How to increase soil carbon storage

How to increase and protect organic carbon

Accelerating the rate of carbon sequestration in natural systems is one option for mitigating the impacts of climate change. This includes increasing the amount of carbon held in soils and vegetation, and deep geological reservoirs.

Carbon capture at source and storage in geological reservoirs is a long term solution that is dependent on further technological innovations.

Soil and vegetation capture can be done now because they only demand a change in how we use and manage our land.

• Increasing carbon sequestrated in vegetation

Growing trees is one way to increase our natural carbon reservoir. The amount of carbon sequestrated by forest depends on the species of tree and the duration of the crop rotation. It can vary between 700 to 800 tonnes of carbon per hectare. Young forests grow rapidly and soak up carbon more quickly than mature forests. In mature forests the carbon balance may reach a steady state as carbon storage is matched by decomposition. Growing wood to use as a fuel is carbon neutral and provides a sustainable alternative to burning fossil fuels.

• Increasing carbon sequestrated in soils

Scotland's soils are already very rich in organic carbon and options to further improve carbon capture are more limited compared with the rest of the UK. Agricultural soils have the greatest potential for increased carbon sequestration.

A wide range of materials, including farm manures and slurries, sewage sludges, composts and other non-agricultural wastes are used in farmland, forestry, land restoration, landfill reclamation, landscaping and domestic gardens. Application of organic materials to land has the potential to increase the carbon stock of Scottish soils at a time when there is evidence that soils may be losing carbon at rates hitherto unforeseen.

Over the next few years there is likely to be a significant increase in the production of composts from green waste and other organic materials that are diverted away from landfill in order to meet the UK's recycling targets. However, the availability of a suitable landbank, at both a national and local level, will be a key factor in deciding to what extent it is feasible and practical to increase recycling of non-agricultural materials in Scotland.

There is also growing interest in biochar (this is charcoal-like material created by pyrolysis of biomass) as a potential means to help tackle climate change by enhancing soil carbon sequestration and limiting carbon flux exchange. In others part of the world, where biochar is traditionally used it also has an added advantage in helping to improve soil fertility. This may be less relevant in already carbon rich Scottish soils like our peatlands and wetlands.