Can You Compost In Winter?

Composting is often thought of as a summertime, or at least warm temperature activity. And as compost being one of the most valuable soil amendments, it is a common concern to new gardeners as to what will happen to their compost in the winter or cold weather.

Well, I’m here to tell you that yes, you can definitely compost in Winter. And you should definitely keep composting throughout the entire cold winter weather. Heck – you can even begin composting in the middle of winter. In fact I will start and finish two large compost piles each winter, and I even manage to keep them hot.

How cold outside temperatures effect compost

The speed at which material compost is directly effected by temperature. As the temperature decreases, bacteria and microbe activity decreases^[1][2]. Also, the heat leaves the compost much faster in the cold further lowering the temperature^[3]. Thus in the colder winter months, the bacteria and microbes work much slower^[4].

Does composting stop in winter?

Compost will stop breaking down if it freezes solid. But if the compost materials are above freezing, then the bacteria/microbes will keep breaking down the material, albeit much more slowly.

How to speed up compost in the winter

No matter if you use a tumbler, bin, or open pile, there are a few common steps that you can take that will have a big impact on keeping your composting going all winter. But to compost in cold weather, follow these key points:

• Keep your compost in the sun
• Don’t turn it as often
• Use high-nitrogen green materials
• Insulate the compost

Tumbler composting in winter

If you are using a compost tumbler or bin, there are a few things you can do to keep it active during winter. First, position it so that it will receive a lot of sunlight. Sun will help heat up the bin, and thus the compost, keeping the bacteria and microbes active. Second, cover your bin at night with an old rug or tarp to help insulate it from cold temperatures. And finally, make sure you add materials high in nitrogen to keep the microbes fueled up.

Compost bins or piles

If you have a DIY compost bin or pile, you will have an easier time keeping your compost active in winter than if you had a tumbler. This is because DIY bins/piles can hold much more volume of materials than tumblers or bins.

Making your compost pile larger than normal is the most important factor in keeping an active compost in Winter. In general I will make my compost piles approximately 50% larger in Winter. This is absolutely necessary to help keep temperature in the center of the pile warm.

So, by increasing the size of your pile, you will keep the center better insulated, meaning that the materials in the center will break down faster, and generate more heat.

How to keep compost active through winter

1 – Use all of your finished compost

Before you start preparing for winter compost, you should use all of your finished compost and top-dress your garden. This will free up any space for you to start a new pile.

You can simply spread it on top of your garden soil. Some people will suggest tilling it, but it is not required. I just spread mine out in a layer over my garden soil. And I’m always hopeful that I have enough to cover the entire garden.

2 – Location, location, location

Composting is temperature dependent, and in Winter we need to take free heat wherever we can get it. Keeping our compost in the sun is key in that the sunlight will heat up the pile. If you have a tumbler, move it into the sun. If you have a wire or pallet bin, consider moving it to the sun.

3 – Maximize the size

If possible, increasing the size of your compost pile/bin will improve the insulation to the center, keeping the pile hotter. This will in turn cause the ingredients to break down faster, and also generate more heat…..which is a positive feedback loop for compost!

4 – Use alternative green material

When winter sets in, we lose one of our most plentiful green materials – grass clippings. So what are we to do? Well, for one we can gather coffee grounds from coffee shops such as Starbucks. Collecting old Halloween pumpkins and gourds is another excellent green material that is abundant in early Winter.

Related ==> 101 household items you can compost (printable)

But the main point is that you will need to be more aggressive about collecting green materials. If you know someone who is preparing Thanksgiving dinner, kindly ask them to set aside vegetable scraps and peelings for you. Any form of fresh plant material can really help keep a compost pile active during winter.

5 – Use a proper Winter Compost Ratio of green to brown

While many authorities suggest using a 3:1 or 3:2 ratio of brown material to green material (by volume), this isn’t as effective in the winter^[1][2]. The reason is that we want our pile to be active, and having extra greens is quite beneficial to keeping warmer temperatures in the center of the pile. So, during winter shoot for a 50/50 ratio green to brown, as this will help keep the temperature of the pile higher! I have proven this over the years that 50/50 ratios are perfectly fine as long as the pile stays aerated. See this video for proof (4 million views).

