Can You Compost Onions?

There are many things that can go in your compost bin. It’s not just for leftovers and other organic waste that can’t be thrown away any other way. Even if something doesn’t seem like it would break down easily, if it was alive at one point and is made of plant materials, you can probably compost it.

Although, there are some things that will keep your compost from working well. If you want to get the most out of your compost, you should avoid putting certain things in it.

If you’ve found yourself wondering “are onions compostable?”, “how do I do it?” and “how long will they take to compost?”: you’ve come to the right place.

Can you put onions in the compost?

Yes, onions are compostable. Adding onions to your compost pile will contribute to creating a nutrient-rich fertiliser that you can use in your garden.

You can compost red, white, and spring onions (scallions).

Can you put them in the waste bin?

If you don’t have a compost bin, you can put vegetables in the appropriate roadside collection bin but biodegradable materials like onions are better off being in a compost pile.

Disposing of organic or compostable waste like vegetables in landfill can contribute to the release of potent greenhouse gases like methane, which has around 80 times the warming power of carbon dioxide.

Methane emissions are significantly reduced by composting suitable food waste and organic materials.

How to compost onions

You should add the skin and ensure you chop them into small pieces before adding them to your compost ile.

As a green material, you should be adding onions and other green nitrogen-rich materials then a layer of brown to cover it. Remember to use a garden fork or a stick to poke holes in your compost every couple of weeks to mix the pile up.

How long will onions take to compost?

It takes around 4 weeks for onions to completely decompose in a compost. Because they decompose relatively quickly, you can add them to your compost fairly regularly.

Onions discarded on the ground or buried in the ground will take longer to decompose.

Are onions a green or brown material?

Onions should be considered a green material when composting.

Materials that are green, like onions, are often more wet and softer recently-living organic material; and are a source of nitrogen (one of the four essential ingredients) for your compost. Green nitrogen-rich materials provide a lot of the vital nutrients that microbes need to speed up the process of decomposition. Ideally your compost mix should consist of about 1 part of green material for every 4 parts of brown material.

Composts rely on green materials like onions to add the neccessary proteins and other nourishment for the microbes to thrive to the pile.

Will composting them attract pests?

No. Onions will not attract pests.

Composting considerations

When composting onions, you should avoid composting the whole bulb as it could take root and regrow in your compost pile

Omar Agor-Wood
Omar Agor-Wood

Omar is a digital marketer by day for one of the UK's largest environmental consultancy companies, and is writing like the world depends on it for Pick Ethical at night. He has a passion for hiking, bouldering, and making a fuss of his dog.

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