Feature: Can Dirt Save the Earth?

Feature: Can Dirt Save the Earth?

For nearly 20 years, Williams worked as a contractor, building houses in Kansas City. But work dried up after the financial crisis hit in 2007. Williams decided to return to the family farm near Waverly, an area of gently rolling plains, and give farming a try. His family had farmed some when he was a teenager before leasing the land to tenants for years, and he knew it was difficult to make ends meet. But he was inspired by an article about a North Dakota rancher and farmer named Gabe Brown, who claimed to have developed, through trial and error, a more efficient and cost-effective way to farm.

The gist of Brown’s argument was that if you focus on the health of the soil and not on yield, eventually you come out ahead, not necessarily because you grow more corn or wheat per acre but because the reduction in spending on fertilizer and other inputs lets you produce each bushel of grain more cheaply. Williams decided to follow Brown’s prescription. “If after three years, I’m bankrupt, I’ll admit it was a bad joke,” Williams remembers thinking.

Seven years later, his gamble seems to have paid off. He started with 60 acres, now farms about 2,000 and, when I visited last fall, had just purchased an additional 200. In one of his fields, we walked down a lane he had mowed through his warm-weather cover crops — plants grown not to be harvested, but to enrich the soil — which towered over us, reaching perhaps eight feet. They included sorghum, a canelike grass with red-tinted tassels spilling from the tops, mung beans and green-topped daikon radishes low to the ground. Each plant was meant to benefit the earth in a different way. The long radishes broke it up and drew nutrients toward the surface; tall grasses like sorghum produced numerous fine rootlets, adding organic material to the land; legumes harbored bacteria that put nitrogen into the soil. His 120-strong herd of British white cattle — he introduced livestock in 2013 — would eventually eat through the field, turning the plants into cow patties and enriching the soil further. Then he would plant his cash crops. “Had I not found this way to farm,” he told me, “we would not be farming.”

A mat of dead vegetation — from cover crops, cash-crop residue and dung — covered Williams’s fields. The mulch, along with his cover crops, inhibited weeds from becoming established, a major concern for conventional farmers, because so many weeds have evolved resistance to herbicides. “I don’t lie awake at night wondering how I’m going to kill weeds,” Williams said.

Williams doesn’t till his fields. By minimizing soil disturbance, no-till farming prevents erosion, helps retain moisture and leaves the soil ecosystem — worms, fungi, roots and more — mostly intact. At one of his soybean fields, Williams showed me how this translated to soil with “structure.” “See how that crumbles into a cottage-cheese look?” he said, massaging a fistful of earth. Small clods fell through his fingers. “That’s what you want.” Worm holes riddled the dirt, giving it a spongelike quality that was critical, he said, for absorbing rain and preventing runoff. Weather patterns seemed to be changing, he noted. Rain used to arrive in numerous light storms. Now fewer storms came, but they were more intense. “We have to be able to capture rain and store it,” he said.

By focusing on soil health, Williams says he has reduced his use of herbicides by 75 percent and fertilizers by 45 percent. He doesn’t use pesticides — he relies instead on beneficial insects for pest control — and he saves money by not buying expensive genetically modified, herbicide-resistant seed. He estimates that he produces a bushel of soybeans for about 20 percent less than his conventionally farming neighbors. Last fall, he claims, his yields ranked among the highest in the county. While doing all this, he has so far raised the amount of soil organic matter, a rough predictor of soil carbon concentrations, from around 2 percent to 3.5 percent in some fields. Gabe Brown, for his part, says he has more than tripled his soil carbon since the 1990s. And an official with the U.S.D.A.’s Agricultural Research Service confirmed to me that the amount of carbon in Brown’s soil — what his farming has pulled from the atmosphere — was between two and three times as high as it was in his neighbors’ land.

The successes of Brown and Williams suggest that farmers can increase carbon in the soil while actually reducing their overall expenses. This could be vital, because in order for carbon farming to have an impact on the climate, as much land as possible, including both crop- and rangeland, will have to be included in the effort.

Critics of regenerative agriculture say that it can’t be adopted broadly and intensively enough to matter — or that if it can, the prices of commodities might be affected unfavorably. Mark Bradford, a professor of soils and ecosystem ecology at Yale, questions what he sees as a quasi-religious belief in the benefits of soil carbon. The recommendation makes sense intuitively, he told me. But the extent to which carbon increases crop yield hasn’t been quantified, making it somewhat “faith-based.”

William Schlesinger, an emeritus soil scientist at Duke, points out that “regenerative” practices might inadvertently cause emissions to rise elsewhere. If you stop tilling to increase soil carbon, for example, but use more herbicides because you have more weeds, then you probably haven’t changed your overall emissions profile, he says. He thinks the climate-mitigation potential of carbon farming has been greatly oversold.

