A sustainability framework for engineering carbon capture soil in transport infrastructure

Recent research has demonstrated considerable potential for artificial soils to be designed for carbon capture. The incorporation of quarry fines enables the accumulation of atmospheric CO2 in newly formed carbonate minerals. However, the rate and trajectory of carbon accumulation has been little studied. The relative contribution of biotic (e.g. vegetation, micro-organisms) and abiotic (water, light, temperature) factors to the carbonation process is also unknown. This article presents a sustainability framework which aims to determine the multi-functionality of soils to which fines have been added not only in their role as carbon sinks but also in their role of providing additional opportunities for improvement to ecosystem services. Such frameworks are required specifically where land designed for CO2 capture must also provide other ecosystem services, such as flood mitigation and biodiversity conservation. Land within linear transport infrastructure provides a case study, focusing on 238,000 ha of vegetated land associated with roadside verges in the UK. Hypothetically this area could remove 2.5 t CO2 per year from the atmosphere, equivalent to 1% 2011 total UK emissions or 2% of current transport emissions and saving an equivalent of £1.1 billion in non-traded mitigation values. Roadside verges should be designed to minimize flooding onto the highway and perform other important functions such as removal of dust and suspended solids from surface waters. Vegetation on 30,000 ha of railway land also provides opportunities for carbon sequestration, but management of this vegetation is subject to similar constraints to protect the rail tracks from debris extending from autumn leaves to fallen trees.