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PRINCIPLES OF COMPOSTING

Raw Material

The process of composting requires a continuous supply of feed in the form of organic waste. Organic material is anything that was once living. Under the correct conditions, this material will decompose into nutrient rich compost.

Carbon to Nitrogen Ratio

although most forms of organic waste supply essential nutrients for optimum growth of microorganisms such as bacteria and fungi, they grow best with the proper level of Carbon and Nitrogen (C:N ratio). Paper, leaves and wood are high in carbon, (referred to as ‘brown’ because they are dry) while grass clippings and most fruit and vegetables are high in nitrogen (called ‘green’ because they are fresh). Decomposition speed will greatly increase with the right balance. The correct C:N ratio can be achieved by adding two parts of green material to one part of brown in the composting bin.

Aeration

Turning the organic material allows more air in and serves to greatly accelerate the composting process. It ensures a constant supply of oxygen (aerobic conditions) for the bacteria to do their job. It also exposes new surfaces for bacteria to decompose and reduces the problem of odours. If you want compost quickly, organic material should be turned once a week. In household, composting coarse materials such as cardboard and twigs will also aid aeration.

MOISTURE

Adequate moisture levels are essential for the activity of micro-organisms. Insufficient moisture results in a reduction in decomposition by aerobic bacteria. If the composting waste is excessively wet and soggy there will be a reduction in aeration and anaerobic conditions will prevail, resulting in odour problems. The organic material should not be too dry and dusty or too wet and clumpy. A good rule of thumb is that your compost should be as moist as a wrung out sponge.

Temperature

The organic waste should not be allowed to get too cold as decomposition is greatly reduced when the temperature of the organic waste drops below approximately 13oC. Turning the organic material distributes heat evenly and speeds up the decomposition process. Composting slows down in the winter, and in the summer the material may need to be turned more regularly to keep it aerated.

Biological Organisms

Biological organisms such as bacteria, fungi, worms, and other insects, feed on and decompose the organic waste. As the temperature rises bacteria break down the organic material and their activity raises the temperature further causing the waste to decompose more quickly. Eventually when the compost cools down, fungi, worms and insects assist the bacteria in further decomposition.