I was curious what it would actually be. Assuming a full offset with expensive direct air capture of CO2 ($238 / tonne [0]), the carbon tax would only be $2.12 per gallon for 8,887 grams CO2 [1].

[0]: https://www.iea.org/commentaries/is-carbon-capture-too-expen... [1]: https://www.epa.gov/greenvehicles/greenhouse-gas-emissions-t...