Extreme rock weathering is a carbon removal technology that is attracting investment from likes of Microsoft
The technology, based on mineral-rich rock such as basalt, has the ability to both sequester carbon in oceans and return nutrients to tired soil
ERW startups are looking to raise money via carbon removal credits, with current rate around $300 a ton
While ERW efficacy not in doubt, technology needs methodologies to verify C02 removal
October 31 – Of all the ideas and technologies being touted around carbon removal, enhanced rock weathering (ERW) seems to garner some of the greatest enthusiasm. Scalable, with a variety of catalytic aggregates available, it also has the ability to both sequester carbon in oceans and return nutrients to tired soils.
There are questions, however, whether the science is yet robust enough to support some of the claims being made for it.
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The technology is relatively simple. First, mineral-rich rock such as basalt iscrushed to form a thin powder, which is spread over fields and grasslands, reacting with CO2 and water in the atmosphere to form carbonates. These lock away the C02 and over time leach from the fields, moving through rivers and streams before finally ending up at the bottom of the ocean.
According to Professor David Beerling, director of the Leverhulme Centre for Climate Change Mitigation at Sheffield University, the idea of capturing carbon and then releasing it into the deep ocean was first discussed in the journal Nature in 1990. Seen as a “pretty leftfield idea,” says Beerling, it was largely forgotten, until 2016 when scientist Olaf Schuiling began to look into the power of a silicate called olivine to capture carbon.
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Interest in the science was rekindled, and the same year the Leverhulme Centre was established, soon setting up a string of international trials into ERW, with a focus on basalt. The centre was also the first to show the dual beneits of ERW and its ability to improve soil health and yields, as well as capture carbon.
The research, says Beerling, has seen the market spiral. “I’ve never seen my work stimulate so much commercial interest,” he says.
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Iceland – basalt column wall
A basalt column wall on the Snæfellsnes peninsula in western Iceland. Basalt is rich in the calcium and magnesium silicates needed to capture carbon, and abundant across the planet. Acquire Licensing Rights
Dubbed the mother rock, basalt is a volcanic mineral and one of the most abundant on the planet. This makes it the obvious one to scale, says Beerling, especially as it is so rich in both the elements needed to capture carbon – calcium and magnesium silicates – as well as nutrients such as phosphorus and potassium for crops.
Olivine, a common mineral in the earth’s sub-surface that is mined across the globe, also has its champions, and Eion Carbon is one of several companies looking t harness its sequestering powers. In the U.S. it has been approved as a soil improver since the 1940s, despite the fact, says Beerling, that it can contain both chromium and nickel, and is mined alongside asbestos, none of which would be welcome in the food chain.
Eion, however, maintains that extensive studies have been carried out of its feedstocks, which all come from the same quarry in Norway, a country that supplies nearly half of all olivine used for industrial purposes. They have shown that asbestos levels are less than that typically found in background air.
In the Netherlands, the company greenSand promotes olivine for use in urban settings, such as cycle paths, car parks and general landscaping, while Vesta is spreading olivine on American beaches, where it can soak up carbon before being washed away by the tide, at the same time, says the charity, helping to neutralise acidity in the sea.
A third possible aggregate is unused concrete. At the moment this is restricted to plverising virgin waste into a fine dust, with the processes needed to sort concrete from other contaminants in demolition waste still being developed.
Silicate Carbon is working with farmers in Ireland to spread the crushed concrete, explains chief executive Maurice Bryson in a written response to The Ethical Corporation. Further trials are planned for the United States and Europe.
Vesta is spreading olivine on U.S. beaches
Vesta is spreading olivine on U.S. beaches where it soaks up carbon before being washed into the sea. Vesta/Handout via REUTERS Acquire Licensing Rights
“Our material is perfectly safe to apply to agricultural land, and meets European regulations for liming materials,” he says. Adding lime to the soil changes its pH and boosts its performance. Returned concrete represents between 1-4% of the 30 billion tonnes of concrete made globally each year, he adds, ensuring a plentiful supply of aggregate.
“ERW has massive potential,” says Bryson. “Once you’ve applied the aterial to the fields, it gets to work – there’s no energy required.” And while it may lack the rich mineral mix of basalt, he adds, concrete weathers 20 times faster, speeding up the sequestering process.
Despite this, basalt remains the clear market leader. Edinburgh-based UNDO was one of the first companies to commercially use basalt, its rapid growth capped by a recent agreement with Microsoft to spread 25,000 tonnes over agricultural land in the UK, permanently removing 5,000 tonnes of CO2 over the next 20 years. The basalt UNDO uses is a waste product produced by extractives industries.
Company founder Jim Mann says UNDO is now beginning trials in Australia, Canada and East Africa, where he believes ERW can also play an important role supporting climate justice, because the work can be done locally. “You’re not using western technology like you would with other high-tech solutions,” he says.
