Can You Compost Onions?


Onions are a vegetable, so you should be able to compost them, right?

There is a continual debate on whether or not you should put onions in compost, but the answer is yes, you can compost onions when you do it the right way.

Follow along as I explain the nitty-gritty when it comes to composting onions in a standard compost bin and whether or not onions are a safe ingredient when vermicomposting.

Once you know the tricks for the best ways to compost onions, you can confidently recycle even more of your kitchen scraps with no worries!

Onions In Compost Bins

Many people hear they should avoid putting onions into their compost because of the smell that can be unpleasant and could attract animals. While these are valid concerns, onions in compost are not harmful.

Related | Does Compost Smell?

Onion skins and peelings make the same beneficial addition to your compost as other vegetable ingredients, so you end up with an organic soil medium rich in an array of nutrients that feed your garden plantings all season long.

You can compost any and all types of onions such as:

  • Yellow, red, and white onions
  • Shallots
  • Sweet onions
  • Scallions
  • Leeks
  • Ramps

Tips For Composting Onions

Onions are very much like potatoes when it comes to prepping them for the compost bin. A little bit of extra thought and effort need to happen so that the onion scraps can break down as fast as possible inside your composter.

Onions do put off quite an odor, so expect some smell when you add them to your compost.

The key is to quickly reduce bad odor by encouraging the fast breakdown of the organic matter by following these tips:

Chop Whole Onions Up

Tossing whole onions into your compost bin is a bad idea.

  • First, the onion will naturally want to regrow and can sprout even inside your composter.
  • Second, a whole onion is dense and wet, which will form a nasty blob inside the bin that takes more time to break down and incorporate into the other materials, even if you turn the container every day.

Cut whole onions into quarters to stop regrowth, but the finer you can chop it up, the quicker the material will decompose.

I get exceptional results when I cut all my veggie scraps going into the compost pile into about quarter-size chunks.

Minimize Odor

Just as onions have a strong aroma when fresh, the smell can become downright awful when in the process of decomposing inside your compost bin.

Help keep odors to a minimum by purposefully layering shredded cardboard or newspaper on top of onion scraps immediately after you introduce them into your bin.

The cardboard or paper will absorb excess moisture, which will keep the ingredients in balance and keep odors in check. If you live in a coastal region, adding in crushed oyster shells is another item that helps offset the onion stink.

As I come across cardboard, office paper, or newsprint waste in my home, I like to tear or shred them up and keep some in a lidded storage bin set near my composter.

When I have onions or other wet or smelly new additions to my bin, it’s convenient to have the material on hand to mix in. I find the paper does a much better job at controlling smell than dry leaves.

Are Onions Safe For Vermicomposting?

Vermicomposting is becoming very popular with avid gardeners and eco-conscious homeowners.

Onions have a high concentration of acids as they decompose, so you may wonder if onions pose a risk to the worms inside your vermicomposting bin.

Related | Best Worm Composters

Worms inside your composter should not die if you mix in small portions of onions to the ingredients, but large amounts of any highly acidic food scraps could cause the death of your worm population.

The key is to chop up onion scraps as finely as possible before introducing modest portions to your vermicomposter.

The issue with adding onions is that worms naturally avoid eating such malodorous material. If you add in too much onion, it’s more than likely that the scraps will just pile up inside your bin and create even more smell.

Over time though, worms will process through the onion scraps just as they would any other plant-based material and continue to thrive.

In Summary

Adding onions to your compost is fine when you keep the balance of green and brown materials at optimal levels.

I hope the information above gives you new insight into composting and vermicomposting onions so you can recycle more food waste while improving the health and beauty of your garden!

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