Many experts think the price of oil will go up and never come down. We might see $6.00 a gallon gasoline in the USA in the next ten years. If that happens, the USA might do well to look to coal as a source of energy to power its transportation system.
During the Energy Crisis of the 1980s, there was a government sponsored research effort to actually turn coal into oil. It was called the synthetic fuel program. I suppose this is the modern equivalent of the ancient alchemical quest to turn lead into gold. Coal can be turned into oil, but it currently can't compete economically with oil extracted from wells. There are also programs to turn various other solid fuels into gasoline. Wood byproducts from lumber mills; biomass from agriculture can also be used. These processes are expensive and complicated. They require first turning the solid fuel into a gas, then liquefying that gas to make gasoline. In addition to being expensive, these procedures waste a lot of the energy in the solid fuels.
An alternate approach would be to convert some of our vehicles to be able to use the solid fuel in palletized form. Processing any kind of solid fuel into pellets is a relatively cheap, low-tech process. It would be very difficult to run an internal combustion engine on fuel pellets, so it would be necessary to use some form of external combustion engine like the steam engine.
A minor Google search tells me big trucks use about 18 billion gallons of fuel a year. A lot of these trucks make long trips so they don't have to do a lot of stop and go which is difficult for a steam engine. They would be ideal candidates to test this idea.
I understand there is enough coal in the USA to last for a long, long time. I recently heard an oil company executive on CSPAN say that the USA was the Saudi Arabia of Coal. And then there is biomass. In Northern California, where I live, rice farmers burn massive amounts of rice hulls every year. In the Midwest, there are lots of corncobs. Other regions have other combustible resources.
Once a vehicle was converted to run on palletized fuel, it could use anything from wood chips to coal, or even chicken, pig, or cattle manure.
It should be possible to make pellets similar to the wood pellets that fuel a lot of modern heating stoves. For coal pellets, it would be good to use the highest possible quality of coal for that purpose, of course. The steam engines could use a system similar to the home-heating units that use wood pellets.
It's not clear whether using steam power for trucks is politically or economically feasible, but it is certainly technically possible. Steam power is a well-understood technology.
Disposing of the ashes could be a problem. Perhaps they have uses as fertilizer or for industrial chemicals. The coal fired electricity industry must have already researched disposal methods.
Pollution would have to be considered, of course, and might be a deal breaker. Here again the electric coal industry research could be a starting point.
If you Google “steam powered trucks”, you get a list of toys and antiques. Perhaps it is time to take another look at this idea from a modern perspective. If we could save even a modest part of the diesel used by big trucks it could have an impact on the price of gasoline, and make the world's oil last longer.
Re-thinking steam power from a modern perspective should yield a steam engine that is lighter, more powerful, and much more convenient than the one that powered the Stanley Steamer which was marketed for more than 20 years in the beginning of the 20th century.
Now we have microprocessors, computer modeling, advanced materials, and a whole lot more experience dealing with motor driven transportation and mechanisms in general.
Even without enhancement, steam engines are more reliable and a lot quieter than diesel. They operate at much lower pressure than diesels. Diesels use high compression ratios to create great pressure, and then there is an explosion, which multiplies that pressure by at least a factor of ten. The energy from the explosion has to be captured and stored in the engines crankshaft and flywheel. That is why diesel engine blocks have to be massive. Steam engines should be a lot easier to make and maintain. Instead of producing a massive amount of energy for a very short time, they produce a constant pressure over the entire rotation of the engine.