Something that could be of help to you is our huge list of household items you can compost.

6 – Only turn the compost weekly in winter

During the summer when many people are using grass clippings in their compost piles, I often find that I need to turn my piles more frequently. But in Winter, I try to only turn my compost once per week. This is because every time we open the pile up when turning the compost we will lose much heat. Turning the pile less frequently will help conserve heat.

7 – Be fast when turning the pile

Although this may seem like common sense, I fell that I should point out that when you do turn your compost, you should try to do so quickly. When we turn and completely aerate our pile, we lose heat. The longer this process takes, the more heat will be lost to the cold outside temperatures. So, be quick about turning your compost!

8 – Add more greens every time you turn your compost

A powerful tactic for keeping your compost active throughout winter is to add more green material every time you turn your pile. This is mainly for those with wire or pallet bins or piles, as tumblers have smaller space limitations.

But adding greens every time you turn the compost will help ‘recharge’ it and provide more food to the bacteria and microbes. As they decompose the material this will generate more heat, and thus keep your pile breaking down faster.

Now, you may be thinking that if we are always adding to the pile, will it ever finish? Well, green materials generally break down very fast – especially kitchen scraps and coffee grounds. So adding each time we turn the compost is not a concern. By Spring all will be finished compost!

9 – Store kitchen scraps in a cold location

Since you shouldn’t be turning your pile more than once per week, that means we need to have a system in place to be able to store a week’s worth of kitchen scraps without them rotting or getting too nasty. Having a two-bucket system will achieve this, as you can have a small bucket you put daily scraps in, and then dump that into a larger bucket stored in a garage or shed.

I have a counter top compost bucket that I put day to day items in. Now, during the summer when I fill that bucket I will just go add it to my pile. But in Winter I will actually go dump it into a 5 gallon bucket with locking lid that I store in my unheated garage. By December the garage temperature is usually in the mid 40’s, which although not as cold as a refrigerator, it is cold enough to prevent my kitchen scraps from stinking too much.

10 – Monitor the temperature

Monitoring the temperature of the compost is the best way to know if it is active and healthy. As long as the center of the pile isn’t frozen, it will be active. But you can also use the temperature to gain an insight as to when you should turn/add more material.

As the temperature of a compost begins to drop, that is an indication that either the green material has been used up, the pile has compressed on itself and lost air, or it is dry (pile almost never dry out in winter). If I see a pile drop from 80-100F down to 50F in freezing temperatures, that is an indication that I need to add more greens and turn/aerate the pile.

Note – if you are using a tumbler, you probably will not see temperature fluctuations as they generally don’t have enough volume to ever get hot, even in the summer.

11 – Don’t worry about steam

When you first construct your compost pile, if there is enough volume then the temperature should rapidly rise. Well, during cold mornings from fall through spring you may notice steam escaping your pile. This is most likely steam, as the cool air temperatures near the ground will mean that water vapor will condense as a fog/steam as it escapes your pile.

If you do have concerns, just purchase a compost thermometer and insert it to the center of your compost. Most likely the temperature is between 90-150F, which is perfectly safe. In fact the clip below is from a pile I made last winter in 2023. And as you can see, the temperature in the center of the pile was over 140F while the ground had snow on it!

While it is possible for compost to catch on fire, it is very unlikely for backyard gardeners. The compost would need to be a very large size, much greater than standard backyard compost set-ups. As long as your compost thermometer isn’t reading 165F or more, you should be safe. If you are measuring temperatures in that range, or are just concerned, you can simply separate the pile into two smaller piles. This will reduce the volume, allowing more heat to escape, and thus lowering the temperature. I’ve actually done this with a massive pile before I had to go out of town for a few days, just to be safe.

12 – Insulation

To help keep heat trapped in the center of your compost, add a layer of insulation^[3]. This is very important for keeping compost active in tumblers or smaller piles, as they don’t generate as much heat. Insulation can be something as simple as piling a large layer of leaves over the bin, or even throwing a tarp or old rug over the tumbler/bin. Anything that slows down the rate of heat transfer will help.

Then, just remove the insulation when you wish to turn the compost.

