What Can and Can’t Go in Your Compost Pile: The Complete List

Understanding the Composting Process

Before diving into the lists, it’s essential to understand how composting works. The process is driven by microorganisms—bacteria, fungi, and actinomycetes—that feed on organic material, breaking it down into humus, the dark, crumbly substance that enriches soil. These microbes need four key things to thrive: carbon, nitrogen, moisture, and oxygen. Carbon-rich materials, known as “browns,” provide energy and structure. These include dried leaves, wood shavings, and paper products. Nitrogen-rich materials, or “greens,” supply protein and moisture. Kitchen scraps, coffee grounds, and grass clippings all fall into this category. When you maintain a proper balance—roughly three parts brown to one part green—the decomposition process works efficiently and produces sweet-smelling compost. But introduce the wrong materials, and your pile could quickly turn anaerobic or contaminated.

What You Can Compost

The good news is that most organic matter from your home and garden can safely go into your compost pile. These materials provide essential nutrients for microbes and decompose readily when mixed properly.

Kitchen Scraps: Fruit and vegetable peels, cores, and rinds are composting gold. Banana peels, apple cores, melon rinds, potato skins, and carrot tops all break down beautifully. Coffee grounds, tea bags (without plastic), and eggshells are excellent additions. These items add nitrogen and calcium, helping to balance the mix of materials.

Yard Waste: Leaves, grass clippings, small branches, and weeds (that haven’t gone to seed) are perfect browns and greens for compost. Shred or chop them first to speed up decomposition. Pine needles, straw, and plant trimmings all add valuable texture and aeration to the pile.

Paper and Cardboard: Shredded newspaper, cardboard, and paper towels can all be composted as long as they are free of plastic coatings, inks, or adhesives. They provide structure and carbon while absorbing excess moisture.

Natural Fibers: Cotton, linen, wool, and jute break down over time, especially if cut into small pieces. Old clothing or fabric scraps made from 100% natural fibers can find new life in your compost heap instead of the landfill.

Other Organic Materials: Hair, pet fur, vacuum dust, and even nail clippings can be composted. These may decompose slowly but contribute valuable nitrogen. Wood ashes from untreated wood, in small quantities, can help neutralize acidity, though moderation is key—too much can make your compost too alkaline.

The “Browns” and “Greens” Balance

A healthy compost pile thrives on balance. Browns (carbon-rich materials) provide bulk and airflow, while greens (nitrogen-rich materials) supply moisture and microbial food. Too many browns, and the pile decomposes slowly; too many greens, and it may become slimy or smelly. Browns include dried leaves, straw, cardboard, and sawdust. Greens include vegetable scraps, grass clippings, and coffee grounds. Layering them like a lasagna—alternating wet and dry, green and brown—creates ideal conditions for composting. This balance also prevents pests and odors, allowing beneficial microbes to do their work efficiently.

What You Can’t Compost

Some materials are better left out of your compost pile. While they may be organic, they can create problems ranging from unpleasant smells to contamination.

Meat and Dairy Products: These items attract rodents, raccoons, and flies. They decompose slowly, produce foul odors, and can harbor harmful bacteria. Bones, cheese, butter, and greasy foods fall into this category.

Oily and Fatty Foods: Cooking oils, salad dressings, and greasy leftovers should never be composted. They create anaerobic conditions that choke out beneficial microbes and attract pests. Even small amounts can coat organic materials, slowing decomposition.

Diseased or Invasive Plants: Composting can kill most weed seeds and plant diseases if the pile heats above 140°F, but backyard systems often don’t reach that temperature consistently. Avoid adding diseased plants or invasive species like bindweed or crabgrass, as they can reemerge in your garden later.

Pet Waste: Dog and cat feces may contain pathogens dangerous to humans. While manure from herbivores like rabbits, chickens, or cows can enrich compost, waste from carnivorous pets should be excluded.

Treated Wood and Ashes: Sawdust or ashes from painted, stained, or pressure-treated wood may contain harmful chemicals that don’t belong in your soil. Only use clean, untreated wood materials.

Synthetic or Non-Biodegradable Materials: Items like plastic bags, rubber, coated paper, foil, and Styrofoam will not break down in compost. Even some “biodegradable” packaging takes years to decompose, so it’s best to avoid these altogether.

Citrus and Onions (in excess): Small amounts are fine, but large quantities of citrus peels and onion skins can make compost too acidic, slowing down microbial activity. If you juice citrus often, balance it with plenty of neutral browns.

Composting Problem Items Safely

Some materials fall into a gray area—they can be composted under specific conditions but require care. For example, bread and grains can attract pests if left exposed but are fine when buried deep in the pile. Cooked vegetables are acceptable in small amounts as long as they aren’t oily or salty. Tea bags can go in the compost only if they’re made from plant fibers, not synthetic mesh. You can also compost paper towels and tissues if they haven’t been used with harsh chemicals or cleaning products. Even wood chips can work well, though they take much longer to decompose and are best used in a separate slow pile. If you’re composting in an enclosed tumbler or worm bin, you’ll have more flexibility with what you can safely add since pests are less likely to become a problem.

Composting Myths That Confuse Beginners

There are many myths about what should or shouldn’t go into compost. One common misconception is that adding citrus or onions kills worms and microbes. In moderation, these materials are fine; it’s excess that causes problems. Another myth is that you can’t compost paper products—when shredded and moistened, they actually provide excellent structure and balance. People often fear that composting diseased plants is always dangerous. While it’s true that pathogens can survive in cool compost, a well-managed hot compost pile can safely process them. The key is maintaining consistent temperatures and proper aeration. Finally, some believe that composting attracts pests no matter what. In reality, properly covered, balanced compost piles don’t smell or attract animals. Problems only arise when too much food waste, fat, or meat is added without sufficient browns or aeration.

Maintaining a Clean, Balanced Compost Pile

A clean compost pile isn’t about eliminating all odors—it’s about cultivating the right ones. A healthy compost should smell earthy and slightly sweet, like a forest floor. If it smells sour or rotten, it’s too wet or rich in nitrogen. Add more browns, turn the pile, and allow oxygen to circulate. Regular turning every week or two prevents compaction, redistributes materials, and speeds up decomposition. Keep your pile moist but not soggy—aim for the texture of a damp sponge. When properly managed, your compost will transform scraps into finished humus in a matter of months, with no unpleasant surprises.

The Environmental Impact of Smart Composting

Learning what to compost and what to avoid isn’t just about maintaining a tidy garden—it’s about sustainability. Every banana peel or coffee ground that goes into your compost bin reduces the volume of waste in landfills, cutting methane emissions and contributing to healthier ecosystems. Smart composting also prevents harmful substances from leaching into your soil. By keeping plastics, treated wood, and chemical residues out of your pile, you protect your plants and groundwater. The result is a pure, organic soil amendment that nurtures plant roots and supports biodiversity. When you compost responsibly, you join a global movement toward waste reduction and regenerative living. Every decision—every peel, clipping, and scrap—becomes part of a cycle that restores rather than depletes.

Bringing It All Together

A compost pile is a living system—a balance of carbon and nitrogen, moisture and air, microorganisms and time. Knowing what belongs in that system keeps it healthy and productive. When you respect the process and feed it wisely, it rewards you with the best soil amendment nature can provide. Think of your compost pile as a recipe: the right ingredients make all the difference. The next time you scrape a plate or rake the yard, take a moment to ask yourself whether that material will feed your soil or fight it. With this knowledge, your compost will thrive—producing rich, dark, sweet-smelling “black gold” that fuels gardens, restores soil, and helps close the loop between waste and renewal.