Compost Tumbler Not Heating Up? Common Causes and Fixes

Compost tumblers work best when the material in them is really hot. If you notice that your compost tumbler isn’t heating up, you may want to fix that as soon as you can.

There are several factors that can cause low heat levels in compost tumblers but there are also many fixes you can implement to create an optimal environment for decomposition.

If you want to learn how to heat up compost so that you’re able to produce compost quickly and steadily, feel free to continue reading this article.

Why does your compost tumbler heat up?

When you have many people exercising in a room, the temperature in the room increases because humans generate heat from engaging in intense physical activity.

The same happens with bacteria. As bacteria feed on nitrogen and carbon-rich materials, they’re also able to generate heat (and reproduce themselves). The end result is a compost bin packed with many active bacteria that eat, reproduce and engage in activities that cause them to release more heat and decompose organic matter over time.

The bacteria that break down kitchen scraps and dry leaves through heat-generation are called thermophilic bacteria. “Thermo” means heat and “philic” means love. They’re most productive at a temperature between 130 degrees and 160 degrees Fahrenheit but they can also decompose organic materials at 113 degrees Fahrenheit.

If the content in your bin is at a temperature below 100 degrees Fahrenheit, your leaves and grass cuttings won’t decompose much because the thermophilic will become lethargic as they can’t operate in the cold. They hate low temperatures and won’t have enough energy to break down the food right in front of them.

How hot is too hot?

While thermophillic bacteria love high temperatures, when the heat inside your bin becomes too much for them, they can start to die off. This can occur at 161 degrees Fahrenheit and higher. When the temperature reaches the peak, it begins to drop, and in some cases, the compost can become stale.

You can add a compost accelerator (link to Amazon), kelp, chicken manure, compost tea and molasses to speed up the rise in temperature. You can also add some finished compost, which is also rich in microbes. These microorganisms like the sweetness of molasses and kelp or chicken manure as sources of nitrogen.

Compost tumbler not heating up? Maybe it’s too dry.

If the material in your tumbler is too dry, you’ll need to add moisture. Do this carefully by only adding a little and observing its effect before you add more. Your aim is to have a spongy combination, not one that’s dripping wet.

If you’ve added just the right amount of water and all other conditions are right for bacterial activity, the temperature in your bin will steadily start to go up. You’ll actually notice a change within a few hours. Rest your hand against the container from time to time and you’ll notice it rising to as much as 141 degrees Fahrenheit over 36 hours.

Once it reaches that temperature, it should stay there for several days. It could even stay at around 136 degrees to 150 degrees for a week or more. You can use a compost thermometer (link to Amazon) to keep track of the temperature inside your tumbler.

Prevent your compost from getting too dry

The content of your compost tumbler must remain fairly moist, particularly if you want to get rich, black gold.

If you find that your compost keeps drying out, you may not have enough starting material or your ratio of green to brown sources may not be ideal.

You can add rainwater regularly, but make sure you only add a little of it, otherwise the chlorine in the rain may harm the bacteria.

Prevent it from getting too wet

If the content in your tumbler is too wet, you can fix that fairly easily.

You’ll need to remove it and spread it out to dry. Find an airy, sunny spot in your yard and spread it out so the water can evaporate easily.

Don’t leave any clumps of vegetation because you know these will just hold on to water. When the content is no longer soppy and has a spongelike consistency, you can put them back in your tumbler. It should look and feel damp.

If you pick it up and it’s still dripping, you can leave it for a while longer in the sun. If you feel like you’re progressing much, it may be the lack of carbon that is making the compost excessively moist.

Twigs, dry leaves and other brown materials help create air pockets that allow oxygen to flow through the material, so the water can evaporate. Straw or hay can also help aerate the compost, so if you’re in a hurry, you could add some of that to help dry it out.

Make sure that after doing so, you still have enough existing green material to keep the right balance of browns and greens.

Not enough green material

If your material is damp but still not heating up, you have to check your ratios.

You might have too much brown material in your compost bin, so you’ll need to add more green material.

You’ll have to open the tumbler and scan the content. If it’s low in greens, you’ll have to add more and potentially add a compost accelerator before you close your tumbler.

If you’re someone that cuts your lawn on a regular basis, you can pick up the clippings and add to the compost. You can also add greens from your kitchen, such as broccoli, cabbage and spinach. Foods scraps are always a good source of nitrogen, though I usually avoid products like meat and dairy.

