Decomposition

• Rate of decay process is dependent on:

  • oxygen availability
  • moisture availability
  • temperature
• Biogas:

  • Anaerobic decay happens when the oxygen supply is insufficient, and results in the production of biogas, which is mainly methane.
• Biogas generator:

  • Biogas generators produce methane gas, which is used as a fuel. It can also be used as a fertiliser.
  • Temperatures are maintained at a suitable level and oxygen is not allowed to enter the site of fermentation.
• Large scale bio gas generators use waste from sugar factories or sewage works
• Small scale biogas generators are used by farms or households and uses human, animal or garden waste
• Decomposers practical aim:

  • investigate the effect of temperature on the rate of decay of fresh milk
• Decomposition method:

  • add 5cm3 of milk in a test tube, 7cm3 of sodium carbonate solution and a few drops of cresol red indicator
  • put thermometer inside test tube
  • add 5cm3 of lipase solution in another test tube
  • place both test tubes in a water bath and leave them until their temperature remains constant
  • add 1cm3 of lipase solution to the milk mixture and start stop watch
  • stir until the indicator changes colour to yellow and record the time taken
  • repeat steps 1-3 at different temperatures