Why compost?a gardener emptying scraps into compost bin

When you throw vegetable scraps and gardening waste into your landfill bin it costs you and the environment.

In many areas the land allocated to waste disposal is rapidly filling up. Approximately half of all household waste is organic. Most of this waste can be recycled through composting - turning waste materials into a rich soil supplement for use in your garden. By composting, not only can you help to reduce the amount of waste that goes into landfill but you can also help to reduce contamination and greenhouse gases.

Composting can reduce the amount of waste going to landfill by 60%.

We pay a high price in both monetary and environmental terms for the disposal of household garbage. By composting the organic parts of household garbage, much of our waste can be recycled, saving money and protecting the environment.

Compost adds life to soil. It improves plant growth, increases the capacity of soil to hold nutrients and the ability of plants to resist disease.

We can reduce our current dependence on artificial fertilisers by returning organic matter to the soil as compost. It is the organic matter in soil which makes it resistant to erosion, maintains its fertility and stabilises its structure. Compost will:

  • improve the ability of soil to absorb water
  • reduce run-off and provide food for beneficial soil organisms such as worms
  • supply nutrients in a slow release form
  • reduce fertiliser requirements
  • maintain good aeration in soil, which helps water penetration
  • reduce soil erosion
  • keep soil cool in summer, warm in winter.

So, what is compost?

Compost is partially decomposed organic matter. It is produced in the natural environment from decaying leaves and left on the forest floor. In the home garden we can achieve the same result, more quickly, by building a compost heap. It is a biological decay process which converts organic wastes into a crumbly, sweet smelling earth-like substance. The micro-organisms which produce compost need oxygen from the air, nitrogen and trace elements from the raw materials, water and a little time to do the job. Finished compost is dark in colour, moist, sweet smelling and colloidal - ie. ability to hold water and nutrients. Plant roots can extract water and nutrients from colloids. When composting, just remember ADAM!

A is for Air

Air is the most important ingredient in your compost. Without air, the bugs and micro-organisms that break down waste into plant foods cannot survive. Your compost will become smelly. To maintain enough air in your compost pile, turn or fluff the pile regularly (garden fork or compost mate)

D is for Diversity

Diversity in your compost pile is very important. A range of food types or organic matter lead to a variety of bugs and organisms working for you. The more you have, the faster your compost breaks down and the healthier it will be. The variety of material you add to your pile helps control the moisture levels and the airflow through your pile.

A is for Aliveness

A good, healthy compost has a lot of bugs and other organisms living together. To encourage "aliveness", place the pile directly on the ground and remember to check the air, the diversity and the moisture level of your pile.

M is for Moisture

The creatures in the compost need air, diversity of food and moisture to survive. Too much moisture and the pile will lack air and the bugs will drown, too little and the bugs cannot survive. The pile needs to feel like a damp sponge. If too dry - add green, moist material, dregs of your tea/coffee or water your pile. If too wet - add some dry/brown material, turn the pile, or leave it uncovered on a warm sunny day.

How to compost

The method

The essential requirements are nutrients, air, water, micro-organisms and time.

Getting the correct balance is the trick.


  • A lot of garden refuse is dry, brown and woody and is high in carbon.
  • Soft green garden waste and kitchen scraps are high in nitrogen.
  • The ideal mix - 20 parts carbon, 1 part nitrogen.
  • High in Carbon - dry leaves, twiggy prunings, sawdust, paper, straw, dry grass and wood ash
  • High in Nitrogen - vegetable scraps, fruit peelings, fresh lawn clippings, farm manure, seaweed

Organic materials not suitable for composting are:

  • meat, fish, oils and fats - attract vermin
  • large volumes of salty water - not good for soil, plants or compost
  • weeds with aerial tubers, corms, bulbs and rhizomes (Madeira vine, onion weed, oxalis and nut grass)
  • fruit and seed from declared noxious weeds
  • fruit and seed from invasive weeds such as privet and lantana
  • dog, cat and human excrement - may contain harmful bacteria
  • large woody prunings - unless shredded, as they take too long to decompose.


If all is well within the compost heap the decay process may take as little as 8-10 weeks.

How do you build a compost heap?

  1. Choose a warm sunny spot where your compost has direct contact with the soil.
  2. Place some coarse twigs on the bottom of the compost pile to help with drainage and aeration. Fill your bin with the easy ABC formula to build a heap layer upon layer.
  3. Make a thin layer of kitchen organics and green garden organics.
  4. Cover with a layer of brown garden organics ensuring no food waste is left exposed. (A sprinkling of soil or finished compost layered on top of food scraps will make a richer compost and help minimise odours.)
  5. Moisten well. Then repeat 1-4. Leave for up to 1 week, then give your compost a "fluff" with your fork to get air into the pile.

Solving compost problems




Foul odours Heap is too wet Add dry leaves, turn the heap to improve drainage, add 250g of garden lime. Cover the heap during rain.
Slow decay Not enough nutrients Add 250g of blood and bone nutrients or another nitrogen-based fertiliser.
  Not enough air Turn the heap more often.
  Not enough water Moisten the heap.
  Too cold in winter Cover the heap with insulation material (Hessian).
Maggots Meat, seafood, fats or faeces in the heap.

Remove the cause.

Cover the maggots with lime.

Add soil to the top of the heap; turn the heap the next day.

Using compost

There are two ways:

  1. mixed into the soil or
  2. used as a mulch on the soil surface.
  • When preparing site for planting, cultivate a wide shallow area and combine compost with the top soil.
  • Do not use compost in the sub soil or at depths greater than 15cm - toxins to plant roots may be released.
  • Compost breaks down in the soil and needs to be replaced regularly.
  • Do not pile up against tree trunks or plant stems. If you have added lime, do not use around acid-loving natives, azaleas, rhododendrons, ericas or camellias.
  • Do not put fresh compost directly in the bottom of the planting hole - too rich, will burn the roots.
  • It's best to use a mulch on top of the soil for established plants/trees.
  • Earthworms will drag it down and mix it with the soil without harming plant roots. For more information call our Waste Management Officer on (02) 4232 0444.

Where can I buy a compost bin?

There are many different types of compost bins available from nurseries, hardware stores and major department stores. Compost Bins are also available for purchase at Kiama Council.  To purchase:

  1. Go to our Customer Service Counter at the main administration building, 11 Manning Street, Kiama to pay for your compost bin.
  2. Present your receipt of purchase to our Works Depot, Belvedere Street, Kiama to collect your compost bin.

Attend a workshop

Learn the basics to successful composting at one of our free home composting workshops.  For more information on the workshops and to register click here.