This is also where basalt’s role as a soil enhancer wins through, he adds, increasing ields in areas where artificial fertiliser is scarce and expensive.
Seattle-based Lithos Carbon is looking at basalt as a replacement for artificial fertiliser first, and its carbon removal potential second. Crushed basalt is currently spread over 130,000 acres across nine US states, and as with UNDO, it’s provided free to farmers.
Dutch firm greenSand is promoting the use of olivine in paths
Dutch firm greenSand is promoting the use of olivine, a common mineral in the earth’s sub-surface, in roads and paths. greenSand/Handout via REUTERS Acquire Licensing Rights
Lithos is one of the businesses to receive investment from Frontier, the collaboration of leading businesses including Alphabet, Shopify and Meta, that acts as an advance market commitment (AMC) to accelerate the development of carbon removal technologies. Last year Lithos also became one of the largest suppliers to Frontier carbon dioxide removal (CDR) credits created through ERW.
This improves collaboration, explains comany co-founder Mary Yap, who works closely with farmers to monitor what happens to the soil. Details about basalt’s impact on different soils, and the amount that needs to be applied, are all added to a data bank, which Lithos uses to demonstrate its effectiveness, says Yap, who has seen yields improve by as much as 47% in some cases.
She believes that nature-based solutions such as ERW are primed to scale, but they need to be shown to work if farmers are to use them, and their sequestration powers rubber-stamped so that individuals and companies can buy carbon removal credits with confidence. “We want to create a carbon removal product about which there is truly no doubt,” she says.
Beerling agrees that measurement, reporting and verification (MRV) is critical. At the moment the standard method is to measure how much basalt has been mixed into the soil, and then regularly measure soil samples to see how much has dissolved. The grey area is “the leakage” and amount of carbonate that s lost on the journey to the sea.
The key standard in the market is the Puro.earth enhanced rock weathering methodology, which was launched in 2022, to be used in the voluntary carbon market and allows the issuance of what Puro calls C02 removal certificates (CORCs). Two U.S.-based organisations, Verra and CarbonPlan, are also working on their own verification frameworks.
Lithos offers “cradle to grave” measurement, says Yap. “We don’t deliver anything until we’ve measured it.” In certain conditions, she says, such as a particularly acidic water environment, the bicarbonate can be re-released as a gas. To counter this, Lithos is working with the U.S. Geological Survey, which uses 2 million data points across the United States river network, to monitor water chemistry.
A cabbage in a field in Meistratzheim, in the French Alsace region
A cabbage in a field in Meistratzheim, in the French Alsace region. Lithos has seen agricultural yields improve by as much as 47% from using basalt in ertiliser. REUTERS/Vincent Kessler Acquire Licensing Rights
Yap says this allows Lithos to remove the carbon element of any leakage, so that when it comes to offering removal credits, they are accurate and transparent.
Lithos is also licensing its technologies, helping agricultural companies as well as NGOs by testing samples of their basalt “to make sure it’s free of heavy metals and safe”, says Yap. They also make sure the crushed basalt has the right particle size so the kinetics and the chemistry of the rock dust is optimised to capture carbon.
“By safely adding it to just a small percentage of croplands across the world, you can start to remove the gigatons (of CO2) that we need,” she adds.
Most ERW startups are looking to raise money by selling CDR credits, with the current rate around $300 a ton. While the efficacy of ERW is not in doubt, some of the claims being made are very ambitious, says Beerling, with companies talking about their ability to deliver megatons of C02 remval without making it clear how they are going to achieve it.
In many cases, he suggests, marketing may have trumped the science, which risks muddying the waters when it comes to selling CDR credits. “Things need to be reported in a verified way … (we) need to see the methodologies that they have used to verify C02 removal.
“What we want to avoid is some of these spurious claims … with no firm evidence that’s out there yet in peer-reviewed literature.”
There is also a need for a clearer international standard for ERW that brings together the hotch-potch of protocols being developed by individual companies, Beerling says. He also wants to see more government support, and is part of a delegation heading to Brussels to convince the EU that ERW deserves a place alongside the likes of direct air capture and biochar in the bloc’s upcoming Carbon Removal Certification Framework (CRCF).
But despite the pressures, Beerling remains confident that ERW is the removal technology that will scae to a gigaton the fastest. “We’re not inventing a new technology,” he says, “it’s readily deployable straight away.”
This article is from The Ethical Corporation magazine’s in-depth briefing on carbon removals. Click here to download the digital PDF.
Opinions expressed are those of the author. They do not reflect the views of Reuters News, which, under the Trust Principles, is committed to integrity, independence, and freedom from bias. Ethical Corporation Magazine, a part of Reuters Professional, is owned by Thomson Reuters and operates independently of Reuters News.