Technological Solutions: Can Innovation and Science Sequester the Rest?

6 minute read

Updated on: 30 Jul 2021

We can use technology to increase natural carbon absorption and even take CO₂ straight out of the air! In this chapter, we’ll look at how this works and what the challenges are…

How technology can speed up natural carbon absorption

Weathering happens when rocks are physically and chemically broken down over time . When silicate rocks (such as volcanic or deep-earth rocks) are broken down, they react with CO₂ in the air to produce new minerals. These are then usually transported to the ocean by rivers .

Image of Natural silicate weathering — Natural silicate weathering

Enhanced weathering increases the rate of natural weathering in order to absorb more CO₂ more quickly than would happen naturally .

This involves grinding up billions of tonnes of rock to increase their surface area. They’re then spread over warm, damp regions such as tropical forests or agricultural land where weathering will occur quickly .

Image of Process of enhanced weathering — Process of enhanced weathering

However, all this crushed rock needs to be transported from the mine to the spreading site, which can be very expensive and a risk to human health if the crushed rock is breathed in . What’s more, grinding the rock into powder uses a lot of energy .

But what if we could remove carbon and generate energy at the same time?

Capturing carbon and energy at the same time

We’ve already seen how plants and trees capture CO₂ from the air at a low cost. However, we also saw that when trees are fully grown, the forests can’t store any more carbon.

So instead of leaving the plants in the ground, what if we harvested them and converted them to useful energy ?

Image of Process of BECCS — Process of BECCS

Burning this material produces CO₂ which can then be captured and stored underground . This whole process is called bioenergy with carbon capture and storage (BECCS).

While this method could remove lots of carbon, it also uses a lot of land: for every gigatonne of CO₂ absorbed, 320-580 thousand km² of land are needed!

Growing crops for biofuel could lead to more deforestation, resulting in habitat loss and carbon release from cut-down trees and disturbed soil .

Growing crops for bioenergy has other environmental impacts too.

Image of Environmental impacts of BECCS — Environmental impacts of BECCS

However, bioenergy can be made using waste materials, such as crop residues and food waste . This reduces the land and resource requirements, as well as the cost. .

Image of Using waste feedstocks reduces BECCS’s impact — Using waste feedstocks reduces BECCS’s impact

So far, we have looked at how technology can enhance natural processes to remove CO₂. But what if we could use machines to remove it from the air directly?

How can we take CO₂ straight out of the air?

Direct air capture (DAC) involves using giant machines to remove CO₂ directly from the air using controlled chemical reactions .

When air passes through these machines, the chemicals inside react with and remove CO₂, allowing the rest of the air to pass through unchanged . These chemicals are called a “capture agent”, and the CO₂ must then be separated from them so they can be reused and the CO₂ can be stored .

As far as we know, the main limit to how much CO₂ we can remove with DAC this century is the cost of the machines ! Working out how to store the carbon, unexpected environmental side-effects, and some land requirements may also limit DAC, though it needs far less land than other methods of carbon removal.

Image of DAC’s high potential for carbon removal — DAC’s high potential for carbon removal

What will we do with all of this captured CO₂?

In order to permanently remove CO₂ from the atmosphere, we need to store it somewhere where it will stay, ideally for thousands of years or longer, without causing problems.

Geological storage is a good option for storing carbon away for a long time. Geological storage involves pumping CO₂ into porous rocks underground (rocks with tiny holes that can contain liquids or gases). CO₂ is compressed using very high pressures and then injected into the rock in this supercritical state (where it acts like both a liquid and a gas).

Image of Geological Carbon Storage — Geological Carbon Storage

After the CO₂ is injected into the rock, a lot of monitoring is needed to check that the CO₂ stays put. We know of about 2,000 GtCO₂ of storage capacity in geological formations today, and we will probably find more if we look harder. We, therefore, won’t be running out of room to store our CO₂ anytime soon.

Conclusion

Although they are usually more expensive than nature-based solutions, modern technologies could provide crucial extra carbon removal. However, as well as money, there needs to be widespread social acceptance of these technologies, and laws to limit any negative side-effects .

There is also serious concern that, by focusing on taking CO₂ out of the atmosphere, carbon removal technologies distract us from working on actually reducing our carbon emissions . To reach net-zero emissions, carbon removal and emissions reductions need to go hand in hand.

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