Even if light-duty transport is beginning to look like a reasonably solvable problem, the situation is murkier for heavy transport. A global agreement is in place to force ships to begin cleaning up their exceedingly dirty “bunker fuel”, but it is not yet clear how they can eliminate emissions entirely. In aviation, a very weak global agreement has been adopted that is expected to force airlines to buy offsets for some of their emissions, but that must be viewed as a stopgap measure at best. Electric aeroplanes may play a limited role on short routes, but batteries are just too heavy to power a plane on long trips. The long-term answer will almost certainly be to develop more sustainable forms of jet fuel. Vegetable oils can be converted into jet fuel, and significant investments have been announced to build factories that can do this, but costs are still high and it is unclear how quickly the airline industry will move to adopt the technology. Once again, a big push is needed from public policy to pull these fuels into the marketplace and begin scaling them to reduce the cost. Strong environmental and ethical standards are also needed in the way the vegetable oils are produced, since they could easily compete with food production. In principle, a system like this could have much lower greenhouse emissions than jet fuel derived from petroleum, but that needs to be proven, not assumed.
Another vexing problem is what to do about lorries. Around the world, most goods in trade move by lorry, not by rail. It is not yet clear how lorries could be electrified and their emissions eliminated. Running them on compressed hydrogen cannot yet be ruled out, though it would be inefficient, given the energy losses involved in producing green hydrogen. Batteries may reach a point of development where they can do the job alone. This is by no means certain, but we may get a test of the proposition soon; Tesla has showed off a prototype of a heavy lorry and is promising to begin commercial production before the end of this year.