Carbon sequestration – the science
Unlike any other industry except forestry, farming has the potential to sequester (absorb) carbon dioxide out of the atmosphere on a large scale. Plants and soils on farms have the potential to sequester vast amounts of carbon, giving farming the potential to be at the forefront of the fight against climate change.
Much of the biomass that commonly occurs on UK farms such as hedges, woodland and permanent pasture is already sequestering carbon at very significant levels. But with some careful management decisions this can be improved to maximise the rate at which carbon sequestration occurs. Furthermore, more biomass usually equates to better habitat for wildlife, particularly insects and birds.
Soil is the farmers’ most important asset in so many ways. A soil that is continually gaining in organic matter, which is certainly possible, is a rich, healthy and resilient soil. Increases in organic matter lead to increased soil fertility, improved structure, healthier crops and carbon sequestration.
How does it work?
When plants photosynthesise they absorb carbon dioxide (CO2). This CO2 is turned in to sugars and then more stable compounds. In woody plants like trees this becomes lignin (wood), and suddenly the CO2 that was once in the atmosphere has become a very stable form of elemental carbon.
Some of the plant’s carbon compounds are also exudated (transferred) into the soil via the roots. Here the carbon compounds become organic matter and build soil organic matter, another very stable form of carbon.
Soils contain organic matter that is created from organic matter from animals, insects, plants and fungi. This organic matter is then decomposed by the vast array of micro-organisms in the soil ecosystem. About half of all organic matter is carbon, and in this form the carbon is very stable and can only turn back to CO2 readily if significant oxidation occurs, such as cultivation.
Eventually soil organic matter turns in to the even more stable form of humus, a highly complex, fertile and stable substance that should be prized by every farmer.