Agricultural Soil Carbon Credits: Making sense of protocols for carbon sequestration and net greenhouse gas removals NATURAL CLIMATE SOLUTIONS About this report This synthesis is for federal and state We contacted each carbon registry and policymakers looking to shape public marketplace to ensure that details investments in climate mitigation presented in this report and through agricultural soil carbon credits, accompanying appendix are accurate. protocol developers, project developers This report does not address carbon and aggregators, buyers of credits and accounting outside of published others interested in learning about the protocols meant to generate verified landscape of soil carbon and net carbon credits. greenhouse gas measurement, reporting While not a focus of the report, we and verification protocols. We use the remain concerned that any end-use of term MRV broadly to encompass the carbon credits as an offset, without range of quantification activities, robust local pollution regulations, will structural considerations and perpetuate the historic and ongoing requirements intended to ensure the negative impacts of carbon trading on integrity of quantified credits. disadvantaged communities and Black, This report is based on careful review Indigenous and other communities of and synthesis of publicly available soil color. Carbon markets have enormous organic carbon MRV protocols published potential to incentivize and reward by nonprofit carbon registries and by climate progress, but markets must be private carbon crediting marketplaces. paired with a strong regulatory backing. Acknowledgements This report was supported through a gift Conservation Cropping Protocol; Miguel to Environmental Defense Fund from the Taboada who provided feedback on the High Meadows Foundation for post- FAO GSOC protocol; Radhika Moolgavkar doctoral fellowships and through the at Nori; Robin Rather, Jim Blackburn, Bezos Earth Fund. Carrie Masiello and Kenneth Walker at We would like to thank the individuals BCarbon; and Karen Graham, Melissa from each organization who took the Varty, Fred Frydoon Far and Konrad time to provide feedback and clarification Muller who provided feedback on the on our interpretation of their protocols: Australian protocols. We thank Carl Sami Osman at CAR; Stefan Jirka at Churchill at Woodwell Climate Research Verra; Giancarlo Raschio at Gold Center for creating Figure 2. We would Standard; Sophia Leiker, Gisel Booman also like to acknowledge Stephen Wood and Sarah Baxendell from Regen of The Nature Conservancy for reviewing Network; Karen Haugen-Kozyra who this document. provided feedback on Alberta’s 2 EDF.ORG/SOILCARBON Contents About this report 2 Acknowledgements 2 Executive summary 4 Box 1: Terminology 8 Introduction 10 Box 2: Investing in agricultural climate solutions 11 Research gaps underlying the premise of emerging soil carbon markets 13 Technical considerations for emerging soil carbon markets: Measurement and uncertainty 15 Key sampling issues: Capturing spatial and temporal variability 15 Box 3: Technological developments for measuring SOC 17 Key sampling issues: Soil carbon at depth and equivalent soil mass 18 Key modeling issues: Uncertainty, scale of model inputs and applicability 19 Box 4: Advancing MRV through model benchmarking efforts 21 Structural considerations of emerging carbon markets: Additionality, leakage, reversals and permanence 22 Assessing overall climate impact 25 Defining the project scale 26 Ensuring equity and environmental justice 28 Credit equivalency 29 Box 5: Current protocol adoption and emerging soil carbon markets and carbon programs 30 Recommendations 32 Appendix A 34 Appendix B 38 Notes 39 How to cite this report: 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. EDF.ORG/SOILCARBON 3 Executive summary Agriculture contributes to climate Differences in the way protocols and change through direct greenhouse gas carbon markets estimate SOC and net emissions and indirect land use change, GHG reductions, as well as the way they and it has the potential to help solve account for issues such as permanence climate change through avoided and additionality of carbon sequestered, emissions and carbon sequestration, as run the risk of creating credits that are well as building resilience to unavoidable not equivalent or even comparable. climate impacts. This variation makes it difficult to The potential for agricultural climate ensure net climate benefits have been solutions overall has fueled growing achieved. A lack of comparability and investment in credits for soil organic standardization will be especially carbon sequestration in particular. The problematic if the U.S. government stakes for climate change and farmers decides to use SOC credits to meet are high, and there is a pressing need to nationally determined contributions or if evaluate emerging SOC measurement, sectors required to reduce emissions reporting and verification protocols to purchase SOC credits to compensate for ensure they result in high-quality credits emissions elsewhere. that identify real net atmospheric Consistent accounting and verification carbon sequestered. of direct emission reductions during Environmental Defense Fund and the agricultural production — reduced nitrous Woodwell Climate Research Center oxide emissions via improved nutrient reviewed 12 published MRV protocols for management, reduced carbon dioxide SOC credits generated on cropland and emissions via reduced tractor use and rangeland — eight from the United reduced methane emissions from States, two from Australia, one from improved manure management — and Canada and one from the Food and from avoided land conversion is a less Agriculture Organization. (See Table 1 for risky and permanent climate solution for additional details.)2 supply chain and other public investment. These protocols take different This approach should result in credits approaches to quantifying SOC and net that could count toward NDCs or GHG removals. Some use soil sampling emission offsets. only, some combine sampling with process-based modeling, and others use only modeling and remote sensing. 4 EDF.ORG/SOILCARBON Improved management practices that approaches that combine episodic soil aim to build SOC can deliver many co- sampling, such as every five years, with benefits, including improved water process-based models. quality, increased yields and yield Confidence that models can produce resilience. Thus, while uncertainty accurate and unbiased estimates of SOC remains about the climate mitigation sequestration is critical, as credits will potential of SOC sequestration, efforts primarily be issued based on modeled to build SOC are still valuable. results in the short term. Little evidence suggests that existing models can This report: accurately capture SOC change at the 1. Identifies critical research gaps field level under all proposed management related to knowledge of SOC accrual interventions for all combinations of soils in response to agricultural and climate. For both sampling-only and management. hybrid sampling and modeling approaches, designing an effective soil 2. Specifies limitations and key sampling strategy that adequately uncertainties associated with captures spatial heterogeneity and different SOC quantification reduces uncertainty in SOC stock approaches. estimates is essential. Soil sampling 3. Synthesizes different protocol details provided by published protocols approaches to issues such as may prove insufficient, depending on the additionality, leakage, reversals and associated challenges to quantifying SOC permanence. and the level of certainty demanded by buyers of credits. 4. Outlines critical actions the public This report outlines research gaps and private sectors can collectively underpinning the understanding of the take to strengthen the potential for mitigation potential of SOC sequestration. SOC markets. It details how the various protocols plan to quantify changes in SOC and associated Research gaps and the GHGs — nitrous oxide and methane. It challenges of quantifying SOC includes important considerations in the Existing cropland protocols assess application of process-based models for carbon sequestered through the GHG estimation, and it highlights adoption of a limited number of technological developments for practices like cover crops, reduced measuring SOC. tillage and crop rotation. Scientists do not, however, have a clear understanding Different protocol approaches to about the degree to which these structural accounting issues conservation practices can sequester In addition to the technical challenges of sufficient atmospheric carbon to have SOC quantification, SOC credits must an appreciable impact in mitigating account for issues of additionality, climate change. leakage, reversals and permanence, all of This uncertainty stems from a lack of which increase the risk of not achieving data on spatial and temporal patterns of desired climate benefits. SOC accrual across working farms and These structural considerations address under different management practices. whether a specific project results in carbon SOC can vary significantly over space, sequestration that would not otherwise and it changes very slowly over time.