March 5. 2024. 1:41

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Process gas emissions: Untapped opportunities to mitigate climate change


Wastewater collection and treatment are essential to protecting both public health and the environment. The latest EU proposal for a revised Urban Wastewater Treatment Directive (UWWTD) is a step forward in ensuring the protection of our water resources, and, ultimately, the health of our citizens.

Alexis de Kerchove is the Senior Director for Client Sustainability at Xylem.

However, wastewater treatment comes at an unforeseen environmental cost that is critical in today’s climate crisis. Worldwide, water utilities account for 2% of greenhouse gas emissions, equal to the total emissions for the shipping sector. Specifically, the emission of process gases like nitrous oxide and methane from wastewater and sludge treatment make up 70% of a plant’s total greenhouse gas emissions.

Nitrous oxide is particularly harmful and has a global warming potential almost 300 times higher than that of carbon dioxide. As we work to reduce our emissions, meet net-zero goals, and protect the future of our planet, the impact of essential processes like wastewater treatment cannot be ignored.

This is why we strongly recommend that the revised UWWTD include a requirement for process gas monitoring. Failing to regulate these emissions would be a missed opportunity to address a significant contributor to climate change.

What Solutions Are Available Today?

The good news is that solutions to this problem are available today, but they require action from policymakers and the water sector. Increased awareness of the impact of nitrous oxide on global warming over the last five years has accelerated the development of monitoring and mitigation technologies.

In a recently published position paper, technology and application experts bring the knowledge and references needed for building credibility on the viability of this monitoring requirement. This opinion invites all stakeholders to connect and learn about the technical and commercial availability of process gas monitoring solutions.

Online sensors, biokinetics and flow mechanics advance, and modelling approaches offer reliable and affordable solutions for monitoring real-time emissions of process gas in wastewater treatment. Multiple full-scale references and mitigation case studies from leading water utilities support the importance of process gas monitoring. Recent full-scale work in Australia and Denmark has reported sustained emissions reductions of 35% and 74% in published studies

But we can go one step further. There are also significant untapped opportunities to develop treatment process optimisation tools and potentially close-to-eliminate process gas emissions entirely. To do this, we need to understand nitrous oxide emissions through site-level monitoring.

Only with a requirement for nitrous oxide monitoring within the UWWTD proposal will Member States be able to accelerate the development of technology needed for advanced wastewater treatment.

Why Now?

It’s critical that this happens soon. The biological processes and plant infrastructures that are responsible for greenhouse gas emissions are widely implemented in Europe, and it would not be conceivable to replace them with alternative treatment within the next 50 years. Therefore, it’s essential to simultaneously advance wastewater treatment and implement readily available monitoring and mitigation solutions to start lowering emissions from our current and future infrastructure.

To make this happen, there needs to be regulatory support. We recommend that Member States be required to monitor the emissions of all process gas, including nitrous oxide, produced by water utilities. This will provide the regulatory framework required to start tackling emissions of nitrous oxide, the greenhouse gas almost 300 times more harmful than CO2.

We can make a profound difference by improving the proposed UWWTD and bringing impactful policy approaches that create a more sustainable Europe for future generations.

More detailed and technical information can be found in the Position Paper drafted by a coalition of technology and application experts, including AM-Team, Bentley, Cobalt Water Global, Jacobs, Ragn-Sells, Royal HaskoningDHV, Suez, Unisense, Variolytics, Veolia and Xylem.