Does Compost Smell – How To Prevent It

If your compost pile has an unpleasant odor, you have a problem.

Compost should have an earthy smell as the natural materials break down. When poor conditions occur within your pile, you need to take steps for compost odor control.

In this article, I discuss the reasons your compost may smell and ways to alleviate bad odors from both your indoor and outdoor compost bins.

Once you know the tricks to keep your compost smelling good, you’ll find the entire process more pleasant, which will keep you on track to creating a free, nutrient-rich soil amendment that’ll keep all your plants looking amazing!

Why Does My Compost Smell?

When you maintain your compost pile properly, compost should smell like moist earth.

When the compost’s internal temperature fails to heat up to the correct level, the organic matter cannot break down quickly enough to rid itself of unpleasant odors.

The only time your compost should smell awful is when you are adding manure to your mixture. Even manure will lose it’s sharp smell as it decomposes amid the other ingredients.

Related | Manure vs Compost

Causes Of Smelly Compost

A foul odor is an indication of compