15 Things You Should Never Compost

Compost pile with safe items

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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.

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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.

  1. They lead to a misbalance of green and brown composting materials.
  2. 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.
  3. These items could introduce diseases, bacteria, and fungi into your compost pile.
  4. You might encourage critters to visit your compost pile.

Let’s Look at 15 Things You Should Never Compost

Take a look at what HGMM recommends not to 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 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 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 it will attract pests.

Think about it; these products will mold and start to stink. That can attract animals who shouldn’t be visitors at 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 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 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.

14. Rice

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

Remembering the things you should never compost is more important than knowing what you can compost!

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40 thoughts on “15 Things You Should Never Compost

  1. This is really cool information. We have just moved in to our new home and I am planning a vegetable garden and also looking at various way to use compost. How did you start your compost pile and is it necessary to be able to rotate it? Thank you for this great list. I feel like I need a print out on my garbage for when I start this process. BlyssYourHeart.com

    1. My compost pile is really basic. It’s a future post actually. I took 4 pallets and nailed them together to create a square. Then, I wrapped hardware cloth around it to prevent everything from falling out and stops pests. Then,a layer of wire over top that I stapled down but I use a bent nail for a hook. Sooo simple. I turn with a shovel every few days, but thats about it! I let nature do its thing. As long as you are adding the right materials, you are ok. You want brown and green materials. So, add those shredded leaves and such as well.

  2. Hmm, I started composting last year and thought I’d done my research. Now that I’m seeing your list here it makes me realize I may have accidentally put stuff in I shouldn’t have (citrus and onions).

    1. Citrus and onions can be ok in small amounts. Like.. if you used one onion and have a few peels. It just shouldn’t be large quantities. My kids can eat two bags of those little cuties in a few days. Instead, I made cleaning vinegar with the orange peels because its way too much citrus for the compost.

    1. As long as you aren’t tossing TONS of them, it’ll be ok! You just don’t want to add dozens of them.

  3. I just started a compost bin around 2 months ago. Can you put unbrewed coffee and all types of vegetables in the compost bin?

    1. I had the original recycling/composting queen in my maternal grandmother. Raised in the depression, she did not let anything go to waste. My Dad was raised on farm, “If we ate it, we grew it.”I am so grateful for Grams’ and Dad’s teachings. Three thoughts I would like to share:
      1. Along with cleaning items and bird feeders, I also use citrus peels to repel ants since they are not fans of the smell. I cut mine up and share them with any colonies or hills I can find around our home. It is another layer of defense in the ongoing battle.
      2. Coffee grounds, used or unused are great to put straight on the garden, just do your research.
      3. If you have the remains of whole fish, freeze what’s left and in the spring, plant them several inches under your tomatoes! Amazing how they nourish the ground! Just get the fish down deep enough so your dogs and cats don’t go hunting for a snack!
      Happy Compsting and Gardening!

      1. I’m not sure if you know this, but the Native Americans taught the Pilgrims to bury fish under their crops. Whether they knew it or not, it acted as a fertilizer, so that’s one of the first fertilizers used in the US.

  4. Great article, however your title says 13 things and your list contains 15.
    Any way would also add Black Walnut anything as this contains toxins that will kill tomatoes and other plants. Poison Ivy, sumac, and poison oak should also be avoided as their oils will remain in the compost and can still cause a reaction.

  5. Another thing: Do NOT put your old tomato plants (after the season is over) in your compost. You could be adding blight spores to your compost and it will haunt you next planting year. Also, composting rotting tomatoes can cause you to have a bumper crop of little tomato plants wherever you use the compost.

  6. The MOST PROBLEMATIC in the compost is the fat. They destroy the soil forever! !!!
    Citrics and onion peels are very ok, just has to be cutted very small pieces….
    I don’t think can be dangerous, but I don’t agree with news papers, because all the paintings on are pure chemicals .

  7. Instead of a compost bin, For past 30 years I have been digging holes in the garden, avoiding the veggies and flowers by staying near the edges or sticking to areas where I’ve just finished for a season. As I bury the compost, I use the end of the round nose shovel to chop up anything larger than a gofball, which speeds up the decomposition process. The holes are usually only about the size of a gallon jug, and I make sure the use a different location each time., until all I see is dirt.

