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  • Writer's pictureAnna Reid

How to capture carbon, permanently

Communities around the world are grappling with the troubling reality that we have too much carbon dioxide in the atmosphere. There are many things we need to do to solve this problem, and one is to capture and remove the carbon.

 

But how can we capture something we cannot see? And what are the differences between natural and technology-based solutions?

 

In this article, you’ll learn the basics about capturing carbon and why it’s important we think carefully not just about how to capture it, but also how to keep it stored safely for as long as possible, so it is permanently removed.



Carbon is life.

View of Mt Aspiring National Park
Mt Aspiring National Park. This breath-taking awesome environment represents millennia of Earth's slow movement, all the while capturing and cycling carbon dioxide through plants, rivers and rocks. Photo by Chris Oze.
 


Carbon dioxide (CO2) is not an enemy to fear. In fact, it’s an essential part of life on Earth and is one of the key elements present since the planet came into existence.

 

For aeons, the Earth has been managing carbon dioxide perfectly all on its own through the natural carbon cycle. Carbon dioxide is one of the core reasons we have a habitable planet as it traps heat from the sun and keeps us at just the right temperature for life. Without it, and the other greenhouse gases in our atmosphere, this place we call home would be frozen.

 

But the amount of greenhouse gases in the atmosphere is a delicate balance, too much means more heat is trapped and that extra warmth changes how the climate works.

 

Our problem with carbon lies in the fact we have built a world that relies heavily on fossil fuels – coal, oil and gas. While these have propelled humanity forward with innovations in energy, materials and agriculture, these fossil fuels have also released incredible amounts of CO2, way more than the Earth’s carbon cycle can cope with.

 

It’s clear, the excessive greenhouse gases in the atmosphere are causing it to warm and that is not a good thing. We must focus all efforts to reduce the amount of CO2 in the atmosphere and stop any more being emitted.

 

But how?


How to remove carbon dioxide, naturally.


Nature gives us the best template for effective and efficient ways to remove carbon dioxide. From planting more trees, restoring old forests, improving agricultural practices and protecting marine ecosystems, nature-based solutions essentially boost the places carbon can ‘sink’ naturally and be stored.



NZ mountain range cloaked in native forest.
NZ mountain range cloaked in native forest. Trees are one of nature's powerhouses that capture and store CO2. Forests of native trees provide the best solution for long term permanent CO2 storage for their additional biodiversity value, but will often take longer to grow than exotic forests such as pine. Photo by Mike Ogle.

 


In the long term, these natural ecosystems will do a beautiful job of keeping the carbon cycle in balance  (as long as we can return the Earth to its balanced state).


But in the short term, Earth’s systems are quite simply not coping with the amount of carbon dioxide the world is generating.


We’ve pushed nature beyond its limits, expecting it to adapt at an unnatural rate. There is not even enough physical space available to scale natural carbon sinks, like forests, to the size needed to capture the excessive amount of CO2 we’ve pumped into the atmosphere.

 

And despite the incredibly important need for more nature-based solutions, these solutions can only deal with the CO2 that is already in the atmosphere.


We still have the big problem of too much being emitted. This is where technology can play a part.


Smog surrounding industrial smokestacks
Smokestacks billowing CO2 into the atmosphere. Industrial decarbonisation is key to reducing global greenhouse gas emissions. Photo by Bryan Williams on Unsplash.
 

How to capture carbon dioxide with technology.


One thing we can be sure of is that if there’s a problem to solve, human beings will rise to the challenge.

 

The quest to remove carbon dioxide from the atmosphere is being met with an ever-growing suite of innovations and adaptations that are either in development or already in use around the world.

 

Of course, with a growing industry comes a range of terminologies: point-source, direct air capture, carbon capture and storage, to name a few.

 

But when we boil it down, there are just two main ways to think about carbon dioxide removal:

-      We capture it directly from the atmosphere,

-      We stop it from entering the atmosphere in the first place.

 

Using technology to remove carbon dioxide requires a great deal of ingenuity.



Close up of industrial fan.
Capturing CO2 directly from the air uses massive fans to suck in ambient air before separating the CO2 for storage, largely underground in depleted oil ad gas reservoirs. Photo by Chris Lutke on Unsplash.
 

Capturing CO2 directly from the atmosphere is already happening, where huge fans quite literally suck it from the air. This approach helps to deal with past emissions, reducing the already high levels of atmospheric CO2. It’s also seen as a solution to offset emissions produced by things like airplanes, digital technology or financial services, because no emissions-free solution exists, or the emissions created are indirect to the work itself.

 

But the emissions problem for the industrial sector is different. Whether large or small, any industrial process that uses fossil fuels will produce CO2 emissions. Here, operational changes can be made to industrial smokestacks that use large ‘scrubbers’ or filters to capture the CO2 before it enters the air.

 

Whether CO2 is being captured directly from the air or filtered out at the point of emission, these technologies are engineering marvels of their own.

 

But the next part is even more important: the storage.


What we do with captured carbon dioxide matters.


