What Not To Compost: 33 Things You Shouldn’t Put In Your Compost Bin
We’re crazy about composting!
It’s one of the most impactful ways to reduce your carbon footprint at home.
Armed with the knowledge of what to compost and what not to compost, anyone can master the art of the cycle of life.
Here we’re focussing on the latter, because not everything is compostable—some food scraps and organic waste included.
What Can’t You Compost?
To harvest the benefits of composting, we need to keep a few things out of our compost to avoid inefficient biodegradation or, worse, contamination of the whole heap.
A waste of all that waste!
Our list is broken down (pun intended) into sections based on different locations around the home, including what food is not compostable and what yard waste should be kept out of your pile or bin.
Learning how to compost as much of your waste as possible is a wonderful way to embrace low-waste living. As you read through the list of things not to compost, think about how to avoid, reuse or recycle those items. We’ll provide some tips.
So, what should you not put in compost?
Let’s take a look.
1. What Not To Compost From The Kitchen
Our “what not to compost list” begins in the kitchen. If you’ve ever wondered what vegetables should not be composted or what other food things not to put in compost, this is a good place to start.
1. Meat, fish, and bones: Meat scraps are probably the biggest “composting don’t” as far as food waste goes. A few specialized composters can handle these items, but your run-of-the-mill compost pile or bin can’t.
Rotting meat and fish smells bad! And anything that stinks, of course, will attract unwanted pests, like raccoons, rodents, and maggots.
2. Dairy products and eggs: As dairy products break down and ferment, they’ll also start to smell. Like REALLY smell. Like rotten eggs and sour milk smell! Which pests and scavengers love.
3. Butter, cooking oil, animal fat, and grease: Oil and water just don’t mix. Since moisture is a key component of the composting process, these non-compostable food waste items won’t break down. Instead, they’ll shift the moisture balance of your pile and attract pests.
This includes paper towels saturated with grease—though you can otherwise compost paper towels.
4. Fat-based condiments and foods: Things like oily salad dressing and peanut butter will not break down any better than straight-up fats, for the same reason as #3.
5. Citrus fruit peels: Can citrus be composted?
Aside from taking a long time to break down, putting acidic citrus peels in compost risks throwing off the pH of your compost bin and slowing the overall decomposition process. Composting citrus is especially forbidden if you have a vermicomposter, because it can kill your hardworking worms.
Instead, you can put citrus peels to use by soaking them to make your own DIY cleaning products.
6. Onions and garlic scraps: If you’re wondering, “Can I compost onions?”, or “Can you compost garlic?”, the answer is: it depends.
As with citrus food scraps, putting garlic and onion in compost can kill worms and other beneficial composting organisms essential for breaking down organic matter.
While they are not recommended for vermicomposters, they should be fine, in small amounts, in your regular compost pile, provided they’re balanced with other items.
Instead of composting, you can also try planting your onion scraps to grow them into new bulbs. Or give them two lives and save them in the freezer with other vegetable scraps to make your homemade vegetable stock before composting.
7. Baked goods and cooked grains: No rice or freshly baked bread products, especially confections with glazes or high sugar content. Both breed harmful bacteria and attract rodents. Cooked rice is especially notorious for growing bad bacteria in a compost pile.
Plain bread that’s stale and hard (the only type of bread you should compost), and uncooked rice and pasta CAN be composted in moderation. Just be sure to bury it as deeply as you can.
8. Coffee pods and tea bags: While composting coffee pods is a pretty obvious no-no, tea bags may seem harmless—but they’re not (unless a zero waste tea company makes them). Many are made of food-grade PET (AKA plastic) or nylon fibers that, at best, will not break down and, at worst, contaminate the whole pile.
Coffee grounds and tea leaves are excellent sources of nutrients for compost, so remove them from their bags and pods.
Better yet, switch to loose-leaf tea and zero waste coffee makers like a moka pot or French press. These won’t put you at risk of brewing up a cup of microplastics and will leave you only with compostable tea leaves and coffee grounds to deal with.
