Turning data-centre waste heat into a resource—can it work?
A new data centre planned for the Danish town of Ølgod will do more than process information. If everything goes according to plan, its waste heat will also help grow fresh produce.
Nordic data-centre operator atNorth has announced a partnership with infrastructure company Selected Group to supply surplus heat from its DEN02 campus to a large greenhouse development next door. The heat is intended to support year-round food production in a country that imports much of its fresh produce, particularly during winter.
The greenhouse will be developed alongside the data centre, with the first phase scheduled for completion in the third quarter of 2028. According to the partners, reusing the heat should reduce reliance on fossil-fuelled greenhouse heating while creating local jobs and shortening food supply chains.
It is an appealing circular-economy proposition. A data centre pays to remove heat from its servers; a greenhouse pays to generate heat for its crops. Put the two beside each other and, theoretically, each can solve part of the other’s problem.
But data-centre heat reuse is not quite as simple as running a pipe between them.
How data-centre heat reuse works
Almost all the electricity consumed by servers eventually becomes heat. In a conventional data centre, cooling systems collect that heat and release it into the air or surrounding water. As artificial intelligence drives demand for increasingly dense racks of power-hungry processors, the amount of heat requiring management is rising.
Data-centre heat reuse captures this excess thermal energy and transfers it to another application, such as district heating, food production or hot-water systems.
The difficulty is that data-centre heat is commonly produced at relatively low temperatures. At Microsoft’s planned Espoo campus in Finland, for example, hot air from the cooling system will be converted into water at approximately 30°C—useful in some situations, but well below the temperature required by many existing district-heating networks.
Heat pumps can raise it to a more useful level, but they require electricity and capital. Pipes, heat exchangers, backup equipment and sometimes thermal storage may also be needed. The further the heat must travel, the more expensive and less efficient the system becomes.
This helps explain the logic of the Ølgod project. Rather than searching for a distant customer after the data centre has been built, the greenhouse will be placed immediately beside it. Both facilities are being conceived as parts of the same local energy system.
Yet the announcement leaves important questions unanswered. atNorth has not disclosed the expected thermal capacity, operating temperature, greenhouse area, need for heat pumps or projected emissions savings. Nor does it say what will heat the greenhouse when the data centre is unavailable or unable to meet peak winter demand.
For now, this is a planned project rather than proof that the model works at scale. Other European data-centre heat-recovery initiatives offer clues about where the strongest opportunities may lie.
Microsoft and Fortum take waste heat to municipal scale
In Finland, Microsoft and energy provider Fortum are pursuing a much larger version of the idea.
Microsoft’s new data-centre region in Espoo and Kirkkonummi is being designed around integration with Fortum’s existing district-heating infrastructure. Heat recovered from server cooling will be upgraded at heat-pump plants and distributed to homes, public buildings and businesses in Espoo, Kauniainen and Kirkkonummi.
Once the system is fully operational, Fortum expects heat recovered from Microsoft’s facilities to cover approximately 40% of the network’s annual district-heating demand. The network serves around 250,000 users. Fortum estimates that about 75% of the heat produced by the data centres could be used over the course of a year, with utilisation falling during the warmer summer months.
Fortum started producing district heat at two data centre sites in Mahy 2026. Initially, however, the heat-pump plants are drawing energy from ambient air. Microsoft says recovery of heat from its servers is scheduled to begin in 2027 as the data centres enter operation.
The project demonstrates the potential scale of data-centre district heating, but also the infrastructure required. Fortum announced investments of approximately €225 million in heat-pump plants and related installations in Espoo and Kirkkonummi.
Finland already has extensive district-heating networks, while its long winters provide sustained demand. The data-centre locations were selected partly because they could be connected to that system.
This is not a model that can simply be copied into every city. Its success rests on municipal energy infrastructure, long-term planning and a customer base large enough to justify the investment.
Green Mountain tests data-centre heat in aquaculture
Some applications require heat at exactly the temperature a data centre produces.
In 2021, Norwegian colocation provider Green Mountain announced a collaboration with Norwegian Lobster Farm to explore using heated seawater from its DC1-Stavanger facility in a planned land-based aquaculture development.
Seawater enters Green Mountain’s cooling system from the fjord at approximately 8°C and leaves at around 20°C. That happens to be close to the temperature European lobsters need for optimal growth. The proposal was to establish the farm beside the data centre and deliver the warmed water directly, avoiding the energy-intensive step of raising it to the temperatures required by conventional heating networks.
The lobster project is best treated as a development initiative rather than a proven commercial operation. Green Mountain’s subsequent sustainability reporting described its lobster and trout heat-reuse work as pilot projects.
The company has since put the underlying principle into practice with Hima Seafood. Its land-based trout farm is located 800 metres from Green Mountain’s data centre in Rjukan. An underground closed-loop system began operating in autumn 2025, carrying warm water to the farm before returning cooled water to the data centre.
The operational phase can transfer up to 1.75 MW of heat, while the companies are studying a possible expansion to 8 MW.
Aquaculture may be a specialised application, but it illustrates a central rule: waste heat becomes considerably easier to reuse when the recipient can work with the temperature already available.
Deep Green brings edge data centres to swimming pools
British start-up Deep Green has approached the location problem from the opposite direction. Instead of building a large data centre and looking for someone nearby who needs heat, it places modular edge data centres at sites that already consume large quantities of it.
Its best-known installation is at Exmouth Leisure Centre in Devon. Computers used for artificial intelligence, machine learning and other intensive workloads are immersed in oil, which carries their heat through a heat exchanger into the swimming pool’s hot-water system.
Deep Green said the installation could reduce the pool’s gas requirements by approximately 62%, although a gas boiler remains available when additional heat is needed.
The model gives the leisure centre heat without requiring it to buy or operate the computing equipment, while Deep Green gains an efficient way to cool its servers.
But it introduces a different challenge: the company must secure enough paying computing workloads to keep its machines operating—and generating heat—when host facilities need it.
When does data-centre heat reuse work?
Together, these projects suggest that four conditions determine whether data-centre heat can become a useful energy resource.
First, the producer and customer must be close. Heat is more expensive to move than data, making proximity crucial.
Second, the temperature must suit the application or justify the cost of a heat pump. An aquaculture facility needing moderately warm water is an easier match than an older district-heating network designed for much higher temperatures.
Third, supply and demand must coincide. Servers generate heat throughout the year, while homes and greenhouses need much more of it in winter. Swimming pools and aquaculture facilities offer steadier demand.
Finally, somebody must pay for the connection. Heat may be surplus, but the equipment needed to capture, upgrade and distribute it is not free. Commercial agreements must also determine who carries the risk if either the data centre or heat customer changes its operations.
EU rules encourage data-centre waste-heat recovery
European regulation is beginning to push the industry in this direction. Under the EU Energy Efficiency Directive, member states must ensure that data centres with a total rated energy input above 1 MW reuse excess heat where technically and economically feasible.
Operators with installed IT power demand of at least 500 kW are also subject to EU energy and sustainability reporting requirements.
The sustainability issues with data centers will not disappear through heat reuse initiatives. Heat reuse cannot cancel out the considerable electricity, water and materials consumed by expanding digital infrastructure. Nor does labelling heat as a resource guarantee that a viable customer exists.
The Ølgod development nevertheless embodies the most promising approach: do not build a data centre first and treat heat reuse as an environmental add-on. Identify the customer, pipes, temperatures and commercial relationships while planning the facility itself.
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