Humanity has developed many ways of sequestering carbon, from placing it underground, to accelerated weathering of rocks, to sinking kelp to the bottom of the ocean. Some forms of carbon sequestration don’t just lock up the carbon, but put it to a valuable use, such as wooden buildings and certain kinds of concrete. Soil carbon falls into this second category: we can simultaneously store carbon and have it provide valuable services.
The capacity for soil to store carbon is significant. Soil already contains more carbon than the atmosphere and all living plants and animals. The challenge is making sure that new farming practices actually result in a net increase of carbon, not a redistribution of existing carbon. This is the subject of ongoing research, but data suggest that certain combinations of practices can result in an increase in total soil carbon.
Soil carbon (in the form of soil organic matter) provides many direct benefits, including increased water absorption, increased water retention, reduced need for fertilizers, and reduced need for pesticides. (The book Growing a Revolution is a good exploration of the value of soil organic matter.)
Reducing fertilizer use has substantial effects for climate change. Fertilizer manufacturing makes heavy use of fossil fuels and fertilizers can release large amounts of nitrous oxide, a strong greenhouse gas. This nitrous oxide has a carbon emission equivalence larger than most other parts of growing plant-based food and reducing it is one of the most powerful changes we can make in agriculture.
Soil carbon being useful carbon has multiple advantages. Even if the soil carbon escapes in the future, it will have already provided a reduction in total greenhouse gas emissions via decreased fertilizer use (along with greenhouse gas reductions related to pesticide and water use). Also, the services provided by soil carbon create an economic incentive to leave the carbon in the soil, since soil-building/soil-maintaining practices are typically net profitable after an initial transition period. (We should explore financial tools to help bridge the transition period.)
At Modular Science we’re working on light-weight fully-electric machinery that builds soil carbon by reducing plowing, reducing soil compaction, and using non-chemical methods for weeding. We’re also working on ways of measuring soil carbon at a high spatial and temporal resolution, while the machines are doing other field work. This can assist research on farming practices that quantify and predict on-site benefits of carbon stored in soil. Beyond storing carbon, these approaches can reduce water pollution, water consumption, loss of soil, and loss of biodiversity (especially insects). Changes in farming can simultaneously improve farmer livelihoods, help with climate change, and address other global environmental issues.