Composting is an easy and effective way to deal with food waste and fertilize your garden. Compost bins are readily available for purchase in a variety of shapes, sizes and materials. You can also easily make your own composter or even simply create a compost pile. Layers of brown material, food scraps and green material decompose, turning into nutrient-rich soil for your garden. Although composting is simple and advantageous, there are still some items that you should never toss into the mix. Here are some compost no-no’s to abide by.

Pet waste

Although it may seem like a natural material, dog poop and cat litter are not suitable for the compost pile. Remember, in essence, if it’s in the compost, it’s on next year’s lettuce. Do you want cat poop in your lettuce? Besides the yuck factor, parasites, bacteria, germs and viruses that are harmful to humans can survive in this waste.

leftover fish in a tin container


Even though fish scales and other parts break down quickly, it’s not quick enough if you have cats in the neighborhood. Fish is best left out of the mix mostly because it is likely to attract animals. Plus, the smell is likely to offend the neighbors.


Meat is another stinky attractant. Not only will your dogs and local wildlife be unable to resist the temptation, but the internal temperatures created during the composting process might not get high enough to kill pathogens.

Related: Compostable, portable Stak pods eliminate the need for individually wrapped snacks

stacks of treated wood planks

Treated wood

Pressure-treated lumber is a durable choice for fencing, decking and other outdoor projects. But when that wood has served its purpose, find a disposal method where it doesn’t end up in your compost. The chemicals in pressure-treated lumber can leach into your food and also compromise the balance of your compost mixture. Untreated lumber and bark chips can go into the compost, as can other natural materials, such as straw. 

Fire ashes

Similar to the reasons explained above, wood ash can contain chemicals that affect the end product of compost. However, if you’re certain the ashes are exclusively from clean, untreated, natural wood, it can be a nice addition to the mix.

half-eaten cheese on a wood serving tray

Dairy products

All animal products are likely to attract unwanted attention to your compost pile, so cheese, yogurt, milk and other dairy products should not be composted. Although some critters, such as worms, are useful for composting, the rodents and flies that would go after the rotting dairy would just cause problems for your compost pile.

Fat, oil and grease

Again, these items attract animals, but they also upset the balance and repel some of the water that is essential to the decomposition process.

plant with diseased leaves

Diseased plants

Although the composter is the perfect spot for plants you’ve pulled from the garden or yard, make sure the plants are disease-free. Any bacteria or other infestations can transfer to other plants down the road, so it’s best to dispose of them instead.


For a backyard composter, the temperatures are often lower than commercial facilities that treat all kinds of yard debris, so use caution with which plants you add. Weeds can often survive the heat limitations of a backyard composter, meaning they can pop up again in the garden after you’ve dispersed the compost.

grass clippings in a burlap sack

Grass clippings with pesticides

Grass clippings are a welcome element and typically make up the “green” portion of the compost recipe. However, if your lawn is treated with pesticides, keep the clippings out of the composter and, subsequently, your food supply. The chemicals in the grass can also kill organisms essential to the composting process.

Black walnut components

While nearly every organic plant, with the exception of weeds, is welcome at the composting party, black walnut trees produce juglone, a substance that can be dangerous or even deadly to many vegetable plants.

green compostable plastic bag in a compost bin


It might seem obvious that these are inorganic materials, but some packaging is deceptive in its phrasing and might claim to be compostable. The truth is that many plastic-like polymers still have to reach temperatures only achieved at commercial facilities. So while the label may say it is compostable, read the fine print. It will usually clarify whether the statement pertains to a commercial facility or is suitable for the backyard. 

The advantages of composting are both obvious and extensive, so don’t derail your efforts by adding the wrong materials. Instead, focus on the many options you do have to create a healthy compost pile. All organic food scraps, mostly those from fruits and vegetables, can be combined with eggshells and even coffee grounds. For the second element, include brown items such as unprinted paper bags, toilet paper rolls, unbleached napkins, small twigs, leaves and bark. Finally, round out your ingredients with the green from healthy plant materials and untreated grass. Once you get started, you’ll find out just how many items can be diverted from the street cart to the compost pile — a win for your garden and the planet.

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