Smaller processes that produce CO2 through actual emissions will probably fall through the gaps, but they're not critical in the big picture. Most will be covered through taxes on the fuel or energy. I'd expect most of the electric truck battery emissions to come from energy, either during the assembly of the cells or production of the ingredients.
> If you tax only direct emissions you motivate companies to amortize emissions by concentrating them during manufacture.
I do not understand. Indirect emissions are direct emissions at some point, and that's where they get taxed. The cost then gets passed along, creating an incentive to either buy from a supplier that can produce the same thing more cheaply by reducing emissions, or finding a substitute product that's cheaper because it's less emissions-intensive to make.
The real problem is imports from countries that do not follow an equivalent tax regime. I suppose here approximations will be necessary, and by making them overly generous, other countries have an incentive to join the scheme.
What if it's a giant shipping boat with thousands of containers?
The diesel fuel that the train company will buy has already been taxed at the refinery (if it's a diesel train). The gas that the power company will burn to generate power for an electric train has been taxed at import. The train company will simply pay the price of these goods, tax included, and pass this cost on to the owners of the goods being shipped. How is up to them.
Likewise, the "hidden" emissions from the production of the train are likewise "hidden" in its price: The steel that the train was made from was already taxed when it left the steel mill (not 100% familiar with steelmaking, but this may be one of the cases where it's insufficient to just tax the inputs since the steel mill might emit GHG that don't just come from fuel). The cost of the energy used in processing that steel already contained the cost of the emissions tax that was initially levied on the fuel. etc.
Firstly, what kind of excuse is this - imagine the same argument applied to social networks, should they just leave child porn on their websites because it too difficult to keep track of? What if a social network has billions of photos? Business has to follow the law, just like I do.
Secondly, we have armies of people collecting data on these containers and doing data science to manage and optimise supply chains, and they have the containers, their weights and contents documented for customs, to make sure they are safe and not overloaded, for insurance purposes, so they can be delivered to the right customer, many containers are independently GPS tagged, etc.
All this data already exists for every major carrier, haulage, etc. The hard part is like one guy delivering donuts part-time, but we don't need to go after that.
That electric car battery might be manufactured in China using coal power and shipped over the ocean in a diesel fueled ship and yet pay no tax, making an American-manufactured battery even less competitive.
Of course there is the question about people that simply _store_ carbon, e.g. what if there's a coal mine where the buyers of the coal don't actually use the coal for its energy purposes but instead for, say, makeup creation, or wood for building? We would probably have to work out special licensing for non-usage purposes and that's where it would probably get tricky.