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Agriculture is one of the sectors under pressure to reduce its carbon footprint. But that can be a tall order for farmers. Researchers, however, may have found a way, and it is all about rocks. Here's Jonathan Ahl of St. Louis Public Radio.
JONATHAN AHL, BYLINE: According to the USDA, agriculture is responsible for more than 10% of U.S. greenhouse gas emissions. The easiest way to reduce that number might be to increase the amount of carbon farmers put back into the ground and out of the atmosphere. Enter crushed basalt rock. Every two to three years, many farmers apply crushed limestone to their fields to regulate soil acidity and keep crops healthy. But scientists are now running tests in fields around the world to see if using crushed basalt will work as well on the soil while also reducing agriculture's contribution to greenhouse gas emissions. Chris Reinhard teaches earth and atmospheric sciences at Georgia Tech. He says while all rocks help sequester carbon when they're buried in the soil, basalt does it better than most.
CHRIS REINHARD: For every ton of rock, it turns out, because of the chemistry of the rock, is higher for crushed basalt than it is for limestone.
AHL: And it does work in the lab. Now researchers are testing how that works out in the field.
GAVI WELBEL: So these are all just kind of smaller beds that mostly we grow food. We have a little flower garden over here, some snap peas.
AHL: Gavi Welbel is pointing out the many fenced-in areas of her family's farm in eastern Illinois on this hot and windy day. She and her twin sister run this farm that is largely focused on small-scale agriculture, but they're also gathering information on how successful replacing crushed limestone with crushed basalt can be on big fields of row crops. She says the results they saw in their 12-acre hay field of alfalfa, oats and timothy grass were encouraging.
WELBEL: We saw a consistently increasing yield in the higher basalt plots, so that was very exciting. But we'll see as years go on if that's replicable.
AHL: Farmers typically apply about two tons of limestone per acre to fields. But the basalt experiment has plots ranging from a half ton to 24 tons per acre. Welbel says the more basalt you use, the more carbon is sequestered in the ground.
WELBEL: So we're looking at basically where we can get maximum carbon capture - and then also, what does it look like at an application rate that would feel more comfortable for farmers and might be more economically feasible?
AHL: The Welbels also used basalt in some of their corn and soybean fields. They'll have more data this fall. But using the eye test, the corn and soybeans in fields treated with basalt are looking as good or better than the ones using limestone. But for now, basalt is more expensive than limestone, and that could make it a deal breaker for many farmers. Yale professor Noah Planavsky is one of the researchers tracking the experiments. He says with data showing that basalt puts a lot of carbon into the ground, farmers could conceivably sell carbon credits to other companies looking to reduce their own footprint. That could give farmers a new profitable commodity to sell.
NOAH PLANAVSKY: You could think of this as another supplementary source of income for farmers. And that could be especially critical where farmers are going to get hit by more and more lousy years from climate extremes.
AHL: The pilot program testing crushed basalt rock will continue for at least two more years as farmers and scientists gather data to test the environmental benefit and financial feasibility of changing over to basalt to treat the soil.
For NPR News I'm Jonathan Ahl.
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