• by:

May 10, 2022

We humans are in something of a pickle, as we’ve put too much carbon dioxide in the atmosphere and caused climate change that might even wipe us out. There may still be people to whom that’s a controversial statement, but knowing something needs to be done about it should be a position for which you don’t necessarily have to be a climate change activist glueing yourself to the gates of a refinery.

It’s obvious that we can reduce our CO2 emissions to tackle the problem, but that’s not the only way that atmospheric CO2 can be reduced. How about removing it from the air? It’s an approach that’s being taken seriously enough for a number of industrial carbon capture solutions to be proposed, and even for a pilot plant to be constructed in Iceland. The most promising idea is that CO2 from power stations can be injected into porous basalt rock where it can react to form calcium carbonate. All of which is very impressive, but is there not a way that this can be achieved without resorting to too much technology? Time for Hackaday to pull out the back-of-envelope calculator, and take a look.


Carbon dioxide emissions by source since 1880
This graph helps illustrate the scale of the problem. Efbrazil, CC BY-SA 4.0.

First of all, whether to gauge the scale of the problem or to demonstrate the futility of trying to deal with it, it’s worth quantifying how much CO2 we release. There are several slightly different figures depending where you are prepared to look, but most of them agree that humans are responsible for somewhere above 40 billion tons of CO2 per year. Viewed on a per-capita basis, Americans are each responsible for 15.52 tons, Canadians for 18.58 tons each, and on the side of the Atlantic where this is being written, Brits each account for 5.5 tons. It’s worth repeating these figures in order to demonstrate the futility of imagining that a few carbon capture plants can scrub the air of CO2 and make a significant difference, because the sheer scale of the problem is such that even the most prolific industrial expansion would find it difficult to keep up.

The first and most obvious way to capture and store large amounts of carbon by non-industrial means is of course in the form of biomass. Growing trees which become enduring forests sounds attractive and on the face of it is pretty easy to do, but how practical is it to make a dent in those emissions? According to National Georgaphic’s reporting of an ETH Zurich study published in 2019 an area the size of the USA covered in new forests could reduce atmospheric CO2 by 25% over a hundred years, which makes for a great soundbite, but it’s hardly as though there’s a handy USA-sized piece of land ready to plant trees on. If the global will to plant was there this might be an achievable target, but aside from lip-service on the part of politicians it’s difficult to imagine much movement on such an ambitious project until the waters of Chesapeake Bay are lapping at the front steps of the White House. It’s clear that while forests will play a part in dealing with our CO2 problem, they can’t solve it alone.

A piece of basalt rock
Could basalt hold the key to reducing atmospheric CO2? Amcyrus2012, CC BY 4.0

Another intriguing idea comes to us via a Sheffield University study, that proposes the UK could reach 45% of its net-zero emissions target by so-called accelerated weathering. CO2 is naturally absorbed by rocks as they are weathered by the weak acidic effect of CO2 dissolved in rainwater, and this idea proposes amplifying this effect through farmers applying powdered rock as a soil dressing.

It’s an on-the-surface take on the basalt injection idea, where the huge surface area of rock involved would cause much more CO2 to be extracted from the air as it weathers. The CO2 is thus locked away, with consequent offset of emissions. Basalt rock is common enough to make it feasible on paper, but they acknowledge the scale of the operation would require careful handling. Are we ready to lose entire mountains of rock in the service of offsetting climate change? Maybe not yet, but yet again the waters of the Thames estuary lapping around Number 10 Downing Street might sharpen attention.

It’s clear that there’s no magic solution to climate change that will allow us to continue emitting CO2 as though nothing is amiss. There’s no super-forest we can plant, no clever factory we can build, and no magic soil dressing that will scrub the air clean. However what does emerge from reading up on these technologies is that each could play their role in offsetting a portion of emissions, and alongside a meaningful effort to reduce emissions in the first place, might help us achieve the coveted net zero. The question is, do we have the public and political will to do it?

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s