Also, consider that rockets themselves emit lots of CO2 as they launch. Sure, you can use a hydrogen/oxygen rocket, but then you need a source for hydrogen. And if you don't want greenhouse emissions, that means you need a huge plant cracking water into H2 and O2. In other words, you effectively need to build a huge energy storage facility. You could just attach a fuel cell to your rocket H2/O2 plant and skip the rocket launch entirely. It is possible to create green rocket launches, but the equipment needed is essentially already a massive base load solar/wind plant.