How the heat from wastewater can be a source of renewable energy

The UK Government has set a target to connect 20% of buildings to heat networks by 2050, but there is a lot of work to do. While it’s not commonly discussed when considering alternative energy methods, wastewater is a highly viable source of heat — yet one of the least tapped. There are many challenges to overcome, not least around public perceptions.

Undaunted, the TORCH project team secured funding from the Ofwat Innovation Fund's Water Breakthrough Challenge. Led by Anglian Water, the collaborative TORCH project focuses on solving heat demand and affordability challenges facing the UK today. Using BMA's leading technology and partnering with expertise from across sectors, the project will unlock the potential of wastewater as a renewable heat energy source. Dr Stefano Giacalone explains.

What is the ultimate goal of the tool you are developing?

We want our tool to be something that planners, councils, developers and water companies can use to quickly assess opportunities for collecting heat energy while identifying any associated risks. Right now, these queries are handled case-by-case, which is time consuming and expensive. Our tool takes a whole-systems approach, connecting heat sources, networks and demand points to identify opportunities that fragmented, case-by-case analysis overlooks.

What heat recovery technologies are being considered?

We’re looking at fairly standard heat exchangers, but they’re specially designed for the sewer environment, which has challenges like biofouling — the process where organisms like bacteria start to grow and attach to surfaces. One key concern for us is to make sure we don’t extract too much heat, which could affect biological processes at treatment works. It’s a delicate balance, and one that we can utilise technology to help us achieve. We need to be able to recover heat without compromising sewer performance or environmental standards.

Can you tell us about the technology you are using?

Built on BMA's industry-leading Decisio™ decision-intelligence platform, TORCH delivers next-generation AI that moves beyond traditional planning limitations to provide whole-systems optimisation across the entire value chain. The Decisio™ platform has long been employed in other asset-intensive sectors, and has been successfully deployed in water and energy sectors for several years — and uses AI and advanced analytics to generate options. These are fed into an optimisation engine that balances cost, carbon and environmental performance. 

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The software is already helping water companies rethink their networks and energy planners explore new interventions. Starting with a pilot study in Peterborough, we’re exploring how much heat is available in the sewer network, what viable options exist to recover it and how it compares to conventional methods like gas boilers and air-source heat pumps.

The tool is still being refined as the project is still relatively new. It kicked off just two months ago and runs for 15 months in total. What’s exciting is that TORCH brings together water and energy sectors in a way that hasn't been done before, using BMA's technology to connect sewer network data with energy demand data to reveal hidden opportunities.

What kind of data are you using?

We’re using publicly available data where possible, like energy performance certificate (EPC) information for demand, and combining it with geographic information system (GIS) and land use data. Then we overlay sewer network data from water companies, and use BMA's cloud computing platform to auto-generate options for connecting heat sources to demand points. Optimisation techniques help us find the least-cost solutions that will still enable us to reduce carbon emissions.

What’s the scale of potential here?

Some estimates suggest that sewage could provide in excess of 20 terawatt hours (TWh) of energy per year, which is enough to power around 1.6 million UK homes annually (https://tinyurl.com/ytnvu5wk). Not all of that is accessible or economical, but it shows the scale. That kind of potential gains significant interest from stakeholders, and really illustrates the transformative power of wastewater heat energy for the energy sector.

What have been the biggest challenges that you have encountered so far?

Data availability and expertise are big ones. Councils often lack the funding and resources to explore low-carbon opportunities. Technically, it’s also tough to bring together data from different systems and standards. That’s why we’re running workshops with local authorities, net zero hubs, water companies and service providers, to highlight the ways that data can be collected and utilised for extracting the most meaningful insights.

Are there any regulatory hurdles that need to be overcome?

Water companies aren’t actually regulated to provide heat, so there’s no obligation for them to give access to sewer networks. There’s interest, but also caution, especially with environmental concerns already putting the sector under scrutiny. Still, there’s recognition of the opportunity that this project provides to contribute to national carbon goals while also cutting their own emissions. TORCH aims to demonstrate a model that could inform future regulatory frameworks.

Can public perception present a challenge?

Definitely. People hear ‘sewage’ and either simply don’t like the idea, or worry about the related contamination risks associated with handling wastewater materials. In reality, we’re only extracting heat, not sewage. It’s a closed-loop system using heat exchangers. And, unlike other waste heat sources, as long as people exist, so will sewage. That makes it a reliable long term heat source with continued presence and availability.

Are there international examples of success?

Yes, places like Copenhagen already serve 90% of homes via heat networks. They tap into various waste heat sources. The concept of moving heat around isn’t new, and other countries are already recovering heat from data centres and natural sources. Projects like this mean we now have a chance to catch up. By making complex planning decisions faster and more data driven, the project aims to help the UK deploy heat recovery more strategically.

For more information about BMA's Decisio™ platform and the TORCH project, visit their website.