Composting is a fantastic way to reduce waste, improve soil health, and create nutrient-rich fertilizer for your garden. But not everything belongs in the compost bin. Some items can slow down decomposition, attract pests, spread disease, or even harm your plants. If you’ve ever noticed your compost taking too long to break down or emitting a nasty smell, the culprit might be something you tossed in without realizing it was a bad idea.
To keep your compost pile healthy, balanced, and effective, avoid adding these 12 common composting mistakes.
1. Meat and Dairy Products
While it might seem natural to toss leftover meat, bones, or dairy products into your compost, these items can quickly turn into a rotting, stinky mess. Not only do they take a long time to break down, but they also attract rodents, flies, and other pests that you definitely don’t want in your compost pile.
If you’re looking for ways to reduce kitchen waste, consider burying meat scraps in a separate area away from your main compost bin or using a Bokashi composting system, which is specifically designed to handle meat and dairy products.
2. Oily and Greasy Foods
Oil, butter, and greasy foods are compost killers. They create a thick, water-repelling barrier that prevents moisture from properly circulating in your compost pile. This slows down decomposition and can lead to foul odors.
Even small amounts of salad dressing, deep-fried foods, or cooking grease can create problems. Instead of composting them, wipe greasy pans with a paper towel and compost the towel instead—as long as it’s not soaked in synthetic chemicals.
3. Diseased or Pest-Infested Plants
Throwing diseased plants, moldy leaves, or pest-ridden clippings into your compost may seem like a good idea, but this is a fast track to spreading disease throughout your garden. Fungal spores, bacterial infections, and insect eggs can survive the composting process—especially if your pile doesn’t get hot enough to kill them.
If you’re dealing with powdery mildew, rust, or blight, it’s best to burn the infected plants or dispose of them in the trash rather than risk contaminating your future compost.
4. Weeds That Have Gone to Seed
Composting weeds can be a great way to return nutrients to the soil, but if the weeds have already gone to seed, you could be unknowingly spreading them all over your garden when you use the compost. Some seeds can survive the composting process, especially in a pile that doesn’t consistently reach high temperatures.
To avoid this problem, only compost young weeds before they flower and seed. If you have a hot composting system (above 140°F), it may be safe to compost some weeds, but it’s still a risk.
5. Glossy or Coated Paper
While shredded newspaper and plain cardboard are great for composting, glossy magazines, coated paper, and printed advertisements are not. These materials often contain synthetic inks, plastic coatings, and chemical dyes that won’t break down naturally and could introduce harmful toxins into your soil.
If you’re unsure whether a paper product is compostable, try ripping it—if it has a plastic-like coating or a shiny surface, it’s best to recycle it instead.
6. Citrus Peels and Onion Skins (In Large Amounts)
A little citrus here and there won’t ruin your compost, but too many orange, lemon, or lime peels can cause problems. Citrus fruits are highly acidic, which can slow down decomposition and disrupt the microbial balance in your pile.
Onion skins can have a similar effect, plus their strong odor can attract pests or make your compost smell unpleasant. If you want to compost citrus and onions, do so in moderation and chop them into small pieces to help them break down faster.
7. Pet Waste
Dog and cat feces contain harmful bacteria, parasites, and pathogens that aren’t safe for your compost pile—especially if you plan to use the compost for food gardens. Even in hot composting systems, these contaminants may survive and spread diseases.
If you want to compost animal waste, stick to manure from herbivores like cows, horses, rabbits, or chickens, as these are rich in nitrogen and beneficial for composting.
8. Treated Wood and Sawdust
Wood scraps and sawdust might seem like a natural addition to compost, but if they come from pressure-treated, stained, or painted wood, they can introduce harmful chemicals, heavy metals, and preservatives into your soil.
If you’re sure the wood is untreated and free of chemicals, sawdust can be composted in small amounts. However, because wood is high in carbon, it should be balanced with plenty of nitrogen-rich materials like food scraps or grass clippings to avoid slowing down decomposition.
9. Synthetic Tea Bags and Coffee Pods
Loose tea leaves and coffee grounds are fantastic compost materials, but not all tea bags and coffee pods are compost-friendly. Many brands contain plastic fibers, which won’t break down and will leave microplastics in your soil.
To avoid this, check whether your tea bags are 100% biodegradable or opt for loose-leaf tea instead. The same goes for coffee—stick with used coffee grounds and compostable coffee filters, but skip plastic coffee pods.
10. Charcoal Ash or Coal Residue
While wood ash from untreated firewood can be beneficial in small amounts, charcoal ash from grills or fireplaces is a big no-no. It contains toxic chemicals and heavy metals that can contaminate your compost and make your soil unsafe for planting.
If you have leftover wood ash from a fireplace, sprinkle it sparingly on your compost pile, but avoid using any ash that comes from chemically treated sources.
11. Cooked Starches (Pasta, Rice, and Bread)
Leftover bread, pasta, and rice might seem compostable, but they break down too quickly, creating a sticky, moldy mess that attracts rodents, flies, and unwanted bacteria. These foods can also clump together, limiting airflow and slowing down the composting process.
Instead of tossing them in the compost, try feeding small amounts to backyard chickens (if you have them) or using them in vermicomposting, where worms can break them down efficiently.
12. Large Branches and Thick Sticks
Wood takes a long time to break down, and large branches or thick sticks can sit in your compost pile for years without decomposing. While small twigs or shredded wood chips are fine, big chunks of wood should be chopped up or used as firewood instead.
If you want to compost wood, use a wood chipper to break it into small pieces, which will speed up decomposition significantly.
*This article was created with the help of AI.