Technological Solutions: Can Innovation and Science Sequester the Rest?
13 minute read
Updated on Fri Jul 30 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.
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.
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
Growing crops for bioenergy has other environmental impacts too.
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?
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.
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).
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.
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.Next Chapter