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Climate change and energy

Why we can’t count on carbon-sucking farms to slow climate change

Even though lots of politicians, environmentalists, and companies are eager to try.


Corporations, politicians, and environmentalists have all embraced carbon farming as the feel-good climate solution of the moment.

Several leading Democratic presidential contenders highlighted the potential to alter farming practices to suck up more carbon dioxide in their climate plans. And the presumptive nominee, Joe Biden, declared last summer: “Soil is the next frontier for storing carbon.”

Companies like BP, General Mills, Kellogg, Microsoft, and Shell have all announced plans or joined initiatives that will direct their suppliers to adopt the techniques or pay farmers who do so to obtain so-called offsets credits. These allow the businesses to claim credit for the carbon dioxide pulled out of the atmosphere, without cutting emissions from their own operations.

In addition, several venture capital-backed startups have set up soil offsets marketplaces that allow companies and nonprofits to purchase credits from farmers. Most notably that includes Indigo Agriculture, which has raised more than $850 million to date to build up its soil carbon business and other operations.

And now an influential California nonprofit, the Climate Action Reserve, is in the process of writing standards for soil carbon offsets, which would offer a stamp of approval likely to spur more people and businesses to buy these credits.

But there’s a big problem: there is little evidence that carbon farming works as well as promised.

The world’s farmlands do have the capacity to store billions of tons of carbon dioxide in the soil annually, according to a National Academies report last year. But there is still uncertainty concerning which farming techniques work, and to what degree, across different soil types, depths, topographies, crop varieties, climate conditions, and time periods.

It’s unclear whether the practices can be carried out over long periods and on a massive scale across the world’s farms without undercutting food production. And there are significant disagreements about what it will take to accurately measure and certify that farms are actually removing and storing increased amounts of carbon dioxide.

These uncertainties further complicate the well-documented challenges in setting up any reliable carbon offsets program. Studies have frequently found these systems can substantially overestimate reductions, as economic, environmental and political pressures all push toward issuing large numbers of offsets credits. The programs can also create opportunities for gamesmanship and greenwashing that undermine real progress on climate change, observers say.

As Climate Action Reserve looks to ramp up the use of these credits, some fear the group is on the verge of creating a standard that may well invite such behavior.

A carbon pump

The basic idea behind carbon farming is that photosynthesis acts as a greenhouse gas pump, pulling CO2 from the air and converting it into sugars stored in leaves, stalks, and roots or excreted into soil. The hope is that farmers can increase the amount of carbon that is left behind in the fields, through practices like planting cover crops between harvests, and drilling seeds instead of continually upturning the soil through tilling.

But the process playing out in California highlights the challenges of establishing reliable standards that can be broadly applied. Such standards certify that the farmers getting paid to carry out the practices are in fact decreasing carbon dioxide in the atmosphere, lending confidence to people or businesses looking to purchase credits.

They’re essential to making offsets work, but hard to get right. Climate Action Reserve, which created the protocols that California largely adopted for the nation’s largest cap-and-trade program, released a draft “soil enrichment protocol” for public comment in April. It was scheduled to bring the standard before its board for a vote this month. But last week, the nonprofit announced a second public comment period after receiving numerous responses, several of which questioned whether the protocol will accurately measure additional levels of carbon uptake.

At least one argued that conflicts of interest may have swayed the process, because Indigo Agriculture contributed an unspecified amount of money, as well as “research and drafting support.” The company works with farmers to pool soil carbon credits that it then sells to corporations and nonprofits, so it has a clear stake in how the standards are set.

“A sponsored protocol development process raises concerns about the integrity of the proposed methods,” reads a response letter from CarbonPlan, a new nonprofit that evaluates the scientific rigor of carbon removal efforts. “That concern is particularly important because many of the critical methodological options in the draft protocol are not fully specified and are instead left open to the design and determination of project owners—presumably including the reserve’s financial sponsor, Indigo Ag.”

Indigo’s involvement in the process “prevented the workgroup from being able to set down what we thought would be a really rigorous set of constraints,” says Grayson Badgley, a postdoctoral fellow with the Black Rock Forest Consortium in Cornwall, New York, who served on the technical workgroup that provided advice on the process and signed the letter. “I felt like whatever set of constraints we proposed had to include what Indigo already wanted to do."

He adds that several representatives from Indigo were on most of the calls he participated in during the process.

In an email to MIT Technology Review, Indigo said that it also hired several other members of the workgroup for projects in the past, but added “those individuals have remained impartial through the working group process.” It didn’t disclose their names to the publication, though the company said it provided such a list to Climate Action Reserve.

One of the chief concerns about the proposed protocol is that it allows project owners to select their own methods for calculating how credits are earned, so long as the model has been reviewed by “a recognized, competent organization” and meets several other criteria.

