Are Onions Good for Compost?


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Onions are the most popular vegetables in our households. We use them to prepare almost every main dish. They are super delicious, and their health benefits are unbeatable.

However, like any other vegetable, onions can go bad over time. Also, onions contribute a significant amount of general household kitchen waste.

If you are a curious gardener, you might wonder whether you can compost onions. You may also ask yourself if onion peels are better than a whole onion when composting.

In this article, we explore the potential of composting onions. We’ll have answered all your questions regarding composting onions by the end of this piece.

Onions in Compost Bins

Most people will discourage you from adding onions to your compost bin. Even the infamous common sense composters will tell you onions will produce odorous compost. While this is true, onions will not ruin your compost.

So, Can You Compost Onions?

Yes, you can compost onions. The truth is that a lot of common sense composters have done it, and the results were impressive. So if your household or restaurant tends to produce more onions waste every other week, you can add them to your compost bin.

Compost turns most of our food waste into valuable nutrients that make our gardens fertile. You can make compost from almost any organic matter.

So if you have thought about composting onions, the idea is viable. It is a great way to recycle kitchen food scraps. And you can use it in place of synthetic fertilizers and other harmful chemicals.

You don’t have to throw away onion waste or bad onions. Instead, you can use the organic matter to compost onions. But first of all, you have to learn how to do it properly. This is because the decomposition process of onions is slightly different.

How to Compost Onions?

The challenge that you may encounter while composting onions is that they will want to grow. And this may affect the entire process. Fortunately, you can steer clear of this obstacle. So, how do you do it?

Break Down the Onions

Chop whole onions into small pieces before adding them to your compost bin. Halves and quarters will work perfectly. Smaller pieces of onions will take a shorter time to decompose.

If you already have onion peelings, you don’t have to worry about them growing. This type of onion waste will not develop any shoots. Instead, consider onion scraps and skins ready for your compost pile.

Controlling Noxious Smells

Onion waste produces an unpleasant smell when rotting. And it may attract unwanted intruders such as dogs, wildlife, or pests. For this reason, you need to dig a deep hole for the composting process.

A depth of 10 inches or 25 centimeters is ideal. Putting a barrier around the compost bin may also help to keep the animals away.

A mask will help you deal with the odorous food scraps when turning the compost pile. Adding crushed oyster shells to the compost pile is another brilliant idea to combat smelly compost.

If you do not have crushed oyster shells, shredded cardboard or paper can help to bring down the smell.

Do Not Use Diseased Onions

When compositing onions, avoid those that are diseased. Otherwise, the disease will end up in your soil when you use the same compost. Pathogens like onion mildew, white rot, and leaf blight are resilient.

However, if you re-introduce them in the soil, they will affect future onion crops. Therefore, always dispose of onions with a disease far from your garden.

Should You Compost Whole Onions or Onion Peelings?

If you are planning on composting onions, you can either use onion peelings or the entire onion. The ultimate objective is to get nutrient-rich compost. Onion skin and scraps are more ready for your traditional compost pile. However, they will negatively affect the bacteria and microbes during the decomposition process.

As you compost onion peelings, you’ll not need to reduce them into smaller pieces and add them directly to your compost heap. But when it comes to the whole onions, take your time to cut them into small pieces that cannot regrow.

Should You Compost Moldy Onions?

Most people like to add vegetable food waste to their compost. Unfortunately, moldy onions are not always fit for human consumption. You may be tempted to open your compost bin and damp moldy onions inside.

But are you sure that it is the right call? It is perfectly fine to add moldy onions to your compost from an expert perspective. The microbes present in them aid in the decomposition process.

Can You Compost Spring Onion?

You can compost any species of onion. All vegetables that we eat are compostable. Spring onions thrive in most climates. They are a great addition to our kitchen and are also degradable. The other types of onions that you can compost include;

  • Ramps
  • Leeks
  • Scallions
  • Sweet onions
  • Shallots
  • Red, yellow and white onions

Can You Compost Cooked Onions?

Bacteria break down cooked onions quickly. If these are part of your food waste, you can add them to your compost piles. However, there is a caveat. Onions that are fried with fat are greasy and odorous foods.

The fat layer that coats them will make it harder for them to decompose. It may also spread out to other sections of your compost pile and delay the entire process.

Rodents such as rats cannot resist the aroma of cooked food. These animals will dig holes in your compost bin and interfere with the decomposition process. Therefore, it is best to avoid adding cooked onions to your composting bin. Additionally, cooked onions may lure pests to your compost piles.

Decomposing fats produce a horrible smell. Although meat and dairy products are worse, decomposing fats in plants will still produce an unsavory aroma. In addition, the smelly compost from cooked foods may cause tremendous discomfort.

Fats in your cooked veggie scraps may also turn your compost anaerobic. Anaerobic bacteria will antagonize the good in your rotting food matter. And in the long run, the fats may increase the acidity and odor in your onion compost.

Onions and Vermicomposting

In recent times, vermicomposting has gained significant traction among gardeners. It is one of the composting methods that deploys earthworms.

These worms break down the organic matter into fertilizer. Worm composting might be among the best composting methods, but it has a few caveats.

Do not try to compost onion peelings or whole onions through vermicomposting. Worms do not like odorous noxious smells. Therefore, the worms may not consume vegetable scraps that contain onions.

Rotting onions left in the vegetable scraps during vermicomposting will worsen the conditions. The odor will only get stronger and unbearable for the earthworms as time goes by.

Advantages of Onion Compost

  • It helps you save money that you could have used on chemical fertilizer
  • Adds nutrients to your garden soil, making it more productive
  • It prolongs your soils life and helps it to retain more moisture
  • Allows you to dispose of vegetable scraps usefully
  • Improves soil structure, allowing roots to spread and reach nutrients easily
  • When dealing with sandy soil, it aids nutrients and moisture retention
  • Reduces soil compaction

How Long Does Onion Waste Take to Compost?

Some people don’t know that onion waste is good enough for composting. This can be attributed to the fact that onions have a low PH. A low PH level is hostile to huge bacteria, making it harder for bacteria to break down onion waste. As a result, onions need more time to decompose.

Benefits of Adding Onion Scraps to Your Compost

You may not have enough onion scraps to make onion compost. However, you can always combine other types of vegetables in your compost pile. Rotting onion skins and scraps will benefit your compost in various ways, including;

  • When you add onions to your compost, you increase the organic matter that will feed the microorganisms and aid decomposition.
  • Onions in compost balance the PH levels in your compost heap
  • Adding onions to compost creates a diverse pool of nutrients for plant health
  • Onions in compost aid the slow release of nutrients and reduce leaching

What Precautions Should You Take When Adding Onions to Your Compost

  • Avoid putting too many onions together in your compost bin to combat the noxious smell
  • Avoid using large pieces of onions in your compost
  • Do not use cooked onions

Adding onions to your compost pile is a great idea. But only if do it right. If you have a lot of onions at your disposal, there is no better way to dispose them of than to make compost with them. They will increase the variety of nutrients that plants require to grow in your garden.






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