TRIMET & Iqony: Aluminium Waste Heat Powers German District Heating

Essen, Germany – A pioneering initiative to bolster energy efficiency and reduce carbon emissions is underway in the Ruhr region of Germany, with the commencement of waste heat recovery from the TRIMET aluminium smelter in Essen. From January 2025, approximately 31,000 megawatt-hours (MWh) of heat annually – a quantity sufficient to meet the heating demands of over 5,500 households – will be diverted from the aluminium production process and fed into the district heating network operated by Iqony Fernwärme GmbH.

The collaboration between TRIMET Aluminium SE and Iqony represents a significant step towards decarbonizing heat supply in Essen, Bottrop, and Gelsenkirchen, according to a joint statement released in April 2023. The project aligns with both companies’ ambitious climate goals: TRIMET aims for climate-neutral aluminium production by 2045, while Iqony targets climate neutrality by 2040.

The recovered heat originates from the fused-salt electrolysis process used in aluminium production, which generates liquid aluminium at temperatures exceeding 900 degrees Celsius. TRIMET has invested approximately six million euros in converting its facilities to capture this previously unused heat. This involved installing heat exchangers on the electrolysis furnaces and a network of four ventilator stations to direct the heat through a water-filled tube bundle, raising the water temperature to around 130 degrees Celsius. Iqony, in turn, has invested over two million euros in constructing approximately 700 meters of connecting pipeline to integrate the recovered heat into its existing district heating network in Bergeborbeck, near Hafenstrasse.

“With this project, TRIMET and Iqony demonstrate what circular economy means in practice in an industrial nation,” stated Matthias Ohl, Managing Director of Iqony Fernwärme. “Instead of letting industrial waste heat dissipate unused, it is being reused in heating networks. Waste heat is a key building block for decarbonising heat supply.” He further noted that Iqony’s district heating network already relies on carbon-neutral sources for approximately 70% of its supply, largely due to the utilization of waste heat, and that the TRIMET partnership will further enhance this sustainability.

Dr. Andreas Lützerath, Member of the Executive Board of TRIMET Aluminium SE, emphasized the project’s significance for both the company and the region. “The fact that we are now heating thousands of homes with the waste heat from our facilities is a milestone for our company and for the region,” he said. “This clearly shows how innovation drives the green transformation. By making aluminium production more flexible, we are moving closer to climate protection targets, strengthening the future viability of our production sites, and working together with Iqony to make an important contribution to energy security.”

The feasibility of utilizing the waste heat became possible following TRIMET’s adaptation of its aluminium production to accommodate fluctuating power supplies from renewable sources, specifically wind and solar energy. This shift allowed for the consistent generation of waste heat suitable for capture and redirection. A 1.6-kilometer pipe system has been installed within the TRIMET plant premises, circulating 36 cubic meters of water under high pressure to an energy centre, where the heat is transferred to the district heating network.

The cooperation between TRIMET and Iqony is formalized through a 20-year agreement established in April 2023, outlining the long-term commitment to utilizing waste heat from the Essen aluminium plant. Following the completion of trial operations, the facility is expected to enter regular operation shortly.

Beyond the immediate environmental benefits, the project highlights a growing trend of industrial symbiosis, where waste products or byproducts from one industrial process are utilized as resources in another. This approach not only reduces environmental impact but also enhances resource efficiency and strengthens regional economic ties. The initiative also builds on existing efforts to expand district heating networks in the Ruhr region, which currently provides heat to over 275,000 residential units, delivering an annual heat supply of 1.6 billion kWh.

TRIMET also intends to supply around 20 gigawatt hours of waste heat from its furnaces into the public district heating network in Gelsenkirchen, further expanding the reach of this innovative energy recovery system. Converting the waste heat into electricity is expected to reduce indirect CO2 emissions, known as Scope 2 emissions, by up to 100 percent, with significant reductions also anticipated in direct emissions.