Building Your Compost


In the Natural world it is the composting process which builds soils. Organic matter such as leaves, dead trees, animal bodies etc. are broken down by a range of microorganisms particularly bacteria and Fungi. The microorganisms involved in the composting process are aerobic, and it is very important that plenty of oxygen is introduced when you make your compost.

I liken building compost as being a little like building a fire. Think of the carbon material as the fuel and the nitrogenous material as the heat. If you have ever had trouble getting a fire to keep going you would probably have spent a bit of time with the door a little open to introduce more oxygen, compost is very similar. The main difference here is that compost does need water as even our tiniest creatures need water to work and multiply.

Composting can get very scientific for those who are wanting to create fungally dominated composts for example. For those who want to get more involved in the process there is a range of reading material around but the best information I have found are you tube clips by Elaine Ingham….Well worth watching.


Your compost can be something which you make in one go after gathering all your ingredients (hot composting) or made over time in a bin (cold composting) Bins, frames etc. are mainly there for convenience and to keep things tidy but aren’t necessary.  Building a hot compost without a frame does make the job a little easier as you are able to move freely around the pile to distribute material.

Your compost works best at around a metre wide by a metre high. Smaller than this and your compost has to large a surface area and will lose heat, too big and the heap is at risk of becoming anaerobic. The heap can be as long as you like (I have seen a horseshoe shaped compost several metres long built by workshop participants)

The process of building a compost whether hot or cold is the same building up layers of ingredients rather like a lasagne. A good compost will have a carbon to nitrogen ratio of about 70:30 very similar to a fire which needs a lot of the carbon to burn but very little heat (nitrogen) to get it going. Different materials will contain different ratios of carbon and nitrogen. As an example Horse manure is mainly used to add nitrogen but does contain small amounts of carbon whereas chook manure is very high in nitrogen with little or no carbon. Grass is a good example of changing ratios. When it is fresh and green it is a high nitrogen source as it dries out much of the nitrogen is lost and it becomes a predominantly carbon material.

As you build your layers keep this ratio in mind but don’t get too caught up in the detail. Starting with sticks on the bottom will help with aeration of the heap. Add a small layer of nitrogen after each layer of carbon and don’t forget to water as you go. Mixing your manures with water as a slurry will help with the moisture of your heap as well as the distribution of the material. The mistake that is often made when building a freestanding heap is they often end up dome shaped. If this happens you will end up with something smaller than the recommended 1 metre x 1 metre. Try to pull the materials out to the side as you go to keep them straight.

The same layering principles can be followed when building a cold compost.  Have a bin or area for storing of carbon or nitrogenous materials to add each time you put material in your compost bin.








Cardboard and paper


Dried grass clippings


Animal manures (poultry, cow, sheep, horse)
Fresh cut grass


Fresh green weeds and leafy material

Food scraps

NOTE:  These are the main ingredients that the average household would use. All your food scraps are compostable some are just not as palatable to your microorganisms and worms i.e. citrus and onion skins. If you have large amounts of these or want to dispose of meat scraps check out the information on Bokashi. This works well in combination with composting too as you can put the end product of your Bokashi in your compost.


If you have built a hot compost you will know if it is working within about 36 hours because it will get quite hot. Ideally you don’t want it to get over 65c , but as most of you will not have a temperature probe , if you can keep your hand in the pile for about 30 seconds your probably on track. You will probably notice the pile drop quite a bit in the first week …a good sign. Once your heap starts cooling down you could turn it to introduce oxygen and heat it back up. But this is not necessary and just means the composting process will be a little slower (some suggest that a slower compost gives a better product)

Is your heap not heating up…..How does it feel, Cold, dry, wet, does it smell. A cold wet compost possibly means there is not enough oxygen. This could mean you didn’t put enough carbon in your heap, or added too much water. A dry heap on the other hand would suggest too much carbon and maybe not enough water. In either case turn your heap adding the missing ingredients as you go.

Smelly compost can be caused by anaerobic conditions as above or too many food scraps (which can have the same result) if putting in a lot of food scraps add a little lime with them.


Compost maturing in a pallet bin