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Compost is one of the keys to a healthy garden. It does wonders for your borders and vegetables, smells great and is really quite easy to make if you follow a few basic rules.

The Process
The process that turns organic waste into nutrient-rich compost involves millions of bacteria and fungi working to transform the raw material into compost. To work almost all of these bacteria need oxygen. Warmth and moisture will encourage them to work faster. You need to provide these conditions for them. The worms will arrive later.

Good compost is made up of a mix of green and brown materials. Green materials are high in nitrogen and break down easily. However there can be so much microbial activity that there is no oxygen and the heap becomes anaerobic (without oxygen), the microbes will not be able to work and the entire heap will become quite smelly and horrid!

Brown materials are high in carbon and break down quite slowly unless mixed with green materials and will not heat up sufficiently. Any soil clinging to weeds of vegetable trimmings can be added to the mixture.

You need to use between 1 and 2 parts green materials to every 1 part of brown to get a great heap of sweet-smelling, fertile compost.

You Need a Bin
You need a bin to hold your heap, or a place to pile your materials. The ubiquitous green or black plastic bins can be less unsightly if you do not have a corner to hide your compost from general view. Or you can make a bin from four stakes in the ground with boards or netting nailed to the stakes. Bins with board sides have more insulation, and retain heat better. There are some commercial models with additional insulation. But really, even a pile of organic matter in a corner of the garden will become compost, so don't go breaking the bank.

The size of the compost heap is important as you need sufficient mass of decomposing materials before the heap will heat up and 'cook' the contents. Make the bin at leastt 1 metre wide by 1 metre deep by 1 metre high. 1.2 metres is better.

Building Your Heap
There is much advice on how to layer your heap. Key is to start with some coarse rubbish, to improve air circulation at the bottom of the heap. A layer of hedge trimmings or prunings, about as thick as a pencil, is ideal.

Then add alternate layers of brown and green matter. Layers should be about 10cm thick (the depth of your fingers). After adding a brown and green layer you can can include a thin layer of animal manure. This will help the pile to heat.

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Keeping out Fido

Keeping out FidoIf pets and pets are getting into your compost heap then look first at the raw materials you are adding. Meat, fats and non-vegetable kitchen waste are a big no-no.

A sturdy wooden or plastic bin type (widely available from hardware stores and garden centres) with a cover are more pet proof. Bury the bin slightly and place some chicken mesh underneath to discourage not only dogs but other unwanted visitors as well.

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Compost systems and worm farm
Compost systems and worm farm

Bacteria and fungi transform raw material into compost, the worms will arrive later
Bacteria and fungi transform raw material into compost, the worms will arrive later

Raw Materials

MaterialsGreen Materials
  • Grass clippings
  • Weeds
  • Vegetable peelings, leaves & stems
  • Kitchen scraps (not meat)
  • Rhubarb leaves
  • Soft green prunings
  • Seaweed
  • Animal manure (sheep, poultry, horse & cow)
Brown materials
  • Sawdust
  • Shredded/chopped newspaper or card
  • Peastraw, lucerne or straw (wet well)
  • Twigs & small branches (shredded)
Things to avoid
  • Weeds such as couch grass, convolulus etc, unless your heap is very hot
  • Autumn leaves- these decompose very slowly
  • Horse manure with sawdust- use with caution
  • Thick hedge trimmings or prunings- decompose slowly
  • Dog and cat waste
  • Diseased vegetable & material
  • Meat scraps- rats love it!
  • Clippings from grass sprayed with weedkiller
  • Plastic, glass, metal

Recyle Hedge Clippings

Compost hedge clippingsDon't burn hedge clippings or put them out for collection. Shred and then compost them. Smaller clippings (e.g. from box hedges) can be run over with the rotary mower, larger clippings require a shredding machine.

A tiny two-bin system

A tiny two-bin system
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Last revised 26 Sep '02