When added to your garden, composted material promotes soil fertility, moisture retention, and encourages plant growth. However, when organic material is disposed of in landfill it decays to produce leachate and greenhouse gases such as methane that need to be contained and managed.

What is compost?

Compost is very different from the material that it is made from. It is free from unpleasant odours, is easy to handle and will store for long periods of time. It is a natural plant food, soil conditioner and mulch, it adds organic matter to the soil and encourages soil life and earthworms. Composting provides the gardener with an excellent material to enrich the soil.

Why compost?

Composting makes good sense. It is a simple, cost-effective and natural way to recycle your kitchen and garden waste. It will reduce the amount of waste you send to landfill. It's a great way to participate in a recycling programme that is helping to create a better future for us all.

Materials you can compost

Materials you can compost come in two categories: 

• Greens – kitchen vegetable and fruit scraps, vegetable peelings, tea leaves, coffee grounds, soft garden debris, lawn clippings. 
• Browns - paper, sawdust, straw, leaves, cereal boxes, cardboard, napkins, tree clippings, woody materials such as cabbage stalks.

Both kitchen and garden material will compost much quicker when chipped, chopped or crushed into smaller pieces. Napkins, paper and cardboard are best ripped into small pieces and soaked in water prior to composting.

Materials you shouldn’t compost

• Meat, fish, fats or cooking /salad oils (these may create odour and fly problems). 
• Wood, bones, inert materials (such as tins, glass or plastic), or diseased plant material. 
• Plant foliage with residue of chemical sprays, especially hormone type weedkillers. 
• Oxalis and other problem weeds such as live twitch, convolvulus, docks and dandelions. 
• Toxic material in general.

The compost recipe

For peak efficiency, you need a good balance of the basic four ingredients:

Types of composting systems

Whether you are in a flat, townhouse or have a large section, there will be a composting method that suits you.

Bin or container composting

Making compost in a bin or container is a tidy way to make compost. You can often make the container yourself at little cost. Alternatively, there are a number of commercially made compost bins that are available at garden centres or hardware stores. These include plastic and wooden units and also compost tumblers.

Locate your compost container or bin in a sheltered, level area of the garden that has good drainage and access. The site should be within reach of a garden hose, and preferably not in full sun. The compost heap should sit directly on the soil.

Making compost in a bin or container

• Before positioning the bin, fork the soil on the site to aid drainage and encourage earthworms into the heap. If you are using an enclosed container it may be necessary to raise it up on a few bricks.
• Always start with a layer 100–150 mm of coarse material to ensure good drainage and ventilation. Coarse, partly decomposed materials from a previous heap can be used. 
• Throw in a bucketful of ‘greens’ a bucketful of ‘browns’. Add a little water as you go if the materials are dry. Mix, stir and fluff after every few additions for a hard working compost stew. The compost needs to be moist and should maintain a consistency of a squeezed out sponge. 
• Within a day or 2, the heap will heat up and start to shrink. This is the start of the composting process. 
• Continue to build the compost heap to the required size as materials become available and then cover with soil or plastic sheeting. If using a bin, when the bin is full, cover it with straw, soil, old sacks or similar materials. This helps to retain the heat and keep out flies. Finally fit the lid and leave the compost to mature. 
• Start another bin or heap. Three bins are ideal so that you can turn the compost into a new bin.

Turning compost

Decomposition takes time. Turning the heap is not essential but will speed up the process.  Composting takes about 3–4 months if the heap is turned. However, if it is not turned, allow up to 9-12 months for the compost to mature. For optimal results, turn the heap once every 4-6 weeks. This will aerate the heap, expose fresh material for more rapid decomposition, redistribute the decomposer organisms and allow you to add water if required.

Using your compost

Your compost can be used at any time of the year but for best results it should be dug into the existing soil in the autumn or spring. Dig the compost into the top 50-100 mm of the soil surface to improve soil texture, structure and fertility. If the compost is quite coarse it may be necessary to sieve it through chicken netting prior to use. Any woody material removed can then be recycled into the next heap. 

Trench composting

If you have the space, trench composting is a great composting method which involves less work but takes longer to mature, taking from 6 months to 2 years depending on the nature of materials used, climate and aeration conditions.
Compost made in this manner will still heat up at first, but not the levels of hot composting. Although this means that it fails to kill most pathogens and weed seeds, this will not be a problem if you do not compost diseased plant material or weeds that have gone to seed.

Advantages

• One of the simplest forms of composting.
• Can rapidly improve poor soils, especially sandy ones. 
• Allows you to add materials a little at a time. 
• Can encourage earthworm activity.

Disadvantages

• Requires a relatively large garden area.  
• Slow rate of decomposition due to tendency to form pockets of anaerobic activity.  
• Possibility of temporary nitrogen deficiency if planted over too soon.  
• To optimise this method, you need to balance carbon and nitrogen as well as wet and dry materials as you go.

Getting started

Dig a trench 300-450 mm wide and one spade depth (about 300 mm) and the length of your garden row. Mound the excavated soil along the sides of the trench. Place weeds, leaves, twigs, lawn clippings, kitchen scraps, etc in the trench plus a little manure if available. Sprinkle garden lime on top and cover lightly with topsoil. It is a good idea to have a supply of dry high carbon materials on hand to layer in with lawn clippings and/or kitchen organics. Water is usually not necessary unless materials are very dry. Continue this process until the row is finished then leave for about 12 months before planting over.
To avoid vermin or pets digging up the compost, do not bury meat, fish, or cooking/salad oils as these may create odours.

EM bokashi (great for apartments and small spaces)

The EM bokashi system is great for those with little space to develop a large compost system. The micro-organisms break down food scraps and at the same time neutralise odours and produce a liquid fertiliser. The solids left can be dug into the garden. It is the most effective methods of composting kitchen waste

What is EM bokashi?

EM bokashi is a bucket composting system using Effective Micro-organisms (EM) as an inoculant or compost starter. Bokashi is a Japanese term that means “fermented organic matter”. It is a bran-based material that has been fermented with EM liquid concentrate and dried for storage. EM bokashi is a pleasant smelling product which you add to you bucket which aids in the fermentation of the organic matter. Always store EM bokashi in a warm dry place and out of direct sunlight e.g. a kitchen cupboard.

Where can I get EM bokashi and find out more?

EM bokashi can be bought in various locations in Canterbury. For information on where to buy EM bokashi in your district see Bokashi NZ  or visit the Christchurch City Council website.

Composting at transfer stations

Green garden waste that has been separated from other waste can be dropped off at most transfer stations in Canterbury for composting.  In some districts, green waste and / or food waste is collected from your kerbside.

See our Waste Facilities section for information on the composting services in your district