What should you never compost at home? Skip these nine: meat, fish, bones, dairy, pet waste, treated wood, coal ash, glossy paper, and sick plants. Each one puts your pile, your garden, or your health at risk.
I learned the meat lesson the hard way at my first house. I dumped a tray of chicken trimmings into my bin one Sunday night without thinking twice. By Tuesday I had a family of raccoons tearing the lid off and dragging scraps across the lawn. Squirrels and rats followed within a week. I had to move the bin to a fenced-off corner and rebuild it from scratch.
The top items on the what not to compost list each have a clear reason behind them. Meat and fish put off strong smells that travel hundreds of feet and pull in rodents, raccoons, and stray dogs. Bones take 3 to 5 years to break down and rarely finish in a home pile. Dairy turns into a slimy mess that goes anaerobic and stinks like rotten eggs.
Pet waste from dogs and cats carries pathogens that survive in cold compost piles. Roundworm eggs, E. coli, and toxoplasmosis can hide in finished compost for months. The EPA warns home gardeners to keep dog and cat waste out of any pile used near food crops. Horse, cow, and chicken manure are fine, but only those from plant eaters.
Treated Wood and Sawdust
- Chemical leak: Pressure-treated lumber from before 2003 holds arsenic that leaches into compost and then into your food crops.
- Modern danger: Newer treated wood uses copper compounds that still build up in soil and harm earthworms and microbes.
- Safe swap: Use untreated hardwood sawdust from a local mill instead, but check the source for any paint or glue residue.
Coal Ash and Charcoal
- Heavy metals: Coal ash adds lead, mercury, and cadmium to your soil that plants pull up into the food you eat at dinner.
- Brick-style ash: Manufactured charcoal briquettes hold petroleum binders and lighter fluid that poison microbes for months.
- Wood ash okay: Plain wood ash in small amounts of 1 cup per bushel is fine and adds potash to the pile.
Glossy Paper and Magazines
- Ink trouble: Color glossy paper holds heavy metals and plastic coatings that do not break down in any home pile.
- Plain works: Black-and-white newsprint shredded into strips composts fine and adds carbon to balance your greens.
- Cardboard yes: Plain brown cardboard with tape removed makes great brown material when torn into small pieces.
Diseased plants need careful handling because spores can survive a cold pile and infect next year's garden. Tomato blight, squash powdery mildew, and rose black spot all spread this way. The EPA notes that hot composting at 140°F (60°C) or higher for three straight days kills most plant pathogens. Cold piles cannot reach those temperatures and should never receive sick plants.
My uncle ignored this rule for years and added blighted tomato vines to his compost each fall. His tomato crop dropped from 40 pounds down to 8 pounds over three seasons before he figured out the link. He pulled the compost from his beds, started a clean pile, and his harvest bounced back the next year.
You have good options for almost every banned item on this list. Many cities run yard waste pickup that takes meat and bones. Those big sites hit 160°F (71°C) heat for weeks. Sick plants can go in the trash or burn pile instead. Pet waste belongs in the regular garbage, not your food garden pile.
Keep these items to keep out of compost on a small list taped inside your kitchen cabinet for quick reference. A glance before you dump scraps takes two seconds and saves you from rebuilding a stinky pile six months from now. Your garden, your nose, and your raccoon-free yard will all be glad you did.
Read the full article: Composting Leaves: Complete Guide