The issue is that much of the soil carbon research to date finds that carbon uptake differs widely across soil types and other conditions, not just from region to region, but from plot to plot. So it’s difficult to develop any model “that can account for this inherent variability,” and requires them all to be rigorously tested and reviewed, says Jane Zelikova, chief scientist at the Carbon180 think tank, who also signed the letter. She argues that any modeling must be supplemented with thorough and randomized soil sampling, across fields, at varying depths and over time.

The draft protocol does require sampling at the­ beginning and every five years thereafter, at least initially. But critics say there are loopholes that could skew the findings, including that the protocol only requires monitoring for the first 30 of the 100 years the offset is supposed to remain in effect, and allows project owners to pick and pay for their own third-parties to conduct the work. For companies that pool soil carbon credits from thousands of farmers, which could eventually include Indigo, less than 1% of the actual sites may need to be verified through physical site visits by a third party, according to CarbonPlan’s reading of the proposal.

Craig Ebert, president of Climate Action Reserve, says that, as a nonprofit, the organization has to rely on outside funding to conduct its work. He declined to disclose how much money Indigo provided, as did the company itself.

But he stresses that the funding didn’t give the company any undue influence over the process, and that they were just one of many stakeholders who provided feedback on the proposals throughout.

“We know they want to sell carbon credits, but they’re only going to be able to sell credits that have a net environmental value,” he says.

“At the end of the day, what we’re trying to do is pay farmers for another commodity that they’re not getting paid for now, which is sustainable agriculture practices that build up carbon,” he says.

Indigo defended sponsoring the process, noting that other organizations that later submitted projects under an earlier Climate Action Reserve protocol had done so as well. It added that questions about specific methods in the carbon farming process were widely debated among all members in the workgroup.

“Through Indigo’s research and industry expertise, we saw tremendous potential in a soil enrichment protocol developed in a rigorous fashion with multi-stakeholder involvement,” the company said.

Robert Parkhurst, owner of environmental consulting firm Sierra View Consulting and another member of the technical group, says Indigo’s involvement isn’t unusual in such a process and didn’t affect this one in a negative way.

"We need a place to sequester all of that carbon and here is a logical place to explore to do that," he says.

Other problems

It’s critical to get these standards right, otherwise carbon farming could overstate any progress on climate change–or even allow greater greenhouse gas emissions.

Studies have found that some of the proposed practices can reduce yields in certain circumstances, which could encourage farmers to clear more land for agriculture. If so, the carbon released in the process of razing forests or grasslands could release far more carbon than was captured by the initial soil sequestration efforts.

Similarly, if a farmer was already carrying out some of these practices, and stopped and restarted to take advantage of the opportunity to sell credits, then they didn’t actually take additional steps to reduce emissions.

And if they only conduct these practices for a few years and stop, then some or all of the carbon gains could be wiped out. In fact, some research finds that if no-till farmers plow their fields every few years, as most do, it may eliminate most of the earlier carbon gains, as researchers at World Resources Institute noted in a recent post and in a response letter to Climate Action Reserve.

Some researchers believe the sheer variability of soil carbon uptake means that relying on it for offsets may be inherently unworkable. The better approach could simply be to pay farmers directly to carry out practices to improve soil health and reduce environmental impacts, while thinking of any additional carbon storage as a welcome co-benefit–but not one that’s strictly relied upon to balance out another organization’s greenhouse gas pollution.

“Trying to precisely quantify carbon offsets is almost an impossibly hard problem and one where the deck is stacked against quality outcomes,” says Danny Cullenward, a lecturer at Stanford Law School and policy director of CarbonPlan. “I find it hard to believe we’re going to do a perfect job on this. But that’s what offsets require, because they allow higher emissions elsewhere.”

Carbon farming’s darling status could also distract the food sector and other industries from more direct and reliable ways of cutting greenhouse gase

"By 2050, we need to produce more food at the same time we're going to have to stop deforestation and drastically cut greenhouse gas emissions," says Richard Waite, senior research associate with World Resources Institute’s food program. "So we're concerned to see an overreliance on this one solution, when there's a whole spectrum of things that can be done from farm to fork."

No bonus points

Carbon farming is seductive. It’s a natural-sounding solution that appeals to environmentalists, supports family farms, buys corporations out of the climate doghouse, and creates new markets for organizations seizing the role of referee. What’s not to love?

But that means policymakers and standard setters have to be all the more careful to resist wishful thinking, and establish rigorous rules and processes.

By midcentury, the world may need to remove as much as 10 billion metric tons of carbon dioxide from the atmosphere each year, to prevent the planet from reaching 2˚ C, according to the National Academies study. So it is essential to explore all of our options for doing so, whether it’s farms, trees or carbon removal machines.

But it also means these techniques and offsets systems need to work. They need to accurately measure the levels of emissions that are being pulled out of the air, and permanently stored.

If they don’t, it means we’re allowing companies to buy certificates that enable them to keep polluting, on the false promise that emissions are declining an equal amount somewhere else in the world.

The climate system doesn’t award bonus points for that. If the actual emissions in the actual atmosphere continue to climb, temperatures will continue to follow.

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Illustration by Rose Wong

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