13 – Adding water to winter compost

The rules for watering compost in winter are the same as in summer. If your pile is dry, add water. Now, this is normally not a problem in winter. But when you turn or check on your compost, if it seems dry, then add water. You should add enough water so that the consistency is similar to a wrung out rag or sponge.

The only other factor to consider when adding water to compost in winter is weather or not the outer layer is frozen. When the temperature stays below freezing for extended periods of time, the outer layer of the compost may freeze. This is ok, and shouldn’t need water, as once it thaws out it will still have plenty of moisture.

Since the outside temperatures are so much lower in Winter, water evaporates much more slowly. This means that you probably won’t need to add water to compost in winter except when you first assemble your ingredients. Plus, most locations will have rain/snow periodically in winter, which will also help add moisture to your pile.

14 – Avoid using seed heads in compost materials

One of the many Fall/Winter gardening chores is cleaning up the garden and cutting plants back, and disposing of old veggie plants. And while it is tempting to add all plant material as an ingredient to a new compost pile, we need to be cautious of seed heads on plant material. This is because winter piles may not get hot enough to kill the seeds.

[see here for detailed info on what temperatures are required to kill seeds in compost]

It is entirely possible to make your pile hot enough, but it will take more effort than normal composting. I’ve written a detailed guide on how to make a hot compost pile in winter, and I have personally achieved temperatures high enough to kill any/all seeds, and you can too if you have the space.

Conclusion

You can (and should) make compost during winter. Even if you live in Minnesota or Saskatchewan you can compost longer if you follow my tips for keeping your compost active in winter. The key thing is to take advantage of sunlight, reduce your turning frequency, and add new greens every time you turn your compost. Those are the three most important points that will keep your above freezing for longer.

I live in zone 6 of Pennsylvania and never have my active piles freeze solid. They stay active all winter long, even when the temperature gets to zero degrees F. I do this by making my piles 50% larger, using plenty of greens, and only turn the compost once a week. But even if you don’t have a ‘pile’, you can still take advantage of sunlight by moving a tumbler or bin into the sun and using potent green materials.

Frequently asked Winter Compost questions

What happens if compost gets too cold?

The rate at which the compost materials decompose will decrease with temperature. If the pile freezes solid, all decomposition will cease^[2]. This can happen depending on where you live and the size of your bin/pile. Keep it located in the sun to help prevent it from freezing.

Can I leave compost outside in winter?

Yes, absolutely. You can compost outside in winter. See my video below to see exactly how to do it!

What temperature does compost break down?

Compost will break down at all temperatures above freezing. But the warmer the pile is, the faster it will break down. Typical active compost piles should be 80-150F in the center of the pile (27-65C)^[1].

How can I speed up my compost in the winter?

Speed up your compost during winter or in cold weather by placing it in the sun, using a green/brown ratio of 50/50 (by volume), and turning the pile no more than once per week.

Should you water compost in winter?

Watering compost in the winter is just like watering compost in the summer – you add water as it is needed. Your goal should be to keep the compost as moist as a wrung out rag of sponge. If you think it is a bit dry, add water.

But, since water will evaporate much slower in winter, it is not likely that you will need to add water. I live in southern Pennsylvania, and I pretty much never add water to my winter compost piles except when I build them.

Is composting slower in winter?

Yes, the composting process takes longer to complete in the winter. This is due to bacteria and microbe activity being positively correlated with temperature^[1][4]. So as the outside air temperature decreases, the activity level of the microbes/bacteria will slow down, ultimately stopping if the compost freezes solid.

Does cold compost smell?

If the compost mixture is balanced between green/brown material and aerated, it will not smell. Smelly compost comes from a lack of oxygen, which happens as a pile decomposes and collapses on itself, squeezing out the air.

Should I stop composting in winter?

NO! Do not stop composting or collecting compost materials in winter. Even if you don’t plan on actively managing your pile, you can still just keep tossing kitchen scraps on top! Then as temperatures do warm up, you will have a stockpile of material that is ready to break down.

How often do you water compost in the winter?

You should add water to compost in winter when the compost feels drier than a wrung out sponge or rag. There is no set schedule when to add water, you just need to do it as needed. I can say from years of experience that it is rare that you need to add water (in zone 6). No matter where you live, if the temperature is lower in the winter, then you will not have to add water as frequently as the summer.

Find more composting tips here