Sounds like a good dose of propaganda written into that article. Funny how the more a person may know about actual events or technical details the less the news reports resemble truth.
I believe it has been posted in threads here before that the North Koreans have been using chunk wood fueled gasifiers for a long time due to scarcity of petroleum. Even the writer of the article contradicts the charcoal claim by referring to the cutting of wood as a direct fuel source, or corn cobs sprayed with used motor oil or possibly used vegetable oil (sounds like a great idea)...
And of course charcoal won't smoke. And neither would any gasifier in operation except at the normal times of start up or refueling. So at best the writer went on a flight of fancy, obviously not based on reliable or first hand information.
It makes sense that the traffic control exempts the wood powered vehicles of road tolls, "fines", as the author says... another good idea.
So from the little bit that can be trusted from the article, the North Koreans are short enough of oil that wood gasification is an economically viable option. They also have a ready built heavy vehicle fleet to be able to respond.
I doubt any other country would be able to respond so effectively. Good for them, sounds like a positive development for the planet, and their population who no doubt rely on transportation. It would be very enlightening to know what technical developments they are no doubt making, and the practical experience and economics of operation. That would be an interesting news article.