Did you know there are things you should never compost?
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. There are 15 things you can’t compost that you should know before you get started.
Composting Benefits for The Garden
Typically, people think that the real composting benefits are that you reduce waste in the home. While yes, that is a HUGE benefit, it’s not the only one. In particular, composting for your garden has several benefits that make it something you NEED to do.
You’ll see why composting is important for all gardeners!
Improves Soil Structure
You might realize that there are different types of soil or soil structures. For example, you could have sandy soil, clay soil, or silt soil. The goal is to have a soil that crumbles to the touch which means it allows air, water, and energy to move throughout.
Improving the soil structure that feels right is important.
Think about it.
If you have hard, clay-like soil, young, delicate roots struggle to move through it and get the nutrients they need. Sandy soil can cause plants to lack the nutrients that they need to thrive.
Adds Nutrient Content
Chances are, you knew about this composting benefit. Composting is the best fertilizer you will ever find – period.
The organic matter that is found in compost adds all of the vital nutrients to your garden. Compost has macronutrients, such as nitrogen, potassium, and phosphorous, as well as plenty of micronutrients that your garden needs.
Retains More Water
When you improve the soil structure, you’ll find that the soil has better soil retention. That means you need to use less water in your garden.
When you add compost into sandy soils, you increase how much moisture the ground can hold. For clay soils, it does reduce how much water it holds, but it prevents waterlogged soils and encourages root growth.
Prevents Plant Diseases
This benefit is unique interesting! The University of Illinois Extension tells gardeners that adding compost to your garden produces plants with fewer pest problems.
Having sterile soil without compost means there are no natural checks and boundaries to stop the spread of diseases and insects.
Why Are Some Things Unsafe for Composting?
Composting is all about keeping things balanced. You need the right balance between green and brown materials.
Green materials are nitrogen-rich items such as grass clippings. Brown materials are carbon-rich things such as shredded, dried leaves.
Aside from the right balance, composting requires everything to be broken down in a specific and similar time frame. When you spread your finished compost over your garden beds, you really don’t want large chunks of food scraps in there.
Then, you need to think about whether or not you are adding diseases or pests into your compost pile. Bacteria and fungi will spread happily throughout a compost pile. Then, when you spread it over your garden, you can infect your entire garden!
Last, you don’t want critters or visitors stopping by your compost pile. Raccoons, flies, opossums, insects, rats, and mice love to find a good, stinky compost.
So, the things you should never compost fall into a few categories.
- They lead to a misbalance of green and brown composting materials.
- The items won’t break down in the right amount of time. Typically, they take much longer, or they might not break down at all.
- These items could introduce diseases, bacteria, and fungi into your compost pile.
- You might encourage critters to visit your compost pile.
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.
Composting dog poop and cat feces is never a good idea because their waste tends to contain microorganisms and parasites that aren’t safe to apply to the soil growing your food.
You need to avoid feces from any carnivorous animal because it’ll contain dangerous parasites. That applies to ALL carnivorous animals.
If you do want to compost dog poop (I get it; I have dogs too!), you need to process it separately from your other compost. You can find special composters for pet waste, and the finished product must be used on non-food crops.
2. Citrus Peels and Onions
The natural acid in citrus peels and onions kills 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 composting orange peels, and I did some further digging into this question.
It turns out, that in many cases, composting 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 they will attract pests.
Think about it; these products will mold and start to stink. That can attract animals who shouldn’t be visitors to your composting bin.
A bit of crust here and there won’t totally damage your compost. My 4-year-old thinks crust is utterly disgusting, so we do toss some from time to time. You never want to compost a loaf of bread or even multiple slices each week.
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!
So, unless you want raccoons and other animals to stop by for dinner, composting meat isn’t a good idea. Also, since it will rot and cause the growth of bacteria, it can add dangerous bacteria to your compost that doesn’t belong in your garden beds.
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. If the wood has been treated with varnish, stain, paint, or pressure treatment, it cannot be added to the compost pile.
Wood is treated with chemicals, and you don’t want those chemicals to end up in your compost pile. Chemicals are toxic and adding them to the compost can negatively affect the microorganisms and plant health.
In fact, if you use pressure-treated wood or sawdust, you’re adding arsenic and cadmium to your compost.
Those are two pretty serious chemicals!
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!
I know; some diapers “claim” that you can compost them, but composting diapers shouldn’t be done in the same bin that you are going to spread over your vegetable garden.
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 in 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.
They’ll never degrade! The purpose of compost is to add degradable items.
13. Coal Ash
It’s fine to add ashes from your woodpile, but composting 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.
Also, composting K-cups is typically a no-go. You can remove the grounds from the plastic if you want, but don’t toss the whole thing into your compost bin.
Can I Compost Branches?
Yes and no.
Large branches take too long to break down, which will delay how soon you can use the compost in your garden.
Branches ARE a carbon-rich material for your compost pile IF you break them down into smaller pieces. You can chip your branches as well. The smaller the pieces, the faster they break down.
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
Related Articles About Composting:
- How to Make a $10 DIY Compost Bin
- 15 Composting Tips for Beginners
- 10 Ways to Use Fall Leaves in Your Garden
- 24 Ways to Make Money From Your Garden