They used to use "gassifiers" during WW2 that used crushed coal, which was then lit, the gasses collected and burned in a regular gas engine.
If you google the subject, you will find some pics of those cars with a device mounted on the front bumper. They also work for wood chips.
Perhaps there is a practical way to extract these gasses compress and liquify them.
There isn't, Carbon Monoxide won't liquify above -140C.
And it's a lousy fuel anyway, delivering little energy for massive CO2 emission
www.liquidcoal.com
www.liquidcoal.com