Can a sprinkle of crushed rock boost crop yields?

DW (English)

Farmers in India test Enhanced Rock Weathering — using volcanic rock dust to enhance production and lock away CO₂. Could ERW be a new climate solution?

Transcript

00:00The farmland outside Saoni, in the heart of Madhya Pradesh, is desperately dry, thanks

00:06also to excessive use of fertilizers disrupting the soil's natural balance.

00:11Around 40% of the state's economic output is generated from agriculture.

00:17But crop harvests are diminishing, and the more recent deployment of heavy-duty tractors

00:23has made the soil so hard in places that it can no longer absorb and retain enough water

00:28during the rainy season.

00:30And the consequences are all too familiar to local farmers like Devender Kumar Alke.

00:36Because of the hardness of the soil, the crop yield has declined and because of this, farmers

00:43are facing significant losses.

00:46This year, he tried out a new idea.

00:49He applied finely crushed basalt rock on two of his four fields and says the difference

00:54is clear to see.

00:57The two treated fields have fewer pests, healthier crops and better soil, which has a higher

01:03level of water retention again.

01:06This is the soil from one field and this is soil from another field.

01:13This one has more moisture and this one has less.

01:19This grey powder is being tested on several farms near Saoni for improving soil health and

01:25trapping carbon dioxide, a greenhouse gas warming our planet.

01:30Rocks contain minerals that naturally absorb CO2.

01:33When crushed into fine dust, they can absorb even more.

01:37Scientists call this faster process Enhanced Rock Weathering or ERW.

01:44When that acidic water hits rocks, it chemically dissolves them.

01:49So that dissolution process releases nutrients and it also releases an aqueous form of carbon

01:56called bicarbonate.

01:58So those nutrients can either be taken up by plants or they could be released from the soils

02:03and enter the rivers and eventually wind up in the ocean.

02:06Minerals in the rock dust, when mixed with rainwater, dissolve, absorb the CO2 and lock it away

02:13for thousands of years.

02:15Supporters of Enhanced Rock Weathering say it could capture carbon on a large scale.

02:24Though the exact amount removed is hard to gauge, companies like Marti Carbon see big potential

02:30in selling tradable CO2 certificates that offset emissions elsewhere.

02:39And their business model includes working extensively with small scale farmers.

02:43I could see that we could scale this in this decade and it was a gigaton scalable pathway.

02:50At the same time, it could actually support and help a lot of small little farmers and make

02:59them climate resilient.

03:00Tests are first carried out in the lab to determine if a plot soil will benefit from the basalt rock

03:07dust and the additional minerals they release.

03:09Even then, there can be no guarantees.

03:11The uncertainties lie in how large the system is.

03:15So if you think about enhanced weathering and the whole system, you apply the rocks to the

03:19soils.

03:20But those dissolved products, once the basalt dissolves, have to make it from there through

03:26the soil system, enter the rivers and eventually wind up into the ocean.

03:30So that's quite a huge system to take into account.

03:33Another challenge is monitoring the entire process and determining exactly how much CO2 is

03:39being absorbed and where.

03:45When you're applying these rock powders, weathering is a very, you know, generally slow process

03:50even when you're enhancing it by increasing the surface area of the rock powders.

03:54It's still a slow process and there's a lot of background noise when you apply these rock

03:58powders to soil.

03:59You have natural soil weathering and microbial processes and there's a lot of background noise

04:06that makes it difficult to detect a weathering signal or how much CO2 is being removed.

04:13And on the farms in the water scarce area around Seoni, not everyone is enthusiastic about

04:19their fields having been treated with the crushed basalt.

04:23Among the disappointed is Vinod Kumar Bishen.

04:29The soil stays sandy and dry.

04:32Once the rainy season ends, we run out of water.

04:35Even after applying rock dust, we had diseases in our crops and our paddy yield was not good.

04:43Scientists believe the soil's properties are a crucial factor in how well ERW works.

04:50So, for example, there might be certain microbes that benefit weathering and can help increase

04:57those reactions and they may not be present in certain fields.

05:00It could also be the pH, the initial pH of the fields.

05:04They might be too basic and therefore that slows weathering down.

05:081,300 kilometres northeast of Seoni in Bengal, a company called Alt Carbon is also using powdered

05:17basalt.

05:18In an attempt to revive tea plantations, paddy fields and bamboo farms.

05:23I'm a tea planter myself.

05:24We realised very early on that to be able to get the Darjean tea industry out of its financial

05:32decline, it's important for us to improve the per acre revenue.

05:37On an average, we see a 15 to 30 percent crop yield increase, which is massive.

05:43You have high monsoon in North Bengal, in Darjean, which ensures that it rocks weather faster.

05:50Alt Carbon likewise makes money from selling CO2 certificates.

05:54The rock itself is mostly sourced from nearby mines, which enhances the economic viability

06:00and sustainability of such companies.

06:02One study suggested that, so the quarrying and mining industry creates about, I think it's

06:08four to seven billion tonnes of rock annually of waste fines, which could be exploited.

06:14I think 20 percent could be exploited for enhanced weathering.

06:16So there's huge potential there.

06:19We don't yet know the long-term impact of the basalt dust.

06:22In some cases, the minerals it releases can improve degraded soil, but certainly not in

06:28all cases.

06:30Mining companies tend to support ERW because they can sell a waste product for a profit,

06:36and trading CO2 certificates with it is another business model.

06:40There are still too many unknowns to say if enhanced rock weathering can truly cut global

06:45emissions.

06:46Even so, exploring carbon capture technologies remains vital.

06:52Which means that, we have a personal experience of people.

06:55It is very busy.

06:56Who has a strong experience in those small businesses?

06:57Can you see how to create a wall?

06:58They have to die.

07:00You may be able to create a wall to build up the pool.

07:03This is a cool experience.

07:04We will see how to create a wall to be achieved.

07:05Your size can be achieved.

07:06It is a cool experience.

07:07If you can create a wall to build up the wall to build up the wall and the wall to build up the wall for

07:18the wall.

07:20That's what you can see.

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