Decomposition

• Organisms that die produce waste products. What organisms break down the dead material ?

  Decomposers
• Decomposers are certain types of bacteria or fungi
• What do Decomposers need to break down waste?

  Oxygen , moisture , a suitable temperature, and a suitable pH
• How do decomposers break down dead waste?

  They secrete enzymes , which partly digest the waste - They then take up the small , soluble , food molecules
• In a compost heap gardeners try and provide optimum conditions for decay - They put dead plant material (e.g. grass) onto the compost heap - over time bacteria and fungi decompose the dead plant material and produce compost - The compost produced is used as a natural fertiliser for growing plants - this is because compost is very rich in the minerals plants need to grow
• What is produced if waste is broken down in anaerobic conditions?

  Methane gas
• Biogas generators can be used to produce biogas from waste , for use as a fuel
• Gardeners often encourage decay in compost heaps. Why do the food industry not encourage this ?

  They want to slow down the decay of food - Food preservation involves removing one of the factors needed for decay
• Why does decomposition take place faster at warmer temperatures?

  Decomposers use enzymes to break down the plant materials , and enzymes work faster in warm conditions
• Why do decomposers work faster in moist compost?

  Many of the chemical reactions in decay require water - This is why gardeners do not let compost heaps dry out
• Why do decomposers need a good supply of oxygen?

  Decomposers carry out aerobic respiration - this requires a good supply of oxygen - This is why many compost bins have holes in the middle , to allow oxygen to enter
• Why do gardeners use a gardening fork to mix their compost regularly?

  It allows more oxygen to pass into the centre of the compost . It also breaks up large clumps of compost and increases the surface area for decomposers to act on
• Biogas generators use plant materials (food waste or animal manure) to provide fuel for homes