Carbon capture and storage using alkaline industrial wastes

Carbon capture and storage (CCS) is gaining momentum as a means for combating climate change. It is viewed as an important bridging technology, allowing emission targets to be met during fossil fuel dependence while sufficient renewable energy generation is installed. Mineral carbon sequestration is the only known form of permanent carbon storage and has the potential to capture and store CO2 in a single step. It is based on the geologic process of natural rock weathering where CO2 dissolved in rain water reacts with alkaline rocks to form carbonate minerals. While the reactions are thermodynamically favourable, in nature the process occurs over thousands of years. The challenge of mineral carbon sequestration is to accelerate carbonation and exploit the heat of reaction with minimal energy and material losses. Minerals commonly selected for carbonation include calcium and magnesium silicates. These minerals require energy-intensive pre-treatments, such as fine grinding, heat treatment, and chemical activation with strong acids, to provide adequate conversions and reaction kinetics. Industrial waste residues present alternative sources of mineral alkalinity that are more reactive than primary minerals and are readily and cheaply available close to CO2 sources. In addition, the carbonation of waste residues often improves their environmental stability. This paper provides an overview of the types of industrials wastes that can be used for mineral carbon sequestration and the process routes available.