Composting FAQ
Produce your own black gold
Contents of Composting FAQ
What is compost? ................................................................................................................................... 2
Why compost? ........................................................................................................................................ 2
Doesn’t my organic waste break down in landfill anyway?.................................................................... 2
What materials can I compost? .............................................................................................................. 3
How much space do I need for a compost bin?...................................................................................... 4
Where should I put my compost bin? ..................................................................................................... 4
How long does it take to make compost? .............................................................................................. 4
Troubleshooting and Tips................................................................................................................... 4
Why does my compost bin smell? .......................................................................................................... 4
Why isn’t my compost breaking down? ................................................................................................. 5
Why are there lots of little flies hovering around my compost bin? ...................................................... 5
I’m going on holiday – what should I do with my compost? .................................................................. 6
How do I harvest my compost? .............................................................................................................. 6
What should I do with my compost? ...................................................................................................... 6
Will my compost bin attract rodents? .................................................................................................... 6
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
What is compost?
Composting is a natural process where billions of microorganisms break down your food scraps and
other natural materials into a stable form. Good compost is the colour of dark chocolate, smells
pleasantly earthy and will do wonders for your garden!
Why compost?
By composting your food scraps you are preventing the release of methane (a potent greenhouse
gas) from landfill, and reconnecting the food cycle by creating a rich, free fertiliser to produce more
food. Compost has many benefits to soil such as:

Adding a slow release source of macro and micro nutrients

Creating excellent soil structure which assists with aeration, water and root penetration

Increasing the ability of your soil to catch and store water, reducing the amount of irrigation
required

Adding a population of beneficial microorganisms to your soil which assist with soil health, pest and
disease control
Doesn’t my organic waste break down in landfill anyway?
Many people imagine that food scraps in landfill quickly break down into soil anyway – but
unfortunately this isn’t the case. Soil microorganisms require moisture and oxygen to transform
organic waste but, in contrast, landfill sites are compacted (anaerobic) and kept dry to minimise
leaching. This means that materials that can decompose rapidly under the right conditions (including
food scraps, garden prunings, paper, cardboard, biodegradable bags etc.) will take centuries to break
down in landfill, while releasing methane (a potent greenhouse gas). In fact, researchers from the
University of Arizona excavating a landfill site uncovered 25 year old hot dogs, corn cobs and grapes
still recognisable, and 50 year old newspapers that were still readable!*
Composting and worm farming, in contrast, are aerobic processes that quickly break down organic
matter into rich soil fertiliser, preventing the release of methane.
*Rybczynski, W. July 5, 1992. “We Are What We Throw Away”. New York Times. Accessed
24th June 2013.
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What materials can I compost?
Technically it’s possible to compost anything that has once lived, but adding too much of the wrong
materials can unbalance the pH, create smells/mould or attract flies and rodents.
Download or print our colourful Compost poster guide here.
The beginner composter can add:

Fruit and vegetable scraps

Cooked food

Coffee grounds & tea bags

Eggshells (crushed)

Grass clippings & green leaves
The experienced composter can also add small amounts of:

Bread or pasta products

Meat and fish

Cooking oils

Citrus and onions

Dairy products
Always add a 10cm layer of Carbon-rich materials on top of your food scraps, like:

Shredded moist newspaper or office paper

Ripped up cardboard

Paper towels

Brown leaves

Straw

Coffee ‘skins’ (from coffee roasters)

Small amounts of woodchips and sawdust (no treated pine)
Never compost:

Plastics

Metals

Chemicals

Weeds & diseased plants

Glossy magazines & brochures
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Gum leaves
How much space do I need for a compost bin?
A compost bin takes up very little space and has a footprint of less than 1m2.
Where should I put my compost bin?
Your compost bin can go in sun or shade, but will benefit from some sun in Winter to speed up the
composting process. It’s a good idea to put your compost bin as close to your kitchen as possible so
that it’s convenient to add scraps and you notice if it needs attention.
How long does it take to make compost?
Your compost may be finished in as little as a month or as long as 6 months. If you’d like your
compost processed faster, chop your materials into smaller pieces and turn or aerate regularly.
Troubleshooting and Tips
Why does my compost bin smell?
A well-managed compost bin should smell pleasantly earthy. If your bin is starting to smell, it
probably means one or more of the following:

Your compost has gone anaerobic (lack of oxygen) due to compaction. Turn the compost with a
garden fork or fluff with a compost aerator.

