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Explainer: How carbon capture works

The United Nations has called climate change the defining issue of our time, and we know that carbon dioxide is the biggest cause of climbing global temperatures and rising ocean levels.

With so much excess carbon dioxide trapped in our atmosphere, there needs to be a way to take it out in order to slow or ultimately reverse the effects. That’s where the idea of carbon capture and storage comes in.

Carbon capture is exactly what it sounds like: capturing the carbon dioxide instead of allowing it into the already carbon-laden atmosphere. Storage is also just that: storing the carbon somewhere other than our atmosphere, and that means deep underground.

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Essentially, this allows emitters like power plants, factories and coal plants to still do what they are doing without the carbon footprint they would otherwise have. These emitters would then store the carbon dioxide deep underground — really putting the CO2 back where it originally came from.

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“Should we build lots of carbon capture and storage plants? I think we have no real alternative if we’re going to stay in a climate which we recognize on the earth,” said Stuart Haszeldine, an expert in carbon removal at the University of Edinburgh. “The number of carbon capture and storage plants needs to increase in a totally unprecedented way in the next 50 years.”

Carbon capture may sound pretty revolutionary, but the idea has been around for decades, said Guloren Turan of the Global CCS Institute, a group that promotes carbon capture as a solution to address climate change.

Turan says carbon capture is effective and safe. “There has not been any observed sort of significant leakage from any facility or any accident or anything of that nature, and as long as the site selection is carried out robustly and the operation is carried out, there are no technical issues in terms of security and safety.”

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Not everyone agrees. Greenpeace has been concerned about the concept of carbon capture and storage for more than 20 years. “We have concerns over the technical risks, so those are the safety aspects and the security of the storage of carbon once it’s injected,” said David Santill, a spokesperson for Greenpeace International.

“Carbon-capturing storage is always going to be a technological approach to trying to fix a problem,” Santill added. “I think we need to be increasingly avoiding the problem by getting ourselves out of fossil fuels.”

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There are 23 plants carbon capture plans in full operation globally. All use a different type of process to capture and then store the carbon dioxide.

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There are three main types: pre-combustion, post-combustion and oxyfuel.

In post-combustion carbon capture, the CO2 is separated from the flue gas, or the gases you see coming out of a smoke stack. This is done by bubbling the gas through an absorber column packed with liquid solvents like ammonia. Once the chemicals in the column become saturated, super-heated steam is then passed through it, which releases, separates and traps the CO2. That carbon dioxide can then be stored.

Pre-combustion carbon capture is a little different. In this method, solid, liquid or gaseous fuel is first converted into a mix of hydrogen and carbon dioxide. The hydrogen is then pumped out and used to fuel hydrogen-cell cars, while the carbon dioxide is pumped out and sent to storage.

Oxyfuel is the third type of carbon capture that is most commonly used. In this method, fuel, like coal, is burnt in a pure oxygen environment. Virtually all of the waste gas that’s produced will be composed of CO2 and water vapour. This means that the CO2 can be piped directly to storage without any separation.

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These three are the most common methods. But there are other types that are now being tested would allow CO2 to be used rather that stored.

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A new technology, called Allam cycle, uses CO2 to run turbines at a demonstration plant in Texas. “It’s aiming to produce electricity with carbon capture at prices that normal natural gas plants do today,” Turan said.

Another initiative is called direct air capture, which aims to remove carbon that has already spewed into the atmosphere.

Carbon Engineering is a B.C.-based company that’s one of only three in the world working on direct air capture, and it is the only company to be turning that captured CO2 into actual fuel.

The company is still in the early stages, but it has proven that it can take CO2 directly from the air around us and make carbon-based fuel that we can put into our vehicles.

“We have a chemical process that captures the CO2 as it comes through the system,” said Steve Oldham, CEO of Carbon Engineering. “We take our CO2, we add hydrogen and make it completely clean fuel (that) you can put in your car tomorrow or you can put it in your truck or in a plane, and that fuel is completely carbon neutral.”

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— with files from Kassidie Cornell

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