Composting is a great way to use up kitchen scraps and reduce your overall contribution to landfills, with the added advantage of providing an organic soil additive. Whether you’re composting with or without a bin, the key to good composting is to set up convenient systems to make it easier for you to compost.
Here’s how to keep compost in a freezer:
- Use airtight containers.
- Make sure your containers are freezable.
- Consider silicone bags or containers.
- Chop up the compost scraps.
- Ensure your containers are clean.
- Reuse old coffee cans or buckets.
- Add newspaper to your containers.
- Use multiple containers.
- Get containers that are conveniently sized.
- Leave space between your containers.
- Mist your compost scraps occasionally.
- Sprinkle baking soda in your container.
In this article, I’ll detail these tips and how you can keep your compost scraps in a freezer before throwing them into your composting unit, so read on!
1. Use Airtight Containers
When freezing compost scraps, put them in an airtight container as this will prevent nutrient loss and the growth of fungus, which might appear as white powder on your compost. Airtight containers and freezing the kitchen scraps will help ensure that neither aerobic nor anaerobic bacteria can start breaking your compost scraps down.
Airtight containers will keep everything else in your freezer separated from any odors, bacteria, or fruit fly eggs that may be present on your kitchen scraps. These containers will also prevent any moisture loss as a result of the low temperatures. This is necessary, as the greens are the primary source of moisture in composting feedstock, apart from watering your compost.
To keep your kitchen scraps fresh and ensure that they don’t start decomposing before you’re ready to throw them in your compost pile, you’ll want to vacuum seal them in bags or containers. Vacuum sealing prevents ice accumulation inside your containers and protects your kitchen scraps from moisture loss.
If you’re using ziplock or resealable bags, you can push the air out yourself, but it won’t work as well as a sealer that directly removes all the air from the bags. There are household vacuum sealers that are designed to remove air from jars as well, so you can use just about any freezer-safe material to save your kitchen scraps.
Vacuum sealers may seem like an unnecessary expense, but they can be used to help you store all kinds of food and keep it fresh in the freezer and used for techniques like sous vide.
They are especially useful in the winter if you live in places where it gets too cold to compost, as the sealer allows you to store your kitchen waste for the winter and keep it fresh for use in the spring.
2. Make Sure Your Containers Are Freezable
Before you put the compost scraps in a freezer, you need to ensure that your containers can be frozen, or your containers can break while in the freezer, creating a mess. Your containers may even break down over some time, releasing toxic chemicals into your kitchen scraps, which will then leech these chemicals into your compost.
When choosing what containers you’re using for your compost scraps, you need to ensure that the containers can withstand temperatures below -40 °F (-40 °C) without the integrity of the material being compromised over some time.
The best option would be to look for containers that are labeled freezer-safe.
While a lot of plastics and plastic derivatives can be used in the freezer, most of them are single-use or very difficult to clean, so it is advisable to avoid thin plastic containers or bags whenever possible.
3. Consider Silicone Bags or Containers
Silicone bags are great reusable alternatives to single-use ziplock bags.
The bags are made of silica and have been classified as non-toxic and food safe according to the FDA. Look for bags or containers that have an FDA stamp and are labeled as food-grade to be sure that you can use them to store your compost scraps safely.
Apart from silicone bags, you can also use silicone containers, usually designed to be collapsible. These containers can be set aside when you’re not using them or adjusted to fit your kitchen scraps and the amount of space you have in your freezer.
Another way you can use silicone to store your compost scraps is by using glass containers with silicone lids and silicone sleeves. The silicone will protect the glass from shattering due to temperature differences, and silicone lids are easy to remove.
This can save you time and fridge space as you won’t have to thaw your containers to remove your scraps and throw them into your composting bin.
Silicone is slightly more expensive than plastic, but these containers are more durable and will last a longer period, making them more sustainable.
4. Chop up the Compost Scraps
Cutting up or shredding your compost scraps before storing them in your freezer is helpful for multiple reasons.
Shredded food scraps allow you to store more scraps at once. You can keep filling your container and pack more in than you would with the odd shapes and sizes of kitchen scraps as they are.
