To prevent catastrophic climate change scientists and governments are rushing to find ways to remove some of the carbon pollution from the air, and to capture what’s still being produced by power plants and industrial facilities.
In its 2022 report, the United Nations Intergovernmental Panel on Climate Change said that “all available studies require at least some kind of carbon dioxide removal to reach net zero” where the world removes as much greenhouse gases from the atmosphere as it emits.
Even if emissions drop significantly, the world would still need to remove between around 10 to 20 billion tons of carbon dioxide every year, according to the IPCC.
“Carbon capture” is often used as a general term for what are actually two sets of technologies – carbon capture and carbon removal. Carbon capture reduces the amount of carbon emissions that would otherwise go into the atmosphere by capturing it at the source of pollution, then storing it or reusing it.
Instead of sending carbon pollution (or “flue gas”) from buring fossil fuels into the atmosphere, it is trapped and sent through a chemical process. The most common way to do this is to put the flue gas into contact with a liquid solvent, which pulls the CO2 out in a process called chemical scrubbing. The CO2 is then compressed to remove the water and sent by pipeline or ship to a location where it can be reused or stored.
For long-term storage the only option is to put it deep underground. This requires the suitable geological conditions such as a porous rock like sandstone and a layer of denser rock on top like shale to stop the carbon from seeping through.
Another way captured carbon can be used, which is more controversial, is in a process called “enhanced oil recovery”. The carbon is injected into wells to force out the hard to reach remnants of oil – allowing fossil fuel companies to squeeze out more oil.
Carbon removal refers to a number of different techiniques which aim to remove carbon pollution that is already in the atmosphere and lock it up permanently. Oceans and trees are natural carbon sinks.
Some techniques are low-tech such as extensive tree planting. Other techniques seek to supercharge natural processes, like seeding the oceans with nutrients to increase the growth of carbon-storing marine life, or spreading crushed rock on land to cause chemical reactions that capture carbron from the air.
Another technique is direct air capture which uses machines to suck in air and then extracts the carbon using chemicals. This can then be reused or injected deep underground.
https://www.cnn.com/2023/05/11/world/carbon-capture-removal-pollution-climate-intl/index.html