Adding food scraps to winter compost pile

If you live in a cold climate, the metabolic activity in your backyard compost will inevitably slow down in the winter. Bacteria and fungi break down your organic matter, but they will be much less active as the temperature dips below freezing, especially for long periods. It’s even possible for your compost pile to freeze solid, although you can always resume its activity in the spring. However, you may be able to keep your compost pile actively digesting material, even in frigid weather.

To achieve this, it’s critical to plan ahead in the fall by taking advantage of the plentiful brown materials available and creating suitable conditions in the winter months to keep those microbes happy. Follow these simple tips to keep your kitchen scraps and yard waste decomposing all winter.

Start With a Healthy Compost Pile

The best way to have a somewhat productive compost heap in the winter is to start with one in the fall. Our composting cheat sheet has all the basic information you need to start and maintain a healthy compost pile free of offensive odors. The three most important things to create healthy compost are the right balance of green and brown inputs, enough air to provide oxygen to the microbes, and the proper moisture level.

Green inputs are nitrogen-rich and include food scraps, manure, and grass clippings. Brown materials, such as dead leaves, dry pine needles, and hay, are rich in carbon. The ideal ratio is about 1:1 or a bit heavier on the browns, but opinions vary on this topic.

Although the brown material helps trap air pockets, turning your compost pile about twice a week is critical. You also want your pile to be moist but not waterlogged.

If your timing was off for getting your backyard compost pile in good shape before winter, you can revive it in the spring. Simply restore a healthy brown to green material ratio, maintain a healthy moisture level, and stir the pile twice a week.

Bulk Up Your Compost for Winter

In the fall, it’s helpful to add some mass and an insulative layer because you want your pile to be as warm as possible. If your backyard compost is too small, it will freeze solid more easily when the temperature dips, ceasing metabolic activity.

The larger the compost pile, the more thermal mass it will have, plus it is easier for it to maintain ideal moisture levels. For most people, the easiest way to bulk up a compost pile is to add layers of leaves or hay in the fall. Some composters add a six to 12-inch insulative layer of leaves, sawdust, or woodchips around the inside of the compost bin, which is an especially good idea in very cold climates, such as hardiness zones 1, 2, or 3.

Don’t Turn Your Compost Pile All Winter

When temperatures dip below freezing, do not turn your compost pile. The microbes generate their own heat as they break down your kitchen scraps and yard waste, which is good. Stirring the compost in the cold winter months is counterproductive because it will result in heat loss. Instead, wait until the spring thaw to resume turning it.

Cut Up Your Kitchen Scraps

It’s beneficial to add kitchen scraps and brown material all winter long. However, as a general rule, smaller inputs break down faster. So, although you can get away with putting larger pieces of organic material in your summer compost, it isn’t a good idea in cold weather.

If you put big pieces in your winter compost pile, the microbes don’t have the proper conditions to break it down, and activity slows. Avoid putting any material larger than an inch cubed into your compost during the colder months.

Keep Brown Materials on Hand

It’s tempting to just dash out to your compost pile in the winter, add your kitchen scraps and run back into the house. However, adding some brown material is always helpful, even in below-freezing temperatures. Therefore, keep some brown materials on hand, like a pile of dead leaves or hay.

Consider an Indoor Composting System

Another approach is to start an indoor vermicomposting system that relies on worms to decompose your organic waste. This is also ideal for apartment dwellers and others who don’t have yard space for a compost pile. For an indoor worm composting system, you’ll need a bin with holes in it, bedding material, and red worms.

Another indoor option is an electric composter, which requires electricity so it isn’t the greenest or thriftiest option. These composters can also be costly; however, the convenience of an electric composter may be worth the expense for people who don’t have other options.

Although it may be discouraging to see your backyard compost pile slow down in the winter, this is inevitable as temperatures dip. However, if you follow our tips, you can keep your microbes active throughout the winter. To make it easier on them, prepare your compost pile in the fall and feed it smaller pieces throughout the winter mixed with brown materials. Avoid turning it, and consider adding leaves or wood chips to insulate it from the cold.

By Sarah Lozanova

Sarah Lozanova is an environmental journalist and copywriter and has worked as a consultant to help large corporations become more sustainable. She is the author of Humane Home: Easy Steps for Sustainable & Green Living, and her renewable energy experience includes residential and commercial solar energy installations. She teaches green business classes to graduate students at Unity College and holds an MBA in sustainable management from the Presidio Graduate School.