Fuels from Microorganisms

  • Created by: Abbie
  • Created on: 13-05-12 09:21

Fuels from Microorganisms

Fuels can be made by fermentation of natural products - often waste products

Fermentation - when bacteria or yeast break down sugar by anaerobic respiration


  • Yeast make ethanol when they break down glucose by anaerobic respiration
  • Glucose -----> ethanol + carbon dioxide + energy
  • Sugar cane juices can be used, or glucose can be derived from maize starch by carbohydrase enzymes
  • Ethanol distilled to seperate from yeast and remaining glucose before use
  • In some countries cars are adapted to run on a mixture of petrol and ethanol called gasohol


  • Biogas is usually about 70% methane and 30% carbon dioxide
  • Lots of different microorganisms are used to produce biogas, they ferment plant and animal waste which contains carbohydrates
  • Sludge waste from e.g. sewage works or sugar factories is used to make biogas on a large scale
  • It's made in a simple fermenter called a digester or a generator
  • Biogas generators need to be kept at a constant temperature to keep the microorganisms respiring
  • There are 2 types of biogas generators - batch generators and continuous generators
  • Biogas can't be stored as a liquid (it needs to high pressure) so it has to be used straight away, for heating, cooking, lighting or to power a turbine to generate electricity

Fuel production can happen on a large scale or a small scale:

Large scale biogas generators are now being set up in a number of countries, in some countries small biogas generators are used to make enough gas…


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