Uncovered Greenhouse Gas Emissions from Wastewater Treatment Plants in Sweden

Strategic Insights -

Researchers at Linkoping University in Sweden have made a significant discovery about the greenhouse gas emissions from wastewater treatment plants (WWTPs) using anaerobic digestion (AD). According to the study, WWTPs emit significantly more greenhouse gases than previously estimated, with sludge being a major source of both methane (CH4) and nitrous oxide (NO). The research, published in Environmental Science & Technology, highlights the need for more accurate emission measurements and for WWTP managers to take effective mitigation measures.

Key Takeaways:

  • Wastewater treatment plants (WWTPs) in Sweden emit 2.4-fold higher greenhouse gases (GHGs) than previously estimated, with combined CO-equivalent emissions from CH4 and NO being 2.4-fold higher than IPCC-recommended emission-factor-based estimates.
  • Sludge storage is a significant source of GHGs, with NO emissions from sludge contributing to half of the total CO-equivalent sludge emissions and being 9% of the CH emissions by weight.
  • The use of anaerobic digestion (AD) in WWTPs may increase emissions, and thus, mitigation is needed to reduce fossil fuel use and greenhouse gas emissions.
  • Accurate emission measurements are crucial for setting effective mitigation priorities, and drone-based measurements can facilitate flux observations by WWTP managers.
  • The study's findings emphasize the importance of monitoring and managing GHG emissions from WWTPs, particularly in the context of increasing AD in WWTPs.

Statistics:

  • Combined CO-equivalent emissions from CH4 and NO from WWTPs with AD and sludge storage were 2.4-fold higher than IPCC-recommended emission-factor-based estimates.
  • NO emissions from sludge contributed to half of the total CO-equivalent sludge emissions.
  • 9% of CH emissions by weight were NO emissions from sludge.
  • The study concluded that sludge was a major source for both CH4 and NO.

Sources:

  • In Situ Observations Reveal Underestimated Greenhouse Gas Emissions from Wastewater Treatment with Anaerobic Digestion - Sludge Was a Major Source for Both CH4 and N2O. Environmental Science & Technology, 2025;59(34):18146-18155.
  • NewsRx. Data on Science Reported by Researchers at Linkoping University (In Situ Observations Reveal Underestimated Greenhouse Gas Emissions from Wastewater Treatment with Anaerobic Digestion - Sludge Was a Major Source for Both CH4 and N2O). Global Warming Focus. September 15, 2025; p 26.