A process for producing magnesia can include contacting CO 2 -containing emissions with a magnesium-containing material to produce magnesium carbonate; subjecting the magnesium carbonate to calcination to produce a CO 2 by-product and magnesia; and recycling at least a portion of the CO 2 by-product for contacting the magnesium-containing material to produce the magnesium carbonate. The magnesium-containing material can include mining residues, such as phyllosilicate or chrysotile mining residue, and the magnesium carbonate produced can include precipitated nesquehonite that is subjected to calcination to produce the magnesia.