Welcome to our weekly newsletter where we highlight environmental trends and solutions that are moving us to a more sustainable world.
Hey, it’s Emily. I’m always amazed by how hot it can get in subway stations. So the idea of cooling them by taking that heat to use elsewhere seems, well, cool to me. I’ve written about heating buildings with waste heat from places like nuclear power plants, paper mills and sewers. So why not subways?
This week:
- Canadian tech aims to cool hot subways in New York City
- The Big Picture: How wildfires generate thunderclouds
- What is ‘wishcycling’ and why are some municipalities cracking down on it?
Canadian tech aims to cool hot subways in New York City
Underground subway stations are hot and getting hotter, drawing complaints from transit riders around the world. That includes those in Canadian cities such as Montreal, where a reporter recently measured the temperature as 38 C.
Now a Canadian company is testing an energy-efficient cooling solution in New York City’s subway system.
Toronto-based Cascara Energy and New York City’s Metropolitan Transportation Authority are installing the radiant cooling system in ceiling arches in East Broadway station. The first units are expected to be running at the end of August and the pilot will continue until the end of 2027.
The system uses loops of chilled water-filled pipes to absorb heat and make passengers feel cooler as they pass underneath.
“The effect is similar to the experience of walking through the refrigerator aisle at a supermarket,” said Lucas Bejarno, a spokesperson for the MTA in an email.
Unlike traditional air conditioning, it doesn’t use any fans, making it more compact. It also promises to be easier to maintain and 25 to 35 per cent more efficient.
The hope is that the system won’t just keep passengers more comfortable but that the heat could be recovered and recycled for other uses, the MTA reported in its October 2025 Climate Resilience Roadmap.
Why subway systems are so hot
There are many sources of heat in a subway system, including people, electronics such as lighting and screens and train braking and air conditioning systems.
Robert Croghan, founder and CEO of Cascara Energy, said normally the walls of the subway can absorb a lot of that heat, but at some point they can’t take in any more. His system aims to catch new heat before it hits the walls as well as gradually cool the walls themselves over time to restore their ability to absorb more heat.
Meanwhile, the heat recovered by the system can be carried away and used elsewhere.
“You’re mining the heat,” he said.
A goal of the project is to see how much heat can be “mined” and available to heat water and buildings.
Croghan said that wouldn’t just displace burning fossil fuels for heat. It’s also far more efficient than drilling boreholes for geothermal heating, which also uses underground heat.
“There is waste heat everywhere,” he said. “We don’t need to be drilling for it.”
Heat is already recycled from the London Underground
The London Underground is already collecting waste heat from the Northern line tunnels of its network year-round in the British capital for its Bunhill 2 Energy Centre, located in the former City Road station. That, in turn, is one of the heat sources for a district heating network connected to thousands of homes, a school and two community centres. The system’s fan can be reversed in the summer to pump cool air into the tunnels.
WATCH | Can this building save the London Underground from overheating?:
Croghan said that’s a more conventional cooling system with high-velocity fans, so it uses more energy than his company’s passive radiant cooling technology. The MTA notes that such conventional systems also need more space for mechanical rooms and street-level cooling towers.
London and New York are especially notorious for their steamy subways, but could recovering heat from subway tunnels and stations also work in Canada?
“For sure. Absolutely,” Croghan said.
He hopes the New York pilot, which his company is mostly funding itself, will show the system works and get other transit systems interested.
– Emily Chung
Old issues of What on Earth? are here. The CBC News climate page is here.
Check out our podcast and radio show. In our latest episode: With people on both sides of the Canada-U.S. border choking on smoke, much of it coming from fires in Canada’s forests, U.S. President Donald Trump is threatening new, fire-related tariffs in retaliation. Climate scientists like Zeke Hausfather say wildfires in Canada’s boreal forest are linked to global warming, but as environmental law expert Godwin Dzah explains, when health hazards cross borders, there are ways to hold governments and companies to account. But the question of liability gets hazy when climate change enters the conversation.
What On Earth24:18Americans want payback for smoky skies. Are they right?
What On Earth drops new podcast episodes every Wednesday and Saturday. You can find them on your favourite podcast app or on demand at CBC Listen. The radio show airs Sundays at 11 a.m., 11:30 a.m. in Newfoundland and Labrador.
Check the CBC News Climate Dashboard for live updates on record-breaking weather and current conditions across the country. Set your location to find out how today’s temperatures compare to historical trends.
