The zerocarbonbritain2030 scenario achieves a 90% reduction of greenhouse gas emissions on 2007 levels, but some few residual emissions remain. We use carbon sequestration (negative emissions) to cover these, bringing the net total to zero.
After appropriate management changes land can remove CO2 from the air and sequester it in soil or above-ground biomass. Carbon can also be sequestered by forming biomass into human artefacts and preserving it, preventing its carbon from being returned to the atmosphere. Neither of these can methods can accumulate carbon indefinitely but they can provide us with a “window” of around 20-30 years, after which other methods of sequestering carbon may be available.
In the zerocarbonbritain2030 scenario we allow for a small amount of trade but otherwise treat the land mass of Great Britain as an isolated entity and identify what can be done with this land mass. The reduction in the consumption of animal products in the scenario frees up land within Great Britain. After food needs have been met, 43% of the remaining “productive non-food” land within Britain is dedicated to growing biomass for carbon sequestration. Carbon is also sequestered in soils through best practice management, encouraged though financial incentives.
• About 10 million tonnes of CO2e per year is sequestered in long lasting biomass products such as buildings and other wood products.
• About 23 million tonnes of CO2e per year is sequestered in engineered biomass silos.
• Carbon management of existing woodland is improved and 1.37 million hectares of new woodland is planted. This increases CO2e stored in-situ in standing timber by an estimated 12 million tonnes a year.
• A soil sink of around 9 million tonnes CO2e per year is achieved through best practice on all soil types.
• 4.3 million tonnes of biochar a year is created and incorporated into soils providing sequestration of around 14 million tonnes per year. Biochar is charcoal that is used as an agricultural amendment. It cannot easily be broken down by decomposers and so may have potential as a more permanent net negative process.
None of these processes can provide absolute security that the carbon will be sequestered in the long term. For example, carbon sequestered in a building is kept from the atmosphere only as long as the building is preserved. It is impossible to be sure for how long this will occur. To allow for some future uncertainty we have therefore reduced the value of all the carbon sequestered in the scenario.
The total value of this carbon sequestration, after adjusting for uncertainty, is about 67 million tonnes of CO2e a year in 2030, about 10% of 2007 British greenhouse gas emissions.