Soil Carbon Terms
SOIL CARBON SEQUESTRATION
The term "soil carbon sequestration" implies the removal of atmospheric CO2 and storage of this fixed carbon as soil organic matter. Soil carbon sequestration is a vital ecosystem service, resulting from the interactions of ecological processes. Human activities affecting these processes can lead to carbon loss or improved storage.
See our Soil Carbon 101 page for more information.
Franzluebbers, A. J., Hubbs, M. D., & Norfleet, M. L. (2012). Evaluating soil organic carbon sequestration potential in the Cotton Belt with the soil conditioning index. Journal of Soil and Water Conservation, 67(5), 378-389.
Todd A. Ontl and Lisa A. Schulte, Department of Natural Resource Ecology Management, Iowa State University
The health of soils is defined as, "the capacity of soil to function as a vital living system, within ecosystem and land-use boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and promote plant and animal health" (Doran and Zeiss, 2000). Soil health is determined by the prevalence of soil organic matter, microbial diversity, and efficiency of nutrient cycling.
What do healthy soils do?
Healthy soils promote water infiltration and retention in soils, a critical aspect of pasture health.
Pasture quality will depend on many factors, including:
Climatic conditions (e.g., temperature, humidity, precipitation)
Types of grass and/or legumes
Plants of different life cycle
Adaptive grazing management
Source: Doran, J. W., & Zeiss, M. R. (2000). Soil health and sustainability: managing the biotic component of soil quality. Applied soil ecology, 15(1), 3-11.
Carbon Market Terms
A carbon credit, or carbon offset, represents one ton of carbon dioxide equivalent being removed from the atmosphere. Offsets can also represent a ton of carbon dioxide that would have been emitted into the atmosphere but was not due to an action taken by the offset producer. The removal or prevention of the greenhouse gas can be measured and recorded as a traceable document or credit. This credit can then be traded by individuals or corporations who want to compensate for their own greenhouse gas emissions. Carbon credits create a market to incentivize the reduction and removal of greenhouse gases and disincentivize the emissions of greenhouse gases. While carbon dioxide is most commonly the greenhouse gas removed and measured, other greenhouse gases, such as methane, can be credited and offset.
In soil carbon markets, carbon credits are calculated by taking soil samples and measuring changes in soil carbon levels over time. Often, the number of credits that a given area can sequester over time will be estimated in advance, considering different factors like soil conditions, climate, and land-use practices. Then those estimates are verified by measuring the real change in soil carbon storage.
A protocol, or methodology, is "a guidance document that contains all relevant rules, standards, deductions, calculations, and parameters for the calculation/estimation of emissions reductions... and for monitoring, verification, and reporting of emission reductions" (Oldfield et al, 2021).
Basically, a protocol serves as a rulebook for a carbon credit project. Different developers adopt different protocols, so it's important to know what the guidelines and parameters are before you sign up.
Source: Oldfield, E.E., A.J. Eagle, R.L Rubin, J. Rudek, J. Sanderman, D.R. Gordon. 2021. Agricultural soil carbon credits: Making sense of protocols for carbon sequestration and net greenhouse gas removals. Environmental Defense Fund, New York, New York. edf.org/sites/default/files/content/agricultural-soil-carbon-credits-protocol-synthesis.pdf
Additionality in carbon markets is the idea that a project’s emissions reductions wouldn’t have happened in the business-as-usual scenario. Typically, a carbon market must drive the change in practices resulting in the new climate benefit.
In the regenerative grazing space, additionality refers to regenerative soil practices that a farm adopts (rotational grazing or no-till farming). Many soil carbon credits require that a farmer add at least one approved regenerative practice to improve environmental quality. Approved regenerative practices vary by methodology but are always practices that will increase or maintain soil carbon sequestration. Soil carbon projects that require additionality can confidently say that the carbon reductions they achieve are in addition to any reductions that might have occurred without the project.
Permanence is an assurance that carbon will stay in the soil for a project. In other words, it looks at how permanent the sequestration of carbon is, which is critical to long-term carbon emission reductions. Farmers must typically commit to at least ten years of permanence to participate in a project, and carbon is expected to remain in the soil for at least as long as the life of the soil carbon credit project. A longer project permanence means the carbon credit issuer (and farmer) is willing to guarantee that the carbon will remain sequestered in the soil for a longer period of time. The carbon credit issuer will typically implement a backup option such as a buffer of extra stored carbon credits to compensate in case of soil carbon loss. Permanence can be controversial because it is challenging to measure, and soil carbon credit projects have significantly different permanence lengths, ranging from 10 to 100 years.
Sequestered carbon in a sink (like soil) means the carbon is not present in the atmosphere. Therefore, the carbon is not contributing to total atmospheric greenhouse gas levels unless/until it is released back into the atmosphere. If a regenerative practice is stopped, the stored carbon will likely be lost from the soil. For example, if a no-till field is suddenly tilled, carbon will be released through exposure to oxygen and the disruption of soil aggregates (clumps).