Biodiesel can be used to replace petroleum-based diesel. It is made from vegetable oil, restaurant frying oil, or cooking oil, e.g., it is made from soybeans, rapeseed, or sunflower. There are a few grades of biodiesel: B20 is a mixture of 20% biodiesel, and 80% petrodiesel. Similarly, there is B5 and B100.
Biodiesel gives out less greenhouse gasses than petrodiesel and gasoline. If you use B20 to replace petrodiesel, the emissions of unburned hydrocarbons are reduced by over 20%, carbon monoxide and particulate matter each by over 10%. Biodiesel is also biodegradable and renewable. Fossil fuels are not renewable and might run out some day.
In 2007, San Francisco converted its fleet of diesel vehicles to biodiesel. They started a program called SF Grease: the city collects restaurants’ used oil to recycle into biodiesel. This is brilliant because San Francisco spends 3.5 million dollars each year to unclog the sewer pipes, sometimes clogged by used cooking oil.
Biodiesel is produced by transesterification, where an alcohol is added to vegetable oil to produce biodiesel plus glycerin. A catalyst such as sodium hydroxide or potassium hydroxide is required. Glycerin can be used to make soap. The process was patented by a Belgian in 1937.
This collage consists of pictures taken at the first B100 biodiesel station in San Francisco. Their biodiesel is made from vegetable oil and stored in an 8000-gallon tank. They sell 300 gallons to cars, trucks, and tour busses everyday. They also collect used oil for SF Grease.
