Chip fat is a type of biodiesel fuel, like rapeseed or sunflower oil. When the oils are heated and combined, they make a fuel that can run car and motor engines. Cars that run on biodiesel give out much lower emissions than standard diesel engines, according to the website Biodiesel-Fuel. Car filters need to be checked regularly if biodiesel is used, because the fuel is more solvent than mineral diesel and more likely to pick up waste particles in a car's fuel tank, says the Renewable Energy UK website.
Remove water from the chip fat by heating it to 120 degrees Celsius using a Bunsen burner. Stop heating once the mixture has stopped spitting and popping as this means there is no water left, according to the website Make Biofuel. Allow to cool.
Mix 250ml of methanol and 4g of sodium hydroxide in a separate beaker. Ensure all the sodium hydroxide has dissolved and then allow to cool, says the Make Biofuel website.
Pour the sodium hydroxide and methanol mixture into a fresh beaker and add the boiled chip fat. The Make Biofuel website says this can only be done once the oil has cooled to less than 60 degrees Celsius. Leave the mixture to sit for two days to allow the biodiesel to separate from the glycerine also made from the reaction. Separate using a beaker with a drain valve at the bottom.
Add an equal amount of water to the biodiesel to remove the excess glycerine not already filtered off. The Biodiesel Make website advises you to leave the water to settle in the beaker for about 12 hours before draining. Repeat this 2-3 three times until the water draining off is clear. Heat the biodiesel up to about 130 degrees Celsius for 20 minutes to evaporate any residual water. Filter the biodiesel in a 5-10 micron filter.
Add some mineral diesel to the solution during cold weather running, according to the Renewable Energy UK website. This will prevent problems with freezing and cold weather starts.
Always carry a spare fuel filter in your car. Biodiesel from chip fat is more solvent than normal diesel and will pick up more particles in the fuel tank, potentially blocking the filters.
Work in a well-ventilated area with access to running water. Step back when heating chip fat in case the hot mixture pops on to skin. Only attempt to run diesel cars on chip fat because biodiesel is not a suitable fuel for petrol spark ignition engines.