Thanks Will Lockett for giving so much detail and making the idea of the Space Catapult quite clear to even those who are not so knowledgeable.
However, the Catapult should consume almost the same amount of Energy as Spaces and although the Catapult may by itself consume electricity but someone somewhere had to generate it and may use polluting fuels as well.
However, I do see significant cost savings - a challenge to Spacex.