ISRU methane fuel for starship is going to be eventually done on earth (and mars) for carbon neutral starship / superheavy launches. https://ntrs.nasa.gov/arch

ISRU methane fuel for starship is going to be eventually done on earth (and mars) for carbon neutral starship / superheavy launches. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120001775.pdf https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/201200... TL;DNR: If you take methane out of the atmosphere and you put it back in the atmosphere, the carbon footprint is neutral.