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A Critical Decade: removing greenhouse gases from wastewater treatment

This is the decade to deliver greenhouse gas emissions mitigation and climate change adaptation to meet the goal of the Paris Agreement – to keep global average temperature rise well below 2oC. Our “A Critical Decade” blog series marks Water UK’s publishing of views on issues which are fundamental to the delivery of Net Zero.

The urgency and pressure facing humanity at COP26 is immense – we need to find the solutions that act fast, cut deep, and encourage others to join in.

This thought rings true as we prepare with our international counterparts to make a global call to action at COP26. Process emissions from treating wastewater will soon become the leading source of greenhouse gas emissions in the water sector globally, as it decarbonises its other activities. The good news is that companies in the UK and across the globe are doing something about it.

Process emissions occur when sewage is treated before returning it to the environment, producing several by-products including the potent greenhouse gases nitrous oxide, biomethane and carbon dioxide – this happens all over the world, it’s just science.

To reduce process emissions the water sector is focusing its attention on two things. The first is to make more accurate estimations of process emissions; and the second is to use this information to develop solutions to reduce them.

Water companies around the world currently estimate levels of nitrous oxide and methane from process emissions using generic emissions factors. In 2019 the Intergovernmental Panel on Climate Change (IPCC) updated its emissions factors for wastewater treatment, but different countries experience different challenges when it comes to wastewater. Different climates, geographies, and composition of wastewater across the globe means these emission factors are not representative of actual emissions across all sites. To overcome this, the water sector is continuously improving its monitoring and measuring of emissions using new equipment at different types of treatment sites to build a clearer picture of the process emissions unique to their technology and location.

With more accurate information about process emissions, companies can find new ways to reduce these emissions, for example by using cutting-edge technology to capture biomethane and use it to generate energy. In contrast, the emission of nitrous oxide is not as well understood. Water companies are working on projects to understand exactly where and when nitrous oxide arises in the biochemical process which will reveal where to adjust the treatment and deploy new technology to mitigate this greenhouse gas.

We need a concerted effort to monitor, measure and reduce process emissions to stop them becoming an ever-growing proportion of companies’ greenhouse gas emissions. This is why research and, crucially, securing investment in research, has become a major priority.

At COP26, Water UK together with our international counterparts will call on governments around the world to recognise the importance of reducing process emissions and provide financial support to meet their Nationally Determined Contributions. With this support we can better understand these hard-to-abate emissions and develop solutions to reduce them. Every country needs to do this to meet their commitments under the Paris Agreement.

With more net- zero-compatible policies the water sector will be able to expand and accelerate global research, catalysing the transition to net zero.