How to make compost


These compost bays were one of the first things we made when we moved into our house. They have removable timber slats on the front which make accessing the compost and turning the heap easier.

About 42% of all Australian household waste that ends up in landfill sites is food or garden waste. There it is buried with all the other rubbish and decomposes anaerobically, resulting in the production of methane (adding to global warming at 25 times the rate of carbon dioxide) and leachates that have the potential to contaminate groundwater and pollute waterways if not contained.

Most of this food and garden waste is valuable organic matter that instead of going to landfill can be composted at home and used to improve your soil and grow amazing vegetables. Recycling your own organic waste into compost is great for the planet and easy to do. Every home should have a compost bin; so here is some advice on how to make compost…

Firstly it helps to have something to make your compost in and contain it. There are countless compost bins and tumblers available on the market that can all make great compost if used correctly. As we have a lot of organic waste to process with all the food we grow, I prefer to use homemade composting bays made from timber and corrugated iron offcuts. We have two bays at home, but you can have three or four for a large household; at work we have twelve bays to process all the organic waste from the kitchen and garden.

So what can you put in a compost heap? Basically any organic material can be used to make compost. That said it is best not to add meat or dairy products to the compost as they can attract vermin. The best things to compost are; weeds (not with bulbs or runners), grass clippings, non-woody garden clippings, kitchen scraps, leaves, animal manures (sheep, cow, goat, chook, horse, but not dog or cat), shredded newspaper, hay, straw and even hair, vacuum cleaner dust and old cotton clothing. Other things you may want to add in small amounts are lime, blood and bone and rock dust.

A good mix of ingredients will have a carbon to nitrogen ratio of 30:1, but what does this mean? I like to think of this ratio as equal parts in volume of dry (usually brown) things to fresh (usually green) things.


Nitrogen rich ingredients


Carbon rich ingredients







Nitrogen rich ingredients include; fresh grass clippings, vegetable scraps, fresh animal manure, lucerne hay, weeds, garden clippings etc. While carbon rich ingredients include; shredded paper, dry grass, straw, autumn leaves, sawdust, shredded cardboard etc. As all the nitrogen rich ingredients also contain carbon, adding the ingredients from the two boxes in the photos above in in equal volumes, will give you a pretty good carbon to nitrogen ratio for making compost.

Hundreds of different types of microorganisms (mainly bacteria and fungi) go to work in your compost heap to break down your organic waste if the conditions are to their liking.   You don’t have to add them to the heap as their spores are everywhere. Their main requirements are the right C:N ratio, oxygen and water. If you have a compost heap of at least one cubic meter, the microbes will thrive and you will notice your heap getting warmer from the heat generated by the microorganisms as they feed. Ideally your heap will reach 60ºC at which point many weed seeds and plant pathogens die. You may need to turn your heap as it cools to kick start the microbial process again if your ingredients are not composted yet. You will also notice the volume of your compost heap decreasing by as much as 30-60% which is caused by the microorganisms consuming much of the carbon in the heap. If your compost heap gets too dry, add more wet ingredients or water your heap (particularly during summer). If your compost heap gets too wet (and it smells), mix through some dry ingredients and get the air back into the heap, it may also help to cover the compost heap with a tarp to keep the rain off.

When the microorganisms have done their thing your heap will start to cool and the worms will move in to finish off the process. Once your compost is ready it should have a pleasant earthy smell and you shouldn’t be able to distinguish the original ingredients. It is now ready to add to your garden beds. I love adding compost to my garden…it improves difficult clay soils and dry sandy soils, helps retain moisture and nutrients in your soil, improves soil structure, adds lots of beneficial microorganisms, it can stabilise the pH of your soil, add trace elements and combat harmful pathogens in your soil…what’s not to love!


Spinach plants love a compost rich soil.