It’s easier to cut the compost scraps before storing them in the freezer when they’re still malleable and easy to handle. Additionally, cutting the scraps up before you store them allows you to store more kitchen scraps at a time.
Storing more in your collection bins allows you to reduce the number of times you must add greens to your compost, so you can go as long as a week or a week and a half. This way, you can turn and aerate your compost, check on it to make sure it’s progressing well, and add a fresh layer of greens and browns to the top all in one trip.
Chopping up your compost scraps before you store them is also a convenient way of keeping the particle sizes of your compost feedstock small and even. Smaller pieces are easier for the microbes to break down, which will ensure that your compost is ready faster.
Cutting the greens also allows you to maintain evenness in the sizes, so there are no inconsistencies in your compost’s heat and decomposition levels. This will prevent the clumping of your greens, which can cause your compost to become too wet and attract pests like white worms into your compost.
5. Ensure Your Containers Are Clean
Clean containers are essential to prevent contamination and the growth of any unwanted bacteria.
Compost is created as a result of aerobic bacteria feeding on and processing the organic materials of the compost feedstock. Anaerobic bacteria also exist and can lead to anaerobic decomposition.
However, anaerobic decomposition is not ideal for home composting, especially in compost bins. It also results in the release of sulfide gasses and other chemicals, which causes the compost to smell terrible. This produces less effective compost than aerobic decomposition.
When containers and kitchen scraps are frozen, the bacteria aren’t killed, and they’re prevented from multiplying as rapidly. As most containers are airtight, the anaerobic bacteria are likelier to survive than aerobic bacteria.
With every use, the bacteria will accumulate in the containers, contaminate the compost scraps, and eventually affect your compost pile.
Handling unclean containers can also make you sick, so it’s important that you clean all containers, surfaces, and your hands after working with kitchen scraps.
6. Reuse Old Coffee Cans or Buckets
Most people start composting in an effort to reduce their overall waste, and a good way to support that is to reuse other materials for your composting processes and systems.
Reuse old coffee cans, buckets, or any other freezer-safe containers for your collection bins. Coffee cans that are made of tin are usually great for use in freezers, as cans were originally used for temperature-proof storage, be it heat or cold.
Tin is great at withstanding hot and cold temperatures.
Cans can also be stacked vertically, which makes them a great option for people who have tall free stand freezers or a lot of vertical but insufficient horizontal space in their freezing units.
Tin or good-quality hard plastic buckets can also be used as collection bins for your kitchen scraps, provided you have enough space in your freezer to accommodate them. Buckets will let you store a larger volume of scraps at one time and is more convenient for when you’re ready to transfer the scraps to your compost pile.
Fashioning an airtight lid for these buckets might seem daunting, but there are a lot of adjustable silicone lids that can be used to seal the buckets completely.
Alternatively, you can use beeswax paper to seal the buckets and make them airtight.
7. Add Newspaper to Your Containers
Kitchen scraps, like all greens in your composting feedstock, are going to leak. This leakage is especially likely in an airtight container, where the air in the refrigerator will not be able to dry out the scraps.
Keeping your greens from drying out is essential to maintaining the moisture levels of your compost. However, handling wet kitchen scraps is not anyone’s idea of a good time. The liquids seeping from your kitchen scraps will also make it harder for you to clean your collection bins.
Liquid seepage is likelier with food scraps like cucumber, watermelons, gourds, and other fruits and vegetables that have high water content. This seepage is caused by the water in the cells of these scraps expanding, causing them to explode.
To use the water and keep your containers clean, you can add torn-up newspaper shreds to your compost. Newspaper is safe to compost and forms part of the browns that you would add to your compost pile.
Just as the browns absorb the moisture from the greens in your compost pile, the newspaper can absorb the moisture from your kitchen scraps in your collection bins. Since newspapers can be composted safely, you can tip all the contents in your collection bin directly into your compost bin or pile.
If you can’t find a newspaper, you can also use shredded untreated paper or cardboard, sawdust, and cotton or wool rags that are torn up into small pieces. Line your collection bins or containers with newspaper or whatever “browns” that are easily accessible before adding your greens.
