Transcript

NEIL EDWARDS

Rock weathering is the process that takes carbon out of the atmosphere on very long geological timescales, tens of millions of years. So what happens in rock weathering is basically, the rain falling on rocks causes the rocks to dissolve, the carbonic acid that’s in the rainwater because of the carbon in the atmosphere. It dissolves the rock. That dissolves the minerals in the rock. And if they’re silicate minerals, then the products of that dissolution eventually flow into the ocean. And some of the carbon that’s taken out of the atmosphere gets permanently removed into the ocean sediments.

ANNE JAY:

OK. So if that’s what happens naturally, what are they hoping to do to my volcano that’s a bit quicker? Because obviously, we haven’t got geological timescales to fix this problem.

NEIL EDWARDS

We don’t have geological time, exactly. So what we need to do is accelerate that process somehow. And the quickest way – the easiest way – to accelerate it is, instead of taking this massive clump of rock, we basically cut it down into much smaller pieces.

ANNE JAY

Something a bit more like this?

NEIL EDWARDS

Something a bit more like that, indeed.

ANNE JAY

This is a nice, powdered rock that I used for some chemistry quite a long time ago. But it’s kind of like flour now. Is that about right?

NEIL EDWARDS:

Exactly. So basically when you powder something, when you powder a rock, the amount of surface area relative to the amount of rock increases. So the smaller the size of the particles, the larger the amount of surface area compared to the mass of the rock.

ANNE JAY:

So what are they gonna do with it?

NEIL EDWARDS:

So the idea is to spread basalt, in this case. Any silicate mineral, in principle, would do. But basalt, there’s lots of it, as you say. If you spread basalt on vegetated areas – if it’s powdered like that, so it has more surface area, and that surface area is where the reactions occur, so that means a more reactive surface – that, basically, will enhance the process of weathering.

ANNE JAY:

So are we going to get farmers in India to sprinkle basalt over their fields?

NEIL EDWARDS:

Well, that’s the suggestion. The question is, can it be done at the scale that’s needed to actually make a difference?

ANNE JAY:

How much is this rock project going to cost?

NEIL EDWARDS:

OK, well, that’s the $64 million question – or even the $60 trillion question. We don’t really know. But we do know that it’s a lot of money, because we’re basically talking about a process that’s going to be carried out over a large proportion of the Earth’s surface area. So, if you imagine spreading a kilogram of rock per square metre over your back garden, that might cost a certain fraction of your gardening budget for the year. If you multiply that by 20 billion people, you’re talking about a major cost. What we do know, though, is that the costs are dominated by the grinding and pulverising of the rock.

But there are other options there, because we know there are large amounts of volcanic ash, glacial tills, and also residues from mine-- waste products from mining that could be used instead. So that’s another issue. Would that make it a lot cheaper? And the answer is probably yes.

ANNE JAY:

So, Neil, what’s your role in this rock scattering exercise?

NEIL EDWARDS:

OK. Well, our role in this rock scattering exercise is to use computer models to study the interaction between the different components of the Earth system. But in particular, what we’re interested in is the interaction between the natural Earth system and what you might call a socioeconomic Earth system. The agricultural economy is involved, so there’s the issue of how the agricultural economy responds to changes in how we use the land surface, and how plants respond in terms of the biogeochemistry of plant growth.

ANNE JAY:

Well, thank you very much Neil.

NEIL EDWARDS:

Thank you.