Urban soils could take CO2 out of the atmosphere
Research at Newcastle and Oxford universities reveals value of soil engineering to sustainable construction
Research carried out by Newcastle and Oxford universities on a site in Newcastle has shown the potential for urban soils to remove CO2 from the atmosphere. Science Central, a 10ha brownfield redevelopment site in the centre of Newcastle, has already ‘captured’ around 38,000 tonnes of CO2 from the atmosphere and has the potential to remove a further 27,000 tonnes.
The former colliery site needs to have 30,000 tonnes of near-surface coal removed to create a platform for development, and is being filled with materials from buildings demolished on the site. It is estimated that the carbon released as a result of coal extraction will be cancelled out by the carbon absorbed by soil on the site.
Professor David Manning of the school of civil engineering and geosciences at Newcastle University, who is one of the leaders on the research, said, “Urban soils tend to be rich in waste materials such as concrete or metal slag that contain calcium and magnesium. These minerals capture and store atmospheric carbon through the processes of weathering to form carbonates which are chemically stable and a permanent store of soil carbon.
“This means that on sites such as Science Central, we can offset carbon-intensive development through soil engineering.”
The researchers analysed the geochemistry of the site to assess its potential to capture and store carbon as carbonate minerals. The site, which is the former home of the Scottish and Newcastle Breweries, is covered by approximately 1 million tonnes of demolition material, spread on the site as a layer of ‘made ground’ from 0.2 m to 6.0 m in thickness. The material on site originally had an overall carbon capture and storage potential of 65,000 tonnes CO2, equivalent to 18,000 tonnes of carbon or 30,000 tonnes of coal, since most coal is only around two thirds carbon. Geochemical analysis suggests that within three years of demolition approximately 60 percent of this potential has been exploited, capturing 37,500 tonnes of CO2 and leaving a remaining capture potential of 27,500 tonnes CO2.
Manning said that data from this research provides further evidence of the importance of secondary carbonate mineral formation: “It suggests that engineered soils could be used for carbon capture and storage with the addition and management of suitable Ca/Mg-rich materials.
“On a wider scale, the findings demonstrate the potential for a carbon capture and storage value to be assigned to some anthropogenic ‘wastes’, which could be utilised in helping to develop and support the urban ecosystem. Introducing a carbon capture and storage function in urban soil design can add environmental value with little additional energy input or expense.”
Science Central will be home to Newcastle University’s Institute for Research on Sustainability (NIReS) and is part of the Newcastle Science City initiative, a partnership of Newcastle University and Newcastle City Council.
The research was backed by the Engineering and Physical Sciences Research Council (EPSRC) and the Natural Environment Research Council (NERC). The findings are published this month in the academic journal Science of the total environment.