Enhanced Rock Weathering

In a bid to restore the balance of carbon in the atmosphere, there is another way to capture some of it from what is basically a waste product.

It's a hard volcanic rock that is neither rare nor particularly remarkable.

But through a process known as 'enhanced rock weathering' it could help to cool our overheating planet.

I spotted this article and was intrigued by the fact that nature has been capturing carbon for millions of years. As we learn more about nature, we can help it do its job properly and this is a natural process, already happening, that just needs a helping hand.

UN scientists are now clear that reducing greenhouse gas emissions alone won't be enough to stop dangerous levels of warming. They say there will need to be some carbon dioxide removal - actively taking it out of the atmosphere.

Enhanced rock weathering lies somewhere in between the natural and the man-made. It takes the naturally occurring but very gradual weathering process and turbo-charges it to remove the carbon faster.

There are quarries that extract rock and reduce it down for use in concrete and road building.

There are tiny pieces of basalt rock that are left over that have a useful property - when they weather in the rain, they remove carbon dioxide from the atmosphere.

This has been happening for thousands of years. Enhanced rock weathering uses tiny pieces to increase the amount of contact between the rain and rock and therefore the amount of weathering and carbon removal.

As a cliff, or piled up in the quarry, the basalt weathers very slowly. To maximise the carbon removal and to speed the process up it needs to be spread across a greater area.

And that's where local farmers come in, helping the planet while getting free fertilizer in return. As well as locking away carbon, the basalt has been shown in trials to improve both crop yields and the quality of grazing.

Trailers loaded with 20 tonnes of basalt are towed by tractors over the fields, and a rotating wheel at the back scatters the tiny rocks.

It's free of charge to the farmers, and improves the quality of the grass

Apparently, a 20 tonne trailer load of basalt absorbs about 5 tonnes of CO2, so the process needs to be scaled up to make a bigger difference.

Scientists calculate that four tonnes of basalt rocks are needed to capture one tonne of CO2 and, as it’s estimated that the average Briton’s CO2 emissions are about 7 tonnes a year, that means each of us needs about thirty tonnes, or one and half trailer loads of basalt, to be scattered annually just to break even.

UNDO, a company specialising in enhanced rock weathering, has plans to rapidly scale up over the next few years and has attracted some serious supporters. Microsoft has agreed to pay for 25,000 tonnes of basalt to be scattered on UK fields. As part of the deal, Microsoft will also help audit the project and verify that it is working as intended.

It’s thought that the idea could end up just a standard part of the way land is farmed.

It's something that can be incorporated into the way we use land at the moment, and deliver a carbon removal benefit alongside other benefits in terms of the way we use land for food and crops.

"At this point in time, there's no downside, it's a win-win for everybody involved," said Jim Mann, CEO of UNDO

This year UNDO is planning to spread 185,000 tonnes of basalt and hopes by 2025 to have removed a million tonnes of CO2. It's still a drop in the ocean compared to emissions (in 2022 it’s thought the world discharged about 37 billion tonnes of CO2 into the atmosphere).

So, a long way to go, but we have to start somewhere, and with other initiatives to capture carbon being rolled out all the time, we can attack the problem from several different directions. And again, small steps add up to something much bigger.

What I like about basalt is that it’s a natural by-product of something that’s already happening. It’s a form of recycling/upcycling that, through the ingenuity of scientists, makes use of what’s already there.

I’ve said that we need to give nature a hand, but in reality it’s us that have caused the problem in the first place – but realising that this is part of the answer to the problem is a small step forward.

Let’s hope that there are more ways to tackle the problem and that our scientists can help put them into practice.