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Garden and food waste

Introduction | Create a low-waste garden | Create your own compost | Worm farming | Bokashi composting | Other options

Create your own eden logoCreate your own compost

Free composting courses for 2011

Auckland City Council is providing free courses for people to learn how to compost, and in turn reduce the waste going to landfill. The courses run for three hours, and will include:

  • how to make compost
  • what to put in and what not
  • the pH factor, moisture, air and trouble shooting
  • worm composting, how to make a worm farm and all about worms
  • a video on worm farming and composting.

Discounted Bokashi buckets, worm farms and compost bins will be available for sale at the course.

View Create Your Own Eden composting courses details and dates.

topGetting started

  • choose a site with care. Ideally, it should be warm and sheltered
  • consider neighbours by siting the heap or bin away from any areas that are too close and could cause offence
  • to work properly, your compost heap should be at least 1m high x 1m wide x 1m deep
  • start with a layer of coarsely chopped twiggy woody material on bare soil or grass
  • add alternate layers of green matter (nitrogen rich) and brown matter (carbon rich) preferably in layers no more than 5 to 10cm deep
  • limit all layers, including grass clippings, to thin layers
  • if you can't be bothered layering, just make sure there is a mixture of green and brown matter
  • avoid cat/dog/human faeces, meat, fish, bones, oil and invasive weeds
  • smaller pieces make quicker compost - for quick compost, fibrous materials should be no bigger than the thickness of your finger (2cm)
  • the heap should have a cover, eg. plastic lid, under felt, tarpaulin
  • be aware that it is difficult to manage rodents if a compost heap is used
  • rodents can be kept out by cutting out a piece of chicken wire larger than the bin base. Place it underneath the bin on the soil and fold the edges 10cm up the sides of the bin.

Keeping it going

  • compost activators or accelerators can be added to hasten the natural break-down process. They usually contain a natural nitrogen or bacterial enzyme and can be bought at most garden centres
  • sprinkling on lime and untreated wood ash can help balance pH and reduce smells
  • the heap should be as moist as a wrung out sponge. Add water if needed
  • avoid excessive moisture by keeping the heap covered
  • to work properly, your compost heap needs to reach temperatures between 30 and 60°C. From time to time, check that it is heating up in the centre - it should feel warm
  • compost needs air - turn and mix it up to aerate and speed up decomposition.

The final touches

Grass clippings being tipped into a compost bin

Grass clippings being tipped into a compost bin

  • once an open heap is 1 metre in height, you should finish it by turning it with a pitchfork and mixing it up every week or two
  • either use a new bin for the new heap, or use your original bin and just keep the old heap covered with under felt, tarpaulin or something similar
  • compost is ready when it becomes a sweet, dark, crumbly material and you cannot distinguish the original materials in it
  • if compost is well maintained and turned often it can be ready in as little as 6 to 8 weeks. If it is never turned, it will be ready in 12 to 18 months
  • when it's ready, put it onto the soil or dig it into your garden. You can also use it for pot plants and for potting up seedlings
  • don't forget to wash your hands when you've finished composting and gardening!

topWhat can and can't be composted

What can

Green - nitrogen rich Brown - carbon rich, dry
  • food scraps
  • manure
  • fresh grass clippings
  • weeds without seeds
  • vegetable scraps
  • seaweed
  • tea leaves and bags
  • coffee grounds
  • torn newspaper/cardboard
  • egg cartons
  • tree prunings
  • dry leaves
  • bark, untreated sawdust
  • wood ash
  • twigs and sticks
  • crushed shells

What can't

Although in theory anything organic can be composted, some things are best avoided when composting at home.

