Composting

What is composting? Composting is the process of producing compost through aerobic decomposition of biodegradable organic matter. Compost produced at the end of the process can be used in farming and gardening to improve soil quality.

Principles of Composting Composting is the controlled decomposition of organic matter. Rather than allowing nature to take its slow course, a composter provides an optimal environment in which decomposers can thrive. To encourage the most active microbes, a compost pile needs the correct mix of the following ingredients: Carbon, Nitrogen (from composting materials) Oxygen (from the air) Water

Type of composting Active (hot) composting ~55 o C Higher temperature kill most pathogens Regularly stirring ensure aeration Faster (take weeks) Passive (cold) composting ~30 o C Much slower (may take months) May develop anaerobic condition, releasing odor and greenhouse gas (e.g. methane)

Carbon : Nitrogen ratio High-carbon sources provide the cellulose needed by the composting bacteria for conversion to sugars and heat. (e.g. starch and cellulose) High-nitrogen sources provide the most concentrated protein, which allow the compost bacteria to survive and multiply. (e.g. animal manures, fruit and vegetable trimmings, leaves) The most rapid composting occurs with the ideal carbon:nitrogen ratio of 25~30: 1 by dry chemical weight.

Links (section 1.2.1) Garden Composting

Composting in Hong Kong Composting in Hong Kong is restricted to livestock waste at this moment. Only 23 tonnes out of 200 tonnes of livestock waste collected daily is used in composting by contractor (EPD, 2003) Take 6-8 weeks for compost to become mature

Location of Sha Ling Livestock Waste Composting Plant (SLCP)

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Further reference Wikipedia Green Hong Kong Campaign—Green School Handbook