Global climate change, greenhouse gas (GHG) emission reduction, capture, and sequestration are currently very important topics that promise to be critical technologies for several decades as humankind strives to meet the needs of today in a sustainable manner with increased population growth, consumption of manufactured products, and modernization of industries world-wide. A multi-faceted approach needs to be developed that would include continuously increasing efficiency in fossil fuel combustion systems, replacement of fossil fuel systems with renewable energy sources or nuclear energy sources, preservation of existing forests, reforestation, algae farming, deep geologic injection, deep oceanic injection, and mineralization.^1–6 Mineralization of CO ₂ into carbonate compounds can be a final resting place unlike practically all other current proposals that may gradually result in re-emission of CO ₂ gas through leakage pathways or natural processes of organic decay.

High-surface area calcium-rich by-product materials which include a source of cement-kiln dust, blast furnace slag, fly ash, lime-kiln dust, and recycled concrete fines were used to sequester CO₂ from ambient atmospheric gas, trapped CO₂ gas, and coal-combustion flue gas. A process is described that utilizes a foam generator with a foaming agent and various CO₂ containing gases to produce a lightweight low-strength (or, adequate strength) material with readily available increased surface area from by-product materials and the available CO₂ for rapid carbonation. The carbonated product is then crushed into a carbonate-rich aggregate suitable for a variety of construction uses. These aggregates were produced with appropriate densities for use as lightweight construction materials.

A theoretical basis for the proposed carbon dioxide sequestration processes, including calculations of the amount of CO₂ converted into carbonate minerals, is provided along with results of laboratory strength and carbonation testing, and finally crushing and screening of the material into aggregates. These successfully produced new by-product based carbonated aggregates are also compared to published data for similar commercially produced aggregate materials.