Carbon negative: First commercial application of accelerated carbonation technology

Carbon dioxide gas can be used as a resource to rapidly harden cementitious materials and manage the risks associated with hazardous waste and contaminated soil. The process is known as Accelerated Carbonation Technology or ACT. Carbon dioxide primarily combines with calcium and/or magnesium minerals present in many industrial thermal residues to form carbonates; this reaction can also be promoted by the addition of, for example, Portland cement. Carbon8 Systems Ltd. was formed in 2006 as spinout-company of the University of Greenwich to commercialise ACT. Carbon8 has applied ACT to hazardous wastes in the production of non-hazardous construction products.By using the Carbon8 process, industrial thermal residues are solidified and stabilised in a hardened pellet form. The pelleted product is a direct substitute for natural aggregate, and can be used in the production of concrete construction blocks. From 2009 to 2012, a series of pilot and full-scale demonstrations of the technology were carried out. The aggregates produced were rigorously tested and given ‘end-of-waste’ designation by the Environment Agency. In early 2012, a bespoke commercial plant was commissioned at Brandon in Suffolk, UK, operated by Carbon8 Aggregates Ltd. This plant, the first of its kind anywhere in the world, produced 24,000 tonnes of aggregate from municipal solid waste incineration (MSWI) air pollution control residues (APCr) in its first year. In 2014, a second production line was added to the Brandon facility, increasing its capacity to 50,000 tonnes per year. The aggregate is supplied to Lignacite, the UK’s largest independent concrete block manufacturer, and other companies. The ACT-produced aggregate is carbon negative as it contains more imbibed carbon than is generated by its production. Consequently, the concrete construction blocks produced by Lignacite are also carbon negative, and are marketed under the name: ‘Carbon Buster’. Plans are at an advanced stage for the construction of a second and third production facility in the UK. These are scheduled to be operational by mid-2015 and will increase aggregate production to 200,000 tonnes per year. The present work discusses the development of the Carbon8 process and describes the commercial application of accelerated carbonation technology for the production of sustainable carbon-negative construction materials