21-07-2025
Hamburg's industrial waste heat project: a model for climate-neutral district heating?
Just a few kilometres from Hamburg's centre, the multi-metal company Aurubis produces more than 400,000 tonnes of copper every year. During the refining process, sulphur in the copper concentrates reacts with oxygen to form sulphuric acid, a valuable subproduct. This chemical reaction also releases large amounts of heat, which is now transferred to water and delivered through the city's district heating network.
From wasted heat to warming homes
Before this system was implemented, this thermal energy had no use.
'We took water from the river Elbe and cooled down the heat that came from the process. It wasn't used for anything. It was just wasted', explains Dr Holger Klaassen, director of corporate energy and climate affairs at Aurubis.
That all changed when the energy supplier Enercity Contracting partnered with Aurubis with the idea of channelling the heat to the district heating system of Hafencity East, a growing residential area that was once part of the city's port.
Both companies invested more than €20 million to bring the project to life.
'We needed a total retrofit of the contact plant where the sulphuric acid is produced. We needed a big heat exchanger, pumps, pipes, very special steel and stones that are able to absorb the heat combined with the acid', Dr Klaassen says.
Enercity Contracting built an energy station to store and pump hot water, along with a gas-fired boiler to back up the system during copper production downtimes. A 3.7-kilometre pipeline now links the Aurubis facility directly to the city.
A replicable model for greener cities
Hamburg's industrial waste heat project is unique in part due to the copper smelter's close proximity to the city and the availability of CO₂-free waste heat.
Still, Dr Klaassen believes the model could be replicated in other cities. 'What would help to make it more economically feasible would be incentivising the production or use of CO2-free heat by, for example, providing free allocations in the European emission trading system or developing some kind of green markets', he concludes.
