Is Compost Supposed to Mold?

The awareness about our environmental impacts is fast rising, and people are looking for safer waste disposal methods. Composting is an easily accessible and manageable way of disposing of organic waste – it’s right in your backyard and doesn’t require any special skills.

But again, you’re new to the game and may find it daunting. For instance, since composting is a uniform method of disposing of household decomposable waste, materials like vegetable waste, leftover food, and tea and coffee grounds will be included.

So, is it normal for mold to grow on all these? After all, we’re dealing with the decomposition process. Well, its occasional appearance in your compost pile isn’t a cause for worry but should be treated accordingly. This blog post will discover why mold appears in your compost pile, the types to expect, and its impact on your compost materials. Dive in!

Why Does My Compost Have Mold?

Undoubtedly, compost and soil share structural and physical attributes. They both contain nutrients needed for plant survival, and combining them can help us raise excellent crops.

If there’s mold on your compost, don’t fret; it happens now and then. It’s natural for us to be wary of this substance because it’s been imprinted in us to indicate the end of a lifespan or shelf life.

So naturally, mold on your compost may turn your stomach. However, it doesn’t mean anything; you only have to wash your hands to reduce its risk. Instead, it’s an indicator that the process has commenced.

It appears in different colors on compost materials more susceptible to decay. Mold is a fungus that appears in white, pink, green, and yellow shades. It assumes diverse forms too – slimy, powdery, or ashy.

These types aren’t harmful, but when you encounter sludgy-looking mold, it indicates something isn’t right.

Now, microbes, oxygen, moisture, and heat are all components required for decomposition. These microbes include fungi and bacteria, and mold is an example of the former.

When mold occasionally appears on your compost materials, it’s not a cause for alarm but an indication that the microbes are active.

What Does Mold looks Like?

If your compost pile yields mold growth on your first composting attempt, you’ll likely believe you did something wrong. However, this substance is merely dead matter and is a sign of decomposition.

Mold is an essential substance in compost, although you may not notice it all the time. When it appears, it’s a sign that biodegradation has begun.

Compost mold can appear in various colors, sizes, and shapes. As a farmer, your ability to identify the type is vital to the growth of your plants. So, let’s explore some of the common types of mold in compost:

Yellow Mold

Yellow mold is marked by its bright yellow color and spongy-looking structure. However, if you discover it after its blooming stage, you’ll see an almost transparent and gooey substance. This type of mold is also called dog vomit slime mold.

Slime mold is harmless and exists to aid the decomposition process. You can also find it in gray, white, and purplish-brown colors.

Green Mold           

When green mold appears on the materials in your compost bin, it still isn’t time to fret. It merely indicates that the moisture content is high. In that case, increase your portion of dry organic matter and water it less in rainy seasons.

Green mold spreads fast if you don’t control the moisture content in the compost pile.

White Mold

White mold stands out from the typical black compost material we’re accustomed to. So, finding this cotton-like substance growing out of your compost pile can be alarming, considering our usual apprehension.

It’s also called mycelium; its growth indicates microbes are actively tearing the organic matter down. Although it looks like fungus, it’s harmless to the compost materials.

Pink Mold

Pink mold is a more problematic type to discover in your compost. However, it’s also easy to control and doesn’t necessarily spell doom for your compost materials.

Is Mold in My Compost Dangerous?

If there’s mold in your compost pile, it’s because you’ve included leftover waste that is prone to developing fungus. That’s because these items produce ethylene gas when they’re in proximity. It attracts bacteria, which become abundant because of the conducive environment.

You’ll find mold in your compost if you include dry rice. This food substance contains just enough bacteria to survive cooking. It multiplies quickly, so mold overcomes a considerable portion of your compost pile.

Naturally, moisture encourages mold growth. So, when coffee grounds, soggy vegetable waste, and watermelon seeds are present in your compost materials, it’s because of the moisture content. It could also be a sign to reduce the amount of water you add to the materials.

Although our natural reaction to mold is well-founded, its presence in compost piles isn’t always destructive. Now, it can grow under other conditions, as we’ve explored. Identifying the types is also pretty easy. So, when does it become a danger to your soil and plants?

Well, if you spot pink mold in your compost, it indicates that chemicals are somehow present in the decomposing materials. This is the only type of mold that can destroy your compost. Often, it’s caused by cleaning agents, and it slows down the biodegradation process.

The other types of mold we’ve discussed won’t destroy the compost materials. However, if you discover a color outside of white, yellow, pink, and green, it’s likely a harmful mold that you can get rid of.

