Cold Composting: Step-by-Step Guide

1. Consider Compost Location

   If you have the space, composting in a shady part of your backyard or garden is very easy.

   You can cold compost on the ground or in a bin. If you have the space and don't want to spend any money, you can just make a pile on the ground. If you have more limited space or want to keep your compost contained, a bin with open sides is another option. You can also make a simple container of sorts out of a circle of woven wire fencing or chicken wire attached to itself at the circumference you'd like for your compost.

2. Prepare Your Composting Space

   Once you've chosen your location, you can start your cold compost. Start with bare ground and layer some brown material—leaves, small branches, dry lawn clippings, newspaper, or torn-up cardboard—to a depth of six inches.

3. Add Your Nitrogen-Rich Green Material

   On top of your brown material, add the compost you've collected from your kitchen, with more in the middle than at the sides. You can add 4-6 inches of green material on top of the brown stuff.

4. Keep Layering

   Add another layer of brown material on top of the kitchen scraps so it covers them to a depth of another 6 inches. Depending on how much of the green material you have, you could add a second layer here (and cover with more brown material) or stop at one layer. You should always end with brown material on top.

5. Wait and Aerate

   Since you're cold composting and not in a rush, you can pretty much just leave your compost heap to do its thing once you've covered it with a layer of carbon-rich brown material.

   Feel free to keep adding green layers and brown layers at the same ratio as above, about 2/3 brown to 1/3 green. Once or twice a week, add the green material in and cover with brown each time.

   Every week or two, turn the compost (before adding new green stuff layers) so that you ensure that plenty of air gets into the compost layers as they break down and compact.

   If it's very dry for a long period of time (a couple of months), or you live in a very dry place, you could sprinkle your compost with water to keep it moist and keep composting happening on a regular basis. You'll want to dampen it so it's similar in wetness to a damp sponge. But if you're OK with the compost taking a bit longer, you can skip this step.

   You can keep adding new material at the 2/3 brown - 1/3 green ratio until your compost bin is full or for about four months. After that, you'll want to either start harvesting your compost, start a new pile, or both.

6. Collect Your Compost

   After 4-6 months (how long depends on rainfall and air temperature), you should notice that your compost pile is the same size or smaller than when you started, even though you have been adding to it. Depending on the speed of the decomposition process it could be 70-80% smaller towards the end of the process. This means your materials have decomposed well.

   Now it's time to reap your compost rewards. How much compost you'll be able to remove from your pile will depend on how fast the compost has degraded, which in a cold compost is very dependent on local moisture and air temperature conditions. But if you are adding about a gallon of material to your pile every week, you should have at least 4-5 gallons of compost at the end of 6 months.

   Compost should look like a dark brown, crumbly material that smells good and moist. There shouldn't be any pieces of what you composted that are recognizable.

7. Use Your Compost

   You can use compost as a soil amendment when repotting houseplants or mix it 50/50 with potting soil when starting seeds. The best time to add compost directly to the soil of a garden bed or container is before planting in the spring or after harvest in the fall.

   You can also add it to the soil when you are planting trees or shrubs, or directly into the beds as you plant annual or perennial flowers or bulbs. You can also use compost (especially if it's not 100% finished breaking down) as mulch to keep weeds down, while simultaneously nourishing the soil as it finishes breaking down. You can even use compost on your lawn in the spring or fall.

Frequently Asked Questions

How long will cold composting take?

You should get compost in 4-6 months, but this is based on average temperate conditions. If you live in a place where temperatures are over 70 degrees for most of the year, your compost will keep going at a steady pace and will happen faster. If you live in a place where days are warm but it freezes easily at night, or it's freezing during the day and the night, the process will be much slower since freezing conditions mean bacteria and microorganisms don't do much work. But moisture also plays a role. To answer this question successfully for your local area, it's worth contacting your local agricultural extension.

Can I convert to hot composting if I've started off cold composting?

Yes, you can switch from one method to another (and back again) as your time, energy, and interest waxes and wanes. Hot composting simply requires more monitoring, care, and attention, so if you have started a cold compost pile, you can switch to hot if you want to—they both work with the same materials and similar quantities.

How do I know my cold compost is really breaking down?

Keep an eye on the bottom of the pile and the size of your compost pile layers. You will know they are breaking down (even if slowly) if, over 4-6 weeks, they decrease in volume. A layer of dark brown compost will develop at the bottom of the pile even before you are ready to harvest it as the first layers turn to compost while you are still adding new compost on top.

What can I do to speed up my cold compost?

If you add water (not too much, but enough to make it like a damp sponge level of moisture), and if you keep your compost under a tarp, which can warm it up, both of these may help speed up composting. Just be sure that it's not getting too hot under the tarp—remember your compost pile shouldn't be in the sunshine. Your bacteria and microorganisms will die at temperatures over 150 degrees.