A backyard compost bin can turn vegetable scraps into garden gold in three months — or attract every raccoon in the county and stink up the property line. The difference is what you toss in. Knowing what not to put in compost matters more than perfecting your green-to-brown ratio. After running residential bins for 15 years, here are the items I never let near my pile.
Meat, Bones, and Fish
Animal flesh is the number-one cause of pest problems. Raw chicken, fish trimmings, and beef scraps draw rats, raccoons, and stray dogs from blocks away. They also rot anaerobically, producing the rotten-egg smell that gets neighbors complaining. Skip them entirely in open or unsealed bins.
Industrial hot composting systems running above 140 degrees Fahrenheit can handle meat safely, but home tumblers rarely sustain those temperatures. If you must compost meat, use a dedicated bokashi bucket indoors first — it ferments the material before you bury the residue.
Dairy Products
Cheese, milk, yogurt, and butter break down slowly and smell aggressively. They go rancid before microbes get to them, and the lingering odor lasts weeks. Sour milk is no exception, despite some online advice. Pour spoiled dairy down the drain or into the trash.
Eggs themselves attract pests, but crushed eggshells are perfect — they add calcium that tomatoes love. Rinse the shells first to remove protein residue, then crush them between two plates before adding to the pile.
Oils, Fats, and Grease
Cooking oil, bacon grease, butter wrappers, and fatty leftovers coat compost particles and block oxygen flow. The pile turns into a sticky, foul anaerobic mass. A teaspoon of olive oil from a salad will not ruin a bin, but draining the deep-fryer into the compost will.
Pour used cooking oil into a sealed jar and recycle it through municipal programs. Many cities collect cooking oil free for biofuel conversion.
Pet Waste from Carnivores
Dog and cat feces carry pathogens — toxoplasma, roundworm, E. coli — that backyard composting temperatures will not kill. Cat litter compounds the problem with clay or silica that does not break down. Bag pet waste and trash it, or use a dedicated pet-waste digester buried in the yard, away from edible gardens.
Manure from herbivores like rabbits, goats, chickens, horses, and cows is fine and actually accelerates composting. Just age horse and cow manure six months first, since fresh manure can burn plants.
Diseased or Pest-Infested Plants
Tomato plants with blight, squash with powdery mildew, and rosebushes with black spot belong in the trash, not the compost. Home compost piles rarely hit the 160-degree internal temperature needed to kill plant pathogens, and infected debris will spread disease across your garden next season.
The same applies to plants infested with vine borers, spider mites, or scale. Bag and trash them. Reserve compost for healthy plant material.
Weeds Gone to Seed
Pulling crabgrass before it heads out is fine — the leaves and roots break down. Tossing in dandelions with seed heads or pigweed full of seed will plant thousands of new weeds across every bed you mulch with finished compost. Bag seeded weeds and trash them.
Invasive runners like bindweed, Bermuda grass, and Japanese knotweed go in the trash too. A single root fragment can survive years and resprout in your beds.
Glossy and Treated Paper
Plain newsprint and brown corrugated cardboard work great as brown material — shred them first. Glossy magazine pages, color advertising inserts, and thermal receipts are different. They contain clay coatings, BPA, or heavy-metal inks that you do not want concentrated in your vegetable garden.
- Yes: newsprint, brown cardboard, plain office paper, paper bags
- No: magazines, glossy ads, thermal receipts, colored junk mail
- No: stickers, packing tape, shipping labels
Pressure-Treated and Painted Wood
Sawdust from raw, untreated lumber composts beautifully — it is high-carbon brown material. Sawdust or chips from pressure-treated lumber, painted wood, or stained boards contains chromium, copper arsenate, or VOC residues. Toss those scraps in regular trash and reserve compost for raw cedar, pine, and oak shavings.
The same goes for plywood and particleboard scraps. The glues holding them together do not break down meaningfully and can leach formaldehyde.
Charcoal Ash and Coal
Wood ash from a fireplace burning untreated logs is fine in small amounts — a sprinkle adds potassium. Briquette ash from BBQ charcoal contains binders, accelerants, and lighter-fluid residue. Coal ash carries sulfur and heavy metals. Dispose of both in the trash, never in the compost or garden.
Synthetic Fabrics and Bioplastics
Cotton scraps and pure wool break down. Polyester, nylon, and rayon do not — they shed microplastics into your soil. Bioplastic cups, forks, and bags labeled “compostable” need 130-plus degrees Fahrenheit for weeks, which only industrial facilities deliver. Send them to municipal compost or trash, not the backyard pile.
The Master Avoid List
- Meat, bones, fish, and seafood shells
- Dairy products and eggs (shells okay)
- Cooking oils, fats, grease
- Dog and cat waste, used cat litter
- Diseased plants and infested debris
- Seeded weeds and invasive root runners
- Glossy paper, magazines, thermal receipts
- Pressure-treated, painted, or stained wood
- Charcoal briquette ash and coal ash
- Synthetic fabrics and certified bioplastics
Stick to plant-based kitchen scraps, yard waste from healthy plants, raw wood materials, and clean paper. Knowing what not to put in compost makes a bigger difference than any fancy tumbler — your pile will heat up faster, smell cleaner, and produce finished compost in 90 days instead of a year of frustration.
