Can Compost Catch Fire? (And How To Prevent Overheating?)

When your compost attains a temperature of 120°F to 160°F, it kills the harmful substances in the mix. But again, too much heat can kill helpful microbes and dry out the compost materials.

It’s not uncommon to worry about compost catching fire because it happens. However, it’s more prevalent in commercial composting because this sector uses larger machinery. When hot composting, a more expansive space increases the chances of a fire. So, since you’re into small-scale composting, you have lesser chances of witnessing a fire from your compost pile.

In this blog post, we’ll explore the factors that can cause a compost fire and how to prevent it from happening.

Can a Compost Pile Catch on Fire?

If you’re new to composting, you’ll certainly have many questions. Composting techniques are diverse – you can attempt hot or cold composting, build a pile yourself, rely on compost tumblers, or explore other appealing options.

Cold composting doesn’t need the introduction of special heat. Often, this technique is practiced at home, in one’s yard. You only need to create a pile or purchase a compost tumbler.

It’s common because it’s one of the conventional methods of composting; it requires no special technique or skills. Although hot composting is an excellent way to accelerate decomposition, cold composting still has a fair advantage because it provides a favorable temperature for helpful bacteria.

On the other hand, hot composting is more labor- and heat-intensive. Here, you’ll introduce the organic matter to a temperature ranging between 120° and 160°F. It’ll be impossible for harmful pathogens to survive this encounter, making this composting method safer.

Farmers prefer hot composting for many reasons. Most importantly, this technique produces a better quality of compost mix – crumbly, rich, and earthy. Hot composting also allows for the production of black gold without depleting the quality of the nutrients present.

Since you’re interested in hot composting, it’s likely because you know about the benefits. However, the process is what scares most people.

You’ll be introducing an additional heat source to this heap, which means there are chances of a fire outbreak. For instance, spontaneous combustion is possible but majorly for large-scale composting.

But again, if you’re in your little compost zone at home, there are significantly low chances of a fire starting. You also must play your part in ensuring the temperature in the pile isn’t excessive because that’s when the chances of overeating or a fire increase considerably.

The maximum temperature for hot composting is 160°F; anything above that will terminate both helpful and harmful microbes. It can also cause overheating when it’s not well controlled.

However, if there’s ample moisture in the compost mix, it won’t catch on fire. Instead, spontaneous combustion can occur in the most extreme cases. But if you have noticed the heat intensity earlier,

A compost may catch fire, but the composting conditions must be extreme. Conventionally, sufficient moisture, oxygen, and heat will keep compost going. And regardless of how hot the pile is, you only need to keep it moist to reduce the chances of spontaneous combustion.

In the same vein, you must remember that even if the compost pile won’t catch on fire, there are beneficial microorganisms present, especially the fungi that’ll break down the compost. But if you consistently expose them to extreme heat, preferably a maximum of 160°F, they’ll die off.

Don’t expect your compost pile or tumbler to catch on fire. It happens, but responsible farming ensures the reported cases are minimal to nonexistent.

What Causes a Compost Pile to Catch on Fire?

Despite the significant heat used for hot composting, it’s scarce for compost piles to catch on fire. Aside from the commercial machines that compost materials on a large scale, the only other scenario where the compost will catch on fire is when spontaneous combustion occurs.

If your compost pile catches on fire, many factors can be responsible, but it’s probably because of insufficient moisture. Using more browns than greens, your compost will be dry and susceptible to extreme heat.

The compost mix may also self-heat until they’re close to overheating, which is why you must pay attention to your compost. Because compost heat is produced not just by the sun, but also by the chemical reactions of microbes within the mix, it can be somewhat challenging to control the temperature.

At What Temperature Does Compost Catch on Fire?

If you leave your compost pile to too much heat, it can catch on fire. There are two heat sources in composting, and both need to be regulated to ensure safety and quality results.

The external heat source is the most powerful, and ranges between 120°F and 160°F. This temperature is vital for killing harmful pathogens, accelerating microbial activities, and speeding up composting. In thirty to ninety days, your compost pile will be ready with supple, crumbly, organic matter.

Internal heat source arises from microbial activities. However, it’s incited by external heat. Bacteria and fungi activate decomposition when you provide a suitable environment for it. Although this heat source is too weak to start a fire independently, if it’s combined with an intense external source of heat, it can cause spontaneous combustion.

If your heat source to exceeds 180°F, then you may not only be dealing with dead helpful microbes in your compost, but may also be setting yourself up for overheating or a fire threat.

Since compost won’t suddenly combust because of the considerable amount of water present, the chances of your compost actually catching on fire are pretty low.

