Decomposition

• Decomposition


  The breakdown of dead matter
• Rate of decay

  The "speed" at which dead matter is broken down by decomposers
• Estimating rate of decay

  1. Measuring changes in pH

  2. Measuring changes in temperature

  3. Measuring changes in moisture
• Factors affecting decay

  • Temperature
  • Oxygen
  • Water
• At colder temperatures


  Enzyme activity decreases, so the rate of decomposition decreases (Why we use fridges)
• Compost


  Dead plants
• Manure


  Animal waste
• How compost and manure improve soil

  1. Decomposing bacteria and fungi break down compost and manure into minerals

  2. Helps recycle minerals so they can be absorbed by new plants

  3. Increases water aeration and water retention in soil
• As the volume of oxygen increases


  The rate of decomposition increases as decomposers need oxygen to respire
• Some decomposers can survive without oxygen (Biogas generators)
• Anaerobic decay

  Decomposition without oxygen
• Water 


  As the volume of water increases so does the rate of decomposition as water is needed for reactions in enzymes
• Investigating the effect of temperature on the decay of fresh milk RP

  1. Place 20cm³ of fresh milk

  2. Decide temperatures you will investigate (e.g. 5°C, 18°C, 30°C)

  3. Use three beakers

  4. Use universal indicator to determine the pH of the milk

  5. Cover each beaker at the appropriate temperature
• Decomposition

  • The rate of decay is measured by the change in pH of the milk
  • The further the milk decays, the lower the pH, as lactic acid is produced by bacteria in the milk reducing the pH
  • The beaker with the lowest pH has decayed the most
• Anaerobic decay


  • Occurs when bacteria and fungi break down dead matter without oxygen
  • Can happen naturally (waterlogged soils) or man-made (overwatering house plants)
• Products of anaerobic decay

  • Methane
  • Carbon dioxide
• Methane and carbon dioxide


  Are greenhouse gases contributing to global warming
• Biogas


  We can use the process of anaerobic decay or decomposition to produce fuel
• Methane and carbon dioxide


  Are a big source of renewable energy and are a biogas together
• Biogas generators


  Can be used to produce methane gas as fuel