Finding a solution that prevents CO2 from re-entering the atmosphere is a critical science to get right. It’s the only way we’ll make progress on permanently reducing CO2 levels. Equally important is that we don’t create any new problems while trying to solve this one.


Like the many terms used to describe carbon removal, there are many ways to describe what to do with it. But in essence we can either store it away or we can store it in materials we use. The method we choose can make the difference between short and long term, generational impact.

 

Going deep underground.

One of the most common way to store CO2 away is geological storage. This basically means pumping captured CO2 deep underground into depleted oil and gas reservoirs, saline aquifers or even un-mineable coal beds. This places the CO2 far away from the atmosphere, back to where most of it has come from.

 

But there are factors and risks to consider with this approach.

 

The captured CO2 needs to be compressed to a density that makes it heavier for more efficient transportation and injection. That compression takes a lot of energy, as does the transportation, so depending on the source of that energy (e.g. fossil fuels), it can negate the CO2 emissions captured.

 

Once compressed and transported, the CO2 is injected deep underground into porous rock like basalt, where the CO2 may react over time with the rock and be locked into it. But it’s important to know there is no way to confirm if that reaction occurs (yet). More likely, the CO2 will remain in a dense but gaseous state which means it relies on the geology of the area to keep it contained. That presents a further problem – leakage – which can be hazardous and undoes all the work undertaken to get the CO2 underground in the first place.



Basalt rock columns
Basalt rock. A porous volcanic rock that contains minerals such as calcium and magnesium. These minerals have high reactivity with CO2, increasing the chances of CO2 storage. Photo by Mick Haupt on Unsplash
 

What’s also important to consider is displacement. When we pump a gas into geological cavities, that can increase the potential for seismic activity. Or it can displace water that’s been polluted by earlier oil extraction activities, creating a health hazard for us and the environment.

 

Finally, storage sites need ongoing monitoring and that needs money. But as underground storage is essentially a storage-only solution, over and above the amount being paid to capture the carbon dioxide, no money is being made to help offset the cost. That makes this solution an expensive one.

 

Turning a problem into a solution.

A more economically sensible approach to carbon removal is to store it in materials and chemicals we use.


If CO2 can be used in valuable products that would traditionally be derived from fossil fuels or mined resources, it creates a two for one deal: it offsets the costs of capturing the carbon, plus it displaces the need for some raw materials.

 

Some examples are to use CO2 as a feedstock in the production of synthetic fuels, chemicals, building materials or even household products like baking soda. For CO2 to be

used in these ways, it needs to be chemically transformed from a gas into either a liquid or a solid.

 

There are considerations of course. Not every application means there’s a meaningful permanent reduction as some of the uses will result in re-emission at a later stage (like fuels).

 

For a more confident method, converting CO2 into a solid material (aka mineralisation), doubles down on impact. Carbon mineralisation is a permanent storage solution and can displace virgin (often mined) resources.

 

Through chemical reactions with elements such as calcium or magnesium, captured CO2 is transformed into stable carbon compounds, called carbonates, locking the CO2 away. This chemical bond can’t be easily undone, it needs either incredibly high temperatures or an acid to break the elements apart. The CO2 is permanently locked in, exactly the result we need for carbon storage.

 

Calcium carbonate (CaCO3) and magnesium carbonate (MgCO3) are valuable ingredients for emissions-intensive industries like cement, construction, agriculture, and pharmaceuticals. These carbonates can even be stored underground in geological formations but in a state that is more robust than non-mineralised forms.


Magnesium carbonate in a test tube
Magnesium carbonate. This compound is formed when CO2 reacts with magnesium, creating a solid state material that has a wide range of applications. Photo: Gareth Moon, Ethik Studio.
 

Using carbonate compounds as a method for carbon storage not only promises permanence but also reduces reliance on precious resources. By using carbon mineralization, industries can achieve their climate obligations and manage their resources more effectively.


Twice the impact for climate change mitigation.


Carbon removal is a pivotal technology in addressing climate change and moving the world closer to a zero emissions future.

 

When we store captured CO2 in materials we use, rather than just store it away, we get twice the impact.  We prevent or remove CO2 from the atmosphere and displace materials that might otherwise need to be mined or made from fossil fuel derivatives.

 

If the goal is to permanently and safely remove CO2 from the atmosphere, and prevent future emissions, mineralising captured carbon dioxide stands apart as the most promising solution to date.


Permanent carbon capture will move us closer to a decarbonised world.


Make no mistake. Whichever technologies we apply to the challenges of climate change, there is no better solution than reducing carbon dioxide by transitioning to clean, fossil fuel-free energy sources. But as we look ahead to that cleaner, greener future, carbon removal and mineralisation offers us a plan for rapid CO2 emissions reduction at scale.


 

Aspiring Materials has developed a unique approach to sequestering carbon dioxide using magnesium-rich rocks. We complement existing carbon capture technologies with our rapid and permanent carbon mineralisation process that creates a magnesium carbonate material, ready for use in a range of industries and applications. Find out more about how we do carbon removal.

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