What it takes to explain soil carbon -

What it takes to explain soil carbon

Renewable agriculture initiatives have imbued food companies’ climate strategies with a questionable narrative fandom: While agriculture is a significant source of emissions, soils on farmland are a viable carbon sink when well managed.

While regenerative practices can have many benefits, soil carbon sequestration is often promoted first because of the financial incentives that carbon credit markets can offer farmers.

However, accurate measurement of changes in soil carbon stocks has historically been expensive and intensive. Scientists have strongly observed soil carbon dynamics on a small percentage of farmland. Most MRV (Monitoring, Reporting, and Verification) solutions for measuring the climate impacts of regenerative practices rely on estimation models from the scientific literature that often indicate uncertainty about the accuracy of these methods.

Currently, there is no standardized, agreed-upon methodology that underlies all measurement, reporting, and verification protocols, and many startups promoting proprietary software are on the market. Not all these MRV solutions are created equal. Food companies that skip the foundational step of measuring soil carbon in farmland on the ground, or rely on inappropriate MRV models, risk investing in changes of practice that may not sequester it.

Given the urgency of the food system transformation, I worry about the veracity of alleged MRV checks and spillover effects of unsubstantiated climate claims. However, recent technological developments and government actions indicate that MRV is undergoing a shift to the MMRV vaccine. MMRV is an improved version of the approach that adds measurement (first M) to the traditional monitoring, reporting, and verification framework. More accurate measurement will enable better farmland management and more impactful investments.

The spotty science behind soil carbon sequestration

A 2007 IPCC report suggested that sequestering soil carbon on agricultural land could be a silver bullet with the potential to mitigate half of all agricultural emissions. Investments in mitigating the agricultural climate began to dominate. But there were serious issues.

Scientists at the World Resources Institute have published concerns about an in-depth revision of the IPCC’s estimates in 2020. They were unable to verify estimates of soil carbon sequestration because they found a dearth of documentation about the variables and assumptions behind the model. Since then, progress has been slow. Last year, the Environmental Defense Fund highlighted uncertainty in the science behind estimates of soil carbon sequestration due to measurement challenges. Earlier this year, Stanford University called for progress on climate-smart agriculture data to support federal investments.

MRV forms may miss the mark

In essence, the models provide an estimate based on observations made elsewhere. They extrapolate. They are great at describing things that have been observed before. But we only observed soil carbon dynamics on a small proportion of agricultural land globally because measurement has traditionally been prohibitively expensive. Many MRV solutions on the market use proprietary software calibrated on biogeochemical models to estimate carbon impact rather than actual field measurements.

(Want to continue the conversation and connect with the thousands of leaders working together to tackle the climate crisis? Learn more at VERGE 23, taking place October 24-26 in San Jose)

Different measurement, reporting, and verification models have different standards and approaches to address critical issues such as uncertainty, permanence, additiveness, reflections, and leakage. These differences mean that the outputs of the different models are not equivalent.

Researchers attempt to use models that closely resemble specific environmental, social and economic conditions in real life. But the accuracy of the model’s estimation depends on how well the model’s assumptions match the field conditions of a given farm.

Drilling towards carbon purity in the soil

As regulators, scientists and investors across the food system increasingly scrutinize corporate climate claims, they are becoming more aware of current uncertainties. They are increasingly asking for better data (such as soil testing on Earth) and more specificity for the estimates used in climate calculations.

For example, the Cool Farm Alliance (an industry alliance that includes major agri-food companies such as ADM, Cargill, Ahold Delhaize and Unilever and promotes renewable agricultural shifts) last week announced the adaptation of the Cool Farm Tool’s calculator, which is primarily calibrated on data based on North America and Europe, to the Australian context. The declaration calls for more region-specific climate assessments to ensure more accurate reporting, and hopes this change is a step in that direction.

There are now tools to measure soil carbon, such as the Yard Stick probe in the spectral domain, to accelerate this trend. The company markets the measurement approach pioneered by Christine Morgan, chief scientific officer of the Soil Health Institute. This technology measures soil carbon stocks using a hand-held probe that allows for more specific and accurate data. Such detailed measurement is the basis for moving from MRV to a more accurate MMRV approach. As a soil measurement service (the company doesn’t sell the technology as a product), the Yark Stick claims it’s 90 percent cheaper than a traditional soil sample lab test with greater accuracy.

Government actions accelerate progress

The USDA has been accelerating on-farm climate-smart practices for a few years. In fact, Yard Stick will provide measurement services for six USDA-funded climate-smart commodity partnerships evaluating soil carbon outcomes in the beef, agroforestry, and biofuel value chains. And last week, the USDA doubled down on its investment in MMRV systems by announcing that it would use $300 million in Reduction Inflation Act funding to create a monitoring and data collection network to determine how much carbon can be captured through these practices. This project represents a critical step towards securing an independent, third-party assurance for soil carbon claims.

Meanwhile, a soil health law requiring standardized soil health monitoring methods across the EU may soon join the bloc’s series of sustainability reporting regulations. Together, these laws incentivize traceability along global supply chains and accurate reporting of the impacts of climate change on businesses.

Despite uncertain climate mitigation benefits for soil carbon, regenerative management changes are still significant. Improvements in soil health bring economic benefits to farmers through increased crop resilience, higher yields, and lower input costs for fertilizers and herbicides. But if food companies and carbon markets are to focus most of their attention on soil carbon sequestration, we need better measurements that show actual climate impacts.

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