Cold composting, also known as slow or inactive, will break down yard and food waste, but at a slower pace than hot composting. Build your pile a little at a time with greens and browns, but be careful with what you add. It doesn’t get hot enough to kill weed seeds, diseases, or pathogens.

Cold composting requires little effort and makes compost within 12 to 24 months. It’s helpful to have two compost bins, so that when one bin is full, you can contribute to the available one.

What You’ll Need

• Compost bin – purchase one or make your own!
• Carbon-rich “brown” materials
• Nitrogen-rich “green” materials
• Water

How to Cold Compost

1. Set up the compost bin in a place that will be convenient to use and maintain. Place it near a water source so it is easier to keep the pile damp and at least 2ft from any buildings to allow air flow.
2. Make a thin layer of coarser brown material for the bottom (optional).
3. Layer browns and greens in the pile as you acquire them. Maintain a mix of two parts brown to one part green. Make sure your top layer consists of brown materials to deter pests.
4. Water the pile (if needed) as you build it so it is as damp as a wrung out sponge.
5. Turn the pile occasionally or not at all. The more often you turn it, the sooner your compost will be ready.
6. When your bin is full, stop adding to it and let nature do its work. If you have a second bin, you can start using this one for additional waste.
7. Check the bin one year after you stopped adding to it. Your compost might be ready to go! If not, check back in a couple of months.

Items to Add & Avoid

For best results, keep your compost pile vegan (plus eggshells) and leave out materials that will cause problems with the finished compost.

*BioBags and other compostable materials were recently banned from backyard and commercial composting sites because of the chemicals they contain.

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Reference:
UW-Extension Master Gardener Manual: Foundations in Horticulture
Ask Them Anything: Kompost Kids, Part 1 & Part 2