A Guide to Composting

Posted on August 12, 2009 by How-to Australia

What is Compost?

Compost is our version of the humus found in nature, and the compost heap is the tool used to produce it. Humus is made of broken down vegetation which releases nutrients back into the soil for healthy plant growth.

The composting process breaks down a rich mixture of ingredients to produce potent humus which will regenerate soil and foster vigorous plant growth.

Virtually anything which has once lived can be composted – although selecting the most appropriate mixture of ingredients which suits your situation is normally the result of experimentation and trial and error.

Compost Vs Chemicals

Strong and healthy plants have their own natural resistance to pests and diseases and compost is the natural, home grown, method of achieving this. Good compost added regularly to your garden will support healthy and rich soil – your plants in turn will thrive in this soil to produce healthy and nutritious food for you.

Chemical fertilisers bypass many of the natural processes used to build healthy plants and thus healthy food. This can create an imbalance in which weeds, pests and diseases are encouraged – which in turn then demands more chemical responses in the form of herbicides, insecticides, fungicides etc.

Turning Your Scraps into Fertiliser

Almost half of our domestic rubbish consists of kitchen and garden waste which can be composted. By composting it reduces the amount of rubbish we throw away, decreases our need for landfill sites and provides a chemical-free fertiliser for our gardens.

Composting is a cheap and hygienic method of converting your kitchen and garden waste into a clean-smelling material used in the garden as a soil conditioner or surface mulch. Properly controlled, it should end up as a dark, crumbly fertiliser with a pleasant, earthy smell.

Compost not only returns nutrients to the soil that would otherwise be lost, but also improves soil structure and increases the water holding capacity of the soil.

Getting Started – A Compost Heap or Compost Bin?

No matter which method you choose, your compost can sometimes be smelly when you turn it, so set it up away from your neighbours. Note: Two bins or heaps allows material to accumulate in one while composting in the other.

Compost Heap

A compost heap is useful for gardeners with large quantities of waste. It should be at least one cubic metre to ensure it reaches a hot temperature. The heap may be enclosed using bricks, chook wire or timber with an access area or work space at the front of the heap for turning the compost. It should be protected from hot sun and heavy rain to prevent excess drying or moisture, which prevents effective composting. A piece of carpet, hessian or plastic sheet will help retain heat and provide protection from the extreme elements.

Compost Bin

Many people choose to compost in a compost bin or tumbler. You may be able to seek advice from your local council regarding an approved bin or tumbler, which should be both fly and vermin-proof. There are a number of commercially available compost bins:

Plastic bins with ventilation holes.
Plastic bins without ventilation.
Metal drum with holes punched in the side and the base removed.
Rotating drum units (tumblers).

A compost bin is better for smaller, suburban gardens. Plastic bins and metal and plastic tumblers can be purchased from nurseries, hardware stores and some local councils.

You could also make one yourself using a 200-litre drum. Bins need a tight fitting lid on the top and should be open at the bottom. The open end is placed in contact with the soil to allow earthworms to enter. Worms speed the decaying process by loosening the compost and allowing air to enter and circulate. Avoid placing the bin or heap too close to houses. Consider placing it directly on level soil in a garden bed.

A compost bin and compost drum

Now What?

Compost works best if you add a balanced mixture of rapidly decomposing “green” material (e.g. fruit and vegetable scraps) and “brown” material, which decomposes slowly (e.g. twigs).

Once you have a mixture of materials (it does not matter in what order they are added), cover with a layer of soil, add some water and a lid to keep the heat in and speed the rotting process.

Composting matter should feel damp, but if it becomes waterlogged it will smell, attract flies and be inefficient. You can help control the moisture level by adding absorbent materials such as sawdust, newspaper, straw or dry manure.

Turning the heap regularly with a fork will help speed up decomposition. The more frequently the material is turned, the faster it will decompose. Care should be taken to ensure that all material is turned into the inner, hottest part of the heap where weed seeds and pathogens are destroyed. A regularly turned heap should be ready for use in a month or two.

A compost heap may be left unturned, but the process could take an extra six to twelve months.

What Can I Use In My Compost?

Most organic materials which decompose readily are suitable for use in a compost heap. For best results, chop or grind coarse material to help speed up the process.

Green

Aquarium water, algae, and plants (from freshwater fish tanks only) – adds moisture and a kick of nitrogen. Seaweed.

Chicken manure – has high amounts of nitrogen, phosphorus, and potassium.

Dead houseplants – adds a dose of nitrogen, but don’t include thorny or diseased plants.

