When you need some happy thoughts to brighten up a cold winter day, I know what you think of—composting, am I right?
OK, so maybe your first thoughts are of spring lettuce and summer tomatoes and you’d rather be hibernating from the cold, but if you want your compost to keep, you’ll need to master composting in the winter.
Some people think you can’t start a compost in the winter, but that’s not true. You can start it just as easily as you would in the summer.
It’s the keeping of the compost in the winter that’s the challenge, for one reason:
- Compost needs to heat up to do the job.
There’s also one big benefit to composting in the winter:
- You don’t need to turn it. According to the extension program at the University of New Hampshire, you shouldn’t turn it because it will result in heat loss. Some people still do, but depending on what temps you’re in, you might be best leaving it alone.
A 2012 study compared four different types of composts to see which would perform better in frigid winter. Research showed that a 4’x4′ bin filled with 1 cubic yard of compost was the ideal amount of space and amount of material for composting. Too little material and it won’t get to temperature. Too much, and there won’t be enough air.
Bin #1 & #2 were constructed using an optimal compost recipe (C:N=25:1 to 35:1), moisture content (55-60%), and adequate porosity. They had a mix of “food scraps from the UNE cafeteria layered with leaves collected from campus clean-up activities during the previous year.”
Bin #3 was the control, using only leaves, mainly maple and oak with some pine needles mixed in.
Bin #4, like Bin 1 & 2, this bin had a mix of food scraps from the UNE cafeteria and leaves from campus, however it contained “approximately 38 percent more food residuals than Bins #1 and #2, was very dense and saturated at the outset.”
In the end, Bins 1 & 2 “were able to gain thermophilic composting temperatures early into the process (by week two), and sustain optimal composting temperatures independent of ambient temperatures throughout the study.” The optimal compost recipe (C:N=25:1 to 35:1), moisture content (55-60%), and adequate porosity kept the winter compost alive.
Bin #3 didn’t compost very much at all, and the leaves were all mostly still intact.
And Bin #4 had strong odorous emissions (likely volatile organic acids) emanating from the bin. “The odors, coupled with an inability to reach thermophilic temperatures, suggest that this bin had poor porosity and was operating anaerobically.”
My take-away from this study is that a winter compost can survive as long as there is balance, just like in the summer. Here’s how you can compost in the winter, with the worst-case scenario being that you need to empty your composter in the spring and start over.
How to Compost in the Winter
- Bring on the sunlight. If you have a compost bin you can move, find a sunny area outdoors that gets the afternoon sun. For more protection, use a tarp to insulate it, rather than bringing it indoors to a garage or shed where pests or bears will go after it. You can also create insulation by stacking hay bales around your composter for the winter. Make sure it’s set up on a flat surface.
- Prepare in the fall. You’ll need plenty of brown material for your compost (leaves, pine needles, straw, cardboard, paper) to use all winter, so it’s best to gather it into its own pile before the winter so you can add it as you need it. When your compost begins to heat up in the spring, you will also likely need extra brown material to keep the slime and smell down.
- Insulate inside the bin to layer it. The University of Wisconsin-Extension suggests leaving a hole in the leaf cover at the top of the heap. Then, when you have kitchen scraps, you can pour them into the hole, and pull in the leaves to cover as you go. This is by far the best advice I’ve ever heard.
- Create pockets. Like the study above, too much food or leaves left no room for pockets of air. In the summer this is important for airflow reasons, but in the winter its purpose is to help insulate the pile by creating pockets of heat. In the winter, woodchips and wood pellets are ideal.
- Compost in easy mode. It may be helpful to reduce the number of things you compost in the winter and shoot for the easiest scraps. For example, fruits and vegetables compost the quickest, whereas things like wood or crab shells take the longest. And when adding to your compost pile, try to break down your materials as much as possible. They compost more quickly and easily that way.
- Aim for 1 cubic yard of compost. In order to decompose, a compost pile needs to reach and maintain an internal temperature in the range of 140-160 degrees Fahrenheit. A small outdoor compost pile is going to have a hard time achieving that. A larger heap in a bin provides more insulation and pockets of air so your compost can stay nice and warm – even when you’re composting in winter. The 1 cubic yard suggestion is from the study above.
- Water your pile. The four components of compost are carbon, nitrogen, water, and air. Winter winds may very well dry out your compost pile, meaning you may need to add some water, but don’t do it before a big freeze. Check closely first, as you don’t want a soggy mess, but if your compost isn’t getting warm and the dry winter air has sucked all the moisture out of your pile. You may need to add a little H2O.
This all sounds like a lot, but here’s how it breaks down: Line your composter with brown material (leaves, straw, shredded paper, cardboard or wood chips – preferably a mix of all the above) leaving a hole for your food scraps, then shuffle a little brown matter over your scraps each time you add them. If you’re using a large bin, you can simply have brown matter next to the bin that you scoop in every time or every few times you drop off a scrap deposit. You’re generally aiming for a 50/50 split of brown/green material (green material is the veggie/food scraps but can also be grass clippings). The worst-case scenario is that it’s wet and slimy in the spring, which is pretty much to be expected anyway. Then you just add brown material to chill that out, and if it still needs work, you can let it dry out and get turning again until it’s ready for primetime.
Composting in the winter is a very slow activity. All those microbes that are working to break down the material aren’t moving a whole lot, so you don’t need to either.
Do you continue composting in the winter? What are your techniques?