Editor’s note: This article has been updated from its original text.
In the autumn, the urban composter may look at the remains of their garden and wonder if they should let their compost go dormant over the winter. This would be an easy thing to do, but you still produce kitchen scraps even when winter has come.
Keeping the outdoor compost active year-round has a range of benefits: it will produce fertilizer for planting in the spring; it can handle more than most indoor systems; and it can even act as a secondary heat source for a greenhouse. To keep compost active over winter, especially in the cold climates, the key is preparation.
Some basic winter composting preparations
Keep adding carbon
First to remember is that the compost has to be fed the right balance of green (nitrogen) and brown (carbon) ingredients. Green scraps will be produced in your kitchen over the winter, but most of the brown matter such as dried leaves, straw and plant debris, will have been produced in the fall. Gather the fall leaves and bag them, or put them in a dry place near the compost, to balance the green scraps that are added through the winter. Bear in mind that slightly more brown matter is needed to balance the green added to the compost.
While leaves can be a great carbon source for the compost, and more are needed for winter composting, there can be too much of a good thing. That is why a separate leaf compost can be set up.
To start a leaf compost pile, gather together the leaves and layer with dirt: use one layer of dirt for each foot of leaves. The pile should be about 4ft in diameter and 3ft deep. Make sure it is damp enough that a drop or two can be squeezed out of a handful from the center of the pile. Cover with plastic, weighing down the edges with rocks. Try not to compress the leaves. The compost will be ready when it is dark and crumbly, in about five to six months. This compost is not for fertilizer, as it really does not have many nutrients in it; but it is an excellent organic addition to soil.
Insulate the active compost
Even in the coldest weather, the microbes in the compost must be kept active. This means making sure they stay warm. In preparation for this, harvest the finished compost in fall to make room for new additions to the mix over the winter. Use it in houseplants; spread it over the lawn, over the gardens and around shrubs. When overhauling the compost system, move the bin into the sun for the winter or into a warmer part of the yard. Be realistic when choosing its location, considering what it will be like to add kitchen waste in heavy rains, wind or just plain cold temperatures. Start rebuilding with a layer of leaves, or with straw, cardboard or sawdust. Put the active part in the middle, and then cover it with more brown matter. This insulates the active compost.
Monitor the moisture
In milder climates, insulation is not so important in keeping compost bacteria active, but there may be other challenges. In cold, rainy locations such as California’s Bay Area, coastal Oregon and Washington State, it is moisture control that’s most important in maintaining active compost through winter. This can be difficult with a pile system, as the rain soaks into the ground and is taken up by the compost. Keep compost piles well covered to prevent the rain from directly falling on the pile.
Compost tumblers are sealed units so rain is not a problem. However, even a sealed composter can be too wet inside during the winter months. This is usually due to a shortage of carbon materials to absorb the moisture from nitrogen materials such as kitchen scraps. High humidity also contributes to excess moisture since most composters are aerated. Add carbon materials such as peat or dry leaves which absorb moisture, and open any drain holes in the composter. To learn more about restoring a wet, inactive compost, read our article How to Fix a Soggy Compost Pile.
The American South varies as to the composting needs in places. In Florida’s semi-tropical climate, residents will find that winter composting is much the same as summer composting. Texas, on the other hand, can provide challenges depending on where in the state the compost pile is located. With its near-desert conditions, West Texas can present a challenge in the summer; but on the Panhandle, which is the Great Plains, the incessant winter wind and blowing snow make moisture control imperative. Check the compost when adding scraps, making sure that the wind has not dried the compost out. This also applies in Washington State, east of the Cascades, and through Montana and the Dakotas.
Composting in the desert can present its own problems. In winter it is a good idea to mound the compost, then make a crater in the top, to catch what rain there is. To make the most of catching the water, a 1-2inch pipe with holes drilled at regular intervals can distribute moisture more deeply into the compost.
The different composting methods have different procedures for overwintering the compost. In essence, they are all about controlling temperature and moisture.
Here’s a look at the basic composting methods and how they can be used to provide compost through the winter months.
Compost tumblers are the most efficient closed-bin systems and make year-round composting relatively easy. A composting tumbler is a bin on a support, so it can be spun to mix the compost. The tumbler has some form of aeration, such as vents, spikes or a perforated tube running up the center for airflow. Its self-containment makes it easy to move, and the dark color helps keep the tumbler warm. Continued feeding with both green and brown matter can keep the bacteria alive and working.
