Taming Nitrous Oxide: Mobilising the Water Sector to Address Potent N₂O Emissions 

As climate targets become increasingly stringent, the water sector is turning its attention to a potent but often under-recognised greenhouse gas: nitrous oxide (N₂O). With a global warming potential 273 times greater than CO₂, N₂O — colloquially known as “laughing gas” — poses a serious challenge for wastewater utilities striving for climate neutrality. 

Workshop “Taming the Laughing Gas”

The 90-minute workshop brought together utilities, researchers, policymakers, and technology providers to explore full-scale strategies for monitoring, modelling, and mitigating N₂O emissions — and to envision a future in which climate-neutral wastewater treatment is standard practice. 

Opening the session, Johann Poinapen (KWR) emphasised the urgency of addressing N₂O emissions: “Our sector has made significant progress in improving effluent quality. However, N₂O remains the ‘sleeping giant’ of wastewater emissions. Achieving climate and CO₂ neutrality requires a targeted, science-based approach to this gas.”
While biological nitrogen removal processes are increasingly well understood, N₂O production remains a complex and variable phenomenon. Real-time monitoring technologies are still evolving, regulatory frameworks are lagging, and mitigation strategies are often site-specific. Nevertheless, the session demonstrated that viable solutions are emerging — and sector-wide momentum is building. 

Four Countries Share Practical Experience

The workshop featured contributions from leading practitioners in the Netherlands and the Nordic region, highlighting concrete approaches to N₂O monitoring and mitigation: 

• The Netherlands — Johann Poinapen (KWR) presented efforts by Dutch water boards to implement continuous N₂O monitoring and process optimisation, supported by the KWR-led TKI Watertechnologie N₂O project and the Versnellingsprogramma Lachgasreductie. 
• Sweden — Kristina Stark Fujii (Stockholm Vatten och Avfall) outlined Swedish utilities’ initiatives in N₂O measurement and reduction. 
• Denmark — Morten Rebsdorf (Aarhus Vand) discussed how Danish utilities are responding to evolving legislation and piloting technologies for N₂O decomposition and destruction. 
• Finland — Anna Kuokkanen (HSY) shared insights from continuous N₂O measurement and mitigation studies in the Helsinki metropolitan area. 

These case studies highlight the importance of integrating research, operational expertise, and digital innovation to transition from pilot projects to scalable implementations. 

Roundtables: Shaping the Sector’s Next Steps

Following the presentations, participants engaged in roundtable discussions focused on four strategic themes: 

• Measurement Standards Development and application of robust standards for measuring N₂O across gas, liquid, and anoxic phases, including best practices for installation, maintenance, and data evaluation. 
• Knowledge Gaps & Modelling Identifying gaps in the understanding of N₂O formation and improving predictive models for emissions. 
• Mitigation & Destruction Evaluating effective methods for reducing or eliminating N₂O emissions, considering feasibility, cost, and monitoring requirements. 
• Collaboration & Synergies Strengthening cross-sector and cross-border collaboration to accelerate N₂O mitigation and scale successful approaches. 

These discussions fostered candid dialogue and practical exchange. Engineers and operators shared field experiences, researchers debated data quality and metadata needs, and policymakers explored the role of future EU standards. Technology providers gained valuable insights into utility needs and priorities. 

KWR and partners at NORDIWA 2025: participants engaged in roundtable discussions about key aspects of N₂O emission management.

Technology, Data and Collaboration: Key Takeaways

Three core messages emerged from the session: 

• Standardised measurement is key — Reliable data is the foundation for effective mitigation. 
• Digital tools enable control — Real-time sensors and machine learning are already delivering measurable reductions in N₂O emissions at pioneering sites. 
• Collaboration drives progress — Alignment between utilities, researchers, technology developers, and regulators is critical to co-developing scalable solutions. 

Beyond technology, the workshop emphasised the importance of trust, knowledge sharing, and international cooperation — principles that KWR actively promotes. 

Workshop on key aspects of N₂O emission management

Beyond facilitating the workshop, KWR contributed to the broader NORDIWA programme through two technical presentations by Siddharth Seshan (KWR), focusing on key aspects of N₂O emission management: 

• Predictive Modelling of N₂O Emissions: Biokinetic, Artificial Intelligence and Hybrid Models for Wastewater Treatment
  This presentation showcased recent advancements in N₂O modelling, based on Seshan’s PhD research. It explored various modelling approaches — including biokinetic, AI-based, and hybrid models — aimed at improving the forecasting and control of N₂O production in wastewater treatment processes. 

• Robust Long-Term Monitoring, Advanced Analytics, and Comparison of Nitrous Oxide Emissions Across Wastewater Treatment Process Configurations
  Drawing on results from the KWR TKI Watertechnologie N₂O project, this presentation highlighted insights from extensive monitoring campaigns and data analyses. It included findings from recent fieldwork at RWZI Utrecht and Nieuwe Waterweg, offering comparative perspectives on emissions across different treatment configurations. 

These contributions reinforced the importance of combining scientific rigour with operational relevance — a hallmark of KWR’s approach to climate-focused water research. 

Why N₂O emission management matters

Wastewater treatment plants operate at the nexus of climate mitigation, public health, and resource recovery. As more countries adopt carbon neutrality targets, utilities must be equipped to monitor, reduce, and ultimately eliminate N₂O emissions.
KWR will continue to collaborate with European partners through initiatives such as the TKI Watertechnologie N₂O project and the Versnellingsprogramma Lachgasreductie. These efforts aim to advance standardised measurement, improve modelling, and implement actionable mitigation strategies.
The NORDIWA 2025 workshop reaffirmed the sector’s commitment to climate action — and demonstrated that addressing N₂O emissions is not only necessary, but entirely achievable.