Since you’re only storing the greens for a short time in your freezer, you only need a thin layer of shredded newspaper in your collection bin, unlike the lasagna layering that you would practice in your compost pile.
8. Use Multiple Containers
Just as you would use multiple composting units to ensure that you’re able to continue composting when one compost bin is full, you’d use multiple collection bins and containers.
Collecting your compost scraps in multiple containers allows you to keep composting without interruptions and follow a continuous cycle of collecting, storing, and composting your kitchen scraps.
This practice is convenient, as it allows you to store your kitchen scraps effectively, even as one container is in the wash. Multiple containers are also useful when you have large composting units since they allow you to store a larger amount of greens before adding them to your composting pile.
It is also helpful in using freezer space effectively.
A single, large unit might be too unwieldy to move in and out of your freezer to add the day’s scraps and use up valuable freezer space.
9. Get Containers That Are Conveniently Sized
When you consider containers or bags for your kitchen scraps, you need to keep in mind the size of your compost bin or pile, as well as how much space you have in your freezer.
Your containers should be easy to move in and out of the freezer as you fill them up with scraps but not so small that they end up wasting space in your freezer. They should also be large enough that when filled up, you’ve enough greens for a layer that’s a few inches (5+ cm) thick inside your composting unit.
10. Leave Space Between Your Containers
While a full freezer is more energy-efficient, you need to leave space in between all the containers inside your freezer to ensure airflow. This will freeze your kitchen scraps faster and stop any bacterial activity in its tracks.
The airflow inside a freezer is essentially to bring and keep the temperatures low. So when you’re stacking your compost in the freezer, be sure that there’s enough space for even airflow and cooling.
11. Mist Your Compost Scraps Occasionally
If you’re storing your kitchen scraps for a long time, such as over winter to compost in spring or storing them to start a very large composting unit, then you must check on them occasionally.
The frozen organic matter eventually dries out over months unless they’ve been completely vacuum-sealed.
To compensate for the moisture loss over the several months that your kitchen scraps are in the freezer, you can pull out the full containers occasionally and mist them very lightly with water.
Be careful not to add too much, as you don’t want your scraps to be soaking wet. Mist them enough to prevent them from becoming hard and rubbery, and keep them about as fresh as they were when they were placed in the freezer.
12. Sprinkle Baking Soda in Your Container
Airtight containers and the act of freezing themselves will ensure that there’s no bacterial activity, so no odors will be released from your compost in the freezer. However, if you don’t want to deal with the smell when you open the container, you can add a small sprinkling of baking soda to your kitchen scraps.
Baking soda is an alkaline salt that neutralizes odors. It’s compostable, and being alkaline contributes to maintaining a healthy pH level in your compost. The ideal pH level of a healthy compost is 7-8.
This pH also discourages pests like white worms and ants from your compost pile.
Why You Should Freeze Kitchen Scraps for Compost
Kitchen scraps provide the “greens” in composting feedstock and are also known as compost scraps. These can include everything from fruit and vegetable peels to ends and other bits that you’re not going to eat.
They are easily compostable, but because they’re rich in nutrients and moisture, they’ll start decomposing easily. Storing your kitchen scraps so you can add a thick enough layer to your composting bin is a good idea and helps increase the weight of your compost bin so it doesn’t blow over.
However, they can attract fruit flies to the collection bin, and you’ll lose the nutrition in the kitchen scraps, which would otherwise enrich your compost. The best way to prevent pests like flies and bad odors from your compost scraps is to freeze them.
Keeping your compost in the freezer is a great way to store your kitchen scraps without dealing with bad odors or pests inside your home.
The best way to store your compost in the freezer is to:
- Use clean, freezer-safe airtight containers that will maintain the moisture levels of your compost.
- Line your containers with newspapers and sprinkle baking soda to absorb excess moisture and odors.
- Use multiple, conveniently sized containers that let you store enough compost to fill your bin.
- Cut your scraps up before you freeze them for easier composting.
You can read my other article on composting with and without a bin here: How to Compost With and Without a Bin (Ultimate Guide)