Vegetable oil fuel
Conventional diesel engines can be modified to help ensure that the viscosity of the vegetable oil is low enough to allow proper atomization of the fuel.
Straight vegetable oil can also be blended with conventional diesel or processed into biodiesel, HVO or bioliquids for use under a wider range of conditions.
The 1970s also saw the formation of the first commercial enterprise to allow consumers to run straight vegetable oil in their automobiles, Elsbett of West Germany.
Principally, the viscosity and surface tension of the SVO/PPO must be reduced by preheating it, typically by using waste heat from the engine or electricity; otherwise, poor atomization, incomplete combustion, and carbonization may result.
The exception is the VW TDI (Turbocharged Direct Injection) engine for which a number of German companies offer single-tank conversions.
For long-term durability it has been found necessary to decrease the oil change interval and pay increased attention to engine maintenance.
Attention to maintenance of the engine, particularly of the fuel injectors, cooling system and glow plugs will help to provide longevity.
[3] The relatively high kinematic viscosity of vegetable oils must be reduced to make them compatible with conventional compression-ignition engines and fuel systems.
Cosolvent blending is a low-cost and easy-to-adapt technology that reduces viscosity by diluting the vegetable oil with a low-molecular-weight solvent.
Noted problems include higher rates of wear and failure in fuel pumps and piston rings when using blends.
However, oils with lower gelling points tend to be less saturated (leading to a higher iodine number) and polymerize more easily in the presence of atmospheric oxygen.
Most metallurgical problems such as corrosion and electrolysis are related to water-based contamination or poor choices of plumbing (such as copper or zinc) which can cause gelling – even with petroleum-based fuels.
If all those 11 billion liters could be recycled and used to replace the energy equivalent amount of petroleum (an ideal case), almost 1% of US oil consumption could be offset.
