Composting method good for environment

PUBLISHED : Wednesday, 08 March, 2000, 12:00am
UPDATED : Wednesday, 08 March, 2000, 12:00am

Instead of sending our unwanted food and food scraps to the tip, we could be utilising them to make valuable compost. The compost material could then be used to improve the quality of the soil used with pot plants and market gardens in Hong Kong.

A compost consists of food waste or organic matter mixed with a quantity of soil.

So long as an adequate supply of oxygen from the air is available this mixture will quite readily break down and be transformed by natural aerobic bacterial action into a good all-round soil improver.

Most soils in pot plants in Hong Kong lack an adequate amount of organic matter. Plants suffer from this inadequacy and can be revitalised by the addition of organic compost.

Soil treated in such a manner will allow water and air to more easily penetrate and provide essential nutrients for growing plants.

Food scraps suitable for composting consist of anything that is organic including left-over food, fruit peel, seeds, tea leaves, discarded pieces of vegetables, egg shell, shrimp and lobster shells.

In short, anything which is organic can be added to a compost.

Here in Hong Kong unwanted food and food scraps can be added to a large galvanised steel bin or alternatively a large ceramic pot.

Each time after adding leftover food to the compost bin a small quantity of soil should be sprinkled over it. The soil acts as a medium to allow suitable bacteria which is present in most soils to be added to the compost.

Liquid waste should not be added. Liquids will reduce the oxygen available to the compost and encourage the growth of anaerobic bacteria. Under these undesirable conditions the food waste will putrefy and produce a disgusting smell. In striking contrast, under the right conditions a good compost will produce very little smell.

Flywire needs to be placed over the top of a compost bin in order to keep out insects. If allowed access, flies will quickly use a compost heap as a place to breed and proliferate. The bin also needs to be protected from rain.

Composting should be seen as a method of soil improvement rather than a soil generator. As the water content of the added food is lost by the normal decomposition and evaporation processes, the level of material in the bin continually decreases. This allows more waste food to be added even though the bin may have previously reached a full level.

Composting provides a number of important benefits. Energy does not have to be wasted in transporting unwanted food and food scraps to landfill sites. Valuable landfill sites do not have to be filled more quickly with material where the main constituent is water.

Unwanted food can be completely recycled at the location where it is generated, in schools, offices, or flats.

Places that have a small outside garden area are ideal. Users can see and be involved in the whole recycling process from start to finish. This is generally not possible or practical with a lot of other recycled materials such as aluminium, paper etc.

We can use the finished composted material and enjoy the benefits of having vigorous, healthy-looking plants and flowers.

Any organisation, whether it is a business, school, or government department, which adopts the use of a waste food recycling programme using the composting method, shows that it has a strong commitment to the environment.

If any readers are interested in starting their own compost I would be happy to share my knowledge and give free advice.

I may be contacted by e-mail on: or by writing to, John Nash, ICS, Lai Yiu Estate, Kwai Chung, N.T.

JOHN NASH New Territories