How to Deal With Mold in Your Kitchen Composter

Dealing with Mold in your kitchen composter

When I first decided to start saving food scraps and using a composter, I thought that it was straight forward.  Throw the food scraps into a bin and let nature do its job.  It didn’t take long before I realized maybe I had oversimplified things just a tiny bit. 

The realization hit that if I was going to use this compost in my garden, I could unintentionally put something in the soil that could be harmful to my family.  That was all it took for me to hunker down and do some serious reading to set my mind at ease. 

So, lets tackle a worry that most of us will deal with when composting.


There are literally thousands of different types of mold, but to be honest we don’t need to be mold experts to navigate this issue.  Some molds have a beneficial purpose, but this is not a subject I would encourage any DIY projects.

Moldy food? 

Don’t eat.

Don’t sniff.

Straight to the trash or composter.

Should I be Concerned if I See Mold in My Kitchen Composter?

The short answer is no.  Mold is a normal and expected part of decomposition.  Where there are food scraps and adequate moisture, you will most likely see mold.  It’s just that common in our environment.

So, if you have mold in your kitchen composter, it’s not a huge issue, just empty your bucket out in the outdoor composter.  Make sure to regularly clean your compost bucket and change your carbon filter.

What If I Have A LOT of Mold in MY Kitchen Compost Bin?

If you open the lid of your composter and are seeing fuzzy mountains of mold, maybe it’s time for a deep clean.  Inadvertently, you’re providing an awesome environment for mold growth.  A little mold is to be expected, but we don’t want a mold farm sitting on our kitchen counter. 

The trouble with mold is it releases spores into the air.  They’re very small, like 1-3 microns small, and they release into the air like tiny dandelions.  To be completely fair, the mechanism isn’t the same, but it gives you a good visual.  To give you an idea of the size of the spore, your human hair thickness is approximately 70 microns thick.  This is why HEPA filters are recommended for people with mold allergies.  HEPA filters can trap very small particles like mold spores.  On the other hand, the carbon filters in your composter is wonderful for preventing smells and keeping the flies out.  They, however, aren’t rated to deal with mold spores. 

It’s not time to panic though.  It’s just time to do some deep cleaning and maybe adjust your habits a bit. 

Clean that Composter

Start off by getting that composter squeaky clean.  If it’s dishwasher safe, pop it into the high heat cycle.  If the dishwasher is out, wash and rinse thoroughly with either a vinegar or bleach wash.  I don’t usually recommend bleach, but it’s still an option for certain situations.  Vinegar does a valiant job at killing most molds but it’s not 100% effective in all cases.

Make sure you get the lid thoroughly clean as well and throw out that carbon filter.  You can try to wash the filter but it would be virtually impossible to get the mold completely out. 

Before you start using your bucket again, let everything completely dry out.

Fresh Start!

If you’ve battled mounds of mold, you probably don’t want to deal with that again any time soon.  So here’s your best recommendations:

  • Make sure you don’t have too much moisture or liquids in your container.
  • Empty your composter more often.  Expecting a once a week trip outside may be a little overly optimistic.
  • Take REALLY moldy food straight out to the outdoor composter. 

Don’t look at me like that.  We’ve all left something in the back of the fridge that has turned into a science project on us.  The science project gets an all expense paid trip straight to the trash or outside. 

What Do I Do if My Carbon Filter Gets Moldy?

What if you’re seeing mold mostly in your carbon filter?  Well, this stinks because you’re having to change your filter much more often.  Some carbon filters can last months, so if you’re battling filter mold, it can be frustrating and expensive. 

Here’s the deal.

There are predominantly two, maybe three things that are assisting with this.  Temperature, moisture and mold spores.  Basically, your filter is getting and staying wet.  Mold in a warm, humid environment is going to blossom into a mold garden.

  • Take a preemptive strike.  If your carbon filter is washable, you can try to proactively tackle the mold issue by washing your filter in a dilute vinegar rinse at regular durations (once a month).  Let it completely dry. 
  • Don’t try to save or clean your carbon filters if your filters have mold.  Toss them.
  • Minimize the moisture.  The whole point of the lid is to keep the stink down and the flies at bay, but it will also help maintain a nice humid environment.
  • Don’t overfill the composter.  Keep the scraps from getting too close to the filter so you can minimize any mold transfer to the filter.
  • Consider where you’re storing your bucket.

Under the kitchen sink is a common storage place for our composters.  It is also a common place for minor leaks and is a ripe location for mold.  Do a check of your storage spot and make sure it’s clean and dry.  Your composter might just be telling you something that will save you buckets of money in repairs!


Kitchen composters are handy little kitchen containers, especially when we don’t want to trek outside in the cold, wet or middle of the night to dump kitchen scraps.  It may seem gross or concerning but don’t sweat the mold unless you’ve got issues with your filters or your bucket is starting to grow fur.  It’s just nature doing its job. 

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