By spreading rock dust over large swathes of farmland, we could cause the soil to absorb significantly more carbon from the air, while also improving crop yields – a double win for farmers and the environment.
According to an article published in the journal Nature, though farmers in China, USA and India all gave improved mineral weathering one try, we could remove a billion metric tonnes of carbon dioxide from the atmosphere per year.
What is improved weathering? The idea is simple: to speed up the natural chemical reactions of farmland by adding minerals in the form of crushed rocks. The chemical processes that break down stones simultaneously trap atmospheric carbon.
As part of Earth’s natural carbon cycle, rainwater dissolves carbonate minerals in crushed rock, forming a solution. Then the carbon dioxide in the air dissolves in the solution, generating bicarbonate ions. Eventually, these ions form carbonate crystals that can hold carbon for millennia, reports the Washington Post.
This could be an effective way to turn farmland into a carbon sponge.
âIt’s an incredibly exciting technology that has a lot of payoff for the company and, frankly, we could deploy it very quickly. “
Natural weathering of the rock already delete more than one gigatonne (one billion tonnes) of CO2 from the atmosphere each year. Scientists believe we could harness this process and get even more, if not a lot more.
The big picture: Scientists generally agree that in order to meet the goal set out in the Paris Agreement of limiting the rise in global temperature below 2 degrees Celsius, we must do more than reduce new carbon emissions. We also need to suck large amounts of CO2 out of the atmosphere and lock it up forever.
Various ideas have been proposed for this – from capturing the air directly with huge machines, to genetically modifying trees to sequester more carbon, to huge fleets of kelp platforms in the ocean.
But compared to the craziest ideas, Enhanced Mineral Weathering seems to be pretty straightforward.
The technique would work if rock dust was applied to just about any large area of ââland, but it is especially effective on agricultural land because farmers are already enriching crops with minerals. They often use broken lime to minimize the acidity of the soil, so they are already prepared with the equipment and know-how to disperse rock dust.
Adding other rocks could improve soil fertility and crop yields, so application may quickly become normal and desired, reports The Guardian.
âStrategies to reduce CO2 emissions that can be scaled up and compatible with existing land uses are urgently needed to tackle climate change, alongside significant reductions in emissions,â said David Beerling of the University of Sheffield, lead author of the Nature study. “[Enhanced rock weathering] is a simple and practical approach.
The study found that China, India and the United States – the three largest emitters of CO2 in the world – along with Brazil, could collectively remove up to two billion tonnes of CO2 per year by improving the alteration of existing agricultural land.
The study estimated that the costs were not negligible (between $ 80 and $ 180 per tonne of CO2 removed) but similar or lower than other carbon capture technologies. And this without counting the ancillary benefits, such as reduced ocean acidification and improved soil quality.
In the field: Agriculture accounts for a significant share of global greenhouse gas emissions – approximately A quarter of the total, making it a critical component in achieving net zero emissions. But agricultural emissions, like those from fertilizers and cattle burps, are even more difficult to avoid than those from electricity, where you could replace coal and gas with nuclear or solar.
Adding rock weathering to the mix could offset many agricultural emissions that cannot be avoided otherwise.
In a second study on mineral weathering, a team of researchers from the Working Lands Innovation Center, a UC Davis research consortium, tested the technique in the field over the past two years. They compare rock dust and other soil additives to see how well they absorb carbon from the atmosphere and store it underground.
“As far as I know”, Ben Houlton, principal investigator of the consortium, Recount Yale Environment 360, âOurs is the larger-scale project of its kind, using this type of intensive science-based approach. “
Houlton and the other researchers are studying the impact of varying amounts of rock dust on hemp fields near Geneva, New York. They are part of a group of researchers who are testing different rocks for their carbon absorbing abilities, as well as their abundance, cost, and safety in the soil. (For example, wollastonite is effective at sequestering carbon, but it is not common enough to be used on a large scale.)
âIt’s an incredibly exciting technology that has a lot of benefits for society and, frankly, we could deploy it very quickly,â Houlton says.
Field trials are very time consuming, and researchers need many trials to understand the benefits and problems of each crop-mineral combination, and with different climates. Initial data from the California plots suggests carbon uptake has doubled, despite the driest conditions on record in the state.
And after? Houlton and Beerling both plan to continue their current studies and plan to publish further results as early as next year.
Beerling began his studies five years ago, with plans for another five years. He told Yale Environment 360, for example, that applying rock dust to fields for mineral weathering can mean farmers can use less nitrogen fertilizer. This could reduce nutrient pollution, which would particularly benefit areas where runoff flows into the Mississippi watershed.
In the future, it may also be possible for farmers to make money by sequestering carbon. Earlier this year, the Biden administration suggested that farmers should be paid for the cultivation of carbon sequestering plants. If a carbon market were to emerge, improved mineral weathering could be the key to âcarbon farmingâ.
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