Technically exploitable mineral carbonat

Mineral carbonation of alkaline wastes can contribute to the sequestration of carbon dioxide (CO2). In this study we examined the CO2 sequestration potential of four dry-discharged waste materials using theoretical and experimental approaches. The materials encompassed biomass bottom ash, biomass fly ash, refuse-derived fuel fly ash, and stainless-steel slag. Their CO2 sequestration potential was determined from the acid neutralization capacity (ANC) and alternatively from the elemental composition using the Steinour equation (StE). Results were compared to experimental data from batch carbonation tests performed with pure CO2 at near atmospheric pressure over 7 days. Influence of water content on the CO2 uptake was determined in short-term carbonation tests over 2 hr. Effects related to the hydration and the subsequent carbonation were investigated by thermogravimetric analysis and leaching tests. Depending on the material the experimental CO2 uptakes ranged from 0.99 to 2.54 mol kg −1. The ANC-based approach either under- or overestimated the experimental CO2 uptake and the StE strongly overestimated the experimental CO2 uptake throughout. Except for biomass fly ash the experimental CO2 uptake within a test period of 2 hr depended on the moisture content. Upon carbonation the leachate pH decreased and amphoteric trace elements tended to be immobilized. In contrast to this, the mobility of oxyanions increased by two orders of magnitude. Our results suggest that for the design of CO2 sequestration strategies experimental investigations of the CO2 uptake are preferable to indirect estimates. When using waste materials for CO2 sequestration, effects on contaminant mobility must be considered since these determine disposal costs.