The United Nations publication GEO6 (the sixth Global Environment Outlook Assessment for the pan-European region) recognises the importance of accelerated carbonation in tackling climate change, as well as supporting the waste hierarchy and recognising the environmental challenge of disposing of waste to landfill.

The report addresses the mineralisation of carbon dioxide in solid waste to create products that can be used in construction, stating:

“The management of CO2 emissions by carbon capture and utilisation (CCU) is a potentially important future part of a balanced strategy for reducing greenhouse gas emissions. CCU-related products and processes will become more cost effective and numerous and will utilise significant quantities of carbon.

One currently available CCU process involves the mineralisation of CO2 in solid waste to produce products that can be used in construction. The technology is a managed version of ‘natural carbonation’ whereby CO2 gas is converted to calcium carbonate (limestone). The carbonate-reaction is managed carefully and can be used to manufacture a substitute for aggregates made from virgin stone. Developed at the University of Greenwich the process is being applied in the UK. Carbonated manufactured aggregates are being made from air pollution control residues. The aggregates, which have a structure similar to natural limestone meet European ‘end of waste’ regulations and materials performance standards, and make a demonstrable contribution to the developing European circular economy.”

The UN report goes on to recognise that:

“Waste volumes continue to grow. Disposal of waste in landfills is the major environmental challenge in several parts of the region, despite progress with recycling in many countries. The waste hierarchy is widely accepted as a guiding framework to increase economic value from resource use and to reduce waste. Closing resource-use loops through the promotion of circular economy principles offers further pathways to minimise waste and maximise resource use.”

Prof Hills continues to represent the company and the university in a number of international consultation groups, including the UN and also the European Association of CO2 Transformation (ASCOT).