So the implementation I like (https://energyinnovationact.org/) would tax the production, but companies could get a tax rebate for non-fuel consumption, such as manufacturing plastics. That puts the onus on companies to get their rebate and is a lot easier to enforce, but is pretty fair -- plastics don't cause emissions aside from the energy used in their production (which would already be taxed if it comes from fossil fuels). I guess one issue would be if you're burning a lot of plastic garbage, like I've heard is common in Japan, though I don't know if that's a big contributor to emissions.