Animal manure – Horse, chicken or cow manure. Note: Do not use cat or dog faeces as you can spread disease.

Kitchen waste – Vegetable peelings, leaves and stalks, fruit peelings and cores, cooked table scraps, tea leaves, coffee grounds, egg shells and stale bread. Make sure they are buried in the pile so they don’t attract animals.

Garden waste – Grass cuttings, non-woody garden pruning, leaves, flowers and vegetable remains. These should be mixed with plenty of drier, brown material, or you’ll risk creating a smelly pile.

Brown

Brown garden debris – such as corn and sunflower stalks, dried legume plants, and dried potato and tomato vines, adds bulk to the pile.

Hedge pruning and twigs help keep a pile fluffy but should be chipped first so they decompose faster.

Leaves are an abundant carbon source and full of nutrients. Stockpile them in Autumn so that you have them on hand in summer.

Pine needles decompose slowly. Add only small amounts to your pile. Use excess needles as mulch.

Straw bulks up a pile, but it should not be confused with hay, which often contains weed and grass seeds and shouldn’t be added to compost (unless you want to deal with the potential consequences).

So-So

Many items found in the average home are non toxic, biodegradable and come from a known source – but they aren’t great compost ingredients because they break down slowly, mat together, or don’t add many nutrients.

Newspaper and office paper – can be used in the compost pile if you’re desperate for brown materials, but must be shredded. It is better to recycle the office paper instead.

Cardboard – is best used for sheet mulching. Shred or chop it into small pieces if composting.

Dryer lint – may contain synthetic fibres that will never decompose. Even natural-fibre lint adds no benefit to compost.

Human and pet hair – can be added in small amounts, if you keep in mind that it breaks down slowly, mats easily, and sheds water.

Natural-fibre cloth – doesn’t add any benefit to the compost pile. Consider using mulch or wood chips to prevent weeds instead.

Sawdust – should be used in moderation, because it breaks down very slowly and can lock up nitrogen. Note: Never use sawdust from treated or painted wood.

Vacuum bags – may contain synthetic carpet fibres and other non biodegradable items.

Wood ash – adds potassium (potash), but it is an extremely alkaline material and should only be used in small amounts.

Wood chips – should really be used as mulch around ornamentals because they break down so slowly.

What Can’t I Use In My Compost?

Woody garden clippings – branches, roots (unless chipped), rose cuttings and other garden wastes with thorns or nettles, conifer pruning or pine needles.
Treated wood products.
Weeds with bulbs.
Diseased plant material – these should be placed in the rubbish bin or burned.
Septic tank sludge or toilet waste
Meat scraps (which can attract rats and mice) and diseased animal carcasses
Animal droppings – cat, dog and pig (including associated bedding) droppings can spread disease, may contain parasites or dangerous pathogens that are harmful to humans, particularly pregnant women, children, and people with compromised immune systems. Never add them to your compost.
Meats, dairy products, bones and fish decompose slowly, smell and attract animals.
Glossy magazines or paper.
Any waste that do not decompose – metals, glass and plastics.
Materials that kill the composting bacteria - fat, oil, salt, disinfectants, antibiotics, herbicides, pesticides, waste recently sprayed with pesticides.

A Healthy Compost Needs:

Water – keep the compost just damp. Over watering will ruin your compost.

Balance – add a mix of green and brown materials to make well balanced compost.

Air - turn the pile over every few weeks or every 4–6 days if using a bin.

Size - a compost heap will mature quickest if it is at least one cubic metre.

Micro-organisms - help break down the compost material. They come from the soil or old compost you add.

Troubleshooting Some Common Problems

Getting the right proportion of moisture and the right combination of ingredients in your compost may take a little practice, but most problems can usually be overcome.

Too wet – add sawdust or shredded newspaper to help absorb moisture. Turn regularly.
Not heating – add a source of nitrogen, such as animal manure, blood and bone or vegetable scraps. Some of the ingredients may need to be chopped up further.
Too dry – water lightly.
Fly or cockroach breeding – fully enclose the compost. Make sure the compost is hot in the centre and turned regularly to ‘cook’ fly and cockroach eggs.
Too hot – if the mixture goes grey and smokes, turn and spread it out to cool the compost down.
Smell – all compost releases some smell when it is turned. You can reduce the smell by keeping the compost damp but not wet. It may need to be aerated more often and if you can, add some dry straw.

How do I use my compost?

Compost is ready to use when it has a crumbly appearance, an earthy smell and identifying the ingredients is difficult.

Also see A Guide to Using Compost