Composting

Composting is the process of decomposing organic household and garden waste. This creates a nutrient-rich fertiliser which can enrich your garden’s soil.

There are many ways to compost at home using a variety of products such as compost bins, worm farms or bokashi bins. Start composting and food waste recycling at home with the help of the information below.

On this page:

• Bokashi Bins
• Create your own worm farm
• Create your own compost
• Grub composters

 

Bokashi Bins

Bokashi is the Japanese word for fermented organic matter.

A bokashi bin or bucket is a practical and convenient way to transform your kitchen waste into nutrient-rich compost for your garden.

It is a unique recycling system that ferments food waste in a sealed, air-tight container. Commercial bokashi buckets can be purchased through selected distributers, or you can make your own.

Fermenting waste

The bokashi process works by fermenting organic waste rather than composting. Compost bins and worm farms work differently and these cannot take things like meat, dairy, citrus and bread, where a bokashi bucket can take almost any food waste.

The secret to the process is the bokashi grain added after each layer of food waste. This grain contains beneficial micro-organisms that act to ferment or pickle the food waste. Bokashi grain can be purchased commercially but it is possible to make your own if you have the right ingredients. You can also get a bokashi spray that contains the same effective micro-organisms.

What can go in a bokashi bin

You can add almost any kitchen food waste, including:

• All fruit and vegetable scraps
• Processed foods
• Cheese and solid dairy products
• Cooked and uncooked meat, including fish and other seafood
• Bread, cake and biscuits
• Tea bags and coffee grounds
• Pasta and rice.

What not to add

• Liquids such as milk, fruit juice or water
• Large bones
• Foods that are rotted or mouldy
• Foods contaminated by chemicals
• Dog and cat excrement
• Packaging materials such as foil or plastic wrap.

How to use your bokashi bin

Step 1: Add a generous handful of bokashi grain to the bottom of the bucket.

Step 2: Cut or mash your kitchen scraps into small pieces and place into the bucket. This will speed up the fermentation process.

Step 3: Add a handful of bokashi grain, or enough to evenly cover the previous layer of food scraps. Repeat this for every layer of food waste you add to the bucket.

Step 4: Push down contents to remove any air pockets and ensure the lid is on tight.

Step 5: When the bucket is full, top off with a generous layer of Bokashi grain and leave in a cool, dark place for a week, before burying somewhere in your garden (minimum 30cm deep). You may also empty the nutrient-rich contents straight into a compost bin or bury immediately, where it will continue to breakdown.

Using your Bokashi juice

Bokashi juice contains nutrients from the food waste and is alive with effective micro-organisms. This makes a terrific fertiliser. To fertilise an existing garden or pot plants use 1 teaspoon to 2-3 litres of water and apply directly to the soil. For trees and shrubs use 2 teaspoons to 2-3 litres of water. Do not apply directly to foliage, as this may burn your plants.

Bokashi juice cannot be stored and must be used within 24 hours after draining from the bucket. If you don’t want to use it all on the garden, try pouring the concentrated bokashi juice down the kitchen/bathroom drains and toilets to help control odour and algae build-up.

Helpful tips

• You cannot add too much Bokashi grain
• Always close the lid tightly and drain the bokashi juice frequently
• When burying the contents from a full bokashi bin, try covering the freshly dug hole with something stable and heavy to prevent animals from digging it up
• The more times you add food waste to your bokashi bin, the more grain you will use. Try storing your food scraps in the fridge and add them to your bin on a weekly basis
• Bokashi compost is acidic when first dug in, but neutralises after 7-10 days. Avoid burying the compost close to other plants and wait at least 2 weeks before planting any new plants.

How to make your own bokashi bin

What you’ll need:

• 2 x 20L identical containers with lids
• Drill
• Tap (optional)
• Old flyscreen
• Bokashi grain or spray.

Step 1: Find two containers with lids (20L Handy pails work well)

Step 2: Get one container and drill a series of small holes in the bottom

Step 3: Place the bucket with the drill holes inside the other. Cut a round piece of flyscreen and attach to the bottom of the bucket above the drill holes (remember to keep a lid for the top container)

The containers need to be identical so that they are able to fit perfectly inside each other and air-tight.

Step 4: You may install a tap at the base of the bottom bucket to extract the Bokashi juice, or alternatively you can simply lift the top bucket out and pour out the juice into a smaller container or bucket. Dilute (1 teaspoon of juice with 2-3L of water) and use on your garden or put down your drains.

Create your own worm farm

A worm farm turns organic waste such as kitchen scraps into fertiliser for your garden.

