I Run a Community Compost. Here’s What Really Doesn’t Belong in the Bin.
I run a community compost operation at a local community garden, so I’ve gotten asked every question you can imagine about what does and doesn’t go in the compost.
From questions of meat and dairy, to various bags and forks labeled as “compostable,” to trying to figure out if that piece of cardboard or paper plate has any plastic in it, I’ve had to make the call.
I’ve watched it decompose (or not), and seen the final result.
Here’s my thought process.
There is no perfect answer to what not to put in your compost, because there’s a balance of several goals with composting.
- Diverting food waste from landfills
- Creating high-quality soil
- Creating lots of soil
- Creating that soil quickly
- Keeping a pleasant, scent-free environment
- Making it convenient for others to drop off
Sometimes these goals are in tension. You can decide based on your priorities. For example, chicken bones and their calcium and other minerals will contribute to a nutrient-rich soil. But they will break down slower than banana peels.
Most Advice Online is Overly Cautious, In My Opinion
I don’t know why this is, but both online and offline there are pervasive myths that you can’t compost certain things.
In general, I find the conventional advice to be more cautious than it should be.
Almost nothing will “break” your compost pile. It may slow it down.
You may need to mix more or bury it to keep out smells. If it’s plastic, you may need to pick it out when you sift. Aside from a few nasty items like poison ivy or dog poop, it’ll all work itself out.
It’s hard to kill a compost bin because what you’re putting in is already dead. (Very philosophical, sit with that for a minute.)
Okay, let’s get into the list.
Things You Shouldn’t Put in the Compost
Pet waste
Pet waste from dogs and cats can contain parasites and pathogens that don’t break down in a typical compost pile. Unless you’re running a hot composting system designed to handle it, keep it out. It’s not worth the risk of contaminating your finished soil.
Pet waste takes so much heat and time to break down that even industrial composting sites don’t usually accept it.
Glossy or coated paper (like magazines or receipts)
Magazines, receipts, and other glossy papers are often coated with plastic or contain thermal inks and chemicals that don’t belong in your soil.
They may break down partially, but you’ll likely end up picking out bits of plastic at the end. It’s better to recycle these or toss them.
Glossy cardboard (like cereal boxes)
Many cereal boxes and similar packaging have a thin plastic lining to keep out moisture. That lining doesn’t break down in compost and just adds microplastics to your pile.
My simple rule is to look for colored ink. If it has colored ink, I don’t want it in my bin. Put that stuff in the recycling.
Certain weeds (like poison ivy)
Weeds like poison ivy, poison oak, or anything invasive with deep taproots or seed heads can survive the composting process unless your pile gets consistently hot. Poison ivy also contains oils that can cause skin irritation even when dead.
Keep them out of your bin.
Chemically treated wood or sawdust
Treated lumber and sawdust from treated wood often contain preservatives and chemicals designed to resist decay. Those same chemicals can harm beneficial microbes and end up in your soil.
Coal ash or charcoal briquettes
Unlike wood ash, coal ash contains heavy metals, additives, and binders that can contaminate your compost. A small sprinkle of clean wood ash is fine, but coal-based products are a no-go.
Fruit stickers
Fruit stickers are my nemesis. I try my best to keep them out. In a community compost setting like mine, they’re almost inevitable, so I end up taking a lot of them out when I sift.
They won’t break down, and you’ll find them scattered throughout your finished compost. Best to peel them off before tossing your scraps if you can.
Produce ties
Plastic or wire produce ties don’t break down in compost and can tangle up your finished soil. Even the “paper” ones often have a metal core. Composting is easier when you keep these out from the start rather than fishing them out later.
Tea bags
Many tea bags are made with or sealed by plastic, even if they look like paper. Over time, the bag breaks down, but the plastic mesh remains. If you’re composting tea, confirm that there’s no plastic.
Old-school tea bags are made of paper and are compostable.
Things That Shouldn’t Go in Your Compost, Unless it Gets Really Hot
Now it’s time to get into the gray area.
“Compostable” Bags
In my experience, even when the bin gets hot, the “compostable” bags don’t fully break down. In fact, I think they will just end up as a sort of “microplastic” in the soil.
I’ve been telling people at this point that it’s better to use a paper bag or, if they want less cleanup, a regular plastic bag.
The compostable bags are for industrial composting.
If you know a specific brand that does break down in a backyard bin, let me know.
