Carbon Dioxide Sequestration in Wastes: The SAPICO2 Project

The sequestration of carbon using industrial and commercial waste is an attractive option, and offers the potential to utilise residues which are often in close proximity to point sources of CO₂. The ability to predict the carbon dioxide sequestration capacity from basic chemical data is essential to effectively employ this technology at industrial scale.

Previous work has shown that the prediction of the maximum carbon dioxide capacity of solid waste is possible. Models have been developed based upon stoichiometry and carbon dioxide reactivity of specific materials or wastes. These include cement waste and steel slag.

In this work, three existing models were applied to calculate the theoretical carbon uptake of wastes. These models were evaluated, and a new general model with enhanced accuracy has been developed.

One hundred samples of different industrial and commercial solid wastes from 13 key groups identified from the European Waste Catalogue were examined. Their physical and chemical properties were determined to obtain the data to apply the existing prediction models. It was observed that wastes displayed significant variation within and between groups. This indicates differences in the raw materials, processing variables, and waste management practices operated by different companies.    

The wastes were exposed to an elevated pressure of carbon dioxide to determine the maximum CO₂ capacity of the wastes. Using the characterisation data, the prediction models were employed to calculate the theoretical maximum uptake. The experimental and theoretical uptake values were compared to determine the accuracy of the models.

The comparison revealed that, although the prediction models were suitable to predict the CO₂ capacity of certain waste groups, they were not applicable to all the waste streams studied.

The results were evaluated further by comparing the elemental composition to the measured results to identify key trends. Using this information, a new model has been developed. In testing this new model exhibited a significantly improved correlation between predicted and actual CO₂ uptake.