Reader feedback
Dan Kells, who lives North Saanich, B.C., wrote in to say, “The story by Nicole Mortillaro about purchasing a used EV is important to help assuage many fears that have been falsely created about EVs. First-person accounts are probably the best way to alleviate some of those fears.
“I am attaching a photo of our 2014 Leaf with a trailer attached. The carmaker recommends a small utility trailer only if you must tow, so we may have pushed the limit a bit here on our moving day.
“I was inspired to write to you because of Nicole’s story and I would like to assure her and all Canadians that an EV is a solid, reliable vehicle that has excellent range in the newer models at the same time as we have an ever-expanding charging infrastructure. In fact, B.C. Hydro just announced a tripling of their EV charging infrastructure.”
Write us at [email protected] (and send photos there too!)
The Big Picture: How wildfires generate thunderclouds
A huge fire in southwest France has generated the country’s first recorded pyrocumulonimbus fire cloud. While they’re rare in Europe, Canada has a reputation for producing the most fire thunderclouds in the world, most recently during the Boston Bar fire in B.C.
The diagram shows how wildfires generate these unusual clouds: The heat from a wildfire causes hot air to rise in an updraft, pulling moisture, smoke and even burning embers up with it. Because the atmosphere is cooler higher up, at some point the vapour and smoke cool and spread out, and the water condenses into a cloud above the smoke column.
When they grow large enough, pyrocumulonimbus clouds start to behave like thunderstorm clouds in other ways, generating strong, erratic winds and lightning. Read more about pyrocumulonimbus clouds and how they can pose a danger during wildfires.
— Emily Chung
Hot and bothered: Provocative ideas from around the web
- Critics worry EVs will crash the grid, but an emerging EV technology will actually help support the grid and make electricity more reliable and more affordable.
What is ‘wishcycling’ and why are some municipalities cracking down on it?
Have you been “wishcycling?”
The word is a portmanteau of “wishful thinking” and “recycling” and is an ongoing challenge for recycling systems.
“Wishcycling is when we see residents or people using the recycling carts throwing material in them that is not recycling in the hopes that somehow the material will end up where it needs to be,” Ben Routledge, the Regional District of Nanaimo’s manager of solid waste services, told CBC’s On the Island.
It’s become such an issue in the Nanaimo, B.C., area that officials are looking at fines for scofflaws.
Recycle B.C., the non-profit that manages residential packaging and paper recycling across the province, says slightly less than six per cent of the loads it receives are contaminated.
Routledge says the most common “wishcycled” items are things that can be recycled through a depot but don’t belong in curbside collection bins, like woven plastic or zipper lock bags. Improperly cleaned containers are also common.
But he says the region is also seeing an alarming increase in scrap metal, household appliances and even hazardous waste like propane tanks, batteries or bear spray.
How to fix a dangerous, costly problem?
“All of that stuff can [mistakenly be put] into a collection truck, which is being compacted,” he said. “And those hazardous [wastes] can either contaminate the material around them, they can explode or they can ignite.”
Contamination makes it harder to sell paper, plastic and glass to end markets where they’re recycled into new material. Loads that are seriously contaminated may end up in the landfill.
Recycle B.C. sets its acceptable contamination threshold at five per cent.
The Regional District of Nanaimo has seen the rate of contamination in its recycling loads climb from four per cent to 5.4 per cent over the last year and a half, with some loads topping 18 per cent, Routledge said.
As a result, outreach teams will start issuing warnings for non-compliance. After three strikes, residents will face a $500 fine — and if they persist, the district will consider stopping pickups.
The City of Richmond, south of Vancouver, is also auditing residents’ bins after its contamination rate climbed to 7.3 per cent for curbside pickup and 11.3 per cent for multifamily residences. People who break the rules will find an “oops” sticker slapped on their blue box.
Getting those numbers down matters — if municipalities let contamination rates rise too high, they can face hefty financial penalties.
“If it stays above the allowable threshold for too long of a period of time, we can face financial penalties that could equal as much as $120,000 per year,” Routledge said.
Recycle B.C. says when a municipality’s contamination routinely exceeds its thresholds, its first step is to work with the community.
“Financial penalties are only considered if contamination remains persistently high after those extended efforts,” the non-profit told CBC News in an email.
If you’re unsure about whether something you’re throwing out belongs in your recycling bin, check with your local recycling service. In B.C., you can check RecycleBC.ca or download the Recycle B.C. app.
— Simon Little
Thanks for reading. If you have questions, criticisms or story tips, please send them to [email protected].
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Editor: Emily Chung | Logo design: Sködt McNalty
