Composting isn’t an exact science, but we’ve learned over many generations that some items are better for composting than others. Some items are simply not biodegradable, while others can slow the process down.
Other items may contain chemicals that can lead to toxic gasses or contaminated soil. On the other hand, some items add extra nutrients, speed up the composting process, or help ensure fewer problems along the way.
Of course, other factors can affect composting, such as the pile size, how much work you put into it, and your composting method.
Covering all these things will take a while, so let’s focus on the most important aspect of composting – what should NOT be added to your composting pile.
13+ Things Not To Put In Compost
Much like recycling, it’s common for people to lump items into a few big categories when not all of those items are created equal.
What follows is not simply a list of what you shouldn’t add but also why and when there are exceptions to the rule.
Alliums, such as chives, garlic, and onions, may be great for our health, but they’re also insecticidal.
Putting these into your compost pile can kill worms and beneficial microorganisms, which is the last thing you want to do.
The good news is that alliums can often be grown from stem cuttings or bulb scraps, so you can use them to create more rather than waste them.
Ash Or Treated Wood
Wood ash from an untreated source is quite good for your compost pile, but treated wood (in pieces, sawdust, or ash) can be highly toxic.
In addition, store-bought charcoal is often coal-based or full of lighter fluid and other chemicals, which are terrible for your compost pile and garden.
One would think the name proves you can compost these materials, but this is misleading.
Not only can the plastics contained be toxic to your compost pile, the temperatures needed to properly degrade the packaging is often well above what your compost pile is capable of.
Cat, Dog, and Human Feces
While herbivorous and insectivorous animals create excellent compostable fecal matter, that of humans and our pets can be highly toxic to the pile due to the risk of pathogens and other contaminants.
This includes all used litter or diapers, except for thoroughly washed, all-natural reusable diaper liners.
Cigarette and Tobacco Waste
Tobacco products are almost always chemically treated, with the wrappers sometimes containing plastics and the filters being very difficult to degrade.
If you have a source of pure, untreated tobacco, this is good for the compost, but anything you find in stores will likely be toxic to your pile.
Citrus is incredibly acidic (almost as bad as pure white vinegar), which can not only throw off your compost’s pH but also kill worms and take a long time to degrade.
However, citrus peels and similar byproducts are absolutely amazing for making homemade cleaning products, so they don’t have to go to waste.
Water is one of the primary composting tools, so it stands to reason that oily or fatty foods and products won’t degrade easily.
Things such as salad dressing will instead put a wrench in the works and slow down the entire process.
Fertilizer and Treated Clippings
Chemical and artificial fertilizers are terrible for a compost pile, as are any herbicides or pesticides you’ve recently used on the lawn and garden.
Avoid using anything contaminated with these products, as you could end up killing all the little helpers that make composting possible.
Fruit and Vegetable Stickers
By law, the stickers (and their glue) must be safe for human consumption because they can be easy to miss.
However, they can actually be a major contaminant if added to a compost pile, so be sure to remove them from any composting materials.
Meat and Poultry Byproducts
While it’s true that meat, fish, eggs, and other similar byproducts are fully biodegradable and have plenty of nutritional value, they can also be problematic.
As these items begin to degrade, they attract a lot of unwanted pests (especially flies), boost the temperature too quickly, can be difficult for worms and other helpers to break down, and absolutely reek.
However, there are some exceptions to this rule, such as rinsed and crushed eggshells, very small amounts of grease, and tiny amounts of fat (fat and grease won’t dissolve in water, but some microorganisms can feed off of the proteins when given in minute amounts), or pizza boxes.
Just be sure to spread these ingredients out so they can be beneficial with minimal side effects.
Packaged Coffee and Tea
Long ago, Sri Lankans packaged tea leaves in silk pouches to protect them on the long trip to England, but some Englishman accidentally dipped the package into his hot water, and the tea bag was thus born.
However, tea bags are rarely made of silk these days and often contain plastics – as do K-cups and other coffee pods.
The used tea leaves and coffee are absolutely amazing for your compost pile, but make sure you take them out of the packaging first, or you could contaminate the pile.
Cardboard in compost is one of the best and easiest composting materials, but certain types of cardboard are simply not healthy for your compost pile.
Heavily waxed cardboard is one good example.
Many types of cardboard have wax coatings, but if you can’t soak off the coating, this can gum up the entire composting process.
Additionally, wax-coated cardboard is often full of dyes or other chemicals, so use some judgment before adding this to your pile.
Similarly, printed cardboard tends to be bad for the compost, as the dyes will contaminate your pile.
The one exception to this is also an exception to many of the rules on this list: pizza boxes.
The grease and cheese crusted onto a pizza box aren’t enough to attract unwanted pests, but it’s more than enough to give your pile a nice boost.
At the same time, the printing is usually not bad enough to cause significant contamination.
Shinies are a third no-no for cardboard.
Shiny wax coatings indicate the presence of plastics, which aren’t biodegradable.
Likewise, you need to be sure to remove any tape or labels from the cardboard before adding it to your compost pile.
Synthetic Soaps and Feminine Products
Let’s face it, not everyone can get hold of homemade soaps (or have the nerve to make their own), and the synthetic stuff you buy at stores will only harm your compost pile.
If you have all-natural homemade (or biodegradable), these can be composted, but otherwise, it’s better to melt your soal scraps together to make new bars.
Likewise, any product contaminated with blood could transmit pathogens that won’t die during the composting process.
However, empty toilet rolls, thoroughly washed reusable cotton liners, and similar products are safe.