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Irrigation and farms
Credit: Ohio State University


Rock Dust Captures Carbon Dioxide From The Atmosphere & Deposits It In The Ocean

A new study published in Nature claims spreading basaltic rock dust on the fields where crops are grown could pull up to 2 billion tons of carbon dioxide out of the atmosphere.

Lowering the amount of carbon dioxide that humans spew into the atmosphere is necessary, but not sufficient to prevent average temperatures on Earth from rising to the point where humans can no longer survive. The second piece of the climate catastrophe prevention puzzle requires removing much of the carbon dioxide that is already in the atmosphere.

Irrigation and farms

Image credit: Ohio State University

If humans stopped burning fossil fuels today (no chance of that happening), our planet would need about 30 years before any significant cooling of the Earth would take place. Getting rid of a few billion tons of the carbon dioxide already in the atmosphere would help accelerate the cooling process. But how to make that happen?

A research team at the Leverhulme Centre for Climate Change Mitigation at the University of Sheffield led by David Beerling says pulverizing basalt, a common variety of rock found worldwide, and spreading it on farmers’ fields could do the trick. Basalt contains minerals such as silicon, iron, calcium, magnesium, and aluminum. When dissolved in rainwater, those minerals pull carbon dioxide out of the atmosphere in a process known as enhanced rock weatherization.

Eventually, that rainwater carries the dissolved minerals and carbon dioxide into rivers and streams which carry it to the ocean. Phytoplankton then eat the dissolved minerals. When they die, their shells fall to the bottom of the ocean where the carbon dioxide remains sequestered for up to 100,000 years.

There’s an additional advantage to the process. The minerals in the pulverized rock may enrich farmland, leading to higher crop yields and more income for farmers. Most farmers already have equipment for spreading lime on their fields. The process of spreading the pulverized basalt would be no different and would require no investment in new equipment.

“Spreading rock dust on agricultural land is a straightforward, practical CO2 drawdown approach with the potential to boost soil health and food production,” Beerling tells the Washington Post. “Our analyses reveal the big emitting nations — China, the U.S., India — have the greatest potential to do this, emphasizing their need to step up to the challenge. Prior to our work, the evidence [on ERW] was scattered,” Beerling, tells Bloomberg, which shared its reporting with CleanTechnica in an e-mail. “Our study is the first detailed, comprehensive analysis of what it might deliver for carbon capture if deployed at scale.”

The study, which was published last week in the journal Nature, says “China, the United States and India are all vulnerable to climate change and resultant sea level rise. Their high risks of economic damage and social disruption provide impetus for creative co-design of agricultural and climate policies.”

Enhanced rock weathering could capture up to 2 billion metric tons of carbon dioxide from the atmosphere at a cost of between $80 and $180 per metric ton, which is in line with the cost of carbon capture technology today. It is also consistent with predictions the World Bank has made about what the cost of carbon should be in order to meet the climate goals set by the Paris climate accords in 2015, says Bloomberg.

Those estimates do not include the financial benefits farmers may realize from having more productive fields. And the cost of ERW are likely to be far less than those associated with geoengineering or sucking carbon out of the air with giant machines. It is unfortunate that cleaning up centuries of human caused pollution will be so expensive but the price of extinction will be far higher.

Like all research, large scale trials will be needed to verify the accuracy of the predictions made by the scientists. Bloomberg says large trials that seek to replicate the workings of a typical commercial farm are underway in Australia, Malaysia, and the US. The results are still years away from being published, but “preliminary data are promising,” says Steven Banwart, head of integrated soil, agriculture, and water research at the University of Leeds, a co-author of the Nature study.

James Hansen, the noted climate scientist who sounded the opening bell on climate change when he testified before Congress in 1958, alerted CleanTechnica to the new Nature study in an e-mail last week.

“Weathering is nature’s process of removing CO2 from the air, balancing the continual addition of CO2 to the air by volcanoes and mountain-building associated with plate tectonics (continental drift). This natural weathering process can be sped up by grinding silicate materials into fine dust and spreading it on soils that can otherwise benefit from the addition. Many farmers are accustomed to liming their fields, and have equipment for such purpose.

“I was attracted to this idea and agreed to work with David Beerling because weathering provides a natural, permanent sink for the carbon. Other CO2 drawdown approaches, such as reforestation, are important, but require management to assure that the carbon sink is maintained. We will need the combination of reforestation, enhanced weathering, and other techniques to help draw down atmospheric CO2 to a safe level.

“Of course, the most important action required to avoid dangerous climate change is to phase over to carbon-free energies as rapidly as is economically justified. However, because we have been slow in moving toward clean energies, we probably need to spur drawdown of atmospheric CO2 if we are to minimize undesirable consequences of climate change.”

Hansen told the Washington Post, “We have passed the safe level of greenhouse gases. Cutting fossil fuel emissions is crucial, but we must also extract atmospheric CO2 with safe, secure and scalable carbon dioxide removal strategies to bend the global CO2 curve and limit future climate change.”

The time to begin implementing such strategies was yesterday yet in an era where the politics of rage are rampant, it’s hard to imagine that humans have the capacity to confront the existential crisis that is climate change with anything like the commitment needed to effectively address the challenge of keeping the planet habitable for those who will follow in out footsteps. One could almost argue whether a species so self indulgent, self absorbed, and self interested even deserves the blessings of a planet that could sustain us for millenia if we would only let it.

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Written By

Steve writes about the interface between technology and sustainability from his home in Florida or anywhere else The Force may lead him. 3000 years ago, Socrates said, "The secret to change is to focus all of your energy not on fighting the old but on building the new." Perhaps it's time we listened?


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