9. Stickers on fruits and vegetables: These bits of plastic are easy to miss, but make sure you peel them off before tossing that banana peel in your pile. They don’t even break down in industrial composting facilities, let alone your home one.
In fact, they’re a huge source of composting contamination all over the world. You can eliminate your consumption of these annoying stickers altogether by buying directly from farmers at farmer’s markets.
10. Coated cardboard packaging: Any non-sustainable food packaging with either a plastic or foil layer is not suitable for your compost pile. This means waxy-lined paper cups, milk cartons, and juice boxes, and foil-lined paper snack, cracker, and cookie bags.
Takeaway coffee cups are also generally not compostable (or recyclable).
11. Bioplastic packaging and cellophane: Beware of any “biodegradable packaging” unless you know for a fact that it’s certified to be home compostable. Many of these are only compostable in industrial composting facilities (which get far hotter than your home compost pile).
While we’re on the subject of bioplastics, be sure to read up on compostable and biodegradable trash bags before you toss them in the worm bin or compost heap. They’re often not as green as they say they are.
2. What Can’t You Compost From The Yard?
12. Large branches or pieces of wood: These take forever to break down. They must first be chipped into small pieces.
13. Coal and charcoal ash: No charcoal from the grill. While wood ashes are safe to mix into your compost pile, coal ashes are not. They contain harmful substances like arsenic and mercury, which can contaminate your ecological garden with the finished compost.
14. Naturally toxic plants: Avoid Oleander leaves and anything from the black walnut tree (including walnuts themselves), which contains juglone, a naturally toxic compound for plants.
15. Treated lumber: Any lumber intended to be used as building materials is usually treated with water repellent coatings that contain toxic chemicals.
Plus, these chemicals will make them more resistant to moisture and, thus, biodegradation. In other words, they’ll take a very long time to break down.
This includes sawdust from treated wood. Sawdust from chopping firewood: okay to compost. Sawdust from your home construction project: add to your “what not to put in compost bin” list.
16. Tomato fruits: Tomato plants and trimmings are fine, provided they are not showing any signs of diseases. Technically, the fruits are fine, too. But unless your compost bin or pile is hot enough, the seeds can survive and lead to baby tomato sprouts anywhere you use the compost.
Instead, pick your overripe tomatoes from your sustainable garden to make some yummy salsa!
17. Synthetic fertilizer: Don’t dump remnants of fertilizer or even soil recently treated with large doses of it in your pile. Synthetic fertilizers may do a few things to compost: kill microorganisms (slowing down the pile’s decomposition rate), alter the pH and nutrient levels, and eventually leach into the ground.
18. Lawn trimmings recently treated with pesticides or herbicides: Grass often has some degree of chemical treatment. The composting process is pretty well suited at breaking those materials down harmlessly, but only in small amounts.
Since lawns are typically treated in high concentrations, a freshly treated lawn shouldn’t go near your compost until the concentration has had time to weaken and dilute. Give it a few weeks.
Unless your composter gets really hot (meaning it’s operating at maximum efficiency, which is unlikely), there’s no guarantee these things will be killed. If they’re not, you could spread diseases around with your compost.
20. Weeds gone to seed and invasive plants: Dandelions and ivy, for example, are persistent weeds that will simply sprout in your compost pile and spread to wherever you use the compost.
21. Cigarette butts: Some are made of plastic, but that aside, cigarettes are filled with chemicals. Straight tobacco is compostable, but unfortunately, that’s not all that’s in cigarettes.
3. Things You Can’t Compost From The Bathroom
22. Synthetic soaps: Soaps shouldn’t go in your compost unless they’re made entirely out of natural skin care ingredients or certified as biodegradable (and thus safe for the environment).
Even if you have a tiny sliver of standard bar soap left over, you’re better off collecting it and once you have a few, melt them together to make a new bar.
