Advancing N₂O Quantification towards Mitigation: Insights from France

The Climate Smart Utilities programme exists to showcase progressive global work on the topic of GHG emissions and the water sector.

This webinar presents work from a French collaborative initiative carried out within the framework of ASTEE (the French Scientific and Technical Association for Water and Waste). The initiative brings together water utilities, practitioners, and researchers to improve the quantification of nitrous oxide (N₂O) emissions across sanitation systems, including treatment processes, effluent discharge, and sludge management. The work develops revised quantification approaches based on operational data and practical experience. The presentations will highlight the methodology used to update emission factors, review the main emission pathways and key results, discuss remaining uncertainties, and conclude with perspectives on ongoing efforts to further refine N₂O quantification methods and support mitigation initiatives within the sanitation sector.

Wastewater Treatment Processes

• Two categories of N₂O emission factors were proposed for wastewater treatment technologies.
• Intensive biofilm technologies, including nitrifying BAFs, were found to exhibit higher N₂O emission factors compared with low-loaded activated sludge systems.
• The methodology was revised to relate N₂O emission factors to treatment performance, using the percentage of TKN removed.

Effluent discharge

• N₂O emissions from treated effluent discharge are explicitly included, extending the assessment boundary beyond the wastewater treatment plant.
• Emission factors for this stage are based on the IPCC approach and updated using published French data.

Sludge Management

• N₂O emissions from sludge management are explicitly considered, extending the assessment to sludge handling pathways.
• The approach builds on existing methods, while highlighting the limited availability of data for sludge-related emissions.

Practitioners from utilities, industry, and academics working on the topic of nitrous oxide monitoring and mitigation.

Participants will be able to:

• Recognise current knowledge gaps in N₂O emissions across sanitation systems
• Understand key considerations when developing N₂O emission factors at the sector scale
• Place their own N₂O-related work in the context of ongoing international research and practice

Moderator

• Erika Varga, IWA Climate Smart Utilities (CSU) (https://www.linkedin.com/in/erika-v-888349144/)

Speakers

• Ahlem Filali, INRAE, France (https://www.linkedin.com/in/ahlem-filali-05710bbb/)

• Romain Lemaire, Veolia, France (https://www.linkedin.com/in/romain-lemaire-281a2687/)

• Mathieu Sperandio, INSA Toulouse / TBI, France (https://www.linkedin.com/in/mathieu-sperandio-68708563/)