How to Compost in Winter

How to Compost in Winter

Even if you live in the snow belt you can still compost all through the winter — I did for 15 years in a homemade three-bin composter west of Boston. A good overview will show you the basics, such as proper materials, layering, air and moisture and, of course, what can and can’t be composted. Still, composting in bitter climates requires a few techniques.

Composting will continue, albeit slowly, as long as your piles are above freezing. If your piles are big enough, they will generate their own heat, but usually not enough. My piles certainly worked, so they were generating heat but it wasn’t until I moved to the Southwest that I realized how fast the process could occur.

So the secret is adding and conserving heat. Use as much solar energy as you can by orienting your bins to the south. Consider covering your bins with translucent plastic to capture the sun’s heat, but remember to add some water to the piles and provide some ventilation. You won’t be adding as many materials or turning the piles as much as you do in the growing season. 

People make compost in Alaska, but in a small glass or plastic-sheeted greenhouse heated by a light bulb. If you have cold frames (hot boxes) consider using one or more for compost; just don’t open the top except to add more materials and to ventilate once in a while.

I made mine by salvaging old storm windows and scrap plywood. I insulated them with one-inch extruded foam. If you are using worms to speed the process, a cover will keep them dry. Trench composting is another alternative, but not where frost penetrates deeply.

I tried a heating strip under my cold frames. It was too weak and used too much electricity. A 25- to 40-watt light bulb supplied more heat. Besides composting, the cold frames were great for an early start to the growing season and also for rooting plants such as some rhododendrons that required a long time and just the right conditions.

In cold winters, be resigned that composting will not happen very quickly. Then realize that, while winters are long in the North, with a little help you might lose only two months of good decomposition. If the pile is warm, it will keep composting going as the temperature drop. With a little heat, you can speed up the beginning in the spring.

Just keep in mind the advantages of good compost in the North: besides every other benefit, it helps plants take better advantage of those long growing days!