Engineering the soil carbon sink: a novel approach to carbon emission abatement

Soils are the greatest land-based reservoir for carbon on the planet, containing three times as much carbon as do plants. Soil-atmosphere interactions exchange a third more CO2 with the atmosphere than do interactions between the atmosphere and the ocean. Soil thus plays a very significant role in controlling atmospheric CO2 levels.In this context, we have an opportunity to engineer soil systems so that the amount of CO2 that they take up is maximised. This a form of carbon abatement that is very cheap, because it is passive (there are no energy inputs once constructed). It is directly analogous to the use of constructed wetlands for the treatment of polluted waters. Our aim is to assess the feasibility of this process for widespread application in the UK, and to assess the associated costs and benefits.We will investigate the soil carbon contents of artificial soils from a number of sources. We will use trial plots constructed for a completely different purpose in 2002 and which we have recently shown to accumulate soil carbonates (the first such found in the UK). We will grow brassicas, as a representative bioenergy crop, in artificial soils in the lab and greenhouse, using calcium-rich wastes as part of the soil. We will sample brownfield and other remediated sites of known age and history. In all cases we will determine the carbon content of the soil in terms of different C reservoirs, and fingerprint each one using stable isotopes so that we can trace its plant origin.Using the information from the samples, we will be able to determine the lifetime of the different soil carbon reservoirs. We will be able to estimate how quickly they build up, if they are stable, and if they transform from one into another. Using this information we can model the behaviour of carbon in artificially planted systems.In the context of UK land use and the arisings of calcium-rich materials that could be used to accelerate the process, we will assess the possible benefits of designing soil systems to act as sites for the passive sequestration of atmospheric CO2. If the process appears to be feasible, we will use contacts initially in NE England to exploit our findings, through Newcastle's Science City which links us to industry, and through the University's CREEL project, funded by One North East and intended to act as an outreach facility for renewable energy.