Material Reason
Cat and dog faeces Can cause disease
Meat, fish, oil, bones, fat Can attract rats
Non-organics eg tin, glass, plastics Won't break down
Invasive weeds, eg kikuyu, wandering willy, jasmine Could spread in or beyond your garden - however they can be composted after treatment
Large amounts of pine needles or gum leaves Allopathic- create environment hostile to compost creatures
Woody materials in pieces larger than the diameter of your finger Too slow to break down
Diseased plants (eg with blight) Disease may spread
Bamboo, flax and cabbage tree leaves Not suitable for composting and not taken by composting companies (bury in the ground, or take to a transfer station for landfilling)

topCommon problems

Problem Cause Solution
Smelly, slimy heap Not enough air
Too wet
Too much nitrogen		 Turn heap
Add brown material (eg dry leaves)
Materials are not decomposing Heap too small
Not enough heat due to lack of green materials or water
Materials in heap are too large		 Increase size of heap
Add green materials (eg manure or blood and bone) and water
Break materials down into small pieces
Pests attracted to heap eg flies, cockroaches, rats, mice Wrong food added
Bin not rodent proof		 Don't use meat/bones/fish
Bury food scraps in centre of heap
Rodent proof your bin
Fruit flies (vinegar flies) Heap is too acidic Sprinkle lime on heap
Ants Heap is too dry Add water and lime
Other "mini-beasts", eg beetles, worms This is not a problem - creatures are essential to the composting process Appreciate the work they do!

topInvasive weeds

It can be difficult for people to accept that well-loved plants like honeysuckle and Mexican daisy are deemed to be pests, but it is essential to control them. Plants like ginger, jasmine and privet can cause serious harm to our native environment and others can threaten the livelihoods of producers of commercial crops.

To find out more and to identify invasive weeds, visit the following websites:

Composting invasive weeds

It is possible to compost invasive weeds, however it is essential that they first go through a 'pre-compost' process in order to ensure that they die.

  • put the weeds in a large plastic bag with a handful of soil and water
  • tie the top and leave for at least two months, until there are no green shoots or other signs of life
  • add them to your compost heap as a green.

If you leave them for long enough, they will turn into soil. There is also another way to handle noxious weeds.

  • put them into a closed bin and cover them with water (or submerge them in a sack)
  • leave for two to three months by which time the water will turn a green/brown colour but it can be used as fertiliser for your plants
  • empty the solids into your compost bin.

topTypes of compost bins

Before you choose a compost bin you should consider what you will be putting in it. Larger, open bins are better for people with large amounts of garden waste. Smaller, enclosed bins are more suitable for households with large quantities of food waste as they provide a barrier to rodents. You may find you need both.

Image of mature compost ready for use.
Mature compost ready for use.

Choosing a bin

There are a number of points to consider before you buy a bin so that you get one appropriate for your needs. These are:

  • the number of people in your home
  • the size of your garden
  • the capacity of the bin, taking the above into consideration
  • your ability to turn compost with a garden fork
  • the bin design (ie whether different parts need be lifted)
  • materials used in the making the bin (eg some are made of recycled plastic)
  • whether the bin is made locally.

Make your own compost bin

If you are making your own bin, you can use a wide range of material, including chicken wire, wood, plywood, bricks, concrete blocks, etcetera. It must be on the soil and no smaller than 1m high x 1m wide x 1m deep and no larger than 5m3.

For large amounts of garden waste, units can be made from wood, bricks or concrete blocks. Ready access from the front is necessary.

Stacking bins have the advantage of being moveable and can be extended to cope with large amounts of waste. Black polythene or sacks may be used for lining, warmth and moisture control. Wrap netting frame around wooden stakes. Line these with newspaper or cardboard to retain heat.

Check for designs in books at your public library in books on compost such as The Suburban/Urban Composter by Mark Cullen.

Some designs can also be found at the following websites:

topWhere to buy bins

There is a range of commercial compost bins which vary in size and complexity. With regard to size, a medium-sized compost bin (240 litres) should cope with all the kitchen waste and garden waste of two to four people.

Bins are usually available from hardware and garden stores, and range in price from $40 to $220. Generally speaking, bins that require less turning are more expensive.

While larger bins are obviously more suitable for larger households, bins may not vary significantly in performance. The most important thing is knowing how to manage your bin so that you make good compost.

Suppliers of compost bins:

  • Hammer Hardware
  • Kings Plant Barn
  • Mitre 10
  • Palmers Gardenworld
  • The Building Depot
  • The Ecostore
  • The Warehouse.

You can also get a free bench top bin for your kitchen scraps when you attend a composting course.

Additional information

More information can be found at the following websites:

Updated January 2011