In 2011, Redditch Borough Council in England tried something that hardly anyone in the UK had heard of before. Staff announced they were going to warm the local swimming pool with heat from a nearby crematorium.

A public firestorm ensued. The plans were met with international headlines, and a labor union official branded them “sick and an insult to residents.” (A spokesman for the union, Unison, says this was not—and is not currently—the organization’s official position.)“All you’re doing is basically heating a radiator and sending the heat down a tube,” says Guy Revans, of Redditch and Bromsgrove Councils, just south of Birmingham. “But death is always an emotive subject, isn’t it?”Eventually, the relentless press coverage faded away. The project won a green award, and the crematorium has warmed Redditch’s swimming pool since 2013.

Although extremely rare in North America, European countries have been harvesting warmth from crematoria for years. The total volume of heat available from crematoria is modest, but as people search for ways of reducing the environmental impact of funeral rites, utilizing crematoria waste heat provides a way to lower their carbon intensity.

Roughly 1,200 cremations are carried out every year in Redditch. A heat exchanger captures heat from flue gases emitted by the facility’s two gas-fired ovens as part of a process to remove vaporized mercury from dental fillings, before venting the remaining gas into the atmosphere.

That’s a common process at many crematoria. In other words, excess heat is often captured by default, meaning the next question is, does it make sense to waste the heat—or use it? In Redditch, the heat exchanger connects to a water loop that travels 200 meters underground, eventually reaching another heat exchanger supplying the swimming pool.

Helpfully, such a sizable body of water “acts as a heat sink”, adds Revans. “You put heat into it during the day, it retains that heat for a considerable length of time.”The recreation center also has gas-fired boilers that can provide more heat when necessary. Overall, the system has saved the council tens of thousands of pounds per year in fuel costs.

Similar projects have emerged elsewhere recently. A school currently under construction in Aberdeen, Scotland, will receive excess heat from the city’s crematorium. The crematorium already relies on waste heat to warm its own premises.

“They were only utilizing a tiny amount of the heat available; the rest was going to the atmosphere,” says Ian Davidson, chief executive of Aberdeen Heat & Power, who says that the system now has full planning permission. The crematorium will provide just under 1 gigawatt-hour of heat annually, roughly half the school’s total requirement. A heat pump will cover the rest of the facility’s needs, and the entire system should be fully operational by February 2027.

Some crematoria are going even further in their pursuit of green credentials. The crematorium that will open in Kangasala, Finland, in 2028 will be connected to the town’s district heat network, a system of pipes that supplies more than 6,500 homes with hot water for heating. The crematorium will be fully electric, powered partly by solar panels on its roof.

“It’s a special thing,” says Timo Heikkilä, an energy and building systems consultant at Thenco Oy, who is working on the project. “I’m really glad I get to be a part of this.”Winter temperatures in Kangasala can remain below 0 degrees Celsius for weeks on end. In Finland, there is a push to use less natural gas for heating, says Heikkilä. Although once cheaply available from neighbouring Russia, that country’s invasion of Ukraine and concerns over climate change have prompted Finland to seek alternatives. In some locations, this means utilizing waste heat from unusual sources, including crematoria.

“Finns,” says Heikkilä, “are quite practical.”Ian Rudkin, who has managed multiple crematoria in the UK and is currently a board member of the Cremation Society of Great Britain, says many crematoria are becoming more eco-conscious. Today, software can schedule the firing of gas ovens to align with funeral services, ensuring they don’t waste energy and are only turned on when needed, for example. And some crematoria hold coffins for up to 72 hours, so that several may be cremated in a sequence, which is more efficient.

“When we first brought that in, [families] seemed a little bit shocked,” says Rudkin. Soon, however, people became more accepting. “They’d make comments like, ‘Dad always used to turn the light off at home to save energy.’”But implementing heat recovery tech at crematoria in the US is more difficult, says Paul Seyler, director of strategy at Matthews Environmental Solutions. There, district heat networks are rare, and crematoria tend to be privately owned. That means the investment needed for heat exchangers and pipework necessary to link buildings together is higher.

“We’re studying this and watching it closely because, when the economics align, we’d like to be in a position to offer a solution,” says Seyler. Wasted heat is, after all, just a waste of resources, he adds. Besides a few small-scale experiments, Seyler says he isn’t aware of any fully operational systems in the US that utilize heat from crematoria.

The closest example is in Canada at a funeral complex in Sainte-Thérèse, Quebec. This 3,255-square-meter building houses family rooms, a large chapel, a crematorium, and a kitchen, among other facilities. Heat exchangers installed just over a decade ago soak up heat from cremation flue gases and distribute it around the complex, including the sidewalks to melt snow in the winter.

“The owner was not immediately on board as he thought it may have posed an ethical dilemma,” recall design engineers Martin Roy and Lianne Cockerton in an article about the project, published in the ASHRAE Journal.

Now, visitors pass an LED screen in the reception area that displays the energy performance of the building, based partly on the heat exchanger’s operation. While gas is still used for some of the building’s heating needs, as well as for cremations, the new system saves an estimated 29 metric tons of greenhouse gas emissions annually.

Recovering heat from cremations is one way of attempting to counter the “devastating impact” that humans have had on the environment, says Hannah Rumble, an associate at the University of Bath’s Centre for Death and Society. “I can see that would be a reason why people might choose to be cremated at a particular crematorium.”

Most crematoria contacted by WIRED say they do not emphasize the presence of heat recovery technology to families or mourners, though a spokeswoman for Aberdeen City Council adds that the council there will “undertake some public awareness-raising on the new system before it is operational to ensure transparency.”Gaynor Doherty, an independent humanist funeral and wedding celebrant in the UK, says using waste heat from crematoria is “sensible,” though she suggests a natural burial, where bodies are simply shrouded or placed in biodegradable coffins and allowed to decompose in the environment, might be preferable to many eco-minded people.

The carbon intensity of cremation varies from facility to facility, but could be around 250 kilograms of carbon per gas-fired cremation. Recovering heat from the process offsets some of those emissions (one company claims savings of 100 kilograms) but not all.

A study published in 2024 estimated that, if all crematoria in the UK were tapped for waste heat, they might only meet 1 percent of the county’s total heating needs. This sounds small, but decarbonizing heat is notoriously difficult, so any interventions to achieve that can be valuable. Plus, some people may feel that sharing the heat from their cremation could carry a lot of meaning.

In Finland, the all-electric crematorium in Kangasala will not produce as much heat as a gas-fired equivalent, though it will run 24/7 because it’s more efficient to operate by using electricity to gently top up heat retained in ceramic materials within the ovens. The connection to the district heat network means that, when mourners return home from funeral services at the new crematorium, it is conceivable that at least a small portion of that warmth they feel after stepping through their front doors will come from the cremation of the person they loved.

Heikkilä says working on the project has prompted some big questions for him. “I have thought about it, and once my time is up, I would like to be cremated, and I would like my waste heat to be recycled,” he says. “It’s the sensible thing. The last favor you can do for the world.”