Composting 101

Why should I compost?

Composting is a great way of reusing your kitchen scraps and garden rubbish and it's fantastic for your garden because:

it improves soil fertility and texture, and retains moisture and nutrients
your garden will require less garden chemicals because compost rich soil grows healthier, more productive plants
it reduces the amount of garden rubbish going to landfills and the amount of methane generated (methane is a greenhouse gas)
it doesn't cost much to do and it's easy to make.

Contact your local council to find out what composting resources are available in your area.

How does composting work?

Composting involves the breaking down of organic material by a large number of bacteria and fungi. These organisms need oxygen, moisture and the right mix of nutrients to operate efficiently. The right combination of these in a compost heap allows the breaking down of organic matter to happen quickly and the process can generate lots of heat - the centre of the pile can reach up to 60 degrees Celsius in a well-operated compost heap. Lower maintenance composting systems can also produce good compost at lower temperatures over a longer time.

There are two types of organic material you can include in a compost heap - greens and browns.

Green materials have lots of nitrogen and include:

grass clippings (so long as they haven't been sprayed with weedkiller)
weeds (but not invasive weeds such as oxalis, onion grass and convovulus - these won't break down in lower temperature piles so you need to use a 'liquid manure' system or send them to a composting plant instead)
kitchen scraps, including coffee grounds and tea bags (but don't put meat or dairy products in unless your compost system is designed to cope with the pests they can attract).

Brown materials have lots of carbon and include:

sawdust (but not from treated wood)
shredded paper
straw
vacuum cleaner dust.

So how do I compost?

People use a variety of methods for composting including:

Compost heap - a pile of material, covered with carpet or polythene.
Compost bin - buy a plastic bin or make your own from timber or concrete blocks. For big gardens you may have several bins going at once.
Rotating drum - materials are place in a drum that is turned regularly to mix the composting material and provide oxygen.
Trenching - for big gardens, bury kitchen rubbish (but not meat or dairy products) in trenches in your garden, cover with a good amount of soil and plant on top.
Worm farming - using worms to help the composting process. Buy a worm bin or make your own from an old bathtub or stack of tyres.

Get the right mix

You need to get the right mix of greens and browns - too much green can lead to overheating, compaction and loss of oxygen, while too much brown can really slow down the composting process. An ideal mix is 1 to 2 parts green and 1 part brown (or 5 centimetres of brown for each 10 centimetres of green) in alternating layers.

Chop or blend

If you want to speed up the composting process you should ensure that material going into the compost is chopped up.

Keep it moist

You need to keep your compost moist. It should be like a damp sponge - too much water may result in a smelly, slimy mess, while not enough water will slow down the breaking down process.

If your greens aren't very soggy, it's a good idea to moisten the browns as you add them.
If you're not using a purchased compost bin with a lid, you should cover your compost with carpet, sacking, corrugated iron or polythene - this keeps in the heat generated by the breaking down process and helps to prevent rain getting in or moisture evaporating away.

Turn, turn, turn

You should try and turn your compost regularly if you can. This ensures that there is an adequate supply of oxygen to aid the break down process. If you can't turn the compost, you can:

put a pipe with holes in it through the middle of the compost to let air in
add twigs and branches as you build your pile.

Look after yourself when working with compost

Compost and soil contain various living organisms that have, on rare occasions, been associated with illness and allergies in humans (usually people with compromised immune systems or respiratory illness). For this reason it is important to take the following precautions when working with compost:

wash your hands after handling soil or compost
protect broken skin by wearing gloves
avoid confined spaces for handling soil or compost
keep compost moist to prevent spores and dust problems.

NEXT: Mulching 101