Biomass and Diesel

Rudolph Diesel

In the late nineteenth century, Rudolph Diesel developed a new kind of internal combustion engine on the principle of using high compression to raise a fuel/air mixture to its ignition temperature (compression-ignition). By this process, the engine can work with a wide variety of fuels. In 1898 Diesel demonstrated his engine at the Exhibition Fair in Paris, France. The engine was run on peanut oil. Diesel thought that the real future of his engine rested with the use of Biomass fuels - plant oils - that are inherently renewable resources.

In 1912, Diesel said, "The use of vegetable oils for engine fuels may seem insignificant today. But such oils may become, in course of time, as important as petroleum and the coal tar products of the present time." It was not until the 1920's and after Diesel's untimely death in 1913 that the early petroleum industry started to muscle out the Biomass vision, instead offering a low-grade refinement byproduct of gasoline as a fuel suitable for diesel engines. Before long, this new and cheap fuel supply had completely replaced Biomass fuels and gave us the diesel engine and fuel we know today.

The major change in engine design that was spawned by petro-diesel fuel was the high-pressure injection pump. This mechanism was redesigned to take advantage of the low viscosity of petro-diesel compared with vegetable oil.

Reclaiming the Injector Pump

Biodiesel has significantly lower viscosity than vegetable oil, but higher than petro-diesel. This poses no problems for standard fuel injection systems; Biodiesel can be used directly in diesel engines without any engine modifications.

With modifications, most diesels can be run on straight vegetable oil (SVO) as long as it is heated sufficiently to drop the viscosity into a usable range. Modifications are also needed to allow the engine to be started and shut-down on biodiesel or petro-diesel to avoid clogging the fuel system when it cools. Using biodiesel avoids the need for such modifications.