Unveiling the Reality of Carbon Capture Technology

Exciting ideas to clean up carbon have made people happy and also caused some arguments

Glenn Burgess

Climate change is a big topic this week because leaders from around the world are meeting at the 2021 United Nations COP26 Climate Change Conference in Glasgow.

People in different industries are talking about whether using technologies and methods to reduce carbon, like storing it, capturing it, converting it, or sequestering it, can really help get rid of carbon dioxide, which is the most common greenhouse gas we release into the air.

Let’s break down what these words mean, see where the technology is right now, and imagine how they would work in real life.

Carbon capture

Carbon capture mainly involves taking carbon dioxide out of different places, like the smoke that comes from power plants using fossil fuels such as coal, oil, or gas, and also from factories and places where things are made.

Capture can also mean getting carbon dioxide directly from the air, which is called Carbon Dioxide Removal (CDR) or Direct Air Capture (DAC).

But here’s the thing: when smoke comes out of a power plant or factory, it has a lot more carbon in it, about 10 to 15 percent carbon dioxide. In contrast, the air around us has a much smaller amount of carbon dioxide, about 400 to 450 parts per million (ppm), which is like 0.04 percent.

Harry Atwater, a professor at the California Institute of Technology, explains that the carbon dioxide in the air, even though it’s important for climate change, is really spread out and not easy to capture. So, scientists and companies have to come up with clever ways to grab it and make it into a concentrated form.

For example, there’s a Swiss company called Climeworks that’s a leader in carbon capture. They have machines in Europe that work like big fans to suck carbon dioxide out of the air and then they heat it up and bury it underground.

Another company, Carbon Engineering, uses a simple chemical called potassium hydroxide to catch & pull down the carbon dioxide (which is a bit acidic) from air.

Harry Atwater mentions that there are different ways to capture carbon directly from the air, and some researchers are also looking into capturing carbon dioxide from the oceans. For example, he’s involved in an ARPA-E project funded by the Department of Energy.

According to reports from the National Academies, we should take these technologies seriously as part of our efforts to fight climate change. They can actively remove carbon dioxide from the air.

Peter Kelemen, a professor at Columbia University, adds that a lot of research has gone into figuring out how to separate carbon dioxide from other gases in the air. But once you’ve captured it, you still need to find a place to store it.

Carbon sequestration & storage

From Peter Kelemen’s perspective, storage and sequestration mean essentially the same thing, except sequestration is used when the storage of carbon dioxide is considered permanent, like when it’s stored underground using methods like geological storage.

For example, the Norwegian Sleipner Project stores dense carbon dioxide fluid under pressure beneath the seabed in the North Sea.

However, carbon sequestration underground has a significant drawback. Harry Atwater points out that the main market for this technology is in enhanced fossil fuel recovery. Some companies want to inject pressurised carbon dioxide into existing oil and gas reservoirs to extract more fossil fuels.

They might argue that they’re carbon-negative because they’re technically taking carbon dioxide from the air and putting it underground. But the process also boosts the release of methane, another greenhouse gas, and more carbon dioxide.

So, it’s crucial to ask whether a company’s overall process is truly carbon-negative, positive, or neutral.

Iceland is doing something interesting by using technology from Climeworks and CarbFix. They not only capture carbon dioxide and pump it underground but also store it as solids. These carbon-bearing minerals, mostly “carbonates” like calcite and magnesite, can lock away carbon dioxide for thousands of years.

Harry Atwater explains that if the right layers of rock allow the conversion of the stored carbon dioxide into a solid form, it becomes much more stable and less likely to escape into the atmosphere. CarbFix figured out how to make this happen by understanding how the injected carbon dioxide interacts with the mineral layers to create stable carbonates.

Instead of just putting excess carbon underground, Harry Atwater suggests that it makes more sense to turn carbon dioxide into a valuable product. Many companies and scientists are exploring this idea. Some researchers are looking into using solid forms of carbon in building materials like steel and cement, which are already big sources of emissions.

Essentially, they want to take the carbon dioxide emitted during the production of construction materials and convert it back into usable materials like carbon fiber composites. This would provide a long-term way to store carbon.

On the other hand, there’s another type of carbon storage that’s less permanent: using carbon as fuel.

Fossil fuels, like gasoline, react with oxygen when we use them in our cars, creating carbon dioxide and water. Many scientists are exploring ways to reverse this reaction, turning carbon dioxide and water back into fuel and oxygen.

Harry Atwater and Caltech are part of the Department of Energy’s Liquid Sunlight Alliance. They’re working on using solar energy to drive this reverse fuel-forming reaction. One big advantage of this method is that it could help us reuse fuel in industries that are hard to make eco-friendly, like aviation, shipping, and steel production.

Imagine being able to recycle and reuse jet fuel in airplanes. It would be carbon-neutral because the carbon dioxide created when the fuel is burned would be balanced by the carbon dioxide turned back into fuel. Airlines are really interested in this idea.

Some companies are already making progress in this area. There’s a Bay Area company called Twelve, named after the atomic mass of carbon, that’s working on turning carbon dioxide back into fuels. And a German company called Atmosfair is creating synthetic carbon-neutral jet fuel by combining hydrogen from wind turbines with captured carbon dioxide. Their first customer is Lufthansa.

The cost of carbon

In the coming years, experts will need to carefully consider the advantages and disadvantages of various methods for removing carbon dioxide from the atmosphere.

Even traditional approaches like planting forests and creating natural biomass to store carbon can be tricky to implement and sustain. Reforestation in developing countries can be complicated due to land ownership issues and the reasons for tree removal. Afforestation and biofuel production also compete with food production for available land.

Moreover, new forests effectively capture significant amounts of carbon only while they are growing. Once they mature, the rate at which they remove carbon dioxide is not much greater than the rate at which carbon dioxide is released through plant respiration and the decomposition of dead biomass. To maintain a large forest-based carbon sink, ongoing harvesting and protection from decay are necessary.

Additionally, the cost is a major concern for carbon capture and sequestration technology. Sequestering carbon requires citizens and leaders of industrialized societies to agree to fund the cost of carbon storage through taxation, but there is currently no global consensus on the price of carbon per tonne.

Although carbon credit markets are emerging in the corporate sector, there is currently a gap between the demand for carbon storage and the available capacity for storage methods. The demand for carbon credits far exceeds the capacity to provide them.

Most carbon-negative technologies are still in their early stages of development, lacking large-scale infrastructure for growth and expansion. To be successful, these technologies will need to create new products such as fuels, specialty chemicals, and materials, with the most significant markets being for fuels, cement, and steel, produced on a massive scale.

These approaches often face controversy, primarily because some argue that carbon capture and storage can let fossil fuel companies off the hook for their substantial carbon emissions.

Harry Atwater points out that to achieve a sustainable reduction in atmospheric carbon levels, we need to decarbonise and electrify as much as possible. However, for industries that are exceptionally challenging to decarbonise, carbon storage can offer a way to put those emissions to productive use.