Removing 1 million tons of carbon a year

From Interesting Engineering

Carbon capture technologies have great potential for helping in the fight against climate change, and big names such as Bill Gates and Elon Musk are showing their faith in the technology by investing in new solutions.

Now, the world looks set for a breakthrough moment in carbon capture technologies, with a new facility set to open in Scotland that will remove up to one million tons of carbon [dioxide] from the air each year, a press statement reveals.

The direct air capture (DAC) facility will be built by UK energy transition company Storegga Geotechnologies in collaboration with the Canadian carbon capture technology firm Carbon Engineering.

The facility, which will be the largest in the world, will extract the equivalent carbon (one million tons) that would be absorbed by 40 million trees over the course of a year. All of the absorbed carbon will then be deposited in storage sites under the sea.

The facility will feature large fans that pull air into a liquid-filled vat that binds the carbon dioxide. Once bound, the captured carbon is refined and transformed into calcium carbonate pellets.

These pellets, in turn, are heated and decompose into a CO2 stream alongside calcium oxide. This stream is then cleaned of impurities, after which it is pumped into an undersea storage site.

The new facility joins a host of other carbon capture technology innovations aimed at meeting the requirement of reducing the amount of CO2 in the atmosphere if we are to reverse the adverse effects of climate change.

As the Union of Concerned Scientists (UCS) points out on its website, "to reach net-zero emissions, we need to do more than just reduce our emissions: we need to actively remove carbon dioxide from the atmosphere or offset its effects."

Another new system, the Bill Gates-backed Carbfix, will extract carbon from the atmosphere and turn it into rocks. One devised by UCLA scientists, meanwhile, takes inspiration from seashells to extract carbon from the ocean, which would, in turn, absorb more out of the air.

While the Scottish facility from Storegga Geotechnologies and Carbon Engineering will mainly be aimed at removing carbon dioxide from the atmosphere, both firms do say they want to eventually sell carbon dioxide collected from their plants.

The two companies are currently seeking a site location for their new facility in the country of Scotland, which was chosen due to the fact that a large number of its labor force is already trained in the skills needed for such projects — renewable energy met over 97 percent of the country's energy demands in 2020.

In their statement, Carbon Engineering says both partners aim for the facility to be operational by 2026.

Sounds good, doesn't it?  But there are a few problems.  First, although a million tonnes a year seems a lot,  China's and the USA's annual emissions total 15 billion tonnes of CO2 a year, about 40% of global emissions.  We would need 15,000 of these plants just to offset the emissions of these countries.  Still, if we put our minds to it, and our shoulders to the wheel, etc., etc., we could in principle achieve that.  

However, that's not the only problem.  To permanently store the CO2, we need to either put it into caverns where it can never escape, otherwise it'll just go straight back into the atmosphere; or convert it to rock by dissolving it in water and pumping it into basalt.  In the manufacturing process, calcium carbonate (i.e., limestone) is produced, which could simply be dumped into the sea, but the calcium needed for this is produced by energy-intensive methods, either electrolysis or by reducing lime at high temperatures. 

Also, these guys are also going to be selling their carbon dioxide.  Which means it's not being withdrawn from the atmosphere.  I understand it's a startup, and they may need temporary expedients to help it survive until the carbon price is high enough to make direct air capture of CO2 profitable.  All the same.

The best way to slash net emissions is to replace coal power stations with wind and solar and other renewables, and to replace ICEVs with EVs or PHEVs.  But carbon capture and storage(CCS) will be needed, if only to reverse the emissions of cement production and air travel, together (depending on your data source) around 10% of global emissions.  These sectors will need to pay a carbon tax to fund this and other CCS schemes.  And if we need to offset just these sectors, the number of CCS plants needed will be much fewer.

So, not as big a step forward as the article is trying to make out, but still worthwhile.