7 Things You Should Never Compost

Don't turn your "black gold" toxic by adding undesirable materials.

November 10, 2015
mulch in a farmer's hands
Avoid Compost Mistakes


Composting is amazing for so many reasons—it keeps waste out of landfills and fills your garden with nutritious fuel for your crops.

But not everything should land on your compost pile. For instance, some seemingly perfect biodegradable materials could be full of microscopic plastic particles or toxic heavy metals that don't break down in the soil. Check out these 7 things you should never compost—and 7 things you should!


cute dog
Pet Waste


Why Avoid It: Waste from your cat, dog, or pet reptile should not be added to your compost pile. Keep associated pet bedding out of there, too, since it could harbor dangerous pathogens, including the Toxoplasma gondii parasite. This common parasite is especially dangerous for pregnant women, but researchers are also tying it to schizophrenia.

Compost This Instead: According to Compostology 1-2-3, you can add your pet's hair to the compost pile after grooming. (Just be sure not to do it when you've recently treated your pet with flea- and tick-fighting insecticides.)

Washing Machine
Dryer Lint


Why Avoid It:  Dryer lint is often loaded with tiny plastic particles that shed from synthetic clothing fibers and never break down in the soil. Add to that the fact that the most popular dryer sheets, fabric softeners, and detergents contain toxic synthetic fragrance chemicals called phthalates, and it's easy to see why this should be tossed straight into the trash.

Compost This Instead: Got a dead houseplant you've been ignoring in your house? As long as it's not diseased, toss that on the compost pile for a nice dose of nitrogen. Household plant trimmings like stems, leaves, and faded blooms are also perfect for tossing into a compost pile.

greasy food
Grease, Fats, Oils


Why Avoid It: According to Compostology 1-2-3, adding these high-fat materials to the compost pile provides an invitation for four-legged pests to visit. While trace amounts are OK, these fats break down very slowly, providing another reason to keep them out of the compost pile.

Compost This Instead: While you should also avoid putting dairy, bones, and meat on your compost pile to keep pests away from your home, you definitely should compost your veggie scraps and eggshells. Just bury them so they don't attract animals to your composting area.

vacuum cleaner bags
Contents Of Vacuum Cleaner Bags


Why Avoid It: Household dust may seem innocent enough, but studies have found it's loaded with harmful pesticide residues, flame retardants from household electronics and couches, and fake fragrance chemicals that spew from products like air fresheners and candles.

Compost This Instead: While adding household waste found in the vacuum cleaner bag to compost is a bad idea, adding waste from your yard is not. All kinds of leaves make valuable additions to any composting operation, according to Compostology 1-2-3. Shred them or run over them with a lawn mower to chop them up, speeding decomposition and helping to prevent them from sticking together into mats that resist composting. (Here are the top ways to troubleshoot common composting problems.)

Drywall Scraps


Why Avoid It: Drywall seems like a great dry material to add to your compost pile, but this building material could be laced with toxins, since it's often made from waste from coal-fired power plants. Plus, remember the Chinese drywall scandal that took place several years ago?

Compost This Instead: You can use sawdust, though only in moderation because it breaks down very slowly and can lock up nitrogen. Never use sawdust from treated or painted wood.

Certain Weeds


Why Avoid It: Composting weeds that have set seed or weeds that root easily from stems or rhizomes, such as field bindweed and Canada thistle, are big no-nos. Beware of weeds that are unusually drought tolerant—Asiatic dayflower (Commelina communis) is one example—as they often have enough moisture in their leaves to survive being pulled up and dumped in a compost heap. Once there, they can easily root and spread, according to Compostology 1-2-3.

Compost This Instead: Most weeds that haven't set seeds are OK to compost. Remember to leave drought-tolerant weeds in a sunny spot for several days until they are thoroughly dead before you add them to compost.

Discard weeds with fast-spreading roots that spread via rhizomes, such as Canada thistles (Cirsium arvense). You can burn them, discard them in the trash, or kill them by wrapping them in a closed trash bag in a sunny spot for several days. Once they've died and turned into a dark goo, you can safely add them to your compost pile.

glossy ribbon
Glossy Paper


Why Avoid It: Paper, especially glossy paper printed with colored ink, may contain heavy metals. It's best to recycle paper instead of tossing it into your compost pile.  

Compost This Instead: According to Compostology 1-2-3, you can compost cardboard in small amounts, provided you tear it into small pieces to speed decomposition. Avoid cardboard printed with colored inks and understand that come cardboard is treated with insecticides to keep pests out of the packaging. (Some people prefer to just recycle it to be safe.)

This article originally published on Rodale Wellness.