The dubious climate gains of turning soil into a carbon sink

“There’s more known about space travel than there is about soil health,” says Tom Gregory, gulping down a cup of tea and glancing out from his farmhouse kitchen at a valley of green fields.

Ten years ago, he and his wife Sophie set up their organic dairy farm in Chard, Somerset. Five years ago, they realised it was not working. The proof was in the earth; by most indicators the farm’s soil had got worse since they began their organic endeavours.

Like many others around the world, Gregory has responded by turning to so-called regenerative agriculture: improving soil quality by better stewardship such as reduced tilling and planting more diverse temporary pasture.

Big food companies are taking an interest in such practices, and not just for ecological reasons. As well as boosting crop yields and potentially cutting fertiliser usage, regenerative agriculture can help increase carbon sequestration — storing carbon in the soil and keeping it out of the atmosphere.

The Gregorys’ farm is part of a regenerative agriculture pilot project run by Arla, a Denmark-based dairy co-operative that is their main customer.

Organic dairy farmers Sophie and Tom Gregory are taking part in a regenerative agriculture pilot project © Jim Wileman/FT

For now, it is voluntary. But soon, says Sophie, all farmers will need to measure their soil carbon stock as regulations begin requiring companies to report the greenhouse gases emitted throughout their supply chains and in the use of their products, known as “scope 3” emissions. As of this month companies incorporated in the EU are required to report this indirect footprint. The US is also working on similar disclosure rules.

Farming and forestry account for almost a quarter of global greenhouse gas emissions and a hefty chunk of the scope 3 emissions of food manufacturers and retailers originate on farms. As they race to curb their on-farm footprints, some of the world’s biggest food suppliers are pouring cash into regenerative agriculture.

At COP28 in Dubai in December, 25 food and agribusiness giants, including Danone, PepsiCo, Nestlé and Cargill, pledged to convert 160mn hectares of land to regenerative practices and committed $2.2bn in funds — on top of an existing $2bn already invested.

But whatever its wider benefits, sceptics warn that regenerative agriculture will not solve the agri-food sector’s emissions problem. There is lively debate over how much carbon can actually be stored in soils, how long for and how effectively it can be measured. Some scientists warn that if sequestration seems too good to be true, it probably is.

Few food and agriculture companies state how much their net zero goals depend on using land as a carbon sink. In many cases, the numbers “simply won’t stack up,” says Pete Smith, professor of soils and global change at the University of Aberdeen. He dismisses the notion that soils are “perpetually soaking up” carbon. Instead, soils have a finite capacity, he argues. Like a bucket of water, “you can only fill it up until the bucket is full.” 

The Gregorys turned to regenerative agriculture after realising that the quality of soil on their organic farm was deteriorating © Jim Wileman/FT

Environmentalists warn that the idea of using carbon stored in soil to offset emissions smacks of the existing nature-based carbon offset market, under which multinationals seeking to reduce their net emissions buy up carbon offsets generated by tree-planting projects.

Many of these were found to make unsubstantiated claims about their carbon reduction benefits and the concept has been derided by some campaigners as a vehicle for corporate greenwashing. But that has not stopped start-up companies pledging to help farmers make money from selling soil-based carbon credits on the voluntary markets. 

Smith says regenerative agriculture “makes a lot of sense” and will deliver a host of benefits for the environment, farmers and food production

“But the carbon angle has been oversold.”

Regenerative agriculture “is basically about regenerating soil,” says Gareth Morgan, head of farming policy at the Soil Association, a food and farming charity that champions organic and nature-friendly practices.

In practice, it means using fewer pesticides and synthetic fertilisers and planting cover crops — non-commercial species that protect and improve soil. It also entails not tilling the fields, as doing so damages their soil structure as well as releasing carbon stored in the soil into the air. The overall aim is to improve degraded soils and replenish the organic matter contained within them, which enables the earth to store more water — and draw more carbon out of the atmosphere.

US food manufacturer General Mills was one of the first to make a big push towards regenerative agriculture practices, announcing in 2019 a target to extend these to 1mn acres of farmland by 2030. 

