Nelson City Council

Methods of composting

Bins

Before you choose to compost in the traditional form of using a bin, there are a number of points to consider before you buy a bin so that you get one appropriate for your needs.Click here for more information on home composting using a bin.

Worm farms

Compost can be produced using worms. This is known as worm farming. It is also called ‘vermiculture’ or vermi-composting.Find out more about composting with a worm farm.

Bokashi

Bokashi was developed in Japan and has a few benefits over traditional composting: you can add products typically discouraged in the usual compost process, it produces a compost product within 2-4 weeks after being buried, no space is required as fermentation takes place in a bucket that can be kept indoors as the smell is inoffensive. Read more about the Bokashi composting system, ideal for small houses, apartments and schools.  

Composting is cheaper by half

Composting kitchen and garden waste is a great way to halve the rubbish you send to the tip and save yourself money. You don't have to pay for as many bags, and your garden will thank you for the goodies by not needing as much watering and delivering a bumper crop of vegetables or flowers.  

Seven great reasons to compost

1. Mulching in the open air doesn't produce methane, a serious greenhouse gas (green waste in landfills rots anaerobically, without oxygen, and this is what produces methane)
2. Backyard burning of greenwaste is banned in urban areas
3. It enriches our soils by increasing organic material
4. It uses local resources instead of imported compost
5. It reduces weeds by disposing of them safely and slowing any re-growth
6. It provides local employment
7. It extends the life of the landfills by reducing the volume of waste  

Council subsidy available to all

Nelson City Council wants to encourage residents to compost instead of throwing scraps in the rubbish. Composting can save you money and your garden will thank you.

Council provides a $15 subsidy when residents purchase a compost bin, a worm bin, or a Bokashi bucket from approved outlets. The subsidy is not, however, available for worm purchases.

Download the compost subsidy coupon (454KB PDF) or call the Council on +64 3 546 0200 for a coupon.  

Getting 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, thin layers of green matter (nitrogen rich) and brown matter (carbon rich) preferably in layers no more than 5-10cm deep.

If you can’t be bothered layering, just make sure there is a mixture of green and brown matter in either your heap or bin. Smaller pieces make quicker compost– for quick compost, fibrous materials should be no bigger than the thickness of your finger (2cm).

Avoid cat/ dog/ human faeces, meat, fish, bones, oil and invasive weeds.

The heap or bin should have a cover, eg, plastic lid, underfelt, 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.  

Green and brown matter

Green matter - nitrogen rich, wet

• Food scraps
• Manure
• Fresh grass clippings
• Weeds without seeds
• Vegetable scraps
• Seaweed
• Tea leaves and bags
• Coffee grounds

Brown matter - carbon rich, dry

These are just a few examples:

• Torn newspaper / cardboard
• Egg cartons
• Tree prunings
• Dry leaves
• Bark, untreated sawdust
• Wood ash
• Twigs and sticks
• Crushed shells
• Straw 

Keeping it going

Compost activators or accelerators can be added to the compost 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 & 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 whether in a heap or bin – turn and mix it up to aerate and speed up decomposition. 

The final touches

Once an open heap is onemetre in height or your bin is full, 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 underfelt, 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 6-8 weeks. If it is never turned, it will be ready in 12-18 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.  

What not to compost

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

• Cat and dog faeces - can cause disease
• Meat, fish, oil, bones, fat - can attract rats
• Non-organics such as tin, glass, plastics won't break down
• Invasive weeds such as kikuyu, wandering willy, jasmine - could spread in or beyond your garden but they can be composted after being treated (read on about how to treat)
• Large amounts of pine needles or gum leaves - they are allopathic, they create an environment hostile to compost creatures
• Woody materials in pieces larger than the diameter of your finger - too slow to break down
• Diseased plants - disease may spread
• Bamboo, flax and cabbage tree leaves - not suitable for composting, bury in ground or take to transfer station 

Common composting problems

If you are having problems with your compost heap or bin, check out these common issues and solutions.

Problem: smelly, slimy heap

Cause

Not enough air
Too wet
Too much nitrogen

Solution

Turn heap
Add brown material

Problem: Materials are not decomposing

Cause

Heap too small
Not enough heat due to lack of green materials or water
Materials in heap are too large

Solution

Increase size of heap
Add green materials and water
Break materials down into small pieces

Problem: Pests attracted to heap (flies, cockroaches, rats, mice)

Cause

Wrong food added
Bin not rodent proof

Solution

Don't use meat/bones/fish
Bury food scraps in centre of heap
Rodent proof bin

Problem: Fruit flies

Cause

Heap is too acidic

Solution

Sprinkle lime on heap

Problem: Ants

Cause

Heap is too dry

Solution

Add water and lime

Problem: Other 'mini beasts' (worms, beetles)

This is not a problem - creatures are essential to the composting process!  

Invasive 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 Department of Conservation website.

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 2-3 months by which time the water will turn a green/ brown colour but it can be used as fertiliser for your plants. Then empty the solids into your compost bin.  

Types 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!

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 to be lifted)
• materials used in the making of the bin (ie some are made of recycled plastic)
• whether the bin is made locally

Buying a bin

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 2-4 people.

Worm bins are especially suitable for households with limited outdoor space and are designed to process kitchen waste, not garden waste.

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.

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, etc. 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: 

• www.digitalseed.com/composter/bins
• www.backyardgardener.com/compost

Questions and answers

How long do I have to wait until my compost is ready?

A well maintained compost bin will produce compost in 3-4 months in summer and up to 6 months in winter. However, it can take a shorter or longer time depending on the method, what goes into the bin, time of year and regularity of turning.

Do I need to add water to my compost bin?

If you keep your compost at about a 50/50 mix of nitrogen, materials which are wet, and carbon materials that are dry, it will be of a crumbly consistency and shouldn't need water. However, in dry conditions, keep an eye on our compost and add some water if it looks to be drying out.

How will compost help my garden?

Compost feeds the soil, helps with water retention and encourages earthworms into your garden. 

Ministry of Health Safe Gardening guidelines

• Minimise the amount of dust when working in the garden.
• Water gardens and indoor plants using a gentle spray.
• Read the warning label on bagged composts or potting mix. 
• Wear gloves. 
• Wear a dust mask so that any dust is filtered out before you can breathe it in. 
• Dampen potting mixes before use. Open bags of soil products slowly, away from the face, in a well-ventilated area.
• Make sure the working area (glasshouse, potting shed) is well ventilated. 
• See a doctor if you develop a flu-like illness which is worsening. 
• Wash hands thoroughly after gardening or handling soil products.

More information

If you would like more information on this or other forms of composting, download the handy Create Your Own Eden 'how to' guide for composting, worm farms, and Bokashi from the Create Your Own Eden website, or call Council on +64 3 546 0200 for a copy. Link to the Create Your Own Eden website to download the 'how to' guide to composting.