Composting using a compost bin is a low cost natural recycling system requiring little effort and knowledge. It reduces your waste disposal costs, the impact on our landfills and improves the condition of your garden soil.
What should I compost?
Virtually anything that once was alive can be put on a compost heap (kitchen scraps, grass clippings, garden weed tops, straw, chicken manure, seaweed, twigs, autumn leaves).
Any larger materials like broccoli stalks, corn cobs, deciduous shrub prunings, should be finely chopped first, or mulched by running over them with the lawn mower. If you prefer not to chop or mulch, larger bits of stalks and wood will still be visible after the composting. These can be further broken down by composting them again.
Evergreen shrub trimmings and pine needles do not break down very well and should be avoided. Large quantities of those can be composted separately, and make a type of compost useful for acid-loving shrubs. Similarly, avoid adding flax, cabbage tree leaves and persistent weed roots such as oxalis, dock, thistle and twitch/couch grass.
Citrus should be added only in moderation. It is a good idea to avoid materials such as meat, fat, cheese and fish, which attract rodents and flies (they can be put instead into a home wormery or Bokashi system, as an alternative to landfill).
Wood ashes from untreated, un-painted wood (and not coal) are fine, as long as they are several days cold and only added in moderate quantities.
What can I do with persistent weeds like oxalis or ginger?
Use a plastic rubbish bin or wheelie bin and put the material in, at intervals cover with water and put a lid on, then leave for 6 months, in which time the weeds will completely rot down.
Should I buy or make a compost bin?
There are many different styles of composting units available from hardware and garden stores and direct online from manufacturers. If you would like to buy a composter, decent models start at approximately $40 and range up to $150 for the basic bin types. A selection of bin types and prices can be found here.
While these units are handy for getting started immediately, home built composters can easily be constructed at home at low or no cost (depending on what materials you have available).
Cost saving tip – call or visit the Earthlink Store at 22 Eastern Hutt Road in Lower Hutt. Earthlink have a wide range of reusable items and recycled materials available at very low cost.
There are varied types of compost bins. They can be made of any reusable or recyclable materials you have access to e.g. concrete blocks, recycled wood (untreated wood), or treated wood (lined with plastic) or even made with wire mesh on a frame.
A popular construction material is untreated pellet wood. Untreated pellets (sometimes called banana pellets) are often available through super markets or where other freight intensive business is occurring (always ask first!). Whatever material you use, the design needs to allow for easy access to turn the compost material.
- For an effective and flexible home-made container, wrap wire netting around wooden stakes and line with cardboard or newspaper.
- Stronger bins can be made from wood, bricks, or concrete blocks. Holes for air and ready access from the front are necessary.
Where should I keep my compost bin?
Composting can be done right in your own backyard with your compost heap sitting directly on the ground. You’ll need:
- good drainage
- sheltered area
- a garden hose within reach
- a spot out of direct sunlight.
How do I make compost?
Compost making – five simple steps:
- Before positioning the bin, fork over the soil where your compost pile will sit to aid drainage and encourage worms. Ensure your bin is aerated through ventilation openings or raise the bin on a few brick.
- Place a layer of coarse twiggy materials (materials from a previous heap may be used) at the bottom of the bin to ensure good drainage and entry of air.
- Build a heap of alternating layers of greens and browns (50:50 ratio) to about 20 cm high. ‘Greens’ are nitrogen rich e.g. fruit, vegetables, lawn clippings etc. and ‘browns’ are carbon rich e.g. leaves, twigs, paper etc. and lightly compress with a fork. If materials are dry, lightly moisten. Optional: add a sprinkle of poultry litter to top brown layer, or animal manure. Seaweed, soil, or your own mature compost can be used if animal manure is not available. Alternatively, use a few handfuls of blood and bone, or sulphate of ammonia fertiliser, or a compost starter kit available from garden shops.
- Continue to build the compost heap with alternating layers, as material becomes available. When the bin is full, cover and leave the heap to mature.
- Turning once a month to aerate the heap and mix the decomposer organisms through the waste material. If you regularly turn the compost heap it will take three to four months to mature, but without turning it will take nine months to a year.
How do I use compost?
- When mature, spread three centimetres of compost and mix into topsoil. Any remaining stalky material can be removed and recycled into the base of your next compost heap
- Mature compost mixed with two parts topsoil and one part sand makes an excellent seed-raising or potting mix
- Compost gives newly-planted trees and shrubs a good start. Mix one or two buckets of compost into the soil prior to planting
Then sit back and relax and watch your garden flourish, knowing that nature’s recycling system is hard at work!
- Compost shouldn’t be too acidic. Try a light sprinkling of dolomite or lime every few layers
- To speed up the process, chop or shred materials into small pieces
- Aerate your compost regularly. Air is essential for odour-free composting
- Dampen your heap regularly in summer to maintain a consistency of a squeezed out sponge – moist but not soggy
- Compost is mature when it has darkened and has a crumbly soil-like material with a pleasant odour
- If offensive odours (such as “rotten eggs”) are produced, turn your compost heap to aerate
- The best compost needs the right mix of carbon (dry stalks or leaves) and nitrogen (green matter, fruit or animal manure). Use four parts of carbon for each part of nitrogen material
- The volume of the compost heap needs to be large enough to insulate itself in order to maintain the heat of microbiological activity. A cubic metre or slightly larger is sufficient
- Vegetable/fruit scraps or peelings
- Tea leaves
- Soft garden debris such as leaves, lawn clippings, weeds (if they have not gone to seed)
- Untreated wood ash, sawdust or straw
- Animal manures
- Meat, fish, fats or cooking/salad oils
- Wood, bones, tin, glass or plastic
- Diseased plant material
- Plant foliage with chemical sprays residue
- Weeds such as oxalis, live twitch, convolvulus, docks, dandelion
- Toxic material
Bokashi is a Japanese word, translated means “fermented organic matter” and is made by treating plant-based by-products with Effective Micro-Organisms (or EM). The by-products of EM suppress other harmful micro-organisms (a sterilising process) and enhance the decomposition of organic matter.While the system costs money to purchase and maintain, it is well suited to indoor applications with smaller volumes of kitchen waste (note: you must still have a garden or have access to a garden for the compost this system generates).Bokashi has been widely used by Christchurch residents after the earthquakes as chemical free emergency composting toilets.
Use the links in the Resource & Links section for more information.
Last updated on 14 Mar 2019