Soil sequestration fails.

Over the past six months, major food companies, like General Mills, Danone North America, Kellogg, and others, have launched efforts to cut their carbon footprint, in part by expanding the use of regenerative agriculture (also called carbon farming) practices. Regenerative agriculture refers to an array of management practices — such as cover cropping, compost amendment, or grazing management — that sequester carbon in agricultural soils.

While these practices have positive soil health benefits, efforts to increase agricultural soil carbon sequestration likely don’t have nearly the level of expected climate benefits. Such poor carbon accounting means that corporations, governments, or individuals seeking to offset their greenhouse gas (GHG) emissions through regenerative agriculture are fooling themselves and the general public.

To be fair, soil carbon sequestration has great potential, at least in theory. If farmers expanded their use of cover crops to all 88 million hectares of US primary cropland, it would cut total emissions from US agricultural production by about a sixth (~100 million metric tons [MMT] CO2e/year). Similarly, planting trees among row crops — a practice commonly called alley cropping — on 10% of US cropland could sequester up to 82 MMT CO2e/year.

Emerging frontier technologies may also make soil carbon sequestration even more attractive in the future. Researchers at the Salk Institute in San Diego are working on genetically engineering the six most common row crops[1]and the three most common cover crops[2]to increase the level of carbon transferred from root systems to soil. If used globally, these high carbon-input crops, according to Salk researchers, could help sequester between a quarter and a half of all annual human emissions.

But any mitigation through carbon capture — no matter if through reforestation, direct air capture systems, or soil carbon sequestration — should meet the standards of carbon accounting systems and carbon offset programs. That is, the sequestered carbon should be permanent and measurable, mitigation efforts should account for inadvertently increased emissions elsewhere, and organizations shouldn’t count mitigation that would have occurred in the absence of their efforts.

Current efforts to sequester carbon by expanding regenerative farming practices rarely meet these standards and therefore overestimate the amount of carbon sequestered. In other words, an estimated one ton of CO2 sequestered in agricultural soils is not the same as an emissions reduction of one ton of CO2. In fact, some types of soil carbon sequestration efforts actually risk increasing emissions. Companies and other organizations should acknowledge and address this in their GHG emissions reporting and climate efforts.

The Uncertain Benefits of Carbon Farming

Permanence is among the greatest liabilities of combating climate change through regenerative agriculture, unlike sequestering CO2 in geological storage, for instance. While soil carbon sequestration can, in theory, be permanent, it often is not, as the carbon will be released again if the farmland is later developed — a heightened concern for farms in areas of rapid urban expansion. Some practices also produce especially vulnerable carbon sequestration. The carbon benefits of no-till farming, for instance, mostly evaporate when the farmer decides to till again, which happens on an estimated 30% of “no-till” farms. Some carbon from soils may also be released as global temperatures, and thus soils, warm.

As with carbon farming practices, permanence is also an issue for set-aside programs like the USDA’s Conservation Reserve Program (CRP), which pays farmers to let areas of their working land go fallow. While this allows for previously cropped fields to grow out without tillage or any practice that would limit carbon sequestration, any sequestered carbon will be lost when these plots of land return to agricultural use, as often happens when CRP contracts expire , especially in years of high crop prices. Between 2013 and 2016, just over half of expiring CRP acreage was returned to crop or animal production, whereas only 36% re-entered the program.

Worse, carbon farming practices can even increase emissions indirectly. This is the problem of carbon “leakage.” Because some of these practices can decrease crop yields, they can lead to the expansion of farmland elsewhere, which converts valuable wildlife habitat to farmland and generates emissions, potentially negating the original carbon sequestration benefits. Take the prominent example of Amazonian forest land being transitioned to soybean production — even if regenerative practices were used on that farmland, the initial emissions from the land-use change would require decades to be offset.

While some carbon farming practices increase yields, like cover cropping, leakage should be a major concern for practices — like perennial cropping, temporary grazing, or alley cropping — that reduce them.