Compost tumbler not heating up? Maybe the volume of the content is too small

The average compost tumbler is made to comfortably hold between four and 15 cubic feet of organic material. That’s ideal for households that make compost from their cabbage leaves, carrot scrapings and other kitchen scraps. The drawback is that it’s hard to keep those relatively small quantities at an ideal temperature for decomposition.

Use 30 cubic feet of material for hot composting. It’s easier to keep this volume of vegetation warm while also retaining moisture. Smaller amounts, like four cubic feet, lose water to the environment more quickly because the surface to volume ratio is smaller than what is found in a fully packed tumbler.

Generally, it’s easy to get around the drawbacks using a small tumbler, but only once you’re aware of them.

Composting masses that are at least 3 cubic feet in volume will usually retain heat from the exothermic reactions that are taking place inside them. The mass inside your tumbler should be at least this size, even if you don’t have enough material to reach the optimal size of 30 cubic feet.

Use an insulated bin

You probably use insulation in your home to prevent energy from being lost to the environment and that helps you save money.

In the same way, you can help your compost tumbler heat up by using insulation. If you can’t purchase a new tumbler with your current budget, you can insulate the one you already have by covering it with a waterproof tarp (this one on Amazon is pretty cool). You can do that right now and observe the difference that it makes.

The next time you buy a compost tumbler, choose one that’s insulated, like the Miracle-Gro (link to Amazon). You want to effectively trap the heat, especially if you live at a high altitude or in a cool climate. When it gets extremely cold in the winter, the rate of decomposition decreases dramatically if you don’t insulate the compost.

Insulated tumblers have layers made of polystyrene, which trap the heat that’s generated inside your compost, so it cooks well, producing the nutritious compost that your plants ultimately appreciate. The trapped heat pushes the temperature in the bin up even more, enabling organic matter to be broken down more quickly.

Compost tumbler isn’t heating up because the material is too bulky

Fans of active composting like to throw carrot shavings, bits of chopped spinach and orange peels in their bins. This is a good idea because you provide bacteria with a large surface area where they can operate more efficiently.

However, the problem arises when you drop a whole spoiled orange or cabbage into the bin — which is what some individuals do when passively composting.

The surface area of the materials effects the time needed for composting. By breaking materials down into smaller parts, the surface area of the materials increases, which allows bacteria to quickly break down materials into compost.

Take a minute or two to increase the surface area of your materials by cutting up vegetable scraps. You can also use an office shredder (link to Amazon) to shred newspapers or cardboard.

If you’re adding wood to your compost tumbler, you can chip it with a chipper shredder first. You’ll also give your compost a lift if you use a lawnmower to shred large piles of leaves into pieces. If you don’t have a lawnmower, jump on the leaves to break them up.

Optimize your starting blend to keep your compost tumbler hot

Just like anything else in life, laying a good foundation for your compost will help you to get the type of product you want.

It’s not always easy to maintain the optimal combination of nitrogen and carbon in your bin. After all, you may find that most of your material comes from fallen leaves. Likewise, you may be a vegetarian who has a small yard or practices container gardening, so you don’t have much brown to add to your starting material.

The greens to browns ratio should be one to two or 1:2 at all times. In other words, for every cup of greens that you put inside the bin at the beginning, you should add two cups of brown. You should lay this foundation to get your compost off to a good start.

High temperatures prevent disease transmission

Human beings use autoclaves and other heat treatment methods to prevent the transmission of pathogens.

Similar processes take place in nature and when the temperature in your tumbler heats up, it also helps to kill any pathogens that may be inside it.

This helps prevent disease-causing agents from being transferred from the carrots and other veggies that you purchase, to young plants in your garden.


Compost tumblers are great assets for passive gardeners but there are still things that you have to keep in mind – like the correct level of moisture or the most effective nitrogen to carbon ratio so that you can build a pile capable of maintaining a warm temperature.

You can also add a compost accelerator to kickstart your compost, or in other words, to provide the existing bacteria with an initial push so that the temperature rises quickly.

In this article, we have covered several causes and fixes for a compost tumbler that is taking a while to pick up steam. Now it’s up to you to diagnose the cause, and implement the right solution.