Can You Compost Onions?

Last Updated on April 24, 2021 by Jeffery Jago

You’re probably wondering if you can compost onions and other vegetables. The answer is yes! You should be able to compost everything from potatoes, carrots, broccoli, apples, oranges, and ONIONS, plus a lot more. However, there are some exceptions.

One major exception is that you should not put onions in your worm bin because they will hurt the worms’ digestion process, At least, that’s the most common opinion.

There is actually a fairly lively debate about this. But first, let’s get this out of the way, In a normal composting pile/bin that doesn’t rely on worms (vermicomposting), then onions are absolutely fine to compost. (Just chop em up, makes it easier to break down).

As for the more complicated matter of vermi-composting, it’s a little trickier.

The main thing to keep in mind is that you’re dealing with worms who are potentially more sensitive than your average compost pile because their gut bacteria have evolved specifically for breaking down those types of vegetable matter. So when they encounter an onion, it can be too much for them to handle and the onions will do harm to the worm digestion process. This may not happen every single time but some people recommend avoiding all together just out of caution.

However, if you wish to ignore that advice, their are a few tricks you can use to reduce the effect of an onion on your worms.

First, you can chop up the onion beforehand and mix it with other vegetable matter such as carrots or cabbage pieces so that they are less likely to be encountered in large chunks. Second, if you have a lot of onions leftover (or just one really big one), then try soaking them for ten minutes before adding them to your worm bin – this might make their reaction less intense. Finally, use a little bit more bedding material than usual when feeding them so that there is some buffer between the food and where they live and the onions.

This is pretty much valid advice for any kind of onion:

  • Red onions
  • Yellow onions
  • White onions
  • Green Onions
  • Rmaps
  • Scallions
  • Leeks
  • Sweet onions
  • Shallots

Much like the humble potato, it takes a bit of prep work to compost an onion properly.

It is important to note that onions are not the only problem when it comes to composting. Garlic, certain types of mushrooms, and even rhubarb can cause a stir in your worm bin as well. It’s best to avoid these altogether if you want a healthy environment for your worms (and that means less work on your end).

Other things to consider, Smell!

Worms health isn’t the only thing you need to worry about. Onions already smell bad enough as it is. Once they start to rot, you’re going to get that strong onion odor wafting throughout your entire yard, But instead of just “mm i like onion smell” it’s also tinted with a pungent hint of decay and rot. Mmm

So if your not a fan of strong smells, we recommend you avoid throwing these bad boys in the compost pile regardless if the worms will be happy or not.

Interested in learning more about vermicomposting? Check out our other articles: