By Dustin Sawyer

Soil carbon is a big deal right now, and it sometimes feels like the fate of the planet hangs in the balance.

The worldwide effort to reduce atmospheric carbon has led researchers into far-reaching and sometimes far-fetched corners of the scientific realm and it seemed only a matter of time until the awesome powers of soil fell into the limelight. Somebody only needed to figure out how to make it work and how to get interested parties to buy in, and the concept of carbon credit trading is a perfect fit. Thus, was born the soil carbon market, and Rock River Laboratory has developed some tools to help it be a success.

The idea is simple enough – agricultural crops (all plants, actually) are made of carbon dioxide (CO2 that the plant has pulled from the atmosphere. Those parts of the plant that aren’t harvested are largely left to decay in the field. During the process of decay, the CO2 that was bound up in the crop residue and roots is reverted to CO2 and re-released into the atmosphere. Field tillage increases this CO2 release by bringing otherwise-buried material to the surface to decay and by releasing trapped CO2 from the soil.

If only the agricultural community could work en masse to delay or even stop this re-release of CO2, we could begin a significant and meaningful reduction in global atmospheric carbon levels. If a farmer agrees to make strides toward locking, or sequestering, the carbon in their soil, they have created a carbon offset that can be sold on the open market to somebody who can’t sequester carbon, but wants to affect a change nonetheless. It’s such a beautifully simplistic idea that one struggles to find an argument against it.

Despite all of the excitement, there is reason to exercise caution in this space. Soil carbon markets offer an enticing new source of revenue to the agricultural community by paying farmers to enact conservation practices in their fields that should reduce the return of CO2 to the atmosphere. Despite criticism for failing to reward those farmers who have been employing such conservation practices all along, soil carbon markets have continued to expand and thrive rapidly. This rapid growth has less to do with the adoption of those with credits to sell (the farmers) and more to do with those looking to purchase credits, meaning the farmers may not always be in the driver’s seat.

There is tremendous social pressure on companies, especially companies that are very much in the public eye, to make efforts toward carbon neutrality or even carbon negativity, making them the primary purchasers of soil carbon credits. These pressures have created a strong demand for carbon credits - which in turn has allowed several brokering services to develop and offer competing services to the industry. While the competition may be good for the industry, there is currently no oversight in the market, particularly in the area of soil testing methodology.

The soil carbon market is based largely on theoretical carbon offsets derived from complex algorithms, and in some cases artificial intelligence. While the mathematics that go into predicting these offsets is undoubtedly impressive, the predictions will invariably require ground-truthing. The current methods for measuring soil carbon stores are time intensive, requiring roughly five minutes per sample. While that may not seem like a lot, it adds up quickly when we look at the sheer number of samples required to validate the predictive models. In most cases, the mathematical models require more than one hundred thousand soil carbon measurements just for the development stage. Following development, the algorithms require continuing maintenance, meaning thousands upon thousands more soil measurements.

It’s important to not lose sight of the real goal intended by soil carbon markets – to sequester a meaningful and significant amount of carbon in the soil. If the predictive algorithms aren’t accurate, the goal may be missed and all may be for naught.

The time and cost commitments required to run enough samples to validate these models are enormous when using the currently available methods of soil analysis, and may frankly impose a limitation that results in the models being incompletely validated.

If the predictive models are going to be fully validated, the industry needs faster and less expensive methods of measuring soil carbon. That said, commercial laboratories have been largely left out of the conversations as the soil carbon industry has developed. While there are certainly academia people working toward this goal, the commercial laboratories are better positioned to understand how to scale methods from the slow, labor-intensive research environment to the high-volume, fast-paced production environment.

The author works for private lab Rock Liver Laboratory, based in Watertown, Wis.

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