Utility Week

28 | SEPTEMBER 2021 | UTILITY WEEK Analysis A suitable case for treatment Treating sewage is an energy- intensive business, but if byproducts can be harnessed it would create a virtuous feedback loop and help the water sector hit its ambitious 2030 net zero target. I f the water sector is to hit its self-imposed 2030 net-zero goal there is much work to be done to drive down the energy inten- sity of its processes, most notably in waste- water treatment. Process emissions from sewage treatment currently account for around two-thirds of the total greenhouse gases output by water and sewerage com- panies. The journey to net zero will require them to vastly lower the energy consumed across their organisations, add renewable supplies and credibly offset where necessary. Companies face a challenge, therefore, to reduce emissions by modernising processes and where possible reusing byproducts, which have previously been regarded as waste, to get secondary benefits from waste or heat energy. There is potential for the company to use this energy as a renewable source or to supply it to other organisations also working to decarbonise. Industry experts speaking at the Utility Week Live Summit in May, sponsored by Cap- ita, discussed the ways companies are mak- ing treatment less energy intensive and the opportunities to recycle the waste products to other sectors. This does not come without obstacles – both from financial and regula- tory viewpoints – and participants at the summit shared insight on overcoming these. For the 2030 commitment, Water UK cre- ated a route map which acknowledges that as things stand not all emissions can be neutralised and a significant amount of off- setting may be needed. Overall, 10 megatons of carbon will need to be cut in this decade based on a 2018/19 baseline. Part of the issue, as explained by Peter Vale, technical lead on innovation at Severn Trent, is that wastewater treatment hasn't really changed in the past 100 years, which means it's prime for innovation. "[These processes] have served us really well, they're robust and enable us to treat water to the highest standard, but they are energy intensive, so the argument to change is becoming more compelling," Vale said. Reliability aside, these linear treatment flow sheets are not so compatible with the low-carbon biodiverse future the sector needs to move to and embrace. Vale said: "Transforming to a circular way of managing assets is key but will demand a real rethink about how we treat wastewater." Understanding of the output gases is growing each day and research on how to drive out nitrous oxide and methane – natu- ral byproducts from treatment processes – over the coming decades is underway. Although damaging to the environment, these byproducts can be used for heating and as an energy source themselves. Energy from biogases can be harnessed as a renew- able supply not just for water companies. Innovative schemes to recover heat and energy to use in heating networks have led to symbiotic partnerships between water com- panies and other industries to recycle the carbon-intense emissions. This rethink means updating and inno- vating treatment processes. Severn Trent, as part of its triple carbon pledge, now gener- ates more than 50 per cent of its energy from renewables, which has allowed the organisa- tion to cut its net carbon emissions by 40 per cent over the past five years. However, Vale recognises the need to go further and faster to meet targets. One area Severn Trent is exploring, with the Water Research Centre (WRC) is captur- ing carbon dioxide via enhanced mineral weathering. David Hodkin from the WRC explained that mineral capture offers longer- term storage of carbon than trees or flora, which can be cut down or destroyed – thus releasing the carbon. As certain minerals weather they release metal ions such as magnesium and calcium into solution. These in turn can increase the alkalinity of water by generating bicarbonate and carbonate ions, which results in the stor- age of CO2 that can then be transferred to and stored in the oceans. Hodkin's work is to increase the rate of weathering of these minerals by increasing their surface area or temperature to increase the amount of carbon drawn down and stored as alkalinity in the seas. The work is currently at an early stage in the study, and Hodkin said funding for inno- vation is crucial but so is the acknowledge- ment that not every idea will succeed. Sharing the risk He praised Ofwat's approach to funding innovation through its £200 million competi- tion during AMP7, which allows and encour- ages companies to shoulder the risk involved in projects. He said that while everyone wants something totally new from innova-

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