23. Used feminine hygiene products: Can you compost tampons?
Nope. No pads (even organic pads), tampons, or even cardboard applicators. Anything with blood can contain hard-to-kill pathogens, which can transfer to your compost. You can compost reusable cotton liners, but only if they’ve been thoroughly washed.
24. Humans feces and diapers: Like blood, human feces poses a significant health risk and can contain diseases and parasites. Keep your poo in the loo and not on the lawn.
As with reusable liner pads, you can compost reusable eco-friendly diapers, provided they’re made with 100% natural fabrics and they’ve been washed. Note that most disposable biodegradable nappies are not yet home-compostable and nor are diapers recyclable.
4. Things You Cannot Compost From The Closet
25. Vacuum cleaner contents: The tiny plastic or synthetic fibers carpets constantly shed could contaminate your compost (as well as the odd price tag connector or LEGO piece that gets sucked up).
26. Dryer lint: Dryer lint contains various fabrics and can also contaminate your pile. Even if you only dry 100% cotton clothing in a separate load (which is compostable clothing), the lint could still contain synthetic fibers from previous loads.
27. Synthetic fabric of any kind: These contain all sorts of harmful chemicals and dyes. Even if your t-shirt is 99% Cotton and just 1% polyester, it can’t be composted. Because even the smallest amount of these fibers can ruin a compost batch, synthetic fabrics should be at the top of your list of what not to put in your compost bin.
28. Leather goods: This means worn-out belts (even sustainable belts), wallets, purses, gloves etc. Due to oil finishes and unknown chemical ingredients, i.e., additives, dyes, and chemical tanning agents, it’s best to keep leather out of your compost bin.
Not only are these ingredients potential contaminants, but they also mean that the leather will take a long time to decompose.
Most vegan leather also can’t be composted as it’s often plastic-based, non-organic material. Exceptions include things like 100% natural cork fabric or untreated fruit-based leathers (as long as they don’t have a PU coating, which many do).
Try to find other clever ways to reuse your old shoes or handbags made of leather instead. Maybe you can still donate them to a non-profit or thrift shop. If not, you might be able to use the leather scraps to make an eco-friendly gift.
5. What Cannot Be Composted From The Office
29. Paper with lots of color printing or Sharpie drawn inks: Colored printer ink and markers such as Sharpies can contain heavy metals and other toxins. Anything saturated with these can contaminate your compost.
30. Glossy Paper: Any paper with a glossy, plastic finish is toxic to your compost pile. This, unfortunately, means some magazines, product catalogs, most wrapping paper (unless it’s zero waste or eco-friendly wrapping paper), and photographs.
6. What Can You Not Compost From Pets And Animals
31. Dog and cat feces and litter: Carnivorous and omnivorous animals’ intestines can play host to a wide range of resilient parasites and pathogens. Cat poop is especially dangerous and even eco-friendly cat littler should generally be thrown in the trash.
This type of animal waste must be composted separately in special, high-temperature pet waste composters (more about this in our zero waste dog article).
Manure from other purely plant-munching pets or livestock, however, is very beneficial. In that sense, vegan cat food is probably ok to compost too.
32. Manure from sick animals: Herbivorous or not, any sick animal can pass on harmful bacteria and viruses through their excrement.
33. Dead animals: One of the more interesting composting facts is that it’s legal to compost human remains in some states, but that doesn’t mean you should try to compost your beloved fur-family members.
For the same reason you shouldn’t compost meat, dead animals will stink, attract pests, and grow potentially unwanted pathogens.
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Final Thoughts On What Is Not Compostable
On the other side of the coin, what you can compost is a lengthy list of organic waste possibilities waiting to be returned to the earth.
But when in doubt, leave it out.
Besides, nothing says “compost buzzkill” like a bit of compost contamination that ruins all your good, well-intentioned work.
If you found this article helpful, consider sharing it with your compost-crazy friends, so we can all avoid a compost killjoy and live a little more zero waste.