Feeding fruit and vegetable scraps to composting worms is a cheap and simple way of recycling food and garden waste. Worm castings make a great fertiliser for gardens.

Worm farms are ideal for people living in flats or houses with small backyards and for dealing with lunch scraps at the office. They don’t take up much room and can be placed on a balcony - all you need is a small, cool, well-shaded spot.

Worm farms can be bought from most hardware or gardening shops. It’s also easy to make your own worm farm out of old containers, bins, tyres or old fridges.

How to set up your worm farm

One style of ready-made worm farm housing, which is normally available from local hardware stores and nurseries, comes as a stack of two, three or four trays. The lowest tray is a drip tray (collector tray), which is then topped with the worms bedding tray and/or feeding tray (working trays).

Some hardware stores and nurseries also sell the live compost worms to go in the farm housing. They can also be purchased separately from any local worm farmer who breeds and sells compost worms.

What to feed the worms

Worms are great eaters and like most vegetable and fruit scraps, except for onions and citrus. Because worms do not have teeth, scraps should be cut into small pieces.

Favourite foods include: watermelon, apple, avocado, pear, grapes, carrot, cabbage, mushroom, pumpkin and many other kinds of vegetable and fruit scraps.

Worms also like: soaked and ripped pizza boxes, shredded and soaked cardboard, newspaper, teabags, coffee grinds, egg shells, leaves, and hair.

What not to feed them

Don’t try to feed worms food such as meat, cheese, jam, butter, biscuits, cake or any other highly processed food. They’ll refuse to eat it, causing the food to spoil and create unpleasant odours in the worm farm.

They also don’t like onions, shallots, garlic or too much acidic food like oranges, mandarins or pineapples.

No meat and dairy products should be added to a worm farm.

How to keep your worms happy

Your worms will be happy as long as you follow a few simple rules:

• Keep the worm farm out of extremes of weather, i.e. out of the sun and rain
• Keep the worm farm damp but not wet. Water every so often or as required
• Give them a range of different foods to keep them interested
• Try not to feed your worms too much or the wrong types of food 
• feed your worms too much or the wrong types of food
• Keep the worm farm clean and hygienic, and it shouldn’t have any unpleasant odours unless they are fed too much or the wrong types of food
• When going on holiday, an established worm farm can be left for 3-4 weeks by making sure it has enough food to last that time. Fresh compost, shredded newspaper or cardboard works well. Make sure it is moist before you leave and is in a protected area.

Useful facts

• Compost worms such as Tiger Worms, Red Wrigglers and Indian Blues love the rich moist conditions of a wormery. Ordinary earthworms can’t survive the rich conditions.
• Worms only breed if there is enough food. In good conditions, the population can double in 2-3 months.
• Compost worms breed every 7-10 days, but when the worm farm reaches capacity, the breeding stops.
• The worms in a small worm farm should eat all the fruit and vegetable waste produced by a household of four.
• Worm castings and the liquid fertiliser are useful additives to any garden bed, as they are organic and have a neutral pH of 7.
  • The castings and liquid fertiliser provide an excellent fertiliser and can be used on all plants.
  • The liquid fertiliser can be used when diluted with water (1 part worm juice to 10 parts water) and the castings spread around the drip line of plants and trees.

Ideal conditions

Worms will tolerate a temperature range from approximately 10-30 degrees celsius. If it gets much hotter than this, move the system into a shady, cool position. In very cold temperatures, cover the system with some old carpet, blankets, or hessian to keep warmth in.

Feed the worms more, it will create some warmth as the food decomposes.

Compost worms require moist conditions all year round, and do not tunnel deep to find moisture. They can only be useful in the garden if you have a thick layer of mulch in your garden.

You can never have too many worms. Worms self-regulate their population according to available space and the amount of food you give them.

Reduce your ecological footprint

Keeping a worm farm helps to reduce your ecological footprint as you reduce your organic waste from going in to landfill.

Approximately 77% of household waste going into landfill could be diverted. Composting and worm farming can remove over 50% and learning to recycle right can reduce it by another 19%.

Where to buy worms

Worms can be bought direct from commercial worm growers or through your local nursery.

They are generally sold by the thousand – 1,000 worms weigh about 250 grams.

How to make your own worm farm

 

Step 1: Choose a nice spot for your worms to live

Make sure the spot is not too hot or cold.

Step 2: Get two boxes

Old containers work well. They need to stack one of top of the other well.

