Designing a carbon capture function into urban soils

Abstract

Soils, if designed and managed correctly, can retain carbon from the atmosphere as accumulated organic matter, refractory forms of carbon (e.g. biochar) or stable, inorganic, carbonate minerals. This soil 'carbon capture function' is highly applicable to the constructed environment in urban areas and should be considered when planning for new or existing developments. The total carbon capture potential of soils in cities may be as high as 7 Mt y -1 within the UK using biochar and accumulated carbonate minerals, which is equivalent in significance to other forms of geoengineering. Furthermore, soil and vegetation management practices may be implemented to accumulate plant-derived organic carbon in urban soils. The potential for substantial soil-based carbon sequestration in urban environments has yet to be realised, and the varied praxis of soil carbon capture presents accreditation and regulatory challenges to the planning system which need to be resolved.

Managing soil carbon stocks to enhance the resilience of urban ecosystems

“…SOC sequestration, in particular, can also enhance soil, water and air quality in urban ecosystems. If designed and managed correctly, urban soils can retain C captured from the atmosphere as accumulated SOC or stable, inorganic, carbonate minerals (Renforth et al, 2011). This soil function should be considered for improving urban environmental quality when planning for new or existing developments.…”

“…A little is known about carbonate formation in urban soils (Renforth et al, 2011). Thus, recommendations of soil and land use management practices for enhancing urban SIC stocks discussed below are preliminary and need to be up-dated.…”

“…The most common rock-forming carbonates are calcite (CaCO3) and dolomite [CaMg(CO3)2], and the most common carbonate in soils is calcite (Ming 2006). Further, some of the carbonate minerals in urban soils may also be a product of concrete/cement-derived material deposited in the soil as a consequence of demolition activity (Renforth et al, 2011). In the following section, SIC dynamics in soils is discussed, along with factors and processes that can be managed to enhance urban SIC stocks.…”

“…Waste materials in urban soils derived from construction materials may contain Ca-and Mg-silicate minerals. Naturally, these minerals occur in basic igneous rocks including those quarried for aggregate (Renforth et al, 2011). The Ca-and Mg-silicate minerals may also be produced in cement, and iron-and steel-making slag.…”

“…Stabilization may increase with increase in soil depth, irrespective of vegetation, soil type, and land use (Schrumpf et al, 2013). However, the reasons for the very long SOC turnover times are not completely understood, and little is also known about how carbonates form in anthropogenic environments (Renforth et al, 2011;Schmidt et al, 2011).…”