The good part, besides the above, is that wildlife cannot access the scraps put in these containers. Tumblers keep the compost contained, all in one place, and odor-free for city dwellers. Composting tumblers are also called batch composters, as they break down one batch at a time. Some models have dual compartments so one batch can be added to while the other matures. Because they are contained and elevated from the ground, compost tumblers are the easiest way of keeping compost active through winter.
Another closed-bin system that is inexpensive is the ‘compost digester’, or standing compost bin. These are usually open-bottom bins which sit directly on the ground. Materials are added from the top and finished composted is removed from the bottom, commonly through a sliding port. Turning the compost is not really feasible since there’s little room to work a pitchfork, so this means it can take months to produce finished compost.
To overwinter a digester bin, add plenty of dry materials such as leaves, thatch, or straw in layers whenever you add food waste or moist materials. The core of the composting mass should remain active through the cold months. If you empty the bin in the fall, move it to a sunny spot for winter, and insulate it during cold snaps.
Compost bins are available in small sizes, and are good for a city dweller with just one or two people providing the scraps to compost. Digester bins are good for continuous composting, and they’re able to handle a wide range of scraps. They are ideal for the homeowner who just wants to toss in their scraps and harvest compost when it is needed. They’re also convenient for the gardener for tossing in shrub prunings and plant skeletons from the harvested vegetable garden.
Compost piles are the simplest composting system, since most organic material left on the ground will eventually compost. To begin a compost pile, start the pile on the ground with a bottom layer of sticks, twigs or straw in order to aerate and to allow earthworms and bugs to climb up. Add compost in layers, starting with green from kitchen scraps, grass clippings and so on, and then brown from dried leaves, sawdust, straw and wood ash. To really jumpstart a pile, find horse or steer manure to get it going. As with the other composting systems, keep it moist, and turn using a pitchfork to aerate. Cover the pile with a tarp to keep the rain out.
Overwintering with a compost pile can have its drawbacks. Even if the pile is kept covered with a tarp, ground moisture can wick up into the pile and slow the composting process. The tarp or cover must be removed each time new materials are added, which can become tedious during periods of snow and freeze-ups. And raccoons, rodents and domestic pets can and will burrow into the pile in search of anything edible among your latest contributions.
Even though it’s usually a messy affair, a compost pile can be maintained through winter. With a dark tarp and generous insulation using straw, newspapers or leaves, the bacteria may remain active except during the coldest times of year. In spring you can shovel through the pile and find plenty of ready-to-use compost at the bottom.
In all but the most active composters, insulation will be needed to ensure the compost remains active through winter.
Insulation can be as simple as cardboard, straw or brown leaves covering a compost pile, or as complex as a shelter built and insulated around a bin. A tumbler system can be moved into a garage, greenhouse or shed for added warmth and protection from the wind. A digester system can have straw bales stacked around it, or a small structure can be built and stuffed with insulation between the box and the bin.
In maintaining the active compost, snow may not be the problem it seems. Snow is a very effective insulator. Look for ways to reduce the wind chill factor, such as locating the composter on the lee side of a building, fence or natural feature.
Indoor methods of composting
Why would anyone want to brave cold and snow just to take scraps out to the compost? Fortunately, there are ways to deal with waste materials over the winter without having to face the winter head-on. One solution is an insulated sealed composter that sits in a corner of the garage. A sealed composter with proper balance of carbon and nitrogen components will not emit any composting odors.
Another method is worm composting, or vermiculture. A Worm Composter is efficient, odorless and can be kept indoors. There are those who may not want to have a worm compost system in their home, for various reasons; however, worm composters can also be kept in the garage or outside.
A third way of composting indoors is to use a food waste digester. These countertop models chop and dehydrate food scraps, reducing them to nutrient-rich fertilizer. Store over the winter in a bag or bucket and apply to your garden come springtime.
Probably the best reason to maintain an active compost over winter is the head start it gives your early spring garden. During winter, your compost will also provide a welcome boost for your houseplants throughout the dreary winter months.
In gardening, so much is preparation. Summer is preparation for winter, to grow food that will see families through the cold months; but rarely is winter seen as preparation for summer. Composting is one of the many ways in which a homeowner can prepare for spring and the growing season. In keeping compost active and producing that black gold the plants love so much, we connect winter to summer, making each complement the other with what nature has to offer; taking the remains of last summer to make new plants this summer. Keeping the compost going over winter is satisfying to the gardener while providing a wonderful bounty for spring.