By 2050, the UK government plans to create `Net zero society'.1 To meet this ambitious target, the deployment of low carbon technologies is an urgent priority. The low carbon heat recovery technologies such as heat recovery from sewage via heat pump can play an important role. It is based on recovering heat from the sewage that is added by the consumer, used and flushed in the sewer. This technology is currently successfully operating in many cities around the world. In the UK, there is also a rising interest to explore this technology after successful sewage heat recovery demonstration project at Borders College, Galashiels, Scotland.2 However, further experimental research is needed to build the evidence base, replicate, and de-risk the concept elsewhere in the UK. The Home Energy 4 Tomorrow (HE4T) project at London South Bank University was created to address this evidence gap. This is the fourth article in the series of outputs on sewage heat recovery and presents some results using sewage data from the UK's capital London. These data are scarce and provide useful information on the variation of flows and temperatures encountered in the sewers of the UK's capital. Lastly, we discuss the recoverable heat potential along with policy implications for the UK heat strategy. Practical application: This work focuses and accentuate that in order to meet climate change targets, substantial improvements can come by heat recovery from the raw (influent) and treated wastewater (effluent from wastewater treatment plant) that is still unexploited in the UK. The estimation presented indicates that there is much theoretical potential in the UK with significant opportunity for future energy and revenue retrieval along with GHGs emission reduction in the longer term to fulfil the `net zero' objective. This work aims to raise awareness and seek support to promote pilot scale studies to help demonstrate technical and economic feasibility in the building industry.
