The Promise and Peril of Soil Organic Carbon Marketplaces

Soil organic carbon’s role in the new carbon marketplace

Drawing down atmospheric carbon and sequestering it into the soil is a promising solution to mitigating runaway climate change while simultaneously boosting soil health and resiliency. The estimated net worth of soil and all of its ecological services — valued at $11.4 trillion — is derived from the myriad benefits afforded the planet by soil, such as regulating hydrology, climate control, erosion prevention, food production, and more.

Putting a price on carbon is an important tool in promoting climate action. But cap and trade schemes and other systems charging polluters to pay for the carbon they emit is fraught with political and economic challenges. By paying farmers to store carbon in the soil, carbon gains an intrinsic value as not only a tradeable “credit,” but as a substance that improves the ecological value of soil through improved soil health.

Source: Unsplash

Working literally from the ground up, soil carbon marketplaces are doing their part to not only put a price on carbon dioxide, but create a hungry market for putting it back where it belongs: In the ground.

How soil organic carbon marketplaces work

Soil carbon offsets work off the premise that soil needs carbon, and drawing it down into the soil is a surefire way to make it happen. Most of the emphasis is on regenerative agricultural practices such as reducing tillage, introducing grazing, and planting cover crops. The culmination of these practices — when done consistently and at-scale — are shown to improve soil health and drawdown carbon from the atmosphere.

How much carbon, you ask? Existing soil already stores more carbon than the atmosphere and all the earth’s plants and animals combined. Increasing the planet’s soil to .54 percent carbon would sequester enough atmospheric carbon dioxide to offset the world's entire transportation sector. And because soils have lost 50-70 percent of the carbon they once had, the world’s arable land is more than capable of ingesting large amounts of atmospheric carbon.

The idea behind soil carbon offsets is paying farmers to do the work of drawing carbon down from the atmosphere and into the soil, then verifying those offsets and issuing them for sale to emitters looking to offset their carbon footprints. Carbon marketplaces, such as Nori, Indigo Ag, and Regen Network, showed early successes of removing CO2 and funding agricultural projects in 2021.

Source: Nori

Soil carbon offsets you can buy today

While there are well over a dozen protocols designed to quantify soil organic carbon (SOC) and verify offsets, only a handful of sellers readily offer soil carbon offsets to consumers:

Indigo Ag

• Protocol used: Climate Action Reserve and Verra
• Offset availability: Not for immediate consumer sale. Contact Indigo Ag for purchasing information.

Nori

• Protocol used: Nori Pilot Croplands Methodology
• Offset availability: Immediately available

Regen Network

• Protocol used: Regen Network Methodology
• Offset availability: Not for immediate consumer sale. Contact Regen Network for purchasing information.

The challenges of soil carbon marketplaces

The IPCC estimates that by 2030, the world’s soil could sequester 5.3 GtCO2 per year. Boosting soil health is a win-win from both a mitigation and adaptation standpoint, but it’s not so simple as measuring carbon sequestered in the soil against historic baselines. Quantifying how much carbon is pulled from the atmosphere and stored in the soil is notoriously difficult. Dozens of factors need to be considered, including:

• Local climate
• Agricultural practice
• Availability of baseline data
• Land use history
• Soil attributes

Soil regenerates slowly, so tracking the seasonal changes in SOC over entire fields and regions is a daunting task. What’s more, recent findings cast doubt on how durably carbon can be stored in soil without being re-released into the atmosphere via decomposition.

Regardless, various registries and companies have created protocols to typify the way farmers can quantify SOC. CarbonPlan’s “A buyer's guide to soil carbon offsets” (2021) determined in a review of 14 existing SOC protocols that none of them do an adequate job in guaranteeing substantive drawdown into soil, identifying two underlying problems associated with the existing SOC protocols:

1. Most of the protocols include avoided emissions (i.e. tractor use and fertilizer-related emissions). Therefore, none of the protocols accurately showed how much carbon exactly was removed from the atmosphere and stored in the soil, a problem for folks and businesses who want clear metrics on drawdown.
2. Protocols must be broad and adaptive to a wide range of geographies, agronomy, climates, economies, and agricultural practices, making it difficult to determine what kind of outcomes can be expected consistently.

All major protocols lack robust additionality testing, rigor, durability and social/environmental safeguards. This doesn’t mean that every credit certified under these protocols is hogwash, though, and most if not all of the credits available through these protocols offer net positive benefit. It does mean potential buyers need to consider how rigorously their offsets are calculated (i.e. soil testing, soil testing and modeling, or modeling alone), if they’re additional (i.e. are the offset projects producing a net climate benefit?), if they’re robust (how permanently carbon is stored in the soil), and how equitable they are.

If a buyer wants confidence that their purchase produces climate benefits, they should ask the following questions of sellers:

• Do you require onsite soil testing? If so, what are your standards?
• Do you base your offsets off models? If so, keep in mind that models are imperfect indicators of soil health. Ask which model they use, and if it's calibrated with onsite soil data.
• How do you determine the additionality of an offset project?
• How durable are your offsets? Ask for data on how long sequestered carbon is to be stored in the soil, and what safeguards are in place to ensure it stays in the ground.
• Do you have a “buffer pool” of offsets set aside to protect against carbon loss in your projects?
• Do you allow backdating? Backdating allows projects to be given “credit” for work done prior to project implementation. This can be a problem, as the carbon sequestered in the past shouldn’t be considered an offset for current emissions.
• Do you take into account the impacts of external inputs like manure, pesticides, and fertilizer?

Explore CarbonPlan’s interactive table comparing existing soil carbon protocols here.

Conclusion

Soil carbon offers promise in soil health, food resiliency, and climate change mitigation. Over a dozen protocols exist creating standards for quantifying SOC, and several companies are now selling soil carbon offsets to individuals and businesses.

But the nebulous nature of soil and inadequacies in the various soil carbon protocols mean offset buyers have some homework to do. Ironically, the shortcomings of existing soil carbon protocols demand that they be verified outside of their own boundaries. Consumers must ask probing questions regarding rigor, additionality, durability, and equity of offsets.

That said, these protocols do offer a “net-positive,” at the very least promoting more sustainable agriculture practices and creating a nascent soil carbon economy. But the magnitude of the climate crisis and the potential of soil to draw down carbon and build healthier food systems merits better protocols that accurately quantify soil carbon, dependably store it for meaningful periods, and prove additionality — all with equity and justice in mind.