Decomposition is the process where microorganisms known as decomposers break down dead and waste organic material. Decomposers are usually bacteria or fungi. Decomposers use the decaying organic material as a substrate for respiration, producing carbon dioxide as a waste product. It is vital for nutrient cycling, returning carbon to the atmosphere and mineral ions (such as nitrates) to the soil.

Decomposition is influenced by several abiotic factors:

1. Temperature

• Warmer temperatures speed up decay because enzymes in decomposers work faster.
• Too hot (above enzyme optimum) or too cold can slow down or stop decay.

2. Water Availability

• Moist conditions increase decay.
• Water is needed for microorganisms to grow and carry out chemical processes.

3. Oxygen Availability

• Aerobic decay (with oxygen) is faster and produces carbon dioxide.
• Anaerobic decay (without oxygen) is slower and produces methane gas.

Human Uses of Decomposition

Composting:

• Gardeners and farmers encourage rapid decay of plant waste to produce compost.
• Compost is a natural fertiliser rich in minerals like nitrates and potassium ions.
• Conditions are optimised: warm, moist, and well-aerated (to ensure aerobic decay).

Biogas Production:

• Anaerobic decay in biogas generators produces methane.
• Methane is collected and used as a fuel (e.g. for heating, cooking, or electricity).
• Biogas systems are used in rural areas or developing countries.

Practice Question