From the website:
Mr. Anton Peterka along with his team, made his '85 Yugo 45, using wood and coal for fuel. It's not a new technology, 125 years old. The process is based on incomplete combustion of wood: due to lack of air, gases are created: carbon monoxide, the main fuels, hydrogen and methane. That mixture of gases is as flammable as gasoline fumes. To get the car moving, it is necessary to "fill it up with wood".