Since then, its competitors have got in on the action. Last year Nestlé announced that it was putting $1.3bn into a plan to ensure that a fifth of its key ingredients are sourced through regenerative farming methods by 2025 and half by 2030, while PepsiCo partnered with trader Archer Daniels Midland to extend regenerative agriculture across their shared supply chain in North America. This could reach 2mn acres of farmland by 2030, they say. 

Cargill, one of ADM’s biggest rivals, also has a goal of transitioning 10mn acres in North America to regenerative agriculture by 2030, and Brazilian meat-producer JBS has ringfenced $100mn for research projects promoting regenerative agriculture that will sequester carbon within the same period.

Arla has a goal to reduce CO₂ emissions from farms by 30 per cent per kilo of milk by 2030, says Paul Savage, agriculture director for the co-operative’s UK branch. It has identified five key areas which have the greatest impact on carbon footprint and used these to develop “a points-based model” for farmers “which aims to reward past and motivate future actions,” he adds.

The drive has created an opportunity for organisations promising to help food businesses achieve their regenerative goals. Earthworm Foundation started 25 years ago helping companies reduce their potential exposure to deforestation. But increased investor interest in climate change in recent years has forced companies to calculate their emissions. Bastien Sachet, Earthworm’s chief executive, says they quickly deduced that agriculture was the biggest contributor “and then they realised that soil was one of the big levers to address this issue.”

Earthworm now works with 30 major suppliers in Europe that provide agricultural products like grains, oil seeds, potatoes and sugar beet to different food brands. The non-profit organisation recently started a pilot project aimed at helping 1,000 farmers in the supply chain of French agricultural giant Vivescia to transition to regenerative farming over the next few years. A consortium of brands that source from Vivescia are paying for the transition, says Sachet. “At the end, the farmer gets a package in his hands that is very worthwhile.”

Better soil health as a result of regenerative practices, also make crops more resilient to extreme weather events © Hollie Adams/Bloomberg

The benefits of regenerative agriculture are not in doubt. On farms in PepsiCo’s supply chain in India, yields have increased 3 per cent while greenhouse gas emissions have fallen 20 per cent, and in Thailand yields have increased 18 per cent with a 36 per cent drop in water use, says Margaret Henry, the food giant’s Global VP for Sustainable Agriculture. 

Henry adds that better soil health as a result of regenerative practices, also make crops more resilient to extreme weather events. Cover crops — non-commercial species planted over winter to protect and improve soil — and increased organic matter create deeper, more extensive root systems. These help water drain when there is too much and allow it to be stored when there is too little.

“When the flood, or the drought, or the early frost, or the hurricane come through, that farm is more likely than its neighbour that has not been investing in regenerative agriculture to still have its crop,” she says.

Another big upshot is soil carbon sequestration, which Henry describes as “one of the best-kept secrets in the world of climate.” It is “win win,” she adds, “the more you sequester carbon in the soil, the healthier the soil, the better the crop . . . and fewer emissions go up into the atmosphere.”

Many others agree: of the 79 major agrifood companies surveyed by investor network Fairr recently, 50 said they were doing regenerative agriculture initiatives, including 36 that were seeking carbon-related outcomes. 

But the wide-ranging benefits of regenerative agriculture are undermined by the industry’s lack of a set definition and clear targets, according to Fairr, which argues that this makes claims hard to substantiate, creates risks for investors and delays progress. 

Only 18 of the 50 projects implementing regenerative agriculture had quantitative targets and just four — including PepsiCo, Nestlé and JBS — were offering to pay farmers to change their practices. In 2021, Cargill also launched RegenConnect, a marketplace that pays farmers for improved soil health and for each tonne of carbon sequestered.

There are more serious flaws with soil sequestration than the lack of a clear definition. One is its capacity; research by Smith, working with other academics at Wageningen University in the Netherlands, recently looked at carbon captured in grassland soils and calculated that some 135 gigatonnes of carbon would be required to offset emissions of methane and nitrous oxide from the grazing livestock sector. That is almost twice the carbon currently contained in managed grasslands. In some regions, carbon stocks would need to increase by 2,000 per cent to offset emissions from livestock farming.

