Composting goes beyond a feel-good eco habit—it’s a powerhouse move for stronger plants and a healthier planet. According to the Environmental Protection Agency, composting not only curbs methane emissions from landfills but also enriches soil and saves water¹.
Yet, not everything in your kitchen or yard is compost-friendly. Some materials, though seemingly benign, can upset the pile’s balance, transforming a garden booster into a potential hazard.
Here’s a look at 17 items you should keep out of your compost to protect both your garden and the environment.
1. Meat & Fish
Tossing meat and fish scraps into your compost pile is a recipe for disaster. These protein-rich items break down slowly and emit strong odors that attract unwanted visitors.
Rats, raccoons, and other scavengers will be drawn to your compost like moths to a flame, potentially spreading diseases and creating a mess.
The decomposition of meat and fish can introduce harmful bacteria into your compost. These pathogens may survive the composting process and contaminate your garden soil, posing health risks to you and your plants.
It’s best to dispose of meat and fish scraps through other means or check if your local commercial composting facility accepts them.
2. Dairy Products
Cheese, milk, yogurt, and other dairy products have no place in your backyard compost bin. Like meat, dairy items are prone to putrefaction, which can create foul odors and attract pests. The high fat content in dairy products can also disrupt the delicate balance of your compost pile.
Dairy products can slow down the decomposition process. They tend to create anaerobic conditions in your compost, which inhibits the growth of beneficial microorganisms.
This can lead to a slimy, smelly mess instead of the rich, crumbly compost you’re aiming for. Save your dairy for consumption or explore alternative disposal methods.
3. Oils & Fats
Cooking oils, animal fats, and greasy foods should be kept far away from your compost pile. These substances can coat organic materials, creating a barrier that prevents air and water from reaching the decomposing matter. This leads to anaerobic conditions and slows down the composting process significantly.
Oils and fats can upset the moisture balance in your compost. They repel water, making it difficult for the pile to maintain the ideal dampness needed for decomposition.
Excess oils can also attract pests and create unpleasant odors. Instead of composting, consider recycling used cooking oil or disposing of it properly according to local guidelines.
4. Diseased Plants
While most plant matter is compostable, diseased plants are a notable exception. Adding infected plant material to your compost pile can spread pathogens throughout your garden.
Many plant diseases can survive the composting process, especially in home compost systems that may not reach high enough temperatures to kill them off.
When you use compost containing diseased plant matter, you risk reintroducing those pathogens to your healthy plants. This can lead to widespread infection in your garden, undoing all your hard work.
It’s safer to dispose of diseased plants through municipal yard waste collection or by burning them if local regulations allow.
5. Pet Waste
Dog and cat feces, as well as used cat litter, should never find their way into your compost bin. These materials can harbor parasites, bacteria, and other pathogens that pose serious health risks to humans.
Even if your compost reaches high temperatures, it may not be enough to kill off all the harmful organisms present in pet waste. Moreover, pet waste can introduce excess nitrogen into your compost, throwing off the carbon-to-nitrogen ratio. This imbalance can lead to ammonia production and unpleasant odors.
Instead of composting, consider flushing pet waste down the toilet or disposing of it in the trash according to local regulations.
6. Citrus Peels & Onions
While fruit and vegetable scraps are generally great for composting, citrus peels and onions are exceptions to this rule. Citrus peels contain oils that can kill beneficial microorganisms in your compost pile. These oils are natural pesticides that can slow down the decomposition process and potentially harm your plants when the compost is used.
Onions, on the other hand, can repel worms, which are crucial for a healthy compost ecosystem. They also have a strong odor that can attract pests.
While small amounts of citrus and onions won’t completely ruin your compost, it’s best to avoid them if possible. Consider using citrus peels for homemade cleaning products and adding onion scraps to your vegetable stock instead.
7. Glossy or Coated Paper
While plain paper products are generally compostable, glossy or coated paper should be kept out of your compost bin. Magazines, catalogs, and other shiny paper products often contain chemicals and inks that can be harmful to your compost and, ultimately, your garden soil.
These materials may introduce toxins that persist even after the composting process is complete.
Coated papers break down very slowly, if at all. They can create clumps in your compost that impede airflow and moisture distribution. Instead of composting, recycle glossy papers whenever possible. If recycling isn’t an option, dispose of them in the regular trash.
8. Treated Wood Products
Sawdust and wood chips from untreated wood can be excellent additions to your compost pile, but treated wood products are a definite no-go. Pressure-treated lumber, painted wood, and wood treated with preservatives contain chemicals that can be harmful to beneficial microorganisms in your compost. These toxins can persist in the finished compost and potentially harm your plants.
Treated wood products often contain heavy metals and other pollutants that can accumulate in your soil over time. This can lead to long-term environmental contamination and health risks.
If you’re unsure whether wood is treated, it’s best to err on the side of caution and keep it out of your compost.
9. Coal Ash
While wood ash can be beneficial for compost in small quantities, coal ash should never be added to your pile. Coal ash contains high levels of toxic substances, including heavy metals like mercury, arsenic, and lead.
