Can You Compost Limes?

By Veronica Fletcher | 
Last updated on April 3, 2021

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When I (along with everyone else) decided gin was my favorite drink, I had a lot more used limes to deal with. Throwing them away wasn’t an option for me, so I started wondering about composting. 

So, can you compost limes? Yes, you can add limes to compost. The skins can be slow to decompose, so we advise chopping them up into very small pieces before you add them to your pile. Also, limes are acidic, so composting too many in one go can lead to an overly acidic compost pile. Too much acid slows down the composting process.

Composting limes myth-busting

In the past, people have avoided composting limes for a variety of different reasons. Some people think limes are too acidic, while others worry about composting them because limes contain d-limonene, a natural pesticide. We debunk these myths and explain why there’s no problem with composting limes!

Are limes too acidic for compost?

Limes are acidic. There’s no denying that. But composting is a chemical process, and unless limes make up the majority of your pile, the compost will be able to self-correct the pH level as the limes decompose.

Anaerobic bacteria take over when compost becomes acidic

The ideal pH for beneficial microbes is between 5.5 and 8. Too much acid will lower the pH, and this is a problem for compost because it inhibits aerobic bacteria from working.

The process will never completely stop because as the aerobic bacteria population shrinks, anaerobic bacteria and fungi, who like acidic conditions, will take over. However, an anaerobic composting process is slower and more smelly.

As the compost pile progresses and the organic material is consumed, the pH stabilizes and will end up somewhere between 7.5 and 8 regardless of the starting pH. 

Limes will only slow the composting process down if they make up a large percentage of the material in your pile. Most people won’t compost enough limes to have any noticeable effect on the pH of the pile. If you do notice the composting process slowing down or turning anaerobic, reduce the number of limes you’re putting in. You can freeze leftover limes while you wait to put them in your compost bin.

Can you compost moldy limes?

Penicillium is a harmful mold that can grow on limes.

Harmful mold can grow on limes

Because it’s not safe for human consumption, not everyone feels comfortable with the thought of the mold growing in their compost pile, and therefore, some people steer clear of composting limes.

However, most shop-bought limes will have an antibacterial coating on them to prevent any penicillium from growing. The coating isn’t dangerous for humans, so it’s fine to add to your compost and won’t cause any problems in your garden. Also, penicillium mold will not survive if the temperature rises above 100 degrees Fahrenheit. Most well-tended home compost piles should heat up enough to kill any penicillium mold spores.

You can use a compost thermometer (check out this one on Amazon) to monitor the temperature in your compost pile and make sure it’s getting hot enough to kill mold spores.

Therefore, you can compost moldy limes without having to worry about any dangerous spores contaminating your compost pile. The only time you need to be careful is if you’re cold composting homegrown limes that have no antibacterial coating.

Can you compost lime skin?

You can compost lime peel, but the peels will be slow to decompose. If you chop the skins up very small before you put them in the compost bin, then they’ll decompose much faster. 

Will limes kill beneficial insects in my compost pile?

Limes contain a substance called d-limonene, which is used as an organic pest control. Because of this, some people worry that limes will kill all the beneficial insects in their compost piles. But this isn’t the case, d-limonene breaks down too quickly to have any lasting impact on your compost pile.

In fact, the strong smell that comes from decomposing limes can help keep scavengers and rodents away from your compost pile. If you’re composting smelly foods like oils or dairy, then adding limes could prove to be quite beneficial!

How to compost limes

Here are a few tips to help you get the most out of composting limes. 

Don’t add calcium carbonate

Some people recommend adding calcium carbonate in the form of garden lime to a compost pile that’s too acidic. We don’t advise this because it will convert the ammonium nitrate in your pile into ammonium gas.

lime-in-a-compost-pile
Adding garden lime to your compost will reduce the nitrogen content

As the gas escapes it’ll lead to an odor problem and also means nitrogen is lost to the air, reducing the nutrient content of the finished compost.

If your compost becomes too acidic, the best thing to do is to turn the compost and aerate it. This will help encourage aerobic bacteria to grow and decrease the acidity. You can also add very thin layers of wood ash through the compost. Wood ash contains a lot of calcium, which will help neutralize any acidity.  

Remove the seeds

If your compost pile runs cold then it’s advisable to remove the seeds from the limes before you add them. The seeds won’t die in the compost and there’s a small risk that the seeds will germinate when you then spread the compost.

If you’re hot composting, there’s no need to remove the seeds as the high temperatures will kill them.

Can worms eat limes?

Worms can eat limes, but they don’t particularly like them. The d-limonene in the lime’s skin is too strong for the worms, so they’ll keep away until this has disappeared. Luckily it disappears pretty quickly as the limes start rotting. The best thing to do is to leave the limes in a separate container to rot down a bit before adding them to your bin. 

Another thing you need to be thinking about is the acidity of your bin. Worms prefer a neutral pH and if the bin becomes too acidic the worms can get sick. Limes are naturally acidic and adding too many will lower the pH. 

If you’re concerned about the pH of your bin, you can measure it using a pH meter (this one on Amazon does the trick perfectly). The pH should be somewhere between 6 and 7.

Keeping the number of limes to a minimum and adding crushed eggshells to your bin every so often will help to keep the pH neutral. The calcium in the eggshells will counteract the acidity of the limes. 

Other ways to use old limes

If you have some leftover limes that you don’t want to compost yet, here are a few ways to use them.

  • You can use them in cleaning products such as homemade dish soap or spray
  • You can freeze wedges to use in cocktails or gin and tonics
  • You can freeze the juice and use it in cooking
  • You can dry the skin and use it as kindling
About Veronica Fletcher

Veronica has a passion for all things eco-friendly. After growing up on a farm in Ireland, she went on to study Chemistry and Environmental Sciences. Veronica has also volunteered in many sustainability roles, including conservation efforts in Bangladesh and teaching Environmental Sciences to schoolchildren in Kenya.