How to build a compost heap

Alternate layers of carbon-rich ‘brown’ materials—straw, hay, dried leaves, sawdust and shredded newspaper and shredded cardboard—with layers of nitrogen-rich ‘green’ materials—animal manures, grass clippings, fresh leaves, prunings, tea bags, coffee grounds, and vegetable and fruit peelings.

Don’t compost meat, grease, cooking oil, dairy products, dead animals, pet faeces, diseased plants or plant material that has been treated with herbicides or other chemicals.

Don’t compost invasive weeds that are going to seed. Although a hot compost heap will kill most seeds, it’s best to be on the safe side and throw them out.

Use a shredder to chop up leaves and thick prunings before adding them to the compost heap. Shredding helps to increase the surface area of the materials, making them more accessible to decomposing agents.

Don’t use packaged compost ‘accelerators’ or ‘activators’—they usually give a quick fix of nitrogen that won’t last long and is of little benefit. Instead use organic sources of nitrogen such as grass clippings or manure.

Add manures such as horse, cow, goat, pig, sheep and chicken, but avoid dog and cat droppings, as they may contain pathogens or wormicides.

Age manure before adding it.

Boost your compost by adding a few shovelfuls of finished compost from the previous heap. Manure and comfrey leaves are also good boosters.

Or add an infusion made from 1 kilogram chopped nettles and 10 litres water, turning the heap with a spade or fork to add air.

1. Turn the heap regularly—at least once a month, but more often to accelerate the process.

2. Don’t let it get too wet or too dry—it should be about as damp as a wrung-out sponge.

3. Don’t add too much of any one material, or decomposition will slow down or stop.

4. Keep a balanced mix of brown and green material.

5. A good-sized heap generates enough heat for decomposition to occur. However, if it is too big, you won’t be able to turn it properly to aerate it. The ideal size is about 1x1 metre.

Most biodegradable materials can be put into the compost heap, but careful screening of scraps will make for better results. The greater the variety of ingredients, the better the compost. For best results, chop up coarse materials.

 What to put in:

✔ Fruit and vegetable peelings and cores—great for getting compost started

✔ Cooked table scraps

✔ Coffee grounds—supply proteins and oils

✔ Tea-leaves and unbleached tea bags—add welcome nitrogen

✔ Old bread

✔ Eggshells

✔ Shredded newspaper—in small amounts

✔Wood shavings, sawdust or fire ash

✔ Household dust and hair

✔ Garden waste—leaves, nonwoody prunings, grass

What to leave out:

✘ Fats and oils

✘ Meat and bones—take too long to break down and can attract pests

✘ Citrus peel—fine in small quantities, but contains a preservative that can inhibit decomposition

✘ Corn cobs—take too long to decompose

✘ Salt

✘ Anything that has been treated with chemicals

✘ Weed seeds

✘ Diseased plant material

✘ Dog or cat faeces