Limestone (calcium carbonate) is even easy to make. You can make it "at home" by dissolving unslaked lime (calcium oxide) in water and blowing bubbles in it wit

Limestone (calcium carbonate) is even easy to make. You can make it "at home" by dissolving unslaked lime (calcium oxide) in water and blowing bubbles in it with a straw. The real problem is that calcium oxide is usually converted from limestone via massive calcining, which releases... CO2.