At its core, WARM reimagines the traditional septic tank not simply as a sanitation unit, but as part of a decentralised renewable energy system. Previous modelling work carried out within the programme anticipates that the combined septic tank and heat recovery configuration could reduce household electricity bills by up to 20% during periods of high energy demand, particularly in winter conditions.
The demonstrator integrates three main components. The first is an insulated septic tank specifically designed to minimise heat dissipation and maintain stable internal temperatures, improving biological treatment processes. The second is an integrated methanotrophic biofilter positioned to capture methane emissions generated during wastewater treatment. Rather than allowing methane to escape into the atmosphere, the biofilter uses naturally occurring methane-oxidising microorganisms to mitigate emissions while simultaneously generating metabolic heat. The third component is a heat recovery unit, consisting of a secondary tank that receives treated effluent from the septic tank. Before the water is discharged, residual thermal energy is recovered using a heat exchanger connected to a heat pump system. Together, these technologies form a compact and transportable platform capable of recovering value from wastewater streams that are traditionally overlooked.
Construction of the WARM demonstrator was completed in early 2026 and the system is currently undergoing preliminary controlled trials at Scottish Water’s Research & Development testing facility in Bo’ness, Scotland. The construction and integration of the demonstrator involved close collaboration with several industrial partners, including George Jackson Engineering (George Jackson), Calcut Ltd (Calum Cuthill), and Source Thermal (Andrew McCahey). Ongoing testing activities are also being supported by staff at the Bo’ness testing site.
A key feature of the WARM system is its mobility. The demonstrator has been specifically designed as a transportable platform that can be deployed and tested in different real-world locations, helping showcase the potential advantages of decentralised wastewater-energy systems under a variety of operating conditions. This next phase of development has also received support from Hydro Nation, which has shown strong interest in the future real-world deployment and implementation of this technology.
The WARM demonstrator presents an alternative vision for decentralised wastewater infrastructure, where sanitation systems can also contribute to renewable energy recovery and greenhouse gas mitigation. The project hopes to demonstrate how on-site wastewater systems could become part of more resilient, low-carbon and resource-efficient rural communities.
