News From a Changing Planet: Mining for Heat

Posted inCreative Voices

What if the same exact coal mines that set the Industrial Revolution (and climate change) in motion could help bring about the clean energy transition?

A few years ago, when I was writing about how a neighborhood in London was using waste heat from an abandoned subway station in a district heating network for homes, a school and a gym, I spoke with Jon Gluyas, a professor of earth sciences at Durham University in Britain who specializes in geoenergy, carbon capture and storage. He mentioned, as an aside, that he was working on developing a new carbon-free heat source for another district network: abandoned coal mines.

Since then, I’ve been thinking about this idea because, to me, it has a rare historical circularity to it. It’s one of those “climate solutions” that has the elegance of simplicity but also offers a unique opportunity to fix some historical mistakes and right some atmospheric wrongs. It will use the exact same coal mines that set the Industrial Revolution (and the accompanying planetary chaos of climate change) in motion to help bring about the clean energy transition, if done well and at scale. How cool would that be?!

Here’s how it works: Around the United Kingdom, there are about 23,000 abandoned coal mines, most of which have filled up, both with groundwater and rainfall, since they were closed. (The last mine closed in the UK in 2020, but the government approved a new deep coal mine last year.) When mines are in use, operators usually have to pump that water out so that miners can go in. In some places, the water is now pumped up to the surface and treated so that it doesn’t contaminate drinking water supplies.


At depths more than 20 feet below the surface, radiating heat from the molten hot core of the Earth maintains a temperature of about 54ºF on average. It is this heat that geothermal energy takes advantage of, and that’s what’s happening here too: the water in the old mines is warmed by the earth and stores the heat. Then, though a network of pipes, heat exchangers, and ground source heat pumps, the heat travels in the water from the mine shafts to any connected buildings. (It’s important to note, however, that the minewater stays within the network, and doesn’t come into contact with the air or enter the buildings.)

District heating itself is an old idea, possibly dating back to the Roman Empire. But in the 20th Century, it came to mean that the heat from underground or from the combustion of biomass or fossil fuels traveled from a centralized location across a network of insulated pipes via a fluid medium (usually water), with much greater efficiency than individual furnaces or boilers. If the heat is a byproduct  – of sewage treatment, data centers, or subways – then it provides non-stop, zero-carbon heat, with none of the problems of intermittency that clean energy sources like wind and solar have.

Charlotte Adams, now a government scientist with the Coal Authority (which manages the country’s mines), alit upon the minewater-for-heat idea when she was a professor at the University of Durham. What if, she thought, we could make use of this huge existing source of heat that is located in or near many residential areas? About a quarter of all buildings in the country sit atop a former coal mine, and the government estimates that there are about 2.2 billion gallons of water in these subterranean rivers, plus an as-yet-unquantified amount of heat storage), which is about 3 times the country’s annual natural gas consumption.

Dr. Gluyas wasn’t always so enthusiastic though. When Dr. Adams first told him the idea, he said, “Initially I thought, ‘This is crazy. Woman, you’re crazy with this idea!’” he said with a laugh. “But being a very supportive fellow, I encouraged her to do more work” and it became clear that this could really work.

It also turned out that this actually is not an entirely new idea. In Pennsylvania and Nova Scotia, this has been in practice for decades, though just in single buildings, not networks. Heerlen, a former mining city in the Netherlands, has been running a district heating network on minewater heat since 2012.

Regardless of whose good idea it was, it could be uniquely suited to the U.K., given its abundance of empty mines and its current energy situation. Supply chain issues caused by pandemic lockdowns and the war in Ukraine have made gas, which is used to heat about 75 percent of British buildings, much more expensive. Though the U.K. doesn’t get any natural gas from Russia, it usually gets some from Norway and elsewhere in Europe. Now, with the ban on Russian gas though, other European countries need more of that gas, with less to export to the U.K.

Gareth Farr, a scientist with the Coal Authority, told me, “COVID heightened our appreciation of our global supply chains for everything, and especially for us over here, the war in Ukraine has had a pretty drastic impact on fuel prices.”

And electricity, which isn’t subsidized by the government like gas, is too expensive to use for home heating for most people. If people were to switch over to electrically powered heating, the country would need to produce more electricity, which would likely be provided by fossil fuels. Warm water on the other hand is free.

“Minewater heating is a secure homegrown source of heat,” said Dr. Gluyas. “Essentially it’s sustainable forever,” he said. 

