How to set up a cold compost system

Your Simple Gesture: Deep dive into how to set up a cold (slow) compost

Curious about composting, but don’t have a lot of time? Concerned with your waste output, but not sure it’s worth the effort?

Composting in any form has a huge part to play in reducing our footprint, with a whopping 8% of greenhouse gases heating the planet are caused by food waste. The methane caused by food waste and agriculture continues to rise, and by reducing the waste we send to landfill we can cut our contribution to this massively. Cold (AKA ‘slow’) composting, is ideal for those with a bit of garden space (your own or shared) with a clear patch of soil for the bin to sit, and is ideal if you have a larger amount of vegetable scraps. A bonus is once you are set up, there are no real associated costs with this system.

This simple and natural solution will cut what you put in the general waste bin in half (at least!), while creating a luscious compost to enrich your garden to grow your own fruits and vegetables. A circular system with minimal waste and so many benefits. You’ll never have to buy plastic bagged compost again!

Action Steps:

Setting up
  • Ideally start with two vermin proof compost bins and a compost screw.
  • Most garden composting bins have an open bottom. Before adding anything to your compost bins, ensure that you cover the bottom with wire mesh to stop the mice and rats from digging their way into the bin. Watch this video to find out more.
  • Once you have filled the first bin and your materials start to decompose, you can add your new incoming waste to the second bin.
  • A place that is out of the way
  • Not in full Sun
  • Away from tree roots
  • Sitting on soil

Place the bin onto the dirt with the wire base installed. Then build a foundation of good carbon materials (think sticks and leaves) to allow for good drainage and airflow.

How to feed your compost bin
  • While there aren’t any hard and fast rules, the key to good compost is diversity of materials and keeping the carbon (brown materials) to nitrogen (green materials) in balance. AKA your C:N ratio.
  • Keep in mind, the ratio may change throughout the year depending on the climate you are in. For example, in winter you might need to add more high nitrogen materials (eg. chicken manure) to kick start the composting process a little bit.
  • It is recommended to not add meat, dairy or cereal products, as they will attract vermin. When adding materials it is also better not to add too much material at once, but adding smaller amounts gradually.
What is green*
  • Fruit and Vegetable waste, tea leaves, coffee grounds, weeds without seeds, green clippings.
What is brown*
  • Leaves (chipped or torn up into smaller pieces), cardboard and paper (shredded), egg cartons broken up, straw.

*Equal amounts of green to brown up to 20 litres per layer. You may need to add a small amount of water when adding browns depending on the conditions.

  • The good microbes (aerobic) in the compost like the ‘goldilocks zone’ – not too dry nor too wet (Anaerobic AKA smelly).
  • The optimal moisture is 50%. Squeeze a handful of the bedding while looking for a drop between your fingers. If it flows out between your fingers, it is too wet, and if there are no drops at all, add a little bit more water.
  • For healthy, balanced compost, turn your pile once a week with a compost screw to keep your compost aerated. This is also a good time to check the moisture remembering that 50% is ideal for good microbial growth. If wet, add more carbon, or if too dry, add a bit more water.
  • Be careful adding moisture as most fresh greens or food scraps will have a moisture content of up to 70%.
Letting compost mature
  • When the bin gets to about 30cm from the top, leave to mature and start your second bin. Leaving the room on the top will allow room for air flow. Continuing to turn each week will also assist in keeping the system aerobic.
  • Monitor the consistency of your bin to decipher when your compost is ready to add to your garden*.

*Finished compost can be added to pot plants, but if you have excess, you can give the compost to family, neighbours or take it to your local community garden!

Extra Resources and Tutorials:


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