how much caco3 is consumed to produce 1500 co2?

If you are decomposing it, you

CaCO3>CO2 + CaO
for every mole of calcium carbonate, you get one mole of CO2.
so 1500 grams of CO2, that is 1500/44 moles of CO2. So you need that many grams of CaCO3, which is (1500/44) *( 44+40+16)