And that’s also very important: The U.K. government committed to reducing their emissions by 68 percent compared to 1990 levels by 2030 in the 2015 Paris agreement, but recent reports suggest they’re falling short. Despite major progress in decarbonizing the electricity sector, reliable carbon-free heating is proving one of the thornier challenges of the transition, especially in Britain, where the housing stock is among the “oldest and worst insulated in Europe.” Heating buildings accounts for about a third of the country’s greenhouse gas emissions.

That too is partly a legacy of coal: homes were built to be drafty, Dr. Gluyas told me, because people burned coal fires inside for heating and cooking. That meant that homes were full of noxious gases, so you actually didn’t want your house to be airtight, or you might have some trouble with carbon monoxide.

“There are no noxious gases coming off minewater heating systems,” Dr. Gluyaid.

So far, two minewater heating schemes have come online, both in County Durham, in the northeast of England. In the town of Gateshead, near Newcastle, the local council took an existing gas-powered heat network and switched it over to run on minewater in March, providing heat to 350 council-owned homes and 18 government buildings, with the capacity to heat the equivalent of 5,000 homes. Nearby, Lanchester Wines, a local business, uses minewater to heat a warehouse. There are also a few other projects in the works, including an ambitious plan for a new housing development, Seaham Garden Village, also in Durham.

In about 70 places, like Seaham, minewater is already pumped out to the surface, according to Dr. Farr, so that it doesn’t contaminate drinking water sources, and is then treated. In these spots, much of the infrastructure is already in place, helping defray the relatively high cost. 

“The projects are referred to as very expensive, which is broadly true,” said Dr. Farr, with the initial expense somewhere between 10 and 20 million pounds. “But they are closer to the cheaper end in terms of large-scale geothermal,” he said. And, he said, the costs will likely come down as the concept becomes realized in more places. Though large, the Seaham project is more straightforward, since it will be bringing in district heating to an entirely new development. Elsewhere, communities and homes will need to be retrofitted, which can be logistically tricky with an upfront cost that may be out of reach for many potential users.

But, they can be revenue generators for local communities. “Our shareholder is the community,” said Jim Gillon, who leads energy development for the city of Gateshead. “We are choosing to reinvest our profits, so when we do get surplus revenue, that’s going back to the council, to underpin the public services we provide to residents,” which could be a boon to many former coal mining communities, which have had a difficult few decades.

Sometimes, clean energy projects run into opposition if they disrupt the local community’s sense of itself — especially when, as in the north of England, much of that sense was derived from extracting fossil fuels. Communities can feel as though they are being maligned or blamed for climate change, instead of given credit for having transformed the world and created so many of the conveniences of modern society that many of us take for granted. Not to mention that much of the wealth that was created by these places didn’t stay there, and when the mines closed, not much came into take its place. These areas, whose economies revolved around mining, have largely been “left behind” in the decades since most of the mines were closed. 

Deprivation Across England graphic; Source: MCHLG/BBC

Many of these communities are in the top 10 percent of the “most deprived” areas of the country, with high rates of unemployment, chronic illness and disability, and lack of social services. But minewater heating projects could help bring investment back to these areas, said Graham Easterlow, the director of East Durham Trust, a local organization.

Horden, a community where Mr. Easterlow works and which is being considered for a minewater heating scheme, was once a superlatively productive coal mine. It held the record for most coal mined in a single day in Europe (6,758 tons) in 1930. But in the last few decades, the town has lost its police and fire stations, secondary school, movie theater, train station, and many local stores

Now, Horden (whose water is already pumped to the surface for treatment) could get its own minewater heat network, and possibly bring jobs and investment back to the area. Mr. Easterlow’s organization provides food to 12,000 people in the county annually, he said, with about a fifth coming from Horden alone, but the community would like to use their minewater to warm a greenhouse to grow food, possibly farm prawns, and create jobs.

“We’ve got to learn from the fact that wealth was created on the back of the people in this area and make sure that doesn’t happen again,” he said.

To a person, everyone I spoke to for this article described the pride these communities take in their mining heritage, and their enthusiasm for the prospect of seeing the mines used again. After all, many of the people who live in these places or their ancestors may have dug the mines themselves, and will know the workings better than anyone else who might come in. It is silly to waste the accrued knowledge of generations that exists anywhere, even if it doesn’t seem immediately relevant, including in places that seem to be stuck in the past.

“The story we’ve had is that the Northeast in particular is very proud of its coal mining heritage,” said Mr. Gillon, “but we’ve been able to turn what was a polluting industry to a green industry, and that has resonated with community, leaders, and councillors, which has been a surprise.

It’s a lovely full circle.

This was originally posted on Tatiana’s Substack News from a Changing Planet, a free twice-monthly newsletter about what on Earth is happening, with articles and essays about climate change and the environment.

Header photo by Emily Wang on Unsplash.