Ca-looping can be used to make the steam reforming process carbon neutral. This is particularly advantageous when making hydrogen powered cars, because there is no benefit to driving a hydrogen powered car if a large amount of CO2 must be emitted in the hydrogen production process. How it works is that CaO is used instead of magnetite (Fe2O3) as the high temperature water-gas shift catalyst. CaO reacts with the CO2 product, removing it from the outlet stream; this has the added advantage of shifting the equilibrium further to the right by Le Chatelier's principle. Thus, a higher CO conversion is possible than with magnetite (95% vs. 80%). There is less need for excess steam in this process (other than that which is necessary to avoid coking), so less volume of gas needs to be processed, and the water-gas shift reactor can afford to have a smaller volume. Additionally, since CO2 is drawn out of the outlet stream, the outlet is a relatively pure (95-99%) stream of hydrogen, on a dry stack basis.