Critics Weigh Merits of Soil Sequestration-Based Carbon Storage

Soil scientists, carbon credit start-ups, and now U.S. President Joe Biden want to enlist American farmers to fight the climate crisis through soil sequestration. Some, however, are questioning whether the benefits are as advertised, or if the initiative is a dangerous distraction from more proven, heavyweight carbon solutions like peatland restoration and forest protection.

While a higher yield was the initial motive for Maryland farmer Trey Hill when he planted soil-restoring winter crops on his 10,000-acre corn, soybean, and wheat farm, funding available to support carbon sequestration helped cement his commitment, reports the Washington Post.

“In early 2020, he became the first seller in a privately-run, farmer-focused marketplace that paid him US$115,000 for practices that, over the past few years, had sequestered just over 8,000 tonnes of carbon in the soil.” Those practices included “no-till” farming—which keeps carbon from converting to CO2 on the soil surface—and planting nitrogen-fixing crops like rye, turnips, and clover over the winter months.

“We know how to do it,” said Nature Conservancy soil scientist Deborah Bossio. Her team led an early 2020 research project that estimated that, “if soil was protected and replenished globally, it could provide nearly 10% of the carbon dioxide drawdown needed to avert near-term climate catastrophe.”

And, adds the Post, “a recent global meta-analysis estimated that if cover crops were planted on 15% of the world’s cropland, soils could soak up between 1 and 2% of all fossil fuel emissions.”

In response to such numbers, the Biden administration has pledged to establish a “carbon bank” during its first 100 days in office, in order to pay ranchers, forest owners, and farmers like Hill to embrace climate-friendly practices.

Some critics, though, are demanding proof that these soil sequestration practices are effective, and not just a form of greenwashing for an agriculture industry that wants to delay real change. According to a study published last year that examined cover crop practices in California and Iowa, such crops don’t build carbon into the soil at a deep enough depth to hold it out of the atmosphere.

“An overfocus on soil carbon is a diversion from the climate strategies that can have a bigger impact,” said Princeton researcher Tim Searchinger, a senior fellow at the World Resources Institute. He told the Post that while cover crops and other such regenerative practices are undeniably good for soil and ecosystems generally, their effect on carbon retention has being overrated.

Better strategies, he said, include peatland restoration, as well as reducing cattle methane and promoting more efficient farming that would reduce the need to raze forests for farmland. Studies have also shown that organic farming does a better job than cover crops at producing “deep reserves of carbon,”

The cost of regenerative farming is a barrier, too. While Trey Hill has become a convert, seeing himself as a foot soldier in the climate fight, he had to invest in specialized equipment, and he has yet to see his newly-adopted practices translate into higher yields.

“It’s a b—- to farm this way,” he told the Post. “It makes life a lot more difficult, and not necessarily more profitable.” If policy-makers want more famers to take up these practices, he added, they’re going to have to pay.

Which is precisely why the idea of soil sequestration may be more chaff than wheat, writes the Post: “Carbon accumulates slowly in soil, and past attempts to pay farmers for it have failed when the costs of verifying carbon gains exceeded what buyers were willing to pay.”

But things are evolving fast, and “backers of new, private sector carbon markets hope computer models fed by data from farm fields, satellites, and handheld carbon sensors can measure and predict soil carbon gains more cheaply and reliably.”

One such market into which Hill is now plugged in is Seattle-based Nori.

“After lengthy negotiations, credits representing carbon stored in some of Hill’s fields went on sale in October 2019 at $16.50 a tonne—around the most an acre of his farmland might capture in a year.” Among the buyers on Nori anxious to offset the carbon they produce: Ottawa tech giant Shopify, and Arizona State University.

But so far, the market has been slow going. While Nori had hoped to have over a 100 farmers enrolled by the end of 2020, “only Hill and an Iowa farmer have sold credits on the marketplace, with three more in the final stage of verification.” Other buyers—including Microsoft—refused to buy because Nori’s credits do not come backed by physical soil samples, which can cost thousands, and instead rely on third-party audits “and a U.S. Agriculture Department computer model called COMET-Farm that estimates greenhouse gas emissions from farms.”

In related news, Inside Climate News reports the Biden administration is breaking new ground with its formal designation of the U.S. Department of Agriculture (USDA) as “a lynchpin” in its climate action strategy. While some observers were disappointed when Biden reappointed Obama-era Agriculture Secretary Tom Vilsack to his previous position, considering him too friendly to larger producers, “climate hawks mostly applaud Vilsack’s eight-year tenure at the agency, during which he set up a network of ‘climate hubs’ where farmers could get information about adapting to climate change and launched an initiative to increase carbon stored in forests and soils.”

Inside Climate says Biden’s carbon banking plan is, as yet, “short on specifics,” and faces one likely obstacle: while the Commodity Credit Corporation (CCC) that will support the bank has up to $30 billion in borrowing capacity, “Vilsack would likely need Congressional approval to tap into it”, something unlikely to happen in a Congress where Democrats hold only a razor-thin majority.

“Critics also worry that establishing a carbon bank would effectively use public funds for exchange in a marketplace that’s currently private, an action that would largely benefit big producers,” Inside Climate adds.

What the U.S. needs is “large-scale land use change, where you get more perennial crops in place,” said Ricardo Salvador, senior scientist and director of the Food and Environment Program at the Union of Concerned Scientists. While carbon-sequestering practices could be adopted into existing systems of producing commodities like corn, soy, and wheat (as Trey Hill is doing), they will still emit more carbon than they save.

“The science is not there in terms of how you would actually measure and verify that you’re permanently storing or significantly storing carbon,” he told Inside Climate.