Carbon sequestration from soils

As well as enhancing soil health and condition, an important reason to accumulate soil carbon is the potential to offset greenhouse gas emissions and reduce the deleterious effects of climate change through carbon sequestration in soils.

Sequestering soil carbon can provide opportunities for land managers to participate in emissions reduction projects and receive financial remuneration.

Soil organic carbon is the form of carbon used to calculate sequestration. For carbon sequestration to occur, there needs to be transfer of carbon from the atmosphere (usually via plants) to storage in the soil. Conversely though, soil can also be a source of greenhouse gas emissions when exposed to soil disturbance such as through erosion, tillage or fire.

When soil organic carbon is sequestered from, or mineralised to, atmospheric CO₂, a conversion factor of 3.67 is used to determine the change in mass due to the loss or gain of oxygen molecules. This is based on the ratio of the molecular weights of carbon (12) and carbon dioxide (44), that is: 44/12 = 3.67

Therefore 1 tonne of soil carbon = 3.67 tonnes of CO₂ (sequestered or emitted)

We know that soil carbon can be increased from increasing organic matter inputs however this can also be easily lost through erosion. The inherent capacity of a soil to permanently store soil organic carbon can be increased with the addition of clay and sufficient organic matter, particularly legumes, manures and nutrients to support microbes to form soil organic carbon.

Find out more:

• Soil Carbon - DEW
• Soil Modification - DEW
• Carbon sequestration - DEW
• Schapel A, Reseigh J, Wurst M, Mallants D, Herrmann T. (2018) Offsetting greenhouse gas emissions through increasing soil organic carbon in SA clay-modified soils: knowledge gap analysis. Goyder Institute for Water Research
• Carbon farming - PIRSA
  
• National Soil Package - DAFF