Out of sky, out of mind
A look at the myriad of solutions to pull carbon out of the atmosphere — here in Nova Scotia, in other areas of the country, and internationally.
Carbon Engineering's DAC facility, sometimes called the Innovation Centre, in Squamish, British Columbia. Photo Courtesy of the 1PointFive online media kit.
It will be necessary to pull gigatonnes of carbon dioxide out of the atmosphere, and to trap it, permanently, underground. Barring that, a stable climate might already be out of reach.
This was the conclusion of the Intergovernmental Panel on Climate Change (IPCC) in its seminal report of 2015, and in every report since. Rapid and universal decarbonization was still necessary, they said, but so much had already been emitted, and so much was still finding its way skyward, that direct and deliberate carbon removal must now to be part of any workable solution.
“All pathways that limit global warming to 1.5°C,” reads the 2015 report, “project the use of carbon dioxide removal (CDR) on the order of 100-1,000 gigatonnes of CO2 over the 21st century.”
It was a startling admission, if for no other reason than because CDR, as a viable technology, didn’t exist. Big ideas for drawing down carbon had been around since the 1980s, but none were proven, much less commercialized.
One of the more conspicuous CDR technologies — not currently here on the East Coast — is something called Direct Air Capture (DAC), presently on the fast track to commercialization. Carbon Removal Canada encourages public and private investment in CDR technologies generally, as well as a regulatory environment in which they might thrive, and DAC, says Bushman, is getting a lot of attention.
Direct Air Capture uses a network of fans to bring ambient air into contact with a capture medium — either a liquid solvent, a solid sorbent, or a specialized membrane — with which its carbon dioxide reacts, converting from a gas to a mineral. The trapped carbon is then liberated from this mineral using extreme heat, pressure, or an electrical current, recycling the capture medium, and yielding a stream of pure, concentrated, carbon dioxide.
“We can remove CO2 from the atmosphere all day long,” says Bushman, “but we have to do something with it.”
Carbon Engineering's DAC facility, sometimes called the Innovation Centre, in Squamish, British Columbia. Photo Courtesy of the 1PointFive online media kit.
Some Canadian startups have gotten creative, like the Dartmouth-based CarbonCure, mineralizing captured carbon into its concrete. Aeon Blue on Cape Breton Island plans to combine captured carbon with hydrogen to create net-zero “efuels” — drop-in replacements for diesel, gasoline, or natural gas. These applications have value, says Bushman, but most captured carbon will ultimately need to go underground.
This can be done by injecting it, kilometres deep, into geological formations which will, by virtue of their structure, keep it trapped. The gold standard, says Bushman, is to inject it into deposits of potassium, magnesium, or calcium with the carbon then reacting to form stable carbonate minerals. Only some regions of Canada have the appropriate geology for burying carbon at scale, he says, namely the Canadian West. There may, however, also be opportunities offshore in Atlantic Canada.
DAC is already at work. In 2021, Canada-based Carbon Engineering finished the world’s first industrial scale pilot plant in Squamish, British Columbia, where it dutifully captures one tonne of CO2 per day, and in Iceland, the largest DAC facility in the world has been wrangling 36,000 tonnes annually since May 2024. These are small potatoes next to the STRATOS facility currently under construction in Texas, which is expected to capture 500,000 tonnes annually. A comparable facility is also planned for Scotland.
Then there’s Deep Sky Alpha, a facility planned for this year in Innisfail, Alberta, which will pilot around ten different DAC technologies simultaneously (recruited from across the planet) in order to identify the most promising for commercialization. Their goal is 3,000 tonnes annually, all powered by the 9-megawatt Lethbridge One Solar Project.
The problem is power. DAC can, in theory, be scaled up to the 100-1,000 gigatonnes called for by the IPCC this century, but unlike more passive solutions, DAC needs electricity to separate out its captured carbon and recycle its capture medium; electricity that needs to be renewable, lest the purpose be defeated. Once you add the costs of infrastructure and burial, DAC gets expensive. The industry’s goal is $200 per sequestered tonne of CO2, or lower, once at scale, but today — and depending on the technology — the price is closer to $500-$800 per tonne.