Other Industrially Compostable Items
“Compostable” wrappers, forks, spoons, and cups that look plastic but are plant-based won’t break down unless they get really hot.
If they look more like cardboard, like many take-out containers that are labeled “compostable,” I’ve had no issue composting them. The ones that look like plastic cause the issues.
Weeds
The problem with weeds is that if the seeds survive, you’ll have to do more weeding wherever you distribute your compost.
However, I don’t take a hard line against this.
First, I always let them dry out in the sun. Second, I put them in a yard waste bag and leave them there for months.
If the compost is extra hot, as it often is in the summer (for most weeds around 130 F), then I’ll toss the dried-up and broken-down ones in my compost bin. I’ve never had issues with the final product.
If they’re particularly dangerous or abundant, I’ll leave them in our mulched part of the garden. Mulch suppresses weeds. If they pop up, I add more mulch. Problem solved.
Large amounts of oil and greasy foods
Some oil and grease are no problem for my bin. However, I don’t want a dumping of leftover frying oil from a restaurant. It can slow down the pile, doesn’t compost well, and can bring smells and pests.
Things That You Can Put in Your Compost, As Long As You Do It Right
For these things, there are a few rules of thumb that reduce the chances of having issues with the smell or quality of your pile.
- If your bin is covered
- If your bin is bigger
- If you’re consistently stirrin
- If you’re adding enough browns (I have a whole article on getting the green to brown ratio right).
Yes, these items may slow down your composting compared to sticking strictly to kitchen scraps and leaves. But they’ll still break down and contribute nutrients if handled right.
Bones
A bone is like composting a stick, but with more nutrients. They don’t create the smells that meat can. If you’re patient and keep your pile active, they’ll enrich your compost with minerals.
Meat
This one depends on your bin, situation, and goals.
The general narrative is that meat will make your bin smell and attract critters. But even with minimal effort, this is easy to avoid.
First, chop it into small pieces. Meat smells when it’s clumped and wet, which blocks oxygen and leads to anaerobic decomposition (the source of the stink).
Second, add lots of browns, like dry leaves or shredded cardboard, to balance the moisture.
Third, bury it deep in the center of the pile, where it’s hottest and out of reach of animals.
If after mixing I can’t see the meat, then I don’t worry about it.
Done right, it breaks down just like anything else.
Dairy
Like meat, it needs to be mixed well and balanced with plenty of browns to avoid smells. Small amounts disappear quickly in a healthy, hot pile.
Citrus and onion scraps
People often say citrus and onions harm worms and slow down composting. In my experience, they break down just fine. Toss them in unless you’re chasing the fastest, finest compost possible.
Paper products (uncoated)
Plain paper towels, napkins, and cardboard are excellent carbon sources. Shred or tear them first so they break down more evenly.
Eggshells
Eggshells break down slowly, but they’re a great source of calcium. Crushing them into small pieces before adding speeds up the process and prevents them from staying intact in your finished compost.
The same goes for other slow-to-break-down stuff like avocado pits and coconut shells.
If you want your soil as fast as possible, you’ll want to keep them out of that bin, but they’re break down.
Coffee grounds & tea bags (plastic-free)
Coffee grounds are a fantastic nitrogen source and help heat up your pile. They can make things soggy, so add some browns to keep the mix balanced. For tea bags, check for plastic mesh—if they’re fully compostable, throw them in; if not, just empty the tea leaves.
Bread, Rice, and Pasta
Like meat, if you bury it, do it in reasonable quantities, and add enough browns, it’s not a problem.
Hair
I’ve literally gotten a haircut at my community garden and thrown my hair into the compost bin after. As long as your hair isn’t coated in a chemical product that you don’t want in the soil, throw it in the bin. In fact, I found it broke down pretty fast in the center of the bin.
Now, I also threw hair in from someone with longer hair, and it got tangled around my compost cranker. It still decomposed quickly. Two weeks later, I didn’t notice it.
In fact, hair has lots of nitrogen.
I encourage You to Experiment
After running a community compost, I’ve learned that there’s rarely a one-size-fits-all rule.
The key is to understand your pile, stay curious, and keep experimenting. Composting is an active process. If you manage it well, it can handle a lot more than most lists suggest.
Industrial Composting: Different Rules
If your town or city is shipping off your compost somewhere else, there are different rules. But the result often isn’t as good either, as I’ve written about.
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