The technology was widely used in Europe post WW2, when fuel was very scarce. Entire factories were powered with this technology for sometime following the war, there was not much of an alternative at that time.
The technology fell out of favor when the availability of conventional fuel returned.
I'd like a system for heating that heats water/air and makes the gas to run a generator. Good use of all the abilities of fire/wood gas. Tons of interesting stuff is used in poor countries. Gasifiers, rocket stoves, solar. We are very spoiled.
The air/fuel mixture was manually adjusted with the older systems, and as long as you don't advance the timing too much, the engines will run a long, long time. This works really well for an electric generator, not so much for applications that require lots of variation in speed. I have a friend in Sweden that has one that is over 60 years old, he keeps it for emergency back up power.