Decomposition (AQA GCSE Biology): Revision Notes

7.2.4 Decomposition

Factors Affecting the Rate of Decomposition

1. Temperature

• Effect: Chemical reactions, including those involved in decomposition, generally occur faster in warmer conditions. However, if the temperature is too high, enzymes that facilitate decomposition can denature, causing the process to slow down or stop altogether.

2. Water Availability

• Effect: Microorganisms responsible for decomposition thrive in moist environments because water is essential for their respiration. Additionally, water helps soften organic material, making it easier for decomposers to digest.

3. Oxygen Availability

• Effect: Most decomposers, such as bacteria and fungi, require oxygen for aerobic respiration. In the presence of ample oxygen, they can decompose materials more efficiently.

Compost

• Use: Compost is a natural fertiliser rich in nutrients, used by gardeners and farmers to improve soil health.
• Optimal Conditions: To create compost efficiently, optimal conditions must be provided:
  • Oxygen: Ensuring that oxygen is available allows microorganisms to respire aerobically, producing heat as a by-product, which further accelerates the rate of decay.
  • Temperature: The increased temperature from aerobic respiration speeds up decomposition, allowing compost to form more quickly.

Methane Gas Production

• Anaerobic Decomposition: When microorganisms decompose organic waste in the absence of oxygen, they produce methane gas.
  • Use: Methane can be captured and burned as a fuel source.
  • Biogas Generators: Devices used to produce methane through anaerobic digestion.
  • Requirements: A constant temperature of around 30°C is necessary to maintain microbial activity and ensure consistent methane production.
  • Storage: Methane cannot be stored as a liquid, so it must be used immediately after production.