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Composting reduces trash output and provides an excellent soil amendment for gardens. Compost adds nutrients back into your soil, but not everything belongs there. In fact, understanding what not to put in a compost ensures that the end product is safe for your garden use.
In your compost, you want to put brown and green materials. Examples include eggshells, veggie and fruit scraps, newspapers, grass clippings, and coffee grounds. Many items you toss each day are compostable.
That doesn’t mean everything is safe.
Let’s Look at 15 Things You Should Never Compost
1. Dog and Cat Feces
It’s safe to add horse, cow, chicken, and rabbit manure to your bin. These forms break down and add valuable nutrients to the soil. The same isn’t true for dog and cat feces. Their waste tends to contain microorganisms and parasites that aren’t safe to apply to the soil growing your food.
2. Citrus Peels and Onions
The natural acid in citrus peels and onions kill off the necessary microorganisms and worms living in your bin. Also, you’ll need to dice the peels up into really small pieces for them to decompose quickly.
They take FOREVER otherwise. If you toss in an occasional citrus peel or onions, it should be ok. But they’re big no-nos for those who practice vermicomposting. Instead of composting my citrus peels, I make homemade cleaners!
UPDATE: I’ve received plenty of questions about citrus in composts, and I did some further digging into this question.
It turns out, that in many cases, citrus peels can be okay. However, they do take time to decompose, so it’s best to dice them up into smaller pieces to encourage faster decomposition.
3. Bread and Other Grain Products
Cake, pasta, and bread aren’t safe choices because it will attract pests.
4. Fish and Meat Products
Fish and meat decompose, but the smell will attract pests and animals from miles away. Chances are you don’t want to smell rotting fish and meat outside either. On the other hand, fishbones make a fantastic natural fertilizer!
5. Sticky Labels on Fruit
You know the labels I’m talking about! The label has the PLU number for the store and may contain a brand name. They’re easy to miss.
The stickers have a glossy coating (see #8 below!). Fruit stickers can trash up your compost, and they’re an issue for professional composting companies.
6. Dairy Products
Chances are you don’t want to invite pests and rodents. So, steer away from adding any dairy products. Milk, cheese, yogurt, butter, and ice cream aren’t a friend to your compost.
7. Cooking Oil
There are a few reasons why you shouldn’t add cooking oil. First, it’ll slow down the decomposition process. Second, the smell attracts animals! Also, it will alter the moisture content of your compost bin.
8. Sawdust From Treated Wood
You CAN compost sawdust, but it needs to be from untreated wood.
9. Glossy Paper
So, you CAN add things like newspaper, cardboard, or old paper towels to a compost bin. These paper products come from trees and decompose normally. You DON’T want to add glossy paper products, such as magazines or wrapping paper. A special chemical coats the paper to create the shine, which contains toxins, and they don’t decompose normally.
10. Personal Hygiene Products
DON’T put any sanitary napkins, used toilet paper, tampons, baby diapers or baby wipes into the bin. These items pose a health risk!
11. Diseased Plants
Never put plants that have a disease or are infested with pests into your compost bin. You are simply spreading the disease, and it won’t be safe to use on your veggie garden.
12. Non-Biodegradable Products
Aside from glossy paper, you also don’t want to add glass, plastic, aluminum foil, or metal into your compost pile. The reason? They’ll never degrade! The purpose of a compost is to add degradable items.
13. Coal Ash
It’s fine to add ashes from your woodpile, but coal ashes are a different story. Coal ashes contain extremely high levels of sulfur and iron that could kill your plants.
Rice isn’t suitable for your compost heap. It will attract pests, but rice also provides a lovely, fertile ground for bacteria that could harm the beneficial nutrients.
15. Tea and Coffee Bags
You can and should add tea and coffee to your compost, but they must be bag-less. Some bags contain synthetic fibers that won’t break down easily in a compost.
Remembering What Not to Compost
There you have it! 15 things you should never add to your compost bin! Luckily, the list of what you CAN add is far longer. If the item doesn’t fall under these categories, there is a good chance it is safe to compost.
Ready to start your own compost bin? Here are my three favorite picks. I love having a countertop composter, so I can toss my scraps in and only make a few walks out to the compost each week.
I also like having a large compost bin. Tumblers are convenient if you don’t want to have to do the mixing yourself.