Fuel from Vegetable Oils
Driving on Vegetable Oil
Chemical treatment of vegetable oil changes it into a much more runny liquid which can be used in diesel engines. This is biodiesel fuel, and it is already in common use as a 5% additive to petrochemical diesel. At this level no engine modification is needed, so it can be used in any diesel vehicle.
Vegetable oils (and animal fats) contain mainly triglycerides. These are esters formed from long chain fatty acids and propane-1, 2, 3-triol ("glycerol"). Click here to find out more about their structure.
The vegetable oil is processed by treating it with excess methanol, which releases the fatty acid chains as methyl esters, leaving glycerol. The reaction is described as transesterification. A strong base, for example sodium hydroxide, is used as a catalyst. The methanol and sodium hydroxide are prepared together first (giving sodium methoxide, CH3ONa), as otherwise the sodium hydroxide is likely to react with fatty acids to produce soap!
The methyl esters are the main components of biodiesel, but the precise composition will depend on the vegetable oil used. The glycerol is separated, purified and sold for use in food, pharmaceuticals and cosmetics.
Used Cooking Oil