Step 3: Make drainage holes

Make small holes in the bottom of one box to let liquid drain and place the box with the holes on top of the other box without holes.

Step 4: Make a tap

Make a tap in the bottom box to let the liquid drain out. Do this by poking a length of hose through one end of the box. Turn the hose upwards to turn the tap off.

Step 5: Make the bedding

Tear up some leaves, newspaper and cardboard to make a layer of bedding about 15-25cm deep. Compost or cow manure can also be used. Soak the bedding before it is added to the box.

Step 6: Add the worms

Add about 1,000 worms to the top of your worm farm. Spread the worms out gently on the surface and allow them to burrow down.

Step 7: Add food waste

Put your kitchen waste on top of the bedding regularly but in small amounts. Over time, as more worms breed, you will be able to give them more to eat.

Some things to remember:

• Don't add too much at once
• Do not feed worms meat, bones, fatty food or dairy products
• Worms may not eat raw potato – but they do eat cooked potato
• Worms don't like oranges, grapefruit and lemons, or raw onions or raw garlic
• Some food waste such as fruit, grains and sugary foods form acid. Adding a little wood ash,  dolomite or lime every few weeks will prevent the worm farm from becoming too acidic. Open the lid and wait until the worms burrow under. When you can't see them anymore, apply the lime or wood ash.

Step 8: Cover the worm bed

Cover the worm bed with newspaper or a piece of hessian. If you are able to get a lid with the containers, put this on too. This will help keep a constant temperature in the worm farm.

Add water to the box whenever it begins to get dry. It should be the consistency of a lightly squeezed sponge; if it is too wet the worms will die.

The worm farms should be placed in a shady spot in your garden or garage.

Step 9: Harvest the worm castings

Harvest the worm castings by moving it all to one side of the bin. Add fresh bedding to the empty side. Many of the worms will move to the fresh bedding in a few days. The valuable worm castings can then be taken out and used to feed plants, add to seedling mixes and potting soils.

In addition, the liquid which is called 'worm tea' that collects in the base or bottom container can be used as a liquid fertiliser, once it has been diluted. It should be diluted at about 1 part worm tea to 10 parts water. As your plants get used to the solution the strength can be increased.

Worm farm problems and solutions

 

Problem	Cause and solutions
My worm farm smells	Giving worms too much food or farm is too wet: Stop feeding the worms, add some garden lime and stir the top tray lightly to aerate the mixture. This will allow the worms to move through it more easily. Start feeding again when all smells are gone.
Flies around farm	Feeding worms too much or too moist: Sometimes small vinegar flies get into the system, however they will not do any harm. If larger flies are present slow your rate of feeding, or if too moist let it dry a little.
Unwelcome visitors? Ants and cockroaches	Too dry: Add some water to raise the moisture levels. Always keep a lid on the farm and keep a hessian/cardboard cover over the food scraps. Keep a lid on the farm or keep a hessian cover over the food scraps. To stop unwelcome visitors from getting into the farm, place the legs of it in a container of water or rub Vaseline on the legs.
It's raining and the worms are gathering in the lid?	Weather is changing: Worms move up into the lid before it rains to avoid drowning. Move the system out of the rain and replace the worms in the bedding
Maggots	Meat scraps: Avoid meat in your worm farm. To remove maggots place bread soaked in milk on the surface. The maggots will be attracted to it and you can remove them after a couple of days.
Worms leave	Don’t like food or soil that’s been added: If worms are not happy with their food or bedding they may climb out of the worm farm. Place another tray with a fresh food supply and some compost on top of the contaminated tray.Once the worms have climbed out of the contaminated tray (about a week) remove the offending food or soil, and use the castings in the garden. Never add soil or dirt as bedding. Only compost, manure or damp coir should be used as worm farm bedding.

Create your own compost

Composting is the accelerated natural breakdown of organic material by microorganisms. The resulting material can be used as an alternative to artificial fertilisers as it provides the full range of nutrients required for plant growth.

Compost can either be made in a pile or bin, depending on the amount of material for composting and the needs and size of your garden. A compost pile is useful for gardens with large quantities of greenwaste and a bin is often better suited to smaller suburban gardens. Compost bins can be purchased from your local hardware store or nursery, or you can make your own.

If compost is turned regularly, it should be ready for use in two to three months. By this time most of the ingredients have broken down into a balanced soil food.

