How the natural process of composting converts your leftovers into valuable fertiliser

WORDS AILSA HARVEY

Leftover food, garden trimmings and other organic waste items don’t need to be discarded. Instead they can be recycled in a process called composting. Composting is the L breaking down, or decomposition, of organic material into nutrient-rich soil. After decomposition, these materials turn into organic molecules made up of carbon dioxide, water, simple sugars and salts. Compost heaps are places where this process is accelerated from years to months or even just a few weeks.

Composting mostly takes place outdoors, and there are two main types: cold, or passive, and hot, also called active compost. Cold composting is much slower but is easier to manage. All you need to do is add the right materials and allow the natural process to take place. The soil created from this process usually can’t be recycled for at least one year, as much of the decomposition takes place slowly without oxygen.

Hot composting is more efficient, but requires you to maintain consistent layers of carbon-rich and nitrogenrich materials while optimising the water and oxygen levels regularly. The ideal temperature for quick active composting is 55 to 60 degrees Celsius. This temperature is achieved when the heap is well aerated with peak composting conditions. Adding piping into the top of a compost heap is a simple way to ensure air is entering the middle of the soil.