Compost Magazine

Composting tips, advice and science.

Combination of grass, citrus and weeds in a small pile on a dark background.

Composting Myths Debunked: The Truth About ‘Non-Compostable’ Items

Have you been panicked into putting half your waste into the trash can instead of the compost bin?

Pretty much every week an article seems to be written on things you CAN’T compost. 

The truth is, pretty much everything that has recently lived is compostable. 

It IS true that some things are more difficult to compost than others. But they can still be composted if you use the right composting method. 

Let’s take a look at some of the myths, before diving into how to compost these items, and which ones require hot composting.

1. The myth of meat and dairy products

Many people think that meat and dairy products cannot be composted because they will attract pests and rodents. 

However, if done correctly, composting meat and dairy products can be perfectly safe and efficient. 

To learn how, see our tips below on how to compost smelly items.

2. The myth of citrus fruits

Some people believe citrus fruits and peels should not be composted because they are too acidic and can harm the compost. 

However, unless you are composting on an orange or a lemon farm, there is rarely enough to make a significant difference to the pH of a compost pile.

If you did only have citrus to compost, or it made up a significant part of the compost, you might want to be more careful.

While researchers have successfully composted citrus, and achieved hot composting, they did add an alkaline material to balance the pH.

(Intriguingly, another study looked at using a citrus-based compost, and found it a viable alternative to peat.)

If you do want to compost large amounts of citrus, it might be worth balancing it with an alkaline material such as lime.

Citrus peels do take longer to break down than other materials due to the adipose in their skins. 

If you can be bothered, you can dry or chop up the skins to speed up the process. Either way, you’ll still get compost in the end.

3. The myth of pet waste

A guilty looking spaniel looks directly at the camera with sad eyes.

Animal waste, especially chicken and dog droppings, can contain pathogens. 

However, the composting process is actually pretty good at suppressing pathogens.

Some pathogens are killed in the hot composting process, but even a cooler compost heap can destroy many pathogens. After all, the same fungus that helps break down compost is also responsible for many of the antibiotics we use. 

You won’t kill all pathogens – but pathogens are everywhere, and some will drop onto the compost anyway. 

And before you ask – yes, you can compost human poo too!

(Before you ask, I have successfully composted dog poo and chicken manure, but due to intense family pressure have avoided composting human poo!)

Out of caution, I would only compost cat and dog poo in a hot composting system. What’s more, I recommend avoiding composting dog poop that has been collected in plastic bags, even those labeled as ‘compostable’.

Also see: The Pathogen Destroying Power of Compost and Humanure

4. The myth of weeds

Hot composting will kill them fast, but even cool composting will kill most weeds over time. 

Weed seeds do need hot composting to kill them, and even then some seeds might survive. But hey, if there’s seeds on your weeds they are going to be all over the garden anyway. 

That said, I am still cautious with invasive weeds, and tend to throw these in a separate compost bin where they sit for years. 

5. The myth of onions and garlic

Some sources tell you not to add onions and garlic because they are too acidic for the compost heap. 

First, as with citrus, there’s likely not going to be enough to make a difference to the pH. 

Secondly, according to Composting Masterclass:

  •  while the ideal pH range of compost is between 6.5 and 8, composting can take place between pH levels of 5 and 9. 
  • whatever the initial range of the pH, the final pH tends to end up between 7 and 8.

6: The myth of diseased plants

Potatoes showing blight on there leaves.

Research has shown that sustained hot composting will kill most diseased plants. The Composting Handbook, the bible of professional composters, states:

“While a few plant pathogens (e.g. tobacco mosaic virus) survive in lower numbers, studies have shown that composting effectively sanitizes the compost of nearly all pathogens of concern.”

Compost Handbook

No-Dig guru Charles Dowding has also experimented with diseased plants, stating:

“Diseased leaves are good to compost, such as mildewed courgette and lettuce leaves, rusty garlic and leek leaves, blighted potato and tomato leaves and also tubers/fruits with late blight…I spread compost which was made with blighted leaves, around tomatoes in the polytunnel, with no ensuing problems.”

Charles Dowding

However, I would prefer to use hot composting with diseased plants just to be safe. 

7. The Myth of Grass Clippings

I compost a huge amount of grass cuttings, so I was surprised to see this listed as a “non-compostable” item on a prominent site. 