If done right, says Bushman, DAC has the advantage of running continuously, of sequestering carbon more or less permanently, and of doing so in easily measured quantities, which matters when you’re selling carbon credits. These strengths will always need to be measured against its costs, and against those of alternatives.
But DAC is obviously not the only game in town, says Tim Bushman, director of policy and research with the nonprofit Carbon Removal Canada.
Diagram of a generic DAC facility. Illustration by Daniel Hildreth for Carbon Removal Canada.
Bushman says that “six or seven years ago, there really wasn’t anyone working on this topic.” There are now hundreds of initiatives globally — startups, removing experimental sums of carbon with tools and techniques of varying maturity; with the majority of those located in Canada doing something called “enhanced weathering.”
Alkaline rocks (magnesium, calcium and potassium) naturally bind with carbon dioxide to form stable carbonate minerals, harmless to climate, and broadly beneficial to soil and water — an unfortunately slow process whereby geology brings these rocks to the Earth’s surface for wind, rain, and snow to then break them into small, reactive pieces.
A slow process, some mining companies have been hastening things, accidentally, for decades, by grinding up the appropriate rocks and dumping them in mine tailings (leftover materials from the processing of mined ore) where increased surface area allows them to react rapidly with CO2 in the air. The Vancouver startup, Arca Climate, has partnered with several such companies to further speed things up by plowing tailings to increase their air exposure, and by targeting the right rocks for future excavation. In this way, these mines could become carbon neutral in the near term, and carbon negative in the long, collectively sequestering hundreds of millions of tonnes of CO2 annually.
Nova Scotia is doing much the same thing, but with an extra ingredient — water. Because oceans and rivers naturally soak up huge sums of carbon from the atmosphere (holding it as carbonic acid) these same alkaline rocks can be added to mineralize it. Planetary Technologies, a startup in Dartmouth, is adding magnesium hydroxide to the waters of Tufts Cove, in the Halifax harbour, converting its waterborne carbon into magnesium carbonate, at which point the ocean, now carbon depleted, will dutifully soak up more from the atmosphere. {See our story on Planetary Technologies]
CarbonRun, recently named ‘Venture of the Year: Scale-up’ at the 2025 Atlantic Canada Cleantech Awards, is a similar venture, but instead of applying magnesium hydroxide to ocean basins, they’re dosing some Nova Scotia rivers with crushed limestone. {See our story on CarbonRun}
CarbonRun technicians collecting data and samples. Photo courtesy of Nick Pearce.
These waterways have been chronically acidic for decades as a consequence of acid rain, and the Nova Scotia Salmon Association has been liming them since 2005 to recover spawning fish. In addition to neutralizing the nitric and sulfuric acids inherent to acid rain, scientists who would go on to found CarbonRun found this liming was also mineralizing carbonic acid, a naturally occurring component of rainwater, absorbing CO2 in the process. CarbonRun has tweaked this limestone dosing to improve this process of carbon absorption while continuing to make the rivers healthier.
“Carbon combines with limestone to create bicarbonates, some of which is used by aquatic species for shells, etcetera, with the rest getting transported to the ocean for storage for thousands of years,” says Dr. Eddie Halfyard, once a freshwater ecologist with the Nova Scotia Salmon Association and now part owner of Carbon Run. “So, that discovery was a lightbulb going off and we realized this was big in terms of carbon markets and an integral part of how we get to net zero.”
And Bushman’s final word on where we find ourselves in the world of carbon removal technology is straight and to the point.
“DAC alone won’t get us to scale,” he says. “Planting trees alone won’t get us to scale. Enhanced rock weathering, or any of the other technologies alone won’t get us to scale. We need so many companies to work. We need so many technologies to work. And we need so many countries to be champions in this space.”
Climate Stories Atlantic is an initiative of Climate Focus, a non-profit organization dedicated to covering stories about community-driven climate solutions.
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