Michael Pollan deemed it agriculture’s “secret weapon” in a December op-ed for the Washington Post. Bill McKibben, in his praise for an upcoming book on the topic, described carbon farming as “a powerful vision,” one that he hopes will “presage major changes in our species’ use of the land.” Paul Hawken went so far as to call it “the foundation of the future of civilization,” with potential to “surpass the productivity of industrial agriculture.†
Why all the hubbub? And, for that matter, what exactly is it about?
Carbon farming is agriculture’s answer to climate change. Simply put, the goal is to take excess carbon out of the atmosphere, where the element causes global warming, and store it in the soil, where carbon aids the growth of plants. The principle is pretty straightforward – the practice, not so much.
Most folks understand that burning fossil fuels puts carbon that was once buried deep beneath the earth into the atmosphere, turning the planet into one big greenhouse in the process. But in addition to petroleum underground, the soil on the surface of the earth contains a sizable store of carbon in the form of organic matter – the stuff that environmentally aware farmers and gardeners are always striving to maximize. Plants add organic matter to the soil when they decompose, and photosynthesis, by definition, removes carbon dioxide from the air and pumps it through the roots of plants and into the soil.
Concern over climate change may have thrust the concept of carbon farming into the limelight – 25 countries pledged to pursue it during the December climate talks in Paris – but ranchers like Gabe Brown, who raises livestock and an array of crops on 5,000 acres outside Bismarck, North Dakota, have preached its virtues for decades. “All soil biology eats carbon, and that’s how nutrients cycle,” explains Brown of the network of microbes and fungi and earthworms underground. “Farmers need to think of carbon as their fertilizer, because it’s what drives a healthy system.†
At first glance, most carbon-farming techniques mirror age-old organic growing methods: Instead of relying on chemical crutches and pulverizing the soil with constant tillage, you enrich it with compost and rotate a diverse array of food and cover crops through the fields each season. (See “Five Tenets of Carbon Sequestration,” below.) But Brown and other practitioners of carbon farming – Virginia’s Joel Salatin and Zimbabwe’s Allan Savory are the best known among them – go to extraordinary lengths to keep carbon-producing organic matter in the soil and out of the atmosphere. Plowing is avoided like the plague. Instead of turning up the earth at the end of a given crop’s cycle, Brown sends his livestock – Angus cattle, Katahdin sheep, hogs, and chickens – into the field to trample and eat the crop. He then uses a seed drill to plant the next crop among the decaying roots of the previous one.
Brown, a former conventional commodity-crop farmer, still grows corn, but with a groundcover of clover or vetch beneath the stalks. He follows each cash crop with a mix of pearl millet, Sudan grass, cowpeas, sunflowers, and other soil-enriching cover crops, combining up to 70 different species in a single planting. Each occupies a slightly different niche in terms of height, root depth, leaf shape, and growth rate, forming a dense blanket of vegetation that pumps carbon from the sky to the soil and provides a rich “cocktail” on which his livestock graze.
Brown says he has greatly increased his profitability since adopting carbon-farming practices more than 20 years ago. In addition to improved yields on the corn, soy, and wheat he’s always sold on the wholesale market, he now supplies beef, pork, eggs, broilers, and honey to local customers.
Another way carbon farming pays off, at least abroad: carbon-credit markets. For the past five years, Australia’s agricultural sector has benefited from a nationally mandated cap-and-trade program that lets farmers who adopt carbon-sequestration practices sell carbon credits to heavily polluting corporations in need of offsetting carbon footprints. And two years ago, the World Bank established a fund to buy carbon credits from Kenyan farmers as a means to incentivize climate- friendly practices in a part of the world known for its slash-and-burn approach to the land.
America has yet to institute a federally mandated carbon-credit system, though nine northeastern and mid-Atlantic states have adopted cap-and-trade schemes covering the emissions of 168 power plants. Only California can claim a wide-reaching cap-and-trade program that requires more than 600 polluters across various industries to offset their emissions, but even there, most farm-based practices for carbon sequestration remain ineligible for credits. Under California’s current system, credits are available mainly to farmers who are themselves big polluters – livestock farmers who install anaerobic digesters to capture methane (one of the three main greenhouse gases) released from their manure lagoons, for example – not those who follow the low-impact practices espoused by the carbon-farming movement.
