Composting is one of the most rewarding practices for gardeners and eco-conscious individuals alike. It turns organic waste into nutrient-rich humus that can help improve your soil, reduce landfill waste, and promote healthier plants. However, despite its benefits, not everything should go into your compost pile. Some materials can disrupt the composting process, create unpleasant odors, attract pests, or even harm your plants. In this article, we’ll go over 13 common things you really shouldn’t compost and why it’s important to avoid them.
The Basics of Composting
Before diving into what not to compost, let’s review the basics of composting. The process involves the decomposition of organic materials through the work of bacteria, fungi, and other microorganisms. To maintain a balanced and effective compost pile, it needs a mix of carbon-rich “brown” materials (such as leaves, straw, and cardboard) and nitrogen-rich “green” materials (such as fruit and vegetable scraps, grass clippings, and coffee grounds).
The goal is to create a balanced, aerated environment where the organic matter can break down into humus—the dark, nutrient-rich material that enriches your soil. Maintaining the right balance of ingredients is key to a healthy compost pile. Adding certain materials, however, can upset this balance and lead to problems. Below, we’ll discuss the 13 common things that should never go into your compost bin or pile.
1. Meat and Dairy Products
While vegetable scraps, eggshells, and fruit peels make great compost materials, meat, fish, and dairy products should be avoided. These items contain fats and proteins that do not break down efficiently in compost and can cause a range of issues.
First, meat and dairy attract unwanted pests, such as rats, raccoons, and flies, which can quickly turn your compost into a smelly, unsanitary mess. Additionally, these materials may take much longer to decompose than plant-based items and can cause unpleasant odors. Furthermore, they may not break down completely, leaving behind scraps that could harbor pathogens that could potentially infect your garden soil.
2. Oils, Grease, and Fats
Whether it’s cooking oils, butter, or grease from your frying pan, oils and fats should never be added to your compost pile. Like meat and dairy, oils and fats are difficult to break down and tend to create a greasy, slimy mess in the compost. These materials can coat other organic matter, preventing oxygen from circulating properly and slowing the decomposition process.
Moreover, excessive oil can reduce the microbial activity in the compost, making it more difficult for bacteria and fungi to thrive. The result is a pile that takes longer to break down and produces fewer valuable nutrients for your garden.
3. Pet Waste
You might think that animal waste could be composted, but pet waste, including dog and cat feces, should never be added to your compost bin. Pet waste often contains harmful pathogens and parasites, such as roundworms, hookworms, and E. coli bacteria, that can survive the composting process and potentially contaminate your soil.
In addition, pet waste is high in nitrogen, which can throw off the balance of your compost pile, leading to excess ammonia that can make the compost pile too acidic or smelly. Instead of composting pet waste, it’s best to dispose of it properly by using designated pet waste composters or flushing it down the toilet.
4. Diseased Plants
While most plants are compostable, it’s important to avoid adding diseased plants to your compost pile. The high heat of a well-maintained compost pile can usually kill pathogens, but certain plant diseases, especially fungal infections, may survive and spread to your other plants when you use the compost in your garden.
If you have plants that show signs of disease, it’s safer to discard them in the trash or burn them rather than risk spreading the disease through your compost pile. This is particularly important when dealing with persistent diseases like blight or powdery mildew.
5. Weeds with Seeds
While weeds are a common composting material, weeds with seeds should not be added to your pile. Weeds can be an incredibly persistent problem in the garden, and adding them to your compost can result in spreading those pesky seeds throughout your garden once you use the compost. Even if your compost pile gets very hot, it might not reach the necessary temperature to kill weed seeds, especially those with hard coatings.
To be safe, either dispose of weedy plants by other means or ensure that your compost pile is large enough and gets hot enough to kill weed seeds (typically above 140°F or 60°C). You can also mulch over weeds in the compost to help break down the seeds more efficiently.
6. Non-Biodegradable Materials
Composting is all about breaking down organic materials into nutrient-rich compost, so non-biodegradable materials, such as plastic, metal, glass, or synthetic fabrics, do not belong in the pile. These materials do not break down naturally and can contaminate the compost, making it less effective.
While items like paper bags, newspaper, and cardboard are fine, avoid things like plastic-coated paper, wrapping paper, or any material with a non-organic coating. Always check your compost materials before adding them to ensure they’re biodegradable and free from synthetic substances.
7. Charcoal Ash
Many gardeners use charcoal for grilling, but charcoal ash should never be added to your compost. Charcoal often contains toxic chemicals from lighter fluid, and the ash can make the soil too alkaline. Additionally, charcoal ash has very little nutritional value for compost, which makes it an unnecessary addition.
Instead of adding it to your compost, dispose of charcoal ash in the trash or use it directly in areas of your garden that could benefit from a little extra alkalinity, such as around acid-loving plants like blueberries or hydrangeas.
8. Citrus Peels
While citrus fruits like oranges, lemons, and limes are delicious, their peels are too acidic for compost. High levels of acidity can disrupt the microbial activity in the compost and slow down the decomposition process. Citrus peels also take longer to break down, which can result in a compost pile that doesn’t heat up enough to break down other materials properly.
If you love eating citrus fruits, consider using the peels in your compost pile in moderation, or use them for other purposes like making citrus-infused water or cleaning solutions.
9. Onion and Garlic Scraps
While onion and garlic scraps are technically compostable, they should be avoided in large quantities due to their strong odor and potential to discourage beneficial microbes in the compost. Onions and garlic contain natural chemicals that can suppress the growth of some plants, so adding too much to your compost may create an environment that’s unfavorable for healthy microbial activity.
To avoid problems, it’s best to compost onion and garlic scraps sparingly. If you’re dealing with large quantities, consider adding them to the trash instead.
10. Treated Wood
Many people have leftover wood from home improvement projects or old furniture, but treated wood—especially pressure-treated wood—should not be composted. The chemicals used to treat the wood, such as chromated copper arsenate (CCA), can leach into the compost and contaminate the soil. These chemicals are harmful to both plants and animals.
If you need to dispose of treated wood, it’s best to check with local waste management services or recycling centers for proper disposal methods.
11. Coal Ash
Coal ash, like charcoal ash, is high in heavy metals and toxins that can contaminate your compost and garden soil. It may also create an imbalance in the pH levels of your compost, making it too alkaline.
Avoid composting coal ash by properly disposing of it in the trash or looking for specialized disposal methods in your area.
12. Glossy Paper
Glossy or shiny paper, such as magazines, catalogs, or some gift wrap, should be kept out of your compost. These materials are coated with chemicals and plastic that make them non-biodegradable. In addition, the glossy coatings may interfere with the composting process, leading to incomplete decomposition.
Instead of composting glossy paper, recycle it if possible or dispose of it through regular trash.
13. Synthetic Fabrics
Synthetic fabrics, like polyester, nylon, and spandex, are made from non-biodegradable materials. These fabrics don’t break down in the compost, and the fibers may even contribute to microplastic pollution.
If you’re clearing out your wardrobe, be sure to donate or recycle clothes made from synthetic fabrics, and avoid adding them to your compost pile.
Conclusion
Composting is an incredibly beneficial practice for gardeners and the environment, but it’s essential to be mindful of what you add to your compost pile. By avoiding these 13 common things that shouldn’t be composted, you can create a healthy, nutrient-rich compost that will improve the quality of your soil and help your garden thrive.
Take the time to properly manage your composting process and keep it clean from harmful or non-biodegradable materials. With the right approach, composting will continue to be an eco-friendly, sustainable way to give back to the earth and your plants. Happy composting!