Biofuels

• Biofuels
• A biofuel is a fuel that comes from a biological source.
• A biological source is anything that is living, e.g. plants.

• Example Biofuel - Biodiesel
• Vegetable oil is used for cooking.
• It is the oil that comes from plants when they are pressed and squeezed.
• Vegetable oil is mostly made of hydrocarbon compounds.
• These hydrocarbon compounds are about the same chain length as diesel.
• This means we can use vegetable oil to run diesel vehicles (the engine has to be modified slightly).
• When we use vegetable oil for this purpose, we call it “biodiesel”.

• Example Biofuel - Ethanol
• Ethanol is a compound with the formula C2H6O.
• It combusts very easily because it already has an oxygen atom in its chemical formula.
• Ethanol can be made by a microorganism called yeast.
• By feeding sugar to yeast and warming it up, ethanol can be made.

• Combustion of Biofuels
• Biofuels still release CO2 in combustion reactions.
• Biodiesel is made from vegetable oils; as the vegetables grow they take in CO­2 from the atmosphere during photosynthesis.
• This means that an equal amount of CO2 is taken in when making biodiesel, as is given off when it is combusted.
• If the manufacture of a fuel takes in as much CO2 as is given off when it is combusted, we call it “carbon neutral”.

• Carbon Neutral Diagram
• Advantages of Biofuels
• Biofuels are good for society because they decrease our dependency on imported oil.
• They are good for the environment as many of them are carbon neutral and do not contain the same impurities as fossil fuels.
• Economically biofuels are good as they can make a lot of money for the farmers growing the biofuel crops.
• Also biofuel industry supports skilled jobs, such as chemists!
• Disadvantages of biofuels
• Biofuel crops take up land that would ordinarily be used for crops, this can push up food prices.
• Biofuels are still very expensive as they are not yet common place.
• This means government has to subsidise the industry, using money that could be spent on schools, hospitals and other vital public services.
• Sometimes forests are cut down for the wood to be used as biofuel. If the forest isn’t replaced, this is not carbon neutral.