  8. I put shredded leaves in a huge pile. After 2years nothing much more than a big pile of wet leaves. And I did turn them occasionally. After 3 years of wintering I had a big pile of starting to compost, but they were more like a 10″ mat full of next door neighbors tiney tree roots. Is there something I could add at the beginning to make them compost correctly? I had to get a rototiller to break them up into the soil. They were from oak and maple trees.

    1. Typically, you want to do layers of green and brown materials. You need green materials as well for a true compost pile. When you kept piling on leaves, you created a carbon-rich compost pile without adding any nitrogen-rich materials. Carbon breaks down very very slowly. Next time, try mixing up green materials. Toss in your coffee grounds, tea bags, veggie and fruit scraps.. etc. Make sure to turn as well. Compost needs the right carbon and nitrogen ratio to grow properly. I hope that helps!

  9. I do a lot of steam juicing and was wondering if I can add the left over pulp to the compost bin?
    I too was worried about the use of weeds in the compost or and have often put it to the curb, good to know I can add them to the compost. Thank you and Happy New Year, May 2019 bring everyone happiness, peace and joy…

    1. This would be an ideal compost additive, as long as there were plenty of “brown”/dry elements in the pile as well! Juice pomace is also a great supplemental feed for many animals, like hens, unless it’s mainly citrus.

  10. Many people make the mistake of adding grass cuttings to their compost. While small amount mixed with leaves and other vegetation is fine, a deep layer of grass will form a stinking slime that you really won’t want and can takes months to break down.

    1. Maintaining the proper carbon to nitrogen ratio is crucial. If you add too much grass clippings, which is basically all nitrogen, you create a terrible odor. I’m going to cover some more composting do’s and don’ts soon 🙂

  11. I have been composting for a few years and we tend to eat a lot of avacados. I start many of the seeds indoors until my husband says I have enough so the rest go in the compost. Last year I had more than a dozen tree starts and some of the richest soil!! I gave some of them away so I had space back in my compost bin.

  12. I live in the north west of England, UK. Fairly wet and quite cool climate. I have a couple of trees in and around the gardens which inevitably produce tons of leaves come fall (autumn). I purchased a garden vacuum (leaf blower) with a shredding feature. The resultant shredded leaves I put into black, refuse sacks into which I puncture several air holes. With the tops tied tightly, the bags are left at the back of the garden shed (out of sight) for about eighteen months or more. At any time, say at the start of the next spring, a couple of shovels-full of poor soil with 3 or four earth worms are added. The resultant compost is fabulous and does wonders for the borders. (P.S. A small amount of human urine really helps the compost breakdown)

    1. Yes I do. you can add pineapple, but make sure you’re dicing them up really small. It won’t decompose as easily if in larger pieces.

    1. I wouldn’t put Clorox wipes into a compost. The chemicals would spread throughout the compost and potentially kill the good microbes needed to decompose the materials. Now, you might be able to find some all-natural wipes that are compostable, but you’d have to read the package closely!

    1. Hey Tracy! So, you could compost your garden plants at the end of the season, depending on few factors.

      You don’t want to compost any garden plants that are diseased or might have pests. The diseases will spread and live in your compost.. and you don’t want to spread diseased compost the next year. The pests could live in the compost too.

      If you have healthy plants at the end of the season, you can compost them, but I highly recommend that you shred or dice them up the best that you can. Perhaps run them over with a mower. The size of the plants would make them hard to decompose fast, but shredded up should be fine.

      Also, make sure you didn’t spray the plants with anything. Otherwise, I would say go ahead and do it!

  13. I have read your advice regarding do’s and don’ts in composting and would question putting any grass cuttings from the first cut after a weed and feed application into your compost that you know has been treated with weed control as these can cause serious problems. A lot of problems in commercial production of composting have been linked to this factor.
    As far as I am aware all non-biological products carry a warning that you should not add at least the first cut to your compost.

    1. That’s a fantastic addition! I almost forget about that because we don’t use any sprays on our grass, but you are absolutely correct. Any pesticides or herbicides sprayed on grass could be detrimental to composting. I’ll make sure to update the post 🙂

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