Each flight of a SpaceX Falcon 9 or any other orbital rocket launch is about the same as a passenger jet like a 777 flying across the Atlantic.
The larger SpaceX Super Heavy Starship will use 1kg of methane for every 3.6 kg of oxygen. The Super Heavy Booster will use 3300 tons of fuel. 717 tons of methane. The Starship will use 1200 tons of fuel or 260 tons of methane. This would be 715 tons of CO2.
Sub-orbital flights should need only need about 25% of the fuel. This would reduce Starship emissions to about 200 tons of CO2 per flight.
The Super Heavy Starship would generate 8 times as much CO2 emissions as the Falcon 9. The Starship alone would be about double the CO2 emissions of the Falcon 9.
Calculations below would have about 2 days payback of the CO2 emissions (versus using coal) from the flights to launch space-based solar power using Super Heavy Starships.
The Falcon 9 rocket runs on highly refined kerosene. Each launch burns 29,600 gallons or 112,184 Kilograms, with each Kg of fuel releasing 3 Kg of CO2, so each launch releases 336,552 Kg of CO2.
A flight from London to New York City has a carbon footprint of 986 Kg, so a SpaceX launch is the equivalent of flying 341 people across the Atlantic. One 777-300 uses 45,220 gallons of fuel. One transatlantic flight of a 777 is considerably 52% more than a flight of the Falcon 9 which is about 513 tons of CO2. The Starship would have 40% more emissions. The Starship would be more equivalent to a crossing of the Pacific Ocean.
The Airbus 380 has 80,000 gallons of fuel. This would be 934 tons of CO2.
The 777 would have less emissions than a SpaceX Starship flight and the Airbus 380 would have more.
Elon Musk is planning to eventually put 1000 people into a Starship. They would ride in seating like a roller coaster and the actual flight would be less than one-hour. This means the per person emissions would be less than a 777 with three times the seating capacity but double the per flight emissions for a trans-Atlantic crossing.
The World currently has about 30,000 large passenger jets. There are 4 billion passenger trips each year and this is increasing and should double by 2035. About 10 million flights per year.
Rocket travel replacing passenger jets would be better in terms of CO2 than existing aviation.