Mineral Carbonation of Biomass Ashes in Relation to Their CO₂ Capture and Storage Potential

Short-term stored, long-term stored, and weathered biomass ashes (BAs) produced from eight biomass varieties were studied to define their composition, mineral carbonation, and CO₂ capture and storage (CCS) potential by a combination of methods. Most of these BAs are highly enriched in alkaline-earth and alkaline oxides, and the minerals responsible for CCS in them include carbonates such as calcite, kalicinite, and fairchildite, and to a lesser extent, butschliite and baylissite. These minerals are a result of reactions between alkaline-earth and alkaline oxyhydroxides in BA and flue CO₂ gas during biomass combustion and atmospheric CO₂ during BA storage and weathering. The mineral composition of the short-term stored, long-term stored, and weathered BAs is similar; however, there are increased proportions of carbonates and especially bicarbonates in the long-term stored BAs and particularly weathered BAs. The carbonation of BAs based on the measurement of CO₂ volatilization determined in fixed temperature ranges is approximately 1-27% (mean 11%) for short-term stored BAs, 2-33% (mean 18%) for long-term stored BAs, and 2-34% (mean 22%) for weathered BAs. Hence, biomass has some extra CCS potential because of sequestration of atmospheric CO₂ in BA, and the forthcoming industrial bioenergy production in a sustainable way can contribute for decreasing CO₂ emissions and can reduce the use of costly CCS technologies.