6.2.6 - Alternative Fuels

• why are alternative fuels needed?

  fossil fuels are non-renewable so will eventually run out

  combustion of fossil fuels produces carbon dioxide which is associated with global warming and the enhanced greenhouse effect
• benefits of fossil fuels

  easily extracted

  produces a large amount of energy when burnt

  reliable
• alternative fuels

  biofuels such as biodiesel and alcohols

  made from living matter over a short time
• how is bioethanol made?

  by fermenting carbohydrates such as starch and sugar in crops like sugarcane which converts it to glucose then ethanol
• benefits of bioethanol

  energy conditions met by burning sugar-cane waste which is a non-food source so doesn't use other fuels or food sources in it's production
• drawbacks of bioethanol

  large-scale deforestation for sugar cane plantations

  higher food prices as food production is displaced
• how is biodiesel made?

  by extracting and refining renewable fats and oils such as vegetable oil or soya beans
• why is using soya beans better than vegetable oil to make biodiesel?

  energy is not needed for distillation during production and less fertilisers and pesticides are used in growing soya beans
• what's a carbon neutral process?

  process where carbon dioxide released is balanced by actions which remove an equivalent amount of carbon dioxide from the atmosphere
• why can biofuels be considered carbon neutral?

  they are made from plants so as crops grow they take carbon dioxide from the air as they photosynthesise

  when they burn carbon dioxide is returned to the air so there's no overall effect on the level of carbon dioxide in the atmosphere
• benefits of biofuels

  considered carbon neutral

  biodiesel and biogas can be made from waste that would go to a landfill

  biofuel production could provide money for less developed countries as they have space to grow crops required
• drawback of biofuels

  petrol car engines would have to be modified to use fuels with high ethanol concentrations

  land used to grow crops for fuel can't be used to grow food so food prices may rise

  carbon dioxide is still given out while refining and transporting the fuel, making fertilisers and powering agricultural machinery to grow and harvest crops