Williams has reduced his herbicide use, not increased it, but Schlesinger’s broader point — about the need for a careful overall accounting of greenhouse gases — is important. Williams, Brown and others like them aren’t focused on climate change; no one really knows if the carbon they put in the ground more than offsets the methane produced by their cows, for example. What they do demonstrate is that augmenting soil carbon while farming is not only possible, but also beneficial, even in a business sense. And that makes the prospect of rolling out these practices on a larger scale much easier to imagine.


Measuring equipment used on a test plot on the Wick-Rathmann ranch, including time-lapse cameras that watch the grass grow.

Jonno Rattman for The New York Times

The carbon-farming idea is gathering momentum at a time when national climate policy is backsliding. The Trump administration has reversed various Obama-era regulations meant to combat or adapt to climate change, including the Clean Power Plan, which required power plants to reduce their carbon emissions, and a rule instructing the federal government to consider sea-level rise and other effects of a changing climate when building new roads, bridges and other infrastructure.

In the absence of federal leadership on climate — and as emissions continue to rise globally, shrinking the time available to forestall worst-case outcomes — state and local governments (as well as nonprofits) have begun to look into carbon farming. Last year, Hawaii passed legislation meant to keep it aligned with the Paris agreement, which President Trump has said he will abandon; the state has also created a task force to research carbon farming. The New York state assemblywoman Didi Barrett introduced legislation that would make tax credits available to farmers who increase soil carbon, presumably through methods like those employed by Darin Williams and Gabe Brown. A bill to educate farmers about soil has been proposed in Massachusetts. And in Maryland, legislation focused on soil health passed in 2017. Other carbon-farming projects are in the works in Colorado, Arizona and Montana.

But it is California, already in the vanguard on climate-mitigation efforts, that has led the way on carbon farming. By 2050, the state aims to reduce greenhouse-gas emissions to 20 percent of what they were in 1990. Nearly half its 58 counties have farmers and ranchers at various stages of developing and implementing carbon-farming plans. San Francisco, which already has the largest urban composting program in the country, hopes to become a model carbon-farming metropolis. Cities don’t have much room to plant trees or undertake other practices that remove carbon from the atmosphere, says Deborah Raphael, the director of San Francisco’s Department of the Environment. But they can certainly produce plenty of compost. “If we can show other cities how doable it is to get green waste out of landfills, we can prove the concept,” Raphael told me. “We like to say that San Francisco rehearses the future.”

Many of California’s carbon-farming efforts owe a debt to Wick, Creque and Silver. In 2008, they founded the Marin Carbon Project, a consortium of ranchers, scientists and land managers. The goal is to develop science-based carbon-farming practices and to help establish the incentives needed to encourage California farmers to adopt them. Silver continues to publish her findings in respected journals. Creque also started a nonprofit, the Carbon Cycle Institute, that assists farmers and ranchers in making carbon-farming plans.

Wick has thrown himself into the policy realm, hiring a lobbyist in Sacramento to push a carbon-farming agenda. (In 2014, he even testified before Congress, outlining the project’s discoveries and explaining how compost could increase soil carbon on public lands. He deliberately mentioned “climate” only once.) Educating policymakers matters because, as Torri Estrada, executive director of the Carbon Cycle Institute, points out, carbon-mitigation efforts that focus on agriculture can be much cheaper per ton of carbon avoided than the flashier energy-efficiency and renewable-energy projects that usually get most of the attention. The major obstacle to their implementation, he says, is that government officials don’t understand or know about them.

California’s Healthy Soils Initiative, which Wick helped shape, explicitly enlists agriculture in the fight against climate change. In principle, that means this carbon farmers can receive money from the state’s climate-mitigation funds not just for compost but also for 34 other soil-improving practices already approved by the Natural Resources Conservation Service. That’s important because the compost needed to cover just a few acres can cost thousands of dollars. Wick has also tried to tap federal funding. Once N.R.C.S. scientists vet Silver’s work, a compost amendment could become the service’s 35th recommendation. As a result, farm bill money, which farmers receive to subsidize food production, could help finance carbon farming done according to Wick’s protocol — not to fight climate change explicitly (which is now seen as politicized), but to bolster the health of soil (which isn’t).

As a carbon-farming tool, compost bears some notable advantages — namely, it works both preventively and correctively. Composting prevents emissions from the starter material — manure, food scraps — that, if allowed to decompose, might emit potent greenhouse gases. (About one-fifth of United States methane emissions comes from food and other organic material decomposing in dumps.) By enhancing plant growth, it also aids in removing carbon from the atmosphere, a corrective process. And because the carbon in nearly all organic material was originally pulled from the atmosphere during photosynthesis, compost that enters the soil represents the storage of carbon removed from the air earlier — the grass eaten by cows that became manure, or the trees that became wood chips — and at a different location. That, too, is corrective.

Calla Rose Ostrander, Wick’s right-hand person at the Marin Carbon Project, told me that the project’s greater goal is to completely reframe how we think about waste, to see it as more than a nuisance — to recognize it as a resource, a tool that can help us garden our way out of the climate problem. Before the modern era, farmers had no choice but to return human and animal waste to the fields. (Wick is looking into the possibility of composting human waste as well; the end product is called humanure.) In a sense, Wick and Ostrander seek to resurrect these ancient practices and, with the aid of modern science, to close the loop among livestock, plants, air and soil — and between cities and the agricultural land that feeds them.