Now, there are some things to be aware of. 

Grass clippings are high in nitrogen and water content, so it is essential to mix them with brown (high carbon) material to maintain a balanced compost. At least some of the brown material should be dry in order to absorb excess moisture.

If you don’t do this, the grass will first get hot (and maybe too hot) and then become a soggy, sticky mess. 

If you don’t have enough browns, you can lay some grass out in the sun to dry and then use it as a brown. 

Also, you should be careful if you treat your grass with herbicides. Depending on the herbicide you use, this could survive through the composting process. 

 I’d suggest avoiding the use of chemical treatments on your grass, if possible. This will allow you to compost your clippings safely AND enjoy a more diverse and eco-friendly lawn.

Edge cases

Glossy or Coated Paper

It is often said that glossy or coated paper cannot be composted, but this is not entirely true. 

While these materials may take longer to break down than regular paper, they can still be composted. What’s more, in countries like the UK strict regulations mean that glossy paper does not contain worrying toxins. 

It is best to shred the paper before composting to speed up the process, and it is important to avoid using too much of it in one compost pile.

A problem does arise when the paper contains plastic, foil, or laminate. These papers should not be composted because they will not decompose.

I personally avoid composting glossy paper to be careful, and because it seems to take a long time to break down.

Tea bags

Box of Yorkshire Tea Bags on a white background.

Tea bags are a tricky one. You can certainly compost them, but many contain plastics that will leave behind microplastics. 

Some contain PLAs or plant-based plastics. These seem to break down at higher temperatures, so might be suitable for hot composting. 

Alternatively, just snip open the bag and pour the tea leaves out. 

See Can You Compost Tea Bags for more information on which brands contain plastic and how to compost them.

Eggshells

Although egg shells are organic and theoretically compostable, they seem to take forever to break down. 

Some people grind their eggshells up before putting them in the compost heap, but you won’t get a lot of compost for your work!

I would give you more advice here, but I tend to crush mine up and feed them back to the chickens!

How to compost ‘non-compostable’ materials

Smelly items

  • You need a hot compost heap to compost smelly items like feces, meat and dairy, as heat-loving bacteria quickly breaks down the materials. See the 5 Rules of Hot Composting to learn how to do that. 
  • Bury smelly items in the compost heap so that they do not attract pests. 
  • You may also wish to go one step further and follow our guides to preventing and controlling rats and mice
  • As we will see, you can also use a system such as a Bokashi Bin to break some materials before they go into the compost heap.

See 9 Easy Ways To Stop Compost From Smelling for more tips and tricks!

Tough items

Items like wood, paper, wool and hair can take a long time to break down, even if your compost is reasonably hot. 

You can speed up the process by shredding, chopping or cutting them.

If you have a large quantity of woody material, consider using a compost shredder

What if you have a cool heap?

If you do have a cooler compost heap, it is worth taking more care with ingredients you can use. 

Let’s get specific (and play on the side of caution).

Okay to compost in a cool heap:

Lemon
Lime
Garlic
Onions

Probably not okay:

Feces
Cooked food
Meat
Diseased plants
Dairy

What items can you pre-compost in a Bokashi bin?

Bokashi Bin picted with Bran. Available on Amazon.com.

I am not the biggest fan of a Bokashi bin, simply because it doesn’t produce finished compost. 

But if you don’t have a hot compost system, it is dead handy for pre-composting. 

These are good for items such as pet waste, cooked food and some dairy products.

Other ways to compost non-compostable items

Don’t forget there are many ways to compost materials. 

Trench composting is often considered a great way to compost smelly food. As the name suggests, this involves digging a trench and placing the items in the trench and then covering it up with soil. 

I have used this method successfully in the past to prepare the ground for runner beans. However, the last time I dug a hole to deal with some smelly material, some animal found it and dug it up! 

While I haven’t tried it, a number of sources also suggest composting dog, cat and even human poo with worms. 

Wrapping up

In summary, if you can hot compost, you can deal with many ‘non-compostable’ items.

And don’t let the perceived complexity of hot composting put you off!

It’s just not that hard. Essentially, to get hot compost you need to get five, fairly simple, elements right – all covered in our Five Rules of Hot Composting guide. 

But even if you have a cooler compost heap, you will still be able to compost many of the items covered in this post. 

And that’s got to be better than throwing it in the trash!

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