Carbon capture in soils has been promoted by the livestock industry as “a get out of jail free card”, says Smith. “‘Yes, we’re producing methane emissions . . . but no need to worry about it, the soils will offset all the emissions’. This [study] is the nail in the coffin of that argument.” 

Grasslands already hold a lot of carbon, so increasing this is especially challenging. Arable land has more potential, because it is depleted by intensive cultivation, but even this has limitations, according to scientists.

It is also tricky to accurately measure the carbon captured in soil. The technology to do so exists, but it is very expensive, says Smith. For farmers and the food companies they supply, he adds, “the cost of doing it can outstrip the value of the carbon.”

As a result, most companies and non-profits specialising in regenerative agriculture and soil carbon removal rely on computer models instead. These use farmers’ self-reported practices to estimate how much carbon is being stored.

According to Sachet, in rare cases some companies want to switch to different calculation tools in order to maximise the amount of carbon they can report as removed.

Earthworm uses computer models “as a proxy”, he says, because that’s what companies are being asked to use by the Science-Based Targets initiative (SBTi, an arbiter of corporate net zero plans) and investors. But he acknowledges that “there is bit of a caveat on the accuracy of those methodologies” and that Earthworm also uses satellite imaging to verify the farmers’ claims.

Ron Hovsepian, the outgoing chief executive of US-based Indigo, disagrees. He argues the computer models, augmented with random soil sampling, are scientifically robust. Indigo is one of several companies that have sprung up to help farmers make money selling soil carbon credits on the voluntary markets. The company has “given birth to over 133,000 tonnes of carbon sequestration”, says Hovsepian, and is now helping food and drink giants such as Nestlé and Anheuser-Busch InBev reduce their scope 3 emissions through soil carbon sequestration.

A more fundamental challenge than measuring carbon is the finite capacity of soil to store it, according to scientists and environmentalists.

Keith Paustian, a soil scientist at Colorado State University, says switching from conventional to regenerative farming can increase the amount of carbon stored in soils, provided the farmer does not revert to industrial practices like using synthetic fertilisers and intensive ploughing.

During these 20 years a food company can use the negative emissions from the soil sequestration to offset their positive ones, he explains. But after a while, usually around 20 years, the soils reach their capacity and once that happens the net emissions rise again.

Carbon stored in the land is also “not very reliable when it comes to the climate benefits”, says Sam van den Plas, policy director at Carbon Market Watch, which scrutinises carbon pricing schemes. “The carbon may be released at a later date and within a timeframe that it still contributes to global warming.” 

Paustian adds that it is not like sequestering carbon deep underground, “where if you don’t have cracks in the rock, it’s going to stay there”. Carbon stored in soil remains biologically active. Paustian says the technology to measure carbon is good enough; the real issue is that without set standards it is easy for those involved in soil carbon credits to “cut corners”.

For van den Plas this is “comparable to what you have in the more classic voluntary carbon market offsetting schemes”, where the monitoring and verification of emission reductions is “fraught with difficulties”. 

Smith, the University of Aberdeen professor, says carbon sequestration can buy food suppliers “time to decarbonise the rest of their supply chains” but it does not eliminate their emissions permanently. 

Tom and Sophie Gregory’s main customer, Danish co-operative Arla, aims ‘to demonstrate how dairy farmers and their cows can be beneficial for healthy functioning ecosystems’ © Jim Wileman/FT

“There’s an over-focus on carbon,” agrees Sachet. “Because financial actors are the ones behind it, they have managed to translate the environmental crisis into one metric, which is carbon.” The limitations in measuring carbon stored in soil mean companies “need to stay humble in their claims”, he adds.

For many farmers, regenerative agriculture is more to do with the health of their land than of their bank balances. In Somerset, Tom Gregory scoffs at the idea of selling carbon from his farm on the voluntary markets. “I could not be less interested,” he says. His wife Sophie adds that “the whole carbon scene is quite cowboy-ish.”

The Gregorys are dubious about payments linked directly to the amount of carbon sequestered in general, whether those payments come from within the supply chain or from selling on carbon markets. They believe farmers should be paid for their stewardship of the land. “We’re doing it for the soil,” says Sophie, “not so much the carbon.”

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