Decomposition (Factors) & Compost & Biogas

What is decomposition?

The breakdown of dead organisms and waste material by decomposers.

What organisms carry out decomposition?

Mainly microorganisms such as bacteria and fungi.

How do decomposers digest dead material?

They secrete enzymes into the environment. The enzymes digest the material into small soluble molecules, which can then diffuse into the microorganism.

How do decomposers recycle materials?

They break down dead organisms and waste, returning mineral ions to the soil and releasing carbon dioxide through respiration.

Which factors affect the rate of decay?

Temperature, water/moisture and oxygen availability.

How does temperature affect decomposition?

Increasing temperature initially increases the rate because decomposer enzymes have more kinetic energy and enzyme-controlled reactions occur faster. Above the optimum, enzymes denature, reducing the rate.

Why is water needed for decomposition?

Microorganisms require water for chemical reactions and growth, so very dry conditions slow decomposition.

Why does oxygen increase decomposition?

Oxygen allows decomposers to carry out aerobic respiration, releasing more energy for growth and activity.

What happens during anaerobic decay?

Decomposition occurs without oxygen and can produce methane.

How can gardeners increase the rate of compost decay?

Maintain warm, moist and oxygenated conditions to provide optimum conditions for decomposer microorganisms.

Why should compost be aerated/turned?

To supply oxygen for aerobic respiration by decomposers.

Why is compost useful?

It can be used as a natural fertiliser, returning mineral ions/nutrients to the soil.

What is biogas?

A mixture containing methane produced by anaerobic decay, which can be used as a fuel.

Why are biogas generators kept without oxygen?

Methane is produced during anaerobic decomposition, so oxygen must be excluded.