That kind of exercise is far more likely to get kinetic than defining "truth" (or whatever) because it is more directly linked to peoples livelihoods and standards of living.
We could just start with the easiest case, which is a product/process that inherently releases pollutants (anything that releases gases) that may have some negative effects on others or the environment (the threshold should be low), then determine the market rate for capturing that pollution back from the environment and tax accordingly. This would also apply to medicines and lotions that don't get metabolized by the users and are inherently are going to end up in the ocean.
It gets trickier when we consider things that directly harm some people nearby, like smoking, and at a certain level of harm, these things should just be banned outright (i.e. you can't really undo lung cancer or mercury poisoning). Or things that aren't inherently pollutants (plastic containers), but in practice end up causing a lot of pollution.
Our government is too incompetent to approach the problem in a first-principles based way like this, but that doesn't mean we shouldn't try. Banning individual things after they get out of control and doing complex mental gymnastics like cap and trade are much worse solutions.
Under this tax regime as long as the homeless person makes sure to promptly file the appropriate forms each year they should not be at risk of jail time.
( Being the internet, this is all a joke )
Accounting for CO2 intensity is all squishy-squashy. But if we tax the actual emissions then the true energy impact will be reflected in prices and the market will adapt to whatever actually really is optimum--whatever lends the most utils of resource use.