At 37:00 of the video below, Tim Dodd concludes that SpaceX's Starship will emit 1.79 metric tons of CO2 per passenger, while a 737 will emit .33 tons. SpaceX

At 37:00 of the video below, Tim Dodd concludes that SpaceX's Starship will emit 1.79 metric tons of CO2 per passenger, while a 737 will emit .33 tons. SpaceX wants to generate Starship's methane from the atmosphere, so it could be zero I found Tim's video to be more informative than the Conversation article https://www.youtube.com/watch?v=C4VHfmiwuv4 https://www.youtube.com/watch?v=C4VHfmiwuv4