What seems to most impress experts about the Marin Carbon Project is the quality of Silver’s research. Eric Toensmeier, the author of “The Carbon Farming Solution” and a lecturer at Yale, says that the project figured out a new way to increase carbon storage on the semiarid grasslands that cover so much of the world. Jason Weller, the former head of the Natural Resources Conservation Service, told me that “the level of science investment is out of the ordinary, or extraordinary, for a group that is really self-started.” Weller added that the agency’s scientists still needed to vet the research, which they are in the midst of doing. In late 2016 the agency oversaw the application of compost to different California regions — inland, Southern, Northern — to see if land in various conditions would, like Wick’s ranch, suck up atmospheric carbon.

But the group also has critics. “I’m very skeptical of their results and their claims,” William Horwath, a soil scientist at the University of California, Davis, told me. He wants to see Silver’s experiments replicated. This is the project’s major weakness: Its big idea is based almost entirely on extrapolation from a few acres in California. At this point, it’s impossible to say whether compost can cause land to become a carbon sponge in all climates and conditions, and for how long treated grassland will continue to take in and retain its carbon.

Cows, a flash point in any discussion about climate change, may also present problems. Ruminants burp methane, and while carbon farming does not require their presence, some argue that merely accepting them on the land undermines the goal of reaching a carbon-neutral or -negative future. Livestock emissions account for almost half the heat-trapping gases associated with agriculture, so an obvious way to reduce emissions is to decrease the number of cows on the planet. Instead of dumping compost on rangeland, says Ian Monroe, a lecturer on energy and climate at Stanford University, why not allow forests cleared for pasture to regrow, and change people’s eating habits so they include less meat?

Criticism is directed at compost too. The stuff requires energy to produce; huge machines are required to shred the material and keep it aerated. And it’s unclear if compost, like synthetic fertilizer, can cause nitrogen pollution when put on the land, or how much greenhouse gas composting itself generates. (As long as compost mounds are regularly aerated to prevent low-oxygen conditions, composting is thought to produce few emissions.)

Organic material from municipal sources can contain bits of plastic and glass, which no one wants on their fields. Manure might carry seeds of invasive plants. (Silver has seen no evidence of this.) Spreading compost on public rangeland could disrupt plant communities, squeezing out species adapted to conditions of scarcity. And in any carbon-farming scheme, who will monitor and verify that far-flung stretches of land are really absorbing and storing the carbon as they’re supposed to?

Horwath considers the amount of compost used in Silver’s research — about 10 times the usual application, he estimates — to be unrealistically high for practical use. “It seems an inordinately large amount to apply to any system,” he told me. And given what he sees as the many unknowns in Silver’s research, that compost would be put to better use on cropland where, he says, scientists know with greater certainty that it could improve water retention and the efficiency of fertilizer.

Then there’s the problem of supply. Demand for San Francisco’s compost, which mostly goes to vineyards in California’s wine country, already outstrips what’s available. But Wick thinks more starter material shouldn’t be hard to find: Americans throw out between 30 and 40 percent of all the food they buy, sending it to landfills where it rots and generates greenhouse gases. Silver has calculated that there’s enough organic waste material in California to treat one-quarter of its rangeland every few decades.

Still, given the energy requirements, the logistical headaches and the cost, skeptics question whether spreading compost across extensive portions of the world’s surface — including conflict zones in the Sahel or Central Asia — is really feasible. Even if it is, soils probably can’t soak up carbon indefinitely. If they have a saturation point, increases in carbon will eventually stop when that moment is reached. And because soil degradation can cause the release of whatever carbon it holds, treated lands would have to be well cared for in perpetuity.

On a cool autumn day at Wick and Rathmann’s ranch house, Wick fielded phone calls while I wandered around the cluttered, semicircular room that served as his office and meeting space. A whiteboard displayed scribbles from a presentation on the carbon cycle. Coils of warmly hued yarn hung from the doorways. They came via a local nonprofit dedicated to climate-friendly ranching practices called Fibershed. And draped over a chair was a T-shirt bearing what might as well have been Wick’s battle cry: “seq-C,” it read, punny shorthand for “sequester carbon.” Under that it read, “Doing it in the dirt.”

Down the road, he showed me a composting facility that Creque dreamed up initially. He and Wick hoped it would serve as a self-sustaining prototype. “Anything that has ever been alive can be composted,” he told me, surveying the 10-foot-tall piles of chicken droppings and feathers, horse bedding (manure and straw) and shredded trees. A tractor mixed woody refuse with animal waste — to get the composting process started requires the right mix of carbon- and nitrogen-rich materials. (That’s why some backyard composters recommend urinating on the pile to kick things off: Urine is rich in nitrogen.)

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