Feature

How to compost

G Magazine

Transform your kitchen scraps and garden waste into a fabulous natural fertiliser with this guide

compost

Credit: iStockphoto

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We're constantly reminded to do the right thing by properly recycling our plastics, glass and paper, but what about organic waste from our kitchen and garden?

Australians toss a staggering half-tonne of organic matter into landfill each year, only for it to sit around in the oxygen-starved environment where it doesn't decompose as it otherwise would.

Whether you have a spacious backyard or some pot plants on a balcony, throwing your kitchen scraps and other organic garden matter into a compost of some description instead is a great way to make sure this type of waste is not wasted.

Composting not only keeps organic matter out of landfill, but it's also great for creating a nutrient-rich, less thirsty soil.

Compost is, essentially, the decomposed remains of organic matter.

It is excellent at improving all types of soil by acting as a natural fertiliser and helping to reduce soil disease. Drainage in clay soils and water retention in sandy soils can be dramatically improved with the addition of compost.

Creating a mound of great compost is not quite as simple as tossing the scraps on a pile. To get the most out of your compost, you should avoid adding certain types of scraps and make sure the heap is appropriately contained with a good amount of water and aeration.

Getting started

While the open heap may be messy, it's a good way to compost lots of organic matter and makes turning and aerating the pile much easier.

The square, plastic and DIY assemble kits are another option and easy to use. Some city councils offer residents compost bins at subsidised prices.

If you go for the bin option, make sure it's accessible. For an outside space, position the bin on the soil and in the shade - ideally under a tree or in an easterly position - to prevent the workaholic earthworms from dying.

Types of scraps

Suitable compost ingredients include:

  • food scraps
  • tea leaves and tea bags
  • coffee grounds
  • pieces of paper and cardboard
  • leaves
  • lawn clippings
  • newspapers
  • crushed eggshells
  • prunings


Avoid adding fats and meat as these may attract vermin (if this happens try cayenne pepper around the base of the bin as a deterrent). Small amounts of onion and citrus peels are not problematic.

Create thin layers of any one ingredient - newspapers and lawn clippings are useful for separating layers.

Work towards an even carbon-to-nitrogen ratio of ingredients, making sure to include an equivalent amounts of nitrogen-laden kitchen scraps and lawn clippings to carbon-rich newspaper, dry leaves, sawdust and hay.
Smaller scraps compost faster, so cut up kitchen scraps, mow over leaves, shred newspapers and mulch garden prunings before tossing them onto the pile.

Keep compost moist but not wet - too much moisture deprives the heap of air, causing it to smell. Conversely, too little water slows the composting process down. A telltale sign of this is the presence of ants, so add water if they're around.

Mixing it up

When you start your compost bin turn the contents once a week to increase aeration and composting activity.

Air vents on side panels of bins are often inadequate. Insert a rake handle in the heap to create airholes.

Composting takes about 8-12 weeks to break down matter into the familiar-looking crumbly brown humus. At this stage it smells sweet and can be added directly to garden soil.

Fork it through the soil around the root zones of your favourite plants.

Healthy compost does not smell unpleasant and should be about as wet as a damp sponge.

If it's too wet, add dry organic matter. Continue to aerate the heap, and add some garden lime or gypsum.

Other compost accelerators include blood and bone, chook manure (e.g. Dynamic Lifter) garden lime, seaweed emulsions such as Seasol and fish fertilisers like Powerfeed or Charlie Carp.

When emptying the compost bin, ensure that you keep some compost aside to mix into the next compost heap so microorganisms can get to work immediately.

Compost Tips
  • Grow comfrey, borage and yarrow beside the compost bin; occasionally add the leaves from these to the bin as compost accelerators.
  • There are now compostable and biodegradable bags designed especially for collecting food waste in the kitchen and throwing it straight into the compost bin. Check your local supermarket aisle.
  • Seaweed is also an excellent ingredient for the compost bin - if you live on the coast seek permission from your local council first before helping yourself to it from the beach.
  • Apartment dwellers can compost with the Bokashi Bucket, based on the popular Japanese kitchen composting bin. By adding layers of sawdust and bran the Bokashi Bucket creates compost perfect for improving the health of your indoor and balcony plants. Approx $99 from garden centres. (www.bokashi.com.au).
  • Always wear gardening gloves when handling compost as a precaution against contracting Legionnaires disease. If you are susceptible to infection and/or asthma you might consider using a facemask.