Utility Week

UTILITY WEEK | NOVEMBER 2021 | 15 Special report Analysis Process emissions: Sizing up the challenge Howard Perry, energy manager at Severn Trent, speaks to Ruth Williams about the company's efforts to begin monitoring process emissions as the first step towards reduction. T o reach the water sector's target of reducing greenhouse gas emissions to net zero by 2030, Severn Trent has adopted an approach of reduce, remove, replace and offset. Like other wastewater companies, it rec- ognises the magnitude of the challenge, esti- mating it will require around £500 million of extra investment from its 2025-30 PR24 business plan to reach the net-zero goal, some generated from non-regulated business activities. The company compiled a baseline of its current carbon equivalent emissions of 470,000 tonnes per year. Of this, an esti- mated 190,000 tonnes are from process emis- sions and 128,000 tonnes from secondary treatment processes at treatment sites. Wastewater treatment works have mul- tiple, very large, activated sludge process (ASP) lanes that each emit nitrous oxide. Perry says these are working just as they were designed to but contribute heavily to emissions. "They have all the treatment ben- efits we have relied on for many years so to fundamentally change that or to capture all the gas from one area and get rid of it seems like a pretty big challenge," he says. Severn Trent led a bid to the Ofwat Breakthrough Challenge to roll out mass monitoring of wastewater treatment sites to accurately record emissions. Despite the urgent need to act if the sector wants to reach its self-imposed target, the bid was not successful. "We know it's a big problem, but we need to understand the problem first. We're doing some monitoring already, but it needs a much broader set of monitoring that needs to begin across a range of sites. The earlier we start that work the better because the more likely to be able to find where emissions come from and how they can be solved," Perry says. The bid was turned down by the panel as a project that should be funded by other sources. Although Severn Trent and other companies will continue with their own self- funded monitoring projects, Perry believes the work needs to be wider to provide more data: "The more data we have, the more likely we are to find a solution." He says both Anglian and Thames have embarked on monitoring, also with an agree- ment to share the results. However, Perry says the innovation fund bid could have enabled more wide-scale, quicker, and more ambitious monitoring. "We need to be collecting that data and science to propose the solutions for 2030 and beyond," he states. "One of the issues with process emissions is they are very seasonal – they vary over time with weather tempera- ture, so we would need a year of monitoring to see the footprint and what types of things are likely to happen at different times of year, plus years can be different with hotter or wetter weather impacting differently. The earlier that starts, the better and the more science we can do in the area." He says monitoring is already under way at some of Severn Trent's sites to measure when, where and how emissions occur, with methane emissions picked up using sensors at sludge treatment areas and thermal imag- ing from drones, and nitrous oxide emis- sions gauged using sensors in secondary treatment areas. "Even over the past few months of moni- toring that has allowed us to identify leaks and fix them, and find spots within the process that have methane losses we didn't know about before. Tangible reductions to greenhouse gas emissions are already hap- pening," he says. Perry says drones are flown over waste- water treatment works at a height of 50 metres and shine down lasers that can gauge methane concentrations within their beams and measure the temperature. The company has employed drones for asset inspections and as a tool in its leak detection arsenal since 2017. He says digestor maintenance has been instigated off the back of these inspections, which are a first for the sector. The company intends to increase its mon- itoring and carry on building up its evidence base over time, with the nitrous oxide and methane monitoring sensors to be in place and operational up to 2030. Perry says these can be used to keep track of how actions are affecting emissions. "As we make improvements and changes these monitors will show that in the data. The survey is also a regular process now that we want to keep up and running to under- stand emissions and track any improve- ments," he says. Secondary treatment He says existing research shows that efficient operational control of secondary treatment processes may be particularly helpful for controlling emissions but this will take more time and monitoring to prove. "We believe some of the work we have done for energy efficiency and process control is improving emissions from what they would otherwise be. Maintenance and repair of leaks is already helping and will continue to help." Optimisation of assets, as well as finding and fixing where gasses may be leaking, are changes the industry can begin to make now, Perry says, but he admits that beyond the pathway remains an unknown. "We have to start to think in terms of capi- tal solutions for an alternative to the process that doesn't result in those emissions or to capture those greenhouse gasses," he says. " What these are and how much they would cost we don't know, but it is something we need to figure out before the next price review." Ruth Williams, water correspondent To see the full article go to https://utilityweek. co.uk/process-emissions-sizing-up-the- challenge/

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