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  • main component : methane

exothermic reaction- produces heat


  • dung
  • farm waste
  • garden waste


  • methane - cooking, heating and refridgeration
  • slurry - fertiliser

many types of bacteria present - different sources of organic material - different bacteria breaks down different material - Biogas generator - wall is reinforced - gases inside expand - put pressure ontank

flammable but creates energy out of waste + is renewable + eco-friendly

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Types of Generators


  • made in small batches
  • manually loaded up with waste
  • by-products have to be cleared away after each session (less convenient)


  • makes biogas all the time
  • waste is continuously fed it (often mechanically - costly)
  • biogas produced at a steady rate (removed mechanically)
  • suited to large scale biogas projects

Other things to consider:

  • waste will smell during delivery - generators should be away from homes or near a waste source
  • biogas is produced most quickly at 35 degrees - below this gas produced slower
  • gas can be lost through leaks
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More Biofuels

starch in maize needs to be broken down by enzymes b4 yeast can use it at fuel for anaerobic respiration

it takes more steps to produce ethanol from maize than sugar cane

maize can grow in many more countries around the world

ethanol-based fuels - can be produced from anaerobic respiration of sugar cane juices + glucose from maize starch - by CARBOHYDRASE

CARBOHYDRASE - enzyme that breaks down carbohydrates

ethanol is distilled from the products of fermentation - used in motor vehicles

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Ethanol in cars

Advantages of usingethanol as a fuel for cars:

  • efficient
  • carbon neutral - carbon dioxide released is taken up during photosynthesis
  • doesn't produce toxic gases when burnt
  • in normal fuel - carbon monoxide + sulphur dioxide + nitrogen oxides are produced - NOT when using ethanol

Disadvantages of using ethanol as a fuel forcars:

  • takes a lot of plant material to produce ethanol
  • car engines have to be modified to run on it
  • to grow lots of plant material you need space and suitable climate
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