How to make your own compost

• Choose a level spot in the backyard with some exposure to the sun, especially if you are using a smaller bin
• Always begin by using twigs or sticks at the bottom for proper aeration and drainage
• Then add kitchen scraps and garden waste to the top of the pile
• Keep the compost moist, and not soaking wet
• Turn it once a week if possible – this will speed up the process, ensure adequate aeration and reduce the likelihood of unpleasant smells
• After 3-12 months the compost will be ready to use. Dig it into new garden beds or spread it on top of established gardens
• The length of time it takes for the process to occur will differ depending on the material used for composting, the amount of air and water available and how often the compost is turned
• When your compost is finished it will have a fine, crumbly texture and a good earthy smell.

How to use compost

Your compost can be used in a variety of ways such as:

• An organic fertiliser for garden beds, providing all essential plant nutrients
• Surface mulch around shrubs and trees –the mulch should not touch the tree trunks
• A top dressing for the lawn – you may have to sieve the compost
• A potting mix for potted plants, using a ratio of 1:1 with garden soil
• To replace or improve lost and disturbed topsoil.

Green foods (nitrogen rich)

Aim to have about 25% of nitrogen rich (green) materials in your compost, including:

• Leaves (green prunings)
• Grass (green clippings)
• Cow, horse or chicken manure
• Fruit and veggie scraps
• Coffee grounds
• Tea bags
• Hair from your brush and comb

Brown foods (carbon rich)

Aim to have about 75% of carbon rich (brown) materials in your compost, including:

• Dried leaves and dried grass clippings
• Sawdust (not treated pine)
• Wood shavings (not treated pine)
• Hay and straw
• Vacuum cleaner dust
• Shredded paper
• Newspaper

What not to compost

Some organic waste items may encourage vermin such as rats, flies and cockroaches, and will smell when they decompose. Some items to avoid include:

• Fats and oils
• Meat products
• Dairy products
• Bread and cake products
• Cat or dog excrement
• Man-made materials such as plastic, steel, aluminium and glass

Maintain your compost

Once established, you should use the popular A.D.A.M principle of composting:

• A is for aliveness – when there are micro-organisms, bugs and worms living in your compost, it is working well.
• D is for diet or diversity – make sure there is a range of different materials in the compost, and in the right proportions i.e. 25% green, 75% brown.
• A is for air – turn your compost every week so there is plenty of air moving around. This reduces bad smells and helps the material break down faster.
• M is for moisture – damp but not wet compost works best.

Compost problems and solutions

Listed are some problems that may occur, the cause and some useful solutions.

Problem	Cause and solutions
Smelly compost	Material is too wet: Incorporate dry materials (e.g. leaves, straw, dry grass, torn newspaper or egg cartons) Cover pile to prevent infiltration of rain water. Not enough air: Turn the heap to improve drainage and aeration Incorporate coarse materials (twigs, prunings, leaves) Establish pile or bin on layer (10 cm) of coarse materials Increase aeration of compost pile or enclosure by using a perforated aeration pipe or by adding more aeration holes to compost bin.
Slow composting process	Too much woody material: Add more easily degradable green materials (grass clippings, garden plants, kitchen scraps) Incorporate appropriate amount of nitrogen-containing fertiliser (e.g. blood & bone). Material is too dry: Turn the pile and add water Place pile/bin in a shady location Cover pile to retain moisture Pile is too small to heat up: Increase size of pile to at least one cubic metre Cover pile to retain generated heat (e.g. plastic, hessian, old carpet).
White maggots	Food scraps: Do not compost these materials Cover the maggots with lime Add soil to cover food scraps Do not use an enclosed bin composting system.
Brown segmented larvae	Not enough air: These are soldier fly larvae, which are beneficial for the composting process However, they may indicate that there is not enough oxygen in the compost pile, which might result in unpleasant smells.
Small vinegar flies	Fruit: These are not fruit flies. Vinegar flies are harmless Cover fruit remains with other materials Do not add fruit remains.
Pile is too acidic	Addition of fruit over time: Add lime to neutralise naturally formed acids (sprinkle lightly) Turn pile more frequently and ensure good aeration.
Vermin	Easy access to food scraps: Use fully enclosed composting bin (e.g. tumbler) Put fine wire mesh underneath the pile/bin Cover food scraps with soil or garden remains Do not compost food scraps. Mice nesting in pile: Turn pile and keep it moist.

Grub composters

Grub composters use native soldier fly grubs to consume a household’s food waste.

Where bokashi bins rely on fermentation and can take a long time to break down your food scraps, soldier fly grubs can consume up to 2kg of food waste within 48 hours.

A garden composter, called a Compot, is available for recycling all of your food waste and works with the help of soldier fly grubs.