Synthetic fuel plants had been bombed, fuel production had stopped and oil imports were blocked or seized on their way in to Germany. What little oil the Germans did salvage was reserved for use by the military to be made in to important aviation fuel or to fill their Panzer vehicles.

Leadership and civilians took up the task of finding an alternative source of fuel to power machinery and vehicles. Gasification became a popular idea which is a process that converts organic- or fossil fuel-based carbonaceous materials into carbon monoxide, hydrogen and carbon dioxide, achieved by reacting the material at high temperatures without combustion, with a controlled amount of oxygen and/or steam. In a nutshell running a vehicle using burning wood.

Most of the WW2 wood burning vehicles (especially KDF Wagen/Kubel) used the Porsche adopted method which worked by having wood heated to a temperature hot enough to decompose but not letting the gas burn. Instead the gas was stored in a chamber and injected into the cylinders of the standard ‘flat4’ engine. The chamber acted like a pressure cooker, with the hot air going through a cooler and a filter and being piped back into the engine which was filtered before getting to the carburettor. A constant fan was needed to keep the combustion process going. Hozelbrenner fuel was available to purchase at special fuelling stations which sold pre-cut small wood chips.

To keep the fire burning under the hood drivers were urged to take autobahn exits in to the small towns and villages as the old fashioned cobblestoned streets would shake up the ashes thus stoking the fire.

This wood burning system although reliable and great to get you from A to B was also known to kill at least half the cars horsepower and give the elegant cars of the time an agricultural and cumbersome look. As for the number of VW’s converted to use the system from 1942 and 1945 is unknown.