September 25, 2023

Fields don’t just feed us. They store carbon. But a big question is how much

DYSART, Iowa (AP) — When Al Schafbuch stopped plowing his Iowa fields decades ago and later started growing cover crops, he was out to save money on fertilizers and reduce erosion. He got those benefits and saw his soil change for the better too: dark, thick, rich organic matter that he says feels like “chocolate cake.”

There’s another big gain that benefits everyone: By working the soil less and growing more cover crops, farmers can store more carbon in fields that warm the planet. More plants absorb more carbon dioxide and soil microbes exhale less carbon when undisturbed. That could mean money for participating farmers in the form of carbon offsets — payments companies can make to support carbon storage in farms and, in theory, balance their emissions elsewhere.

“The more carbon you store from the atmosphere with your crops, and the more crops grown year-round, you offset some of your waste, your wasted energy,” said Shalamar Armstrong, an associate professor of agronomy at Purdue University. “Because you’ve been storing carbon that would have been emitted into the atmosphere.”

It is an area that is receiving more attention from legislators, researchers and industry professionals. The U.S. Department of Agriculture this week announced a $300 million investment to monitor agricultural emissions, including establishing a research network to monitor soil carbon. And U.S. Senator Tina Smith, D-Minn., and Todd Young, R-Ind., introduced a bill that Smith said would support the research needed to “properly credit carbon sequestration in the soil.”

The USDA announcement and the legislation both address the difficult question of how to quantify carbon stored in soils. It is an obstacle that must be overcome if the young and fast-growing soil carbon market is to avoid the scrutiny and skepticism of the carbon credit markets.

“The science piece[of carbon credits]has really lagged behind, especially when it comes to things like monitoring, reporting and verification,” says Cristel Zoebisch, deputy director of policy at climate organization Climate 180. “These are huge obstacles to not only carbon sequestration in the soil, but really any solution for carbon removal on land.”

Armstrong has tried to solve that problem. He runs a lab where researchers study how agricultural management affects the amount of soil carbon in different landscapes. He and others at Purdue have been studying soil samples more than 40 years old, comparing different tillage types and cover crops to determine their long-term effects on carbon storage. It could take years of field work, careful lab chemistry, and a lot of expensive equipment to figure that out.

He hopes his precise calculations will help farmers make decisions that allow them to receive valuable incentives for carbon sequestration while preserving their existing profits.

But other academics worry that even paying farmers to store soil carbon won’t solve a bigger problem: that carbon markets often don’t work.

Compensations are legitimate if they meet four criteria. They have to store carbon that would otherwise be emitted; they must be verifiable in data; they must be immediate (planting a tree that can grow in 20 years does not cut it); and they should last, says John Sterman, a professor of management at the Massachusetts Institute of Technology.

Better quantifying soil carbon storage through research can make offsets more verifiable, but other factors are not addressed. For example, many farmers lease the land they farm and cannot guarantee that the carbon stored on their land will last for decades if someone else farms it.

Barbara Haya, director of the Berkeley Carbon Trading Project at the University of California, Berkeley, has worked on research that she says shows that the effects of carbon offset projects are often overstated, sometimes vastly.

“Carbon trading is a mechanism that has failed miserably for the past 20 years and we really need to get away from it,” Haya said.

U.S. Representative Jared Huffman, D-Calif., introduced a bipartisan bill last month to support farmers improve soil health with incentives that don’t necessarily relate to the carbon market. He said farmers in his district have also described the benefits of regenerative practices, and that many would be interested in participating in carbon markets with “robust” accounting systems. But he added that those hoping for serious climate action should not rely solely on offsets.

“It’s really not the silver bullet in my opinion,” Huffman said. “I think offsets are inherently fuzzy.”

Some farmers proceed with caution.

Brad Wetli, an Indiana farmer who works with Armstrong, is trying out techniques that require less tillage and has been planting cover crops like rye for a few years now. He’s happy with the way his current fields look – “It feels like you’re doing something” to contribute to sustainability, he said – but he’s still weighing his options with potential carbon credit contracts, doing the math and waiting to see if the price is justified, as many offset agreements can last for several years.

“I’m going to do maybe a field or two at a time, and as I learn more, hopefully I’ll incorporate the carbon or carbon credits more into the operation,” he said.

Schafbuch, for his part, is skeptical of carbon credits but would have been enthusiastic about regenerative agriculture, regardless of the upfront cost. He said he was an early adopter in the face of neighbors laughing and suggesting he would “eventually go broke” – but he’s proven them wrong.

“I’m convinced that if you do it right, anyone can do it,” he said.


Associated Press journalist Joshua Bickel contributed to this report from Fowler, Indiana.


Follow Melina Walling on Twitter @MelinaWalling.


The Associated Press’ climate and environmental coverage is supported by several private foundations. Read more about AP’s climate initiative here. The AP is solely responsible for all content.

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