are responsible for about 47 million metric tons of carbon dioxide (CO2) emissions per year. This figure shows just how consequential this sector is with respect to overall climate change, which Dunn argues should urgently be focused on. “A clearer picture of wastewater treatment’s contribution to climate change will help pinpoint where decarbonization efforts can be most effective,” Dunn stated.
The Scale of Emissions
Wastewater treatment plants are the unsung heroes of municipal public works, tirelessly cleaning 240 trillion gallons of water annually. Nevertheless, the analysis exposes a substantial environmental footprint. In fact, according to current government estimates, methane and nitrous oxide emissions are already underestimated by as much as 41%. Methane and nitrous oxide are two strong greenhouse gases, and their emissions from wastewater treatment have been underestimated up until now.
In fact, nitrous oxide was the biggest culprit shocker, making up 24% of the emissions found by the study. That’s equivalent to almost 12 million metric tons of CO2. This key finding sheds a light on the lack of accurate assessments for the emissions greenhouse gases from wastewater treatment facilities. Dunn underscored that these emissions are a huge sector—one that needs swift focus and movement.
The Role of Anaerobic Digestion
One prevalent way of treating these wastewater solids, or sewage sludge, is using anaerobic digestion. This method is favored for the efficiency it brings to waste management. It creates methane as a byproduct. This important aspect of wastewater treatment has not been fully realized in its role as a greenhouse gas emissions source.
The good news, as Dunn noted, is that there are real and tangible fixes to leaks and inefficiencies in these processes. Smart changes in technology and better operational practices can make a big dent in emissions coming from wastewater treatment plants. By focusing on these areas, facilities can contribute to lowering their climate impact while maintaining their essential function of cleaning water.
Pathways to Decarbonization
The results from this study indicate that at least at the federal‐level, there’s a defined path toward decreasing emissions from wastewater treatment plants. As Dunn explained, by first identifying where emissions are concentrated, we can pinpoint the places that need decarbonization strategies most urgently. This might mean replacing aging equipment, adding enhanced monitoring capabilities, or utilizing new ways to process or reduce waste.
The study’s approach can be used on any wastewater treatment plant that possesses the proper data. This model provides an incredibly useful blueprint for institutions across the country to assess their environmental footprint. By adopting these tactics, the freight industry can position itself in step with climate objectives at the national and global levels.