A carbon emission often overlooked in whole life carbon assessments is the release of carbon from ground disturbance, or, in the case of construction projects, site strips and excavations. Up 20% of the worlds CO2 emissions come from the release of carbon stored in the ground as a result of ground disturbance (notably agricultural tilling and ploughing). Healthy soils can act as a carbon sink absorbing carbon and storing it. It is estimated that up to133 billion metric tonnes of carbon have been