Are Onions Bad For Compost?

Are Onions Bad For Compost

Composting is likely one of the cheapest and easiest ways to obtain rich, organic fertilizer that contains the desired nutrients. Compost holds a multitude of nutrients that are essential for plants for healthy growth and abundant yields. In addition to that, it also helps you manage the amount of waste you send out in the trash.

Now, while composting is an excellent fertilizer solution, a few questions arise regarding what exactly you can compost. Most of the garden waste and some of the kitchen waste can be easily composted; however, there are some that require more specific techniques. If the proper composting techniques are not followed, it may end up damaging the compost itself or the plants it’s used to fertilize.

Is Onion OK For Compost?

Onion is okay for compost as long as you follow the correct techniques to do so. It is one of those finicky items that, if done incorrectly, can cause more harm to the plants than good.

Unfortunately, onion is a rather odorous vegetable that can cause unpleasant smells when added to the compost. If the onion made your eyes water when it was fresh, the rotting smell might send you to your knees. Strangely enough, it is this unpleasant odor that attracts rodents.

While all of this might seem like reasons for you not to compost onions, I can assure you that it is okay if you follow certain techniques.

Here are a few suggestions on how to help prevent the horrible odor from wafting out of your compost piles:

  • Do not add large amounts of onions to the compost bin. Adding copious amounts of onions can overweigh any composable material in your compost bin. This would leave you with a box of rotting onions, not the compost you have been working hard to create.
  • Cut the onions into pieces. Before tossing the whole onion into the compost, take a little bit of time to chop it up into smaller pieces. This increases the surface area, allowing the microorganisms to break down the vegetable at a quicker rate.
  • Add more brown materials. Real quick, brown materials refer to compostable materials that contain higher amounts of carbon, such as sawdust, shredded newspaper, or chopped cardboard. Said brown materials help mask the odors of the decomposing onions.
  • Place the onions deep down in the compost bin. Ideally, you will put the onions at the bottom or middle of the compost bin. This placement helps not only with the odor but also with the temperature of the compost, allowing the onions to break down quicker.

How To Compost Onions

Onions in Compost

To help clear up any confusion, here is a step-by-step guide on how to compost your onions:

  1. Prepare the compost bin: A good compost bin will have holes on the lid’s bottom, sides, and top. The holes allow air movement in and out of the bin, an essential part of the breakdown of the compost.
    • If you don’t have holes in your bin, you can easily create them with a screwdriver. Ideally, a compost bin with has approximately 5 holes on the lid and bottom of the bin and 10 holes on the sides of the bin. Of course, if you have a large compost bin, make sure you add holes appropriately.
  2. Place the compost bin in the appropriate location: The best spot for a compost bin is on a flat section of land that has direct sunlight. A flat location will help prevent the bin from overturning. Direct sunlight helps ensure there is heat generated to help speed up the breakdown of materials.
  3. Add brown materials: We briefly touched on browns earlier, which can be shredded newspaper, chopped hay, straw, dry leaves, or sawdust. Brown materials should make up the first layer of the compostable materials and should be approximately 5 inches high.
  4. Add garden soil: Following the brown materials, add a layer of garden soil. Soil helps increase aeration and brings in other decomposing microorganisms like earthworms.
  5. Add the onion scraps and other greens: Before adding the onion scraps, mix them with other organic matter such as banana peels or coffee grounds. Once you have created a mixture of materials, add them all into the compost bin, making sure you have about 5 inches in the bin.
  6. Alternate the greens and the browns: Continue adding the brown materials and the green mixture as you go. Alternate each layer as you go until the compost bin is full.
  7. Turn the compost regularly: When the compost bin is full, cover it with a lid in which you have drilled holes. After approximately 2 weeks to a month, turn the compost. This helps increase air movement through the bin, increasing the decomposition of the material.
    • During this time, keep an eye out for rodents or other pests. If you notice an odor, simply add more sawdust, shredded newspaper, or other brown materials.

What Vegetables Should Not Be Composted?

Great question! It might seem like you can compost just about anything. However, there are a few things you will want to avoid tossing into your compost bin.

  • While we talked about the onion being compostable, the onion skin or peel is not. Going hand in hand with onion peels is garlic peels. These peels produce a very potent odor that attracts pests to the plants when the compost is used on them.
    • Your best option here is to simply toss the garlic and onion peels into the trash and save yourself the headache later on down the road.
  • Vertagables with a high citric acid content should be thrown in the trash instead of the compost. Highly citric vegetables include broccoli, peppers, carrots, and lemons. The citric acid in these vegetables destroys worms that may be present in the compost, which is crucial to the decomposition of the materials in your compost bucket.
  • Lastly, try to avoid composting tomatoes. While the tomato itself is not the issue, it is the potential that it contains seeds. The last thing you need is to be growing a tomato plant in your compost bin unintentionally.