The cost of cultivating cooling: the relative contributions of financial incentives for soil carbon sequestration in agriculture to reducing global surface temperatures

Sequestration of atmospheric carbon in agricultural soils presents a low-tech, and inexpensive strategy to contribute to meeting climate goals. While agricultural management practices to improve soil carbon are often beneficial from a holistic perspective, their use as a carbon removal strategy are not guaranteed to continue indefinitely and stored soil C could possibly be re-emitted back to the atmosphere under future management. The combination of the potential impermanence of soil carbon, patchwork spatial and temporal aspects of contracted agricultural land, and measurement and verification challenges require that financial incentive structures be carefully considered from an atmospheric climate forcing perspective.

We modeled and compared the potential climate forcing reduction for three common financial incentive structures for agricultural carbon sequestration in the USA: private market contracts that pay per-ton of additional C sequestered, the Environmental Quality Incentives Program 5-year payment-for-practice contracts that require instating a new (fully additional C removal) management practice, and the Conservation Reserve Program 10-15 year payment-for-practice contract with a historical 40% renewal rate (60% additional C removal). For each contract structure, we estimated the associated cost for each fraction of a degree Celsius reduced over the next 25 to 150 years. We hypothesize that the trade-off between active carbon removal in the short term and maintaining stored carbon in the long-term favors longer, renewable (15+ year) contracts for climate-smart management practices as the most cost-effective strategy to reduce climate forcing over the next 50 to 150 years. We anticipate that the results of this study will clarify the optimal balance of additionality of carbon removal from the atmosphere and maintenance of soil carbon stocks over time and quantify their relative contribution to mitigating climate change.

Prepared by LLNL under Contract DE-AC52-07NA27344.