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Is Compost Harmful To Cats?

The old saying ‘curiosity killed the cat’ has never been more true than in the context of compost.

Both homemade and store bought compost can be harmful to cats, causing severe illness and even death. This is because compost contains mold neurotoxins – more specifically tremorgenic mycotoxins – which cause symptoms such as vomiting, diarrhea, tremors and panting.

In this article we’ll discover in more detail why compost is dangerous for cats, what symptoms to look out for – and what to do when your cat has eaten compost. We’ll also consider ways of keeping your curious feline away from the compost in the first place.

Why is Compost Harmful To Cats?

Is compost harmful to cats – yes! 

Be careful to keep dogs and cats away from compost. Compost falls under the general category of moldy foods. Molds can produce neurotoxins that are deadly for cats.

Mold is everywhere – there are over 100,000 types of mold. Most are harmless but some are linked to chronic diseases like cancer and multiple sclerosis. Most sinus infections are caused by molds. Mold has been used as a biological weapon, but the world-changing antibiotic, penicillin, is mold-based.

Molds start growing on moist, porous surfaces within 24 to 48 hours. Molds grow best in warm temperatures – 77°F to 88°F. They don’t need light to grow. 

Mold grows on food, rocks, paper, carpet, trees, and a lot more. In fact, mold destroys more trees than termites, floods and fires combined.

Moldy foods in compost (and trash cans) can contain neurotoxins. The number one toxin is tremorgenic mycotoxins. This toxin is produced by molds growing on organic food waste that is high in lipids, like cheese, fruits, bread, husks, and nuts.

Besides mold, compost may have other things that are bad for cats. Coffee grounds are high in caffeine. Who can live without caffeine in the morning? Answer – your pets. Caffeine is toxic to cats.

Another thing that can happen in a compost bin is fermentation. Sugary fruits and grains can produce ethanol, another pet toxin.

Commonly, gardeners trim plants and add the trimmings to the compost pile. That’s good for the compost pile but may be toxic for your cat. Here’s a list of plants that are toxic to cats.

Can Both Store Bagged & Organic Compost Harm Cats?

Yes – both homebrewed compost and bagged compost can be harmful.

There are many bagged composts on the market. Many are labeled “organic”. Even the organic ones can be toxic if eaten by cats. “Organic” ingredients include bone meal, blood meal, feather meal and fish meal. While these may smell delicious to your cat, they should not eat them.

The Symptoms of Compost Poisoning in Cats

If your cat eats moldy food containing tremorgenic mycotoxins, you will know right away.

Within 30 minutes to three hours, your cat will show symptoms. Common symptoms are agitation, diarrhea, tremors and panting. Vomiting, drooling, foaming, wobbling while walking, hyperactivity and high temperatures are also symptoms. In severe cases, there will be convulsions.

These effects can last several days or end in death, so act quickly.

If your cat has only walked through compost, not eaten it, then it should be fine. Monitor your cat for the symptoms above and call your vet if you see any.

What To Do if Your Cat Has Eaten Compost

If you suspect your cat has gotten into some compost (or raided the trash) or shows any of the symptoms, get help from a vet right away.

Once you get your cat to the vet, they may induce vomiting or administer activated charcoal. An IV may be needed to flush the toxins from the bloodstream and to administer anti-seizure medication.

How Do You Keep Cats Out of Compost?

We all know that cats are programmed to bury their waste. It’s a natural thing. We also know that even though your cat may have the sweetest, freshest kitty litter, they seem to prefer the potted plants. What now?

Compost can be found in a bin in the kitchen, in a garden bin and amended into your garden soil. Perhaps all three.

Kitchen compost bins can be adorable. But to ensure that your cat can’t nose their way into it, choose a kitchen bin that seals tightly. Then, choose a cabinet that your inquisitive cat can’t get into – at all. Consider a baby lock on the cabinet door.

Garden compost bins are trickier. While dogs may be foiled by a fence, cats won’t be. Cats can scale most fences easily. If your outside compost bin is a DIY one, consider constructing a heavy lid. Or, add wooden slats with heavy rocks on top to discourage cats (or other wildlife). 

If you are shopping for outside compost bins, there are many models that have tight lids. For others, a simple locking mechanism could be added.

Of course, you want to add compost to your potted plants, garden, and maybe your yard. That’s the point! For potted plants, an easy solution is – rocks. Decorative rocks. Or cut some heavy weed fabric or screening to cover the composted soil, then top it with glass beads, small pebbles, or sterilized potting soil.

In the garden, solutions get a little trickier. If you want an organic approach, try prickly stuff. Cats love digging in soft sand or dirt. It’s easy. Cats won’t love it so much if you have seeded your garden with pinecones, stones, holly cuttings, or rose canes.

For plants in a row, like a vegetable garden, you can put down strips of chicken wire, lattice, or plastic fencing. Weed fabric works as well.

Cats also won’t like it so much if you plant rosemary, rue, lavender, pennyroyal or lemon thyme. Or try an essential oil, like rosemary. Simply add 10 drops to a spray bottle filled with water and spray it on your garden. 

Another plant you can add to your garden is called the “Scaredy Cat Coleus” (Coleus canina), which has a skunk smell (yuck!!) but nice flowers.

Cats are turned off by citrus scents, so throw your lemon and orange peels out there. Ultrasonic repellents may work on cats and bunnies in your garden.

Please DON’T use coffee grounds, mothballs or plastic forks set as spikes in your garden!

When you are adding compost to your lawn (top dressing), the procedure should ensure that no compost is lying around for your cats, so don’t worry.

Can compost hurt cats?

Is Normal Garden Soil Harmful For Cats?

Can walking or digging in normal garden soil hurt cats – no. But if you cat is eating normal garden soil, is that bad? Well, maybe.

To be precise, potting soil is not “normal”. Potting soil has several additives, including compost, that can be harmful to cats. “Normal” garden soil has no amendments, no additives, nothing.

Cats are sometimes inexplicable. They can be mysterious and unpredictable. Quirky. Cats sometimes do eat dirt out of curiosity, stress, or boredom. But sometimes, there’s a background problem like anemia, nutritional deficiencies or something called pica

Bottom line: if your cat or kitten eats dirt once or twice, no biggie. If you notice more than that, get in touch with your vet.

How To Compost Safely For Cats

You can homebrew compost for your garden, your lawn, your planet – and keep your cat safe too.

  • If you are considering diving into composting, good for you! Before you buy a kitchen and outside container, check out ones that are sturdy with strong, locking lids to protect pets and wildlife.
  • If you already have a kitchen container, try keeping it in a cabinet that locks.
  • If you already have an outside compost container, and it doesn’t have a good, tight lid, then DIY a solution.
  • After adding compost to plant pots, add a layer of heavy stones, weed fabric or screening on top.
  • After adding compost to your flower beds, spray the area with an organic cat deterrent mixture, like rosemary oil extract. Or add plants that cats dislike, like Scaredy Cat Coleus.
  • In a row vegetable patch, add strips of chicken wire, trellis, or plastic fences over the dirt.


You have to be careful with compost and cats. Both homemade or ‘homebrewed’ compost and store bought bagged compost can be very bad for cats – making them ill or even causing death.

This is because compost contains mold, which in turn contains neurotoxins – more specifically tremorgenic mycotoxins – which can cause vomiting and severe illness in both cats and dogs.

The best thing to do is keep all compost bins covered at all times – and shut those pets inside when you’re spreading your compost in the garden.

Mark H.

Homeowner and property investor Mark H. aspires to bring you the very best outdoor living content, based on his years of experience managing outside spaces. Read more >