“Farmers need to think of carbon as their fertilizer, because it’s what drives a healthy system.†
That’s starting to change, thanks in part to the efforts of a group of dairy farmers in Marin County. The challenge involves quantifying the amount of carbon sequestered and providing assurance that the numbers can be reliably replicated, according to John Wick, cofounder of the Marin Carbon Project. Last year, Wick’s organization – in conjunction with ecologists at the University of California, Berkeley – managed to convince the agency that administers the state’s voluntary carbon-credit exchange (as opposed to its government-mandated one) to grant credits to farmers who spread com-post over grazed grasslands. “We’re at that pivotal moment,” Wick says, “between demonstrating scale, which we’ve done, and implementation.†
Many consider livestock on pastureland the ideal system for sequestering carbon. Each time an animal nibbles on a blade of grass, the roots release a bit of carbon into the soil; pasture-raised beasts and birds also convert grass into marketable products like meat, dairy, and eggs. But opponents argue that animals emit as much carbon as they help sequester, pointing to the belches and manure of ruminant animals as a major source of green-house gases.
Eric Toensmeier – author of The Carbon Farming Solution, the new book that has Hawken, McKibben, and other activists buzzing – offers a reality check and a realistic solution. “There’s this conversation happening that suggests grazing is the only way to go, yet the rates [of sequestration] are among the lowest of all carbon-farming practices,” he explains. “It’s quite complicated when you really drill down into it.†
A proponent of long-lived perennials as the best carbon capturers, Toensmeier urges ranchers to consider “silvopasture,” the practice of grazing livestock among trees, spaced widely to allow enough sunlight to reach the fields, as compensation for the carbon released by the animals. Yet he acknowledges the many variables that influence a farm-er’s decision-making process: “It’s a matter of what practices are suited to your climate and fit in your marketing mix, as well as the mechanisms for financing the transition.†
The U.S. Department of Agriculture is helping farmers transition to carbon-sequestering practices with a free web-based tool called COMET-Farm, which provides an approximate carbon footprint based on user-supplied data and allows farmers to experiment with different land management scenarios to see which works best. USDA air-quality scientist Adam Chambers says the data the tool provides should help pave the way for farmers to monetize sequestration practices as the carbon market matures. “This is the cookbook, if you will, for how farmers can accomplish emission reductions,” he explains.
Through a partnership with the USDA, Chevrolet recently purchased 40,000 carbon credits from 23 ranchers in North Dakota who have voluntarily pledged to adopt no-till methods on their combined 11,000 acres of grazing land. Chambers hopes the transaction, which equates to taking 5,000 cars off the road and is the largest of its kind to date in the United States, will jump-start the market for farm-based carbon sequestration. As one of the world’s largest auto companies, it’s fitting that Chevy should start that ball rolling.
Five Tenets of Carbon Sequestration
NO-TILL Tilling mixes soil with air, allowing carbon to oxidize back into the atmosphere. Instead, focus on perennial crops that don’t require tillage, or use a no-till seed drill for large-scale annual plantings.
ORGANIC MULCH Cover the soil around small-scale plantings with a wood chip or straw mulch to prevent carbon losses. On large plantings, leave crop residue in place as mulch. As it decomposes, the residue fuels the carbon cycle in the soil.
COMPOST Compost is rich in a stable (not easily oxidized) form of carbon. Carbon farmers recommend dusting it over the surface of the soil – you can spread it directly over the grass in your pasture – rather than tilling it in.
LIVESTOCK ROTATION Moving concentrated herds and flocks of animals through a series of small paddocks on a regular basis is preferable to letting the animals forage continuously over a single large area. Many carbon farmers move their animals every day and try to let each paddock “rest” as long as possible between grazings.
COVER CROPS Fast-growing species such as clover and vetch keep the soil covered and enriched with carbon through the winter and may also be planted together with cash crops during the growing season to compensate for carbon lost when those crops are harvested.
Correction 3/29: A previous version of this story implied, incorrectly, that reducing fertilizer use on corn qualified for carbon credits under California’s cap-and-trade system. While credits for that purpose are approved under some carbon credit registries, that is not the case in California.