Hot composting is a relatively speedy process of decomposition; within a short period, we’re certain the materials will take the crumbly shape that’s associated with organic matter.

It’s fortified with enough moisture, reducing the chances of the compost mix catching on fire. 

To avoid unforeseen circumstances, we recommend sticking with the acceptable temperature for hot composting – find a suitable temperature between 120 to 180°F and make that your go-to compost heat.

How Can I Tell if My Compost Pile is Too Hot?

Hot composting is a faster method of creating black gold for plants, and heating up is vital to set the decomposition process in motion.

It kills weeds faster, eliminates harmful bacteria and pathogens, breaks down chemicals like pesticide and insecticide thirty-two times more quickly than cold composting.

The chemical processes of decomposers like bacteria and fungi break down the organic matter in the compost pile. However, they can only decompose biodegradable materials, so you’ll have to be selective when assembling the content for your compost mix.

A compost pile that’s too hot never bodes well for the microbes responsible for decomposition. Granted, the heat produced by microbial chemical reactions is insufficient for accelerated composting, but if the external source exceeds 180°F, it begins to terminate helpful fungi and bacteria.

They’ll cease decomposition, rendering the compost pile inert.

Turning the compost mix at least once weekly will help you regulate the heat. You can also use it as an opportunity to monitor its progress.

What Can I Do to Prevent My Compost Pile from Overheating?

If you don’t manage your moisture content correctly, your compost pile will probably burn. With inadequate airflow, too, overheating fast becomes inevitable.

When the fire gets too hot, it kills helpful and nasty microbes. It can also dry out and catch on fire in extreme cases.

It’s best to determine a suitable temperature that you can always stick with when hot composting. It must be tolerable for the microorganisms that’ll spark up the decomposition process.

However, getting the right temperature is somewhat tricky, and you’d have to ensure the pile doesn’t overheat. These tips will help you get a firmer grip over your compost pile:

1. Use a small surface area

It’s best to use a smaller surface area when hot composting, especially for the first time, because it affords you more control.

Your pile should not exceed twelve feet, while the width should be a minimum of a cubic yard.

2. Don’t neglect your compost pile

Hot composting requires adequate attention – you cannot abandon your compost pile. If you perceive any burning smell, kindly inspect it immediately. If you also see smoke, it indicates that the temperature in the pile is too high.

3. Fluff your pile regularly

You can use a compost thermometer to track the temperature. When it goes down, it indicates that more heat is required. Fluffing your pile now and then will help you control the temperature.

4. Monitor the moisture content

Adequate water is vital in hot composting because your mix can burn if it gets too dry. If you notice it needs more water, you can add some more greens like vegetable matter.

You can water the layers while composting to ensure each level has ample moisture. This reduces the chances of your compost mix burning out because the materials will be adequately soaked but not soggy.

5. Ensure proper aeration

Proper aeration is vital for the composting process to begin. If the pile is dry, it can cause air pockets in the compost material. If it’s too wet, it also blocks out air, so adjust your moisture content to accommodate respiration.

6. Consider your green materials

Your green and brown materials need an excellent proportion to ensure balance in the compost pile. You can explore the most suitable method, but browns should typically be more than greens.

How to Keep Compost From Catching on Fire?

Even though spontaneous combustion isn’t particularly common in small-scale composting, it can still happen. It narrows down to our practices and the techniques we adopt.

To keep your compost from catching on fire, it needs adequate attention. Hot composting can take anywhere between a month to three, and you must prepare to monitor the conditions if you want a quality result.

If the content in the compost pile is too dry, the chances that it’ll overheat increase. In that case, you can add some greens – vegetable matter from your kitchen will suffice. Alternatively, you can also use some rainwater or tap water that’s been left to settle overnight.

A compost pile that’s well insulated but lacks adequate oxygen can also combust. It’ll be an internal reaction that can cause combustion, which is why it’s best to rotate the mix now and then. Depending on the type of compost method you’re adopting, you may have to fluff it once in three to five days.

If the conditions in your compost pile are well regulated, a fire is one of the least challenges you’ll bother with. So, ensure you find the ideal moisture content, oxygen supply, and heat source.


A compost pile can catch fire, but it’s less likely to happen in small-scale composting. However, there are preventive measures you can adopt to stay safe without compromising the quality of your compost pile. We’ve explored them in this piece, so we hope you use this information to make better environmentally-related choices

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About Rinkesh

A true environmentalist by heart ❤️. Founded Conserve Energy Future with the sole motto of providing helpful information related to our rapidly depleting environment. Unless you strongly believe in Elon Musk‘s idea of making Mars as another habitable planet, do remember that there really is no 'Planet B' in this whole universe.