How to Heat Up a Compost Tumbler (10+1 Ways to Speed up Composting)

how to heat up a compost tumbler

Are you worried your compost tumbler isn’t heating up?

The heat generated by composting microbes is a sign that the decomposition process is well on the way. And this is especially important in the beginning stages.

No heat means no microbial activity. And Slower composting results.

So what do you do to heat things up?

In this article, I’ll go over the best ways to make sure your compost tumbler is warming up properly and what you can do to improve inactive compost.

How do I heat up my compost tumbler?

You can do a few things to heat up your compost tumbler and speed up the composting process.

But remember…

If you’re home composting in your backyard with a tumbler, you’re probably not going to get extreme temperatures! So it helps to be realistic about your goals.

At any particular time, the chances are the compost inside your tumbler is a few degrees above ambient temperatures. And as long as the temperature remains around 55°F (13°C), you have an effective composting process going on.

Why is my compost not heating up?

There can be several reasons why your compost isn’t heating up, but most likely, it’s due to one of the following:

Airflow, moisture levels, the quantity, ratio, and kinds of materials, the type and size of tumbler you use, maintenance issues, or ambient temperatures.

Any of these could result in the composting process slowing down.

How hot can a compost tumbler get?

In most situations, a tumbler will probably never reach the temperatures you find in larger-scale compost methods.

This is because the compost is in direct contact with the sides in a tumbler, which helps to cool it down.

When you think about it, the size of most commercial tumblers is small compared to a traditional open pile. They have a relatively large surface area compared to their volume. This bigger surface area makes it easy to lose heat. Consequently, the heat generated by the composting bacteria will be rapidly dissipated through the sides of the tumbler.

The volume and mass of composting materials is just one factor affecting the way compost “heats up.”

10+1 ways to heat up a compost tumbler

Here are a few tips for heating up your compost tumbler and speeding up the process!

1. Increase the amount of compost materials

The more materials you have in your tumbler, the more heat generated. This is because there is a greater mass of material for the bacteria to decompose.

So if your compost isn’t heating up, add more organic matter!

But be careful not to overfill the tumbler. You still need to leave room for air to circulate so the bacteria can do their work.

2. Add more green nitrogen-based materials.

Add some “green” materials. Materials high in nitrogen are great for heating up compost. This includes things like grass clippings, kitchen scraps, and coffee grounds.

But be careful not to add too much, or your compost will become soggy and wet.

3. Shred compost materials beforehand

You can also shred or chop up the organic matter before adding it to the tumbler. This will help it to decompose faster and generate more heat.

This works because the shredded matter has a greater surface area for the microbes to work on.

And the smaller the pieces, the easier it is for them to break down.

4. Compact branchy materials

branchy carbon compost materials

“Brown” materials like twigs and branches can be problematic in a tumbler. However, these are high in carbon and help balance out the nitrogen-rich materials.

But if they are not broken up, they leave significant gaps. This might be allowing too much air movement and causing heat to dissipate.

Reduce their size by compacting them or chopping them up into smaller pieces before adding them to the tumbler.

5. Innoculate the compost with soil

Another way to heat up your compost is by inoculating it with soil. This will introduce new bacteria into the mix that will help to get things moving.

You can do this by adding a shovelful of soil to the tumbler every time you add new materials.

6. Are you turning the compost enough?

Perhaps you need to turn the compost more often?

If your compost isn’t heating up, turning it more often can help get things moving again. This is because when you turn the compost, it mixes the materials and allows for better air circulation. Also, organic materials on the compost’s outer layers get a chance to be in the center where temperatures and microbial activity are higher.

Mix the materials thoroughly. Make sure to mix the materials well so that they decompose evenly.

7. Position the tumbler in the sun

you can use the sun to heat up a tumbler

If you have a sunny spot in your garden, try positioning the tumbler in direct sunlight. This will help to heat it up. Especially since most tumblers have dark-colored exteriors that absorb more solar energy.

Ambient temperature and the surface temperature of the tumbler will keep the contents warm, which is helpful to the composting microbes.

But be careful not to let it get too hot, or the compost could cook!

Use a thermometer (link to Amazon) to control your compost temperature. Expect temperatures of between 55° and 115° Fahrenheit in the early stages of decomposition.

8. Add a compost starter.

If you’re having trouble getting your compost to heat up, you can add a compost activator to jump-start the process. Compost activators are made from natural ingredients like seaweed or kelp.

You can find them at garden centers or online. Simply add a handful to the ​mixture when you first start composting ​with a tumbler or each time you add new ingredients.

Read this article for a helpful list of different compost accelerators, including natural and DIY starters.

9. Make sure the compost moist

Moisture is essential for the composting process. So add water if your compost seems too dry.

You need sufficient moisture to allow composting microbes to decompose wastes efficiently. In fact, if they don’t get enough water, they will die off!

The ideal moisture level for compost is between 40-60 percent.

If you live in a cold climate, you can even try hot water to speed up the process.

10. Use an insulated tumbler.

If you live in a cold climate, an insulated tumbler can help to keep the compost warm and prevent heat from escaping.

The mantis back porch tumbler is an excellent example of an all-season tumbler.

You can also insulate your tumbler by covering it with an old length of carpet or several sheets of cardboard.

11. Get a bigger tumbler?

If you’ve tried all of these tips and your compost still isn’t heating up, you might need a bigger tumbler. This will allow more material to be processed at one time, which means more heat production.

A big tumbler can also help if you have a lot of organic matter to dispose of.

Sum up

Once you’ve tried all of these tips, your compost tumbler should be heating up nicely. Just make sure to mix the materials well, turn them often, and add water if necessary. And don’t forget to inoculate it with soil for extra help! After all, it’s free!

Happy composting! 🙂


How do I keep my compost tumbler warm in the winter?

There are a few things you can do to keep your compost tumbler warm in the winter. One is to position it in a sunny spot, if possible. Another is to use an insulated tumbler. You can also insulate your tumbler with a sheet of material with good insulating properties, such as an insulated camping tarp (Amazon link).

Can you hot compost in a tumbler?

No. It’s unlikely you’ll be able to hot compost in a standard tumbler.

Hot composting occurs at temperatures from 115° up to 160° Fahrenheit.

Most tumblers are just too small to create enough composting mass, and they tend to lose heat too quickly.

However, you have a better chance with a large insulated tumbler like this Jora JK-270 model!

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