Can You Put Moldy Food in Compost?

Mold is vital in breaking down the compost materials. As such, it’s okay to put moldy food in compost.

However, there are some hacks for putting moldy food in compost. They include:

  • Wrap the moldy food with a layer of newspaper, straw, or plant clippings. It binds the heat in, thereby speeding up the decomposition process.
  • Regulate the water content in the compost pile – ensure it’s not too small to prevent dryness and crumbling. At the same time, it shouldn’t be too soggy to prevent mold from growing.
  • Also, ensure there’s adequate access to oxygen in your compost pile.
  • Avoid putting dairy products, grease, and confectionery in compost piles because of the rodents they attract.
  • Finally, it’s best always to wear gloves when dealing with moldy substances in your compost pile.

Food Items that Get Moldy Quickly

As food ages, mold is a natural decomposition material that sets it. It’s activated by exposure to oxygen. Some food items are even more prone to this because of their composition and storage; they’re susceptible to microscopic spores that produce mold on organic matter.

Before mold germinates, it remains on the colonized surface, in the form of particles. This substance has different effects on us – while some experience little to no adverse effects of consuming it, others have a digestive system that is much too sensitive to withstand them.

Some of the common side effects of consuming mold include diarrhea, nausea, vomiting, and a fever. You may develop asthmatic symptoms, damage your liver, or suffer from dental issues in severe cases.

Some food items that get moldy quickly include:

Soft cheese

Fresh cheese has a limited shelf life, although it can typically last a week or two after you open it. However, if you’re not mindful of your storage medium, mold can grow on it even before that period. The fungi are a freely moving substance that can travel for miles so that they can wind up on your cheese at any point.

It’s best to avoid exposing items like this to the atmosphere because you can never tell what’s in the air.

Even if you don’t end up feeding on mold, you’ll still be consuming the fungi that create it.

No cheese is spared – cottage, sliced, crumbles, or shredded.

Soft fruits and vegetables

Fruits like strawberries, tomatoes, and cucumbers are susceptible to the fungi that birth mold because they contain ample moisture. We’re confident you’re already aware that mold thrives in a moist environment, which vegetables represent.


It’s best to avoid exposing items like baked goods and bread to the elements. They provide a pliable surface for fungi to infest.

Again, you’ll be unable to see it until it decomposes. We recommend keeping it wrapped and refrigerated until you’re ready to eat up.

Cooked food

Items like pasta, meat, casseroles, and rice are prone to fungus infestations. If you leave your meal exposed for a significant period, it can provide ample room for fungus to perch on it.

Jam and jellies

Finally, never leave your jar of jam and jellies open. Always crew it close after use because fungi are also partial to hydrated surfaces like this.

How to Fix Struggling Compost?

As the compost reduces in size, porosity is the immediate recipient, causing the roots to lose access to ample oxygen and nutrients. Moisture won’t have adequate access either, and when it does, it accumulates in the compost.

Unregulated water is never good for soil and plants; the abundance of moisture in the compost will drown the root, expose it to fungal infections, and possibly root rot. However, if it’s doing well, an ideal condition for plant growth will be created when it’s time for the application.

The different materials present supply potassium, phosphorus, iron, manganese, zinc, and sodium, to name a few. Again, there’s a regulated formula for creating the ideal compost and soil environment. If you adopt a proper proportion, you’ll scarcely need to deal with struggling compost.

Although mold doesn’t necessarily depict that your compost is struggling, it may also be a pointer, especially if you’re dealing with pink mold. This is an indication that chemicals are present in the materials.

Other common symptoms include a potent stench from the area, the inability of brown leaves to break down, sticks refusing to decompose, and the pile being ultimately devoid of bugs and worms.

If that’s the case, your compost is struggling. However, the solution is pretty straightforward.

Now, if the problem is a stunted decomposition, the materials are merely moist and not wet. An immediate solution is to use a pitchfork to mix it for ample moisture distribution. A longer-lasting solution is aerating the pile.

If there is too much water in your compost pile, you’ll discover it through wet, smelly, sticky compost materials. Introduce some dry matter like sawdust, pine needles, and straw.

You can identify a healthy compost pile through the smell exudes. Take a handful and check if you perceive a soft and earthy aroma, which indicates recent fermentation or an abundance of harmful ammonia.


It’s not unnatural to discover mold in your compost. If anything, it indicates proper decomposition. However, you experience it only occasionally because some foods are more prone to it than others.

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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.