Decomposition (Triple)

Introduction

• Decomposition = breakdown of waste materials and dead remains by microorganisms (bacteria & fungi).

• Returns carbon to the atmosphere and mineral ions to the soil.

• Important in natural recycling (e.g. compost heaps).

Compost Heaps

• Made from dead plant material (e.g. grass).

• Decomposed by microorganisms → produces compost.

• Compost is used as a natural fertiliser (rich in minerals plants need for growth).

Conditions for Rapid Decomposition

1. Temperature

• Warmer = faster decomposition.

• Microorganisms use enzymes that work faster in warm conditions.

• Compost heaps naturally warm (energy released from respiration).

• Too hot = enzymes denature, decomposers may die.

2. Water

• Microorganisms work faster if compost is moist.

• Many decomposition reactions require water.

• Compost must not be allowed to dry out.

3. Oxygen

• Decomposers respire aerobically, need oxygen.

• Compost bins often have holes for air.

• Gardeners mix compost with a fork → more oxygen, breaks clumps, increases surface area.

Anaerobic Decay

• Happens when no oxygen is present.

• Microorganisms carry out anaerobic respiration.

• Produces gases (including methane) → called biogas.

• Biogas generators:

  • Use plant waste or animal manure.

  • Provide fuel for homes in many parts of the world.

✅ Key Points / Summary

• Optimal decomposition conditions: Warm, moist, oxygen-rich.

• Compost = natural fertiliser (nutrient recycling).

• Lack of oxygen → anaerobic decay → biogas (methane).