3Soil Carbon Practices
Our atmosphere contains only one-third as much carbon as our global soils, which hold an estimated 25,000 gigatons (Gt) of CO2. Due to our deep connection to the land and historic reliance on it, soil carbon practices are an important part of a complete portfolio of climate restoration solutions.
Soil carbon practices seek to increase the amount of CO2 captured by plants via photo-synthesis, and then stored as carbon in their leaves, stems, roots, and soil. These practices also encompass regenerative agriculture, which refers to processes that can increase soil carbon content and health. Some regenerative agriculture definitions focus on processes, some on outcomes, and others on both. In all cases, regenerative agriculture is intended to restore carbon — and therefore health — to soils. Such processes include integrating crops and animals, using low to no-till practices, reducing or stopping the use of synthetic fertilizers and pesticides, and planting cover crops.
Collectively, we refer to these different solutions as soil carbon practices. Positive outcomes and co-benefits include enhancing carbon storage, improving soil health, increasing biodiversity, improving water resources, and increasing communities’ social and economic well-being.
Plant diversity above ground directly corresponds to microbial diversity below ground, fostering and supporting soil health and carbon storage.
Soil carbon practices vary in their durability, financeability, scalability, and equity. Each of these factors plays a key role in soil carbon’s capacity to contribute to restoring our climate. As a result, the carbon burden depends on these factors and the variables described below.
Durability
The timescale for soil carbon sequestration depends on the storage method used and the continuation of carbon-enhancing practices. On the high end, soils can store carbon for hundreds of thousands of years if undisturbed, and on the low end, captured carbon can be released immediately if practices are not maintained, e.g., if a farmer starts tilling soil that had previously been managed with no-till practices.
Financeability
Depending on physical and socio-economic conditions, the costs of soil carbon sequestration can range from $45 to $100 per ton of CO2. Agricultural soils in the United States alone have the capacity to store up to 10% of annual domestic CO2 emissions for as little as $10 per ton. But large-scale deployment and maintenance costs remain barriers to greater adoption. Overcoming these barriers will require stakeholder alignment and significant funding from federal and state governments, carbon markets, and the private sector.
Scalability
Global estimates of the maximum scale of soil carbon sequestration range from 1 to 22 Gt annually by 2050. While many factors determine this scale and range, measuring the amount of carbon stored in soils over time is a major obstacle to refining these estimates. Such constraints along with different stakeholder objectives and a lack of aligned standards make this all the more challenging. More research is needed to learn which practices are most effective at boosting soil carbon, and to monitor, report, and verify the results.
Equity
Research has shown that beneficial regenerative agriculture and soil carbon practices have been carried out by BIPOC communities for generations. And yet past policies have prevented these groups from gaining government support and securing land tenure. To scale up these practices equitably it is essential to engage these communities directly in the scale-up processes and to bestow tangible benefits that address past inequities through reparative justice.