These contaminants can persist in your compost and eventually make their way into your garden soil and plants.
Coal ash can significantly alter the pH of your compost, making it too alkaline for many plants to thrive. This pH imbalance can also disrupt the activity of beneficial microorganisms in your compost. It should be disposed of according to local regulations instead of composting, as its toxic nature may require special handling.
10. Large Branches
While small twigs and plant matter are great for composting, large branches should be avoided. These woody materials take an extremely long time to break down, often outlasting the rest of your compost pile. They can create air pockets that are too large, disrupting the balance of your compost and potentially drying it out.
Large branches can make it difficult to turn and manage your compost pile effectively. If you have a lot of woody material, consider chipping or shredding it before adding it to your compost.
Alternatively, you can use larger branches for other garden projects like creating natural borders or as supports for climbing plants.
11. Synthetic Fabrics
Natural fibers like cotton and wool can be composted, but synthetic fabrics should stay out of your compost bin. Materials like polyester, nylon, and acrylic are essentially plastics that won’t break down in your compost pile. These synthetic fibers can persist in the environment for hundreds of years, contributing to microplastic pollution.
Synthetic fabrics often contain dyes and chemical treatments that can be harmful to the microorganisms in your compost. Even if they do eventually break down, they may release toxic substances into your compost.
Instead of composting, consider donating wearable synthetic clothing or recycling it through specialized textile recycling programs.
12. Bread & Baked Goods
While bread and other baked goods are biodegradable, they’re not ideal for home composting. These items tend to mold quickly, which can introduce unwanted fungal spores into your compost pile.
The mold can spread to other materials in your compost, potentially slowing down the decomposition process.
Bread and baked goods can attract pests like rodents and insects to your compost pile. These unwanted visitors can disrupt the composting process and create unsanitary conditions.
If you have small amounts of stale bread, consider feeding it to birds or using it in recipes like breadcrumbs instead of composting.
13. Human or Pet Hair
While hair is organic and will eventually decompose, it’s not an ideal addition to your compost pile. Human and pet hair break down very slowly, often taking longer than the rest of your compost materials.
This can lead to clumps of hair in your finished compost, which isn’t aesthetically pleasing or beneficial for your garden.
Hair can also contain residues from shampoos, dyes, and other hair products that may introduce unwanted chemicals into your compost. If you do choose to compost hair, use it sparingly and ensure it’s evenly distributed throughout the pile to avoid clumping.
14. Dryer Lint
Dryer lint might seem like a harmless addition to your compost, but it’s best to avoid it. While lint from 100% natural fibers can be composted, most modern clothing contains synthetic materials.
The lint from these mixed fabrics can introduce microplastics into your compost and, ultimately, your garden soil. Moreover, dryer lint often contains chemicals from laundry detergents and fabric softeners. These residues can be harmful to the beneficial microorganisms in your compost pile.
Instead of composting, consider using dryer lint for other purposes, such as fire starters for camping or as stuffing for craft projects.
15. Tea & Coffee Bags
Loose tea leaves and coffee grounds are excellent additions to compost, but tea bags and coffee filters can be problematic. Many tea bags contain plastic fibers that won’t break down in your compost. These microplastics can persist in the environment and potentially harm soil organisms.
Coffee filters, while often biodegradable, may be bleached or contain other additives that aren’t ideal for composting. If you want to compost your tea and coffee waste, consider using loose tea leaves and grounds without the bags or filters.
Alternatively, look for tea bags and coffee filters that are specifically labeled as compostable.
16. Stickers on Fruits & Vegetables
Those tiny stickers on fruits and vegetables might seem insignificant, but they can cause big problems in your compost pile. These stickers are often made of plastic or vinyl and won’t break down during the composting process.
They can persist in your finished compost and eventually end up in your garden soil.
These stickers can be mistaken for food by worms and other beneficial organisms in your compost, potentially harming them. Make it a habit to remove all stickers from your produce before adding the scraps to your compost bin.
It’s a small step that can make a big difference in the quality of your compost.
17. Biodegradable or Compostable Plastics
Biodegradable or compostable plastics might seem like a good addition to your compost, but they often require industrial composting facilities to break down properly. Home compost piles typically don’t reach the high temperatures needed to decompose these materials effectively.
As a result, they can persist in your compost, creating plastic pollution in your garden. Moreover, some “biodegradable” plastics are designed to break down into smaller pieces rather than fully decompose. This can lead to microplastic contamination in your soil.
Unless a product is specifically labeled as suitable for home composting, it’s best to dispose of it according to local recycling guidelines.
Composting is a powerful tool for sustainable gardening, but it requires careful consideration of what goes into your pile. By avoiding these 18 items, you’ll ensure your compost remains healthy, effective, and safe for your garden.
Source:
Don’t Miss These:
Davin is a jack-of-all-trades but has professional training and experience in various home and garden subjects. He leans on other experts when needed and edits and fact-checks all articles.