Hi and welcome to this week’s Fix the Planet. I’ve been chatting to people about a method of carbon-dioxide removal that doesn’t grab the headlines in the way that CO2-absoring machines and tree planting do: scattering pulverised rock over the Earth’s surface. Many rocks naturally absorb COc, but this doesn’t happen fast enough to avert the sort of dangerous warming we're headed for.

“Essentially, it’s a natural process that happens anyway in the world, but at a comparatively slow rate,” says Mike Kelland at the University of Sheffield, UK. Breaking up the rock, a process known as enhanced weathering, increases its surface area, and the rate at which CO2 is absorbed.

The principle isn’t new, as long-standing New Scientist readers will point out. But fresh research out on Tuesday shows how it might be a boon for farmers, and one of the many Fixes we need to curb climate change.

Basalt: unlikely climate change saviour. Michael Dwyer / Alamy

What’s new?

Previous research has looked at using finely ground rock in oceans and rainforests to absorb CO2, but there hasn’t been a huge focus on agriculture. So a UK team spread ground-up basalt on clay loam soil at a controlled facility run by the University of Sheffield. The aim: to see what impact it had on storing CO2 in the soil and on growing Sorghum bicolor, a grass cultivated for food and animal feed.

And what did they find?

The amount of CO2 that the soil could store increased by four times, to a total of between 2 and 4 tonnes of CO2 per hectare for up to five years afterwards. Perhaps most eye-catchingly for farmers, yields of the crop went up by a fifth. “They are quite big numbers. That’s encouraging,” says Kelland. Another benefit for farmers is an increase in concentrations of silicon, which can improve the structural stability of plants and stop them tipping over.

What’s the catch?

Kelland admits that such large increases might not be replicated on a working farm, because of the optimal conditions in the controlled environment the team used. “We have to be careful of how far we extrapolate, but the signs are good [for commercial agriculture],” he says. Some previous work on enhanced weathering used crushed dunite – which contains a lot of the mineral olivine – because it reacts quickly with CO2. But olivine contains nickel and chromium, which has raised concerns about pollution of the soils with these elements – potentially limiting how many years you can use rock dust. Although the basalt that the UK team used does contain olivine, it is at much lower concentrations, and tests of the soil, rock and plants didn’t throw up problems with nickel and chromium.
Growing sorghum for the trial. Photo: University of Sheffield.

Is that all?

Well, no. There are also questions about where you get all the rock, how much CO2 is produced by quarrying, grinding and transporting it, and how it works on different types of soil, says Tim Krugman at the University of Oxford. There is also the issue of public acceptance. While few people would argue with increased crop yields, they might not like the idea of more mines, and the noise and dust they create. “To understand if it’s feasible is not just to understand if it’s technically but socially feasible as well,” says Krugman.

Are those deal-breakers?

Kelland has thought about these issues. On the CO2 front, he points to a 2014 study finding that transport and mining of the rock account for relatively little CO2 – most of the CO2 emissions come from the energy used to pulverise it. For that reason, Kelland reckons that the best option if we want to scale up enhanced weathering is to use pulverised rock already being produced by the aggregates and mining industries. Miners often break up a lot of basalt they don’t need and might even pay people to take it away, he says.

Where does this idea stand in the pantheon of CO2-removal options?

One key advantage is it has the potential to remove serious amounts of CO2. “I think enhanced weathering is one of the techniques which has quite a lot of scalability,” says Krugman. However, it is more expensive than some other options, such as trees, and it won’t happen without financial incentives for farmers or other groups to store the CO2, he says. “There is no panacea for climate change,” says Kelland, who sees enhanced weathering as playing a vital role alongside other CO2 removal approaches, like this.
Mike Kelland digging up clay loam soil for the project. Photo: University of Sheffield.


Transforming the world’s energy systems to renewables would boost global GDP by an extra $98 trillion by 2050, a report for the International Renewable Energy Agency found this week.

Sweden has closed its last coal power station. The Värtaverket plant in Stockholm stopped production two years earlier than planned. Expect the UK to become one of the next European states to go coal-free, perhaps as soon as 2022 for economic reasons, and certainly no later than 2024 due to a government phase-out.

Now is a good time for governments to introduce new fossil fuel taxes, says Chris Stark at the Committee on Climate Change, the UK government’s statutory climate advisers. Speaking at a virtual event organised by UK think tank Green Alliance this week, he argued that low demand due to the coronavirus crisis means low fossil fuel prices for consumers for some time, so the timing is right.

Yesterday was the 50th anniversary of Earth Day – this year’s event had climate action as its theme. For more, read my interview with one of its founders, Denis Hayes.
That’s it for now. Keep safe and see you this time next week.
In the meantime, remember, you can always email me on the address below to suggest an idea for a future Fix the Planet newsletter. You can message me on Twitter and Facebook too. 
Adam Vaughan

Chief Reporter, New Scientist
Email me at to get in touch
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