Your compost has gone anaerobic (lack of oxygen) because it is saturated with water. The material in
your compost bin should produce a drop of liquid when a handful is squeezed. If it seems too wet,
check the bin can drain adequately, add absorbent materials like newspaper, and ensure lid stays on
to shed rain.

Your compost contains too much nitrogen rich material. The microbes in your bin need a balanced
diet of carbon and nitrogen materials. Aim for a balance between your nitrogen rich food scraps and
carbon rich materials like autumn leaves, paper, cardboard or straw.

Your compost has too much of the wrong materials. Check the list of allowable materials.
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Why isn’t my compost breaking down?
If your compost doesn’t seem to be breaking down, it probably means one or more of the following:

Your compost has gone anaerobic (lack of oxygen). If your compost smells unpleasant, check the
advice in the question above and make adjustments as needed.

Your compost is too dry. The material in your compost bin should produce a drop of liquid when a
handful is squeezed. Add water until the materials feels like a moist sponge.

Your compost contains too much carbon rich material. The microbes in your bin need a balanced diet
of carbon and nitrogen materials. Aim for a balance between your nitrogen rich food scraps and
carbon rich materials like autumn leaves, paper, cardboard or straw.
Why are there lots of little flies hovering around my compost bin?
A well-managed compost bin does not smell or attract flies. However if it is unbalanced, vinegar flies
are attracted to rotting food and can quickly build up large populations in your compost bin. This
species – Drosophila melanogaster- is studied in genetics labs because of their hardiness and fast
breeding cycle! While there is no instant fix, these steps will bring the fly population down as soon as
possible:
1) Destroy the fly breeding ground by turning the compost using a garden fork or compost aerator
and bury the fresh food in the centre of the heap.
2) Every time you add kitchen scraps, cover the surface of your compost with a layer of carbon-rich
materials like dried leaves, straw, newspaper or cardboard.
3) If the flies are a nuisance you can set traps to bring down fly populations faster. Stir ¼ cup vinegar,
¼ cup water and a squeeze of dishwashing detergent in a cup and place near your compost bin. Flies
are attracted to the vinegar and the dishwashing liquid reduces the surface tension so they drown.
Alternatively you could buy sticky yellow insect traps from a nursery.
Example of simple homemade vinegar fly trap
More ideas:

Try planting some dense shrubs around your compost bin to provide habitat for small insectivorous
birds that love to feed on vinegar flies.
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
Position your compost bin so that a few flies aren’t a problem and accept occasional vinegar flies as
part of the natural decomposition cycle!
I’m going on holiday – what should I do with my compost?
Compost is very forgiving and you don’t need to do anything special to your compost bin before you
go away. When you return, aerate your compost, check the moisture level, and continue adding your
kitchen scraps and carbon layers as before.
How do I harvest my compost?
Finished compost looks like dark, crumbly soil and smells pleasantly earthy. Depending on how you
have managed your compost bin, your compost will be ready from 2 – 6 months. To harvest small
amounts of compost you can lift one side of your compost bin and scrape finished compost from the
bottom layer. Alternatively you could lift off the bin, extract all the finished compost and start a new
pile including any remaining undecomposed materials, or start another bin and leave the first to
mature before harvesting.
What should I do with my compost?
Compost is an excellent slow release fertiliser and can be used on pot plants, vegies, fruit trees, and
ornamentals. Compost has many other benefits besides nutrients – it contains beneficial
microorganisms that help create healthy soil structure, allow plants to access nutrients in your
existing soil and protect them from pests and disease. Compost also retains water in your soil and
helps your garden survive during droughts. Unlike other fertilisers, you can’t ‘burn’ plants with too
much compost, so apply freely to moist soil and either dig in or cover with mulch.
Will my compost bin attract rodents?
Correctly managed and regularly aerated compost bins are less likely to attract vermin, however if
you are concerned or notice signs of rodent activity then you have several options.

Fix some galvanised, rodent proof wire mesh (sold for mouse, rabbit and guinea pig cages) to the
base of your bin. Make sure that you can undo the mesh to harvest your compost

Switch to a commercial rodent-proof contained compost system like a tumbler or Aerobin, or a
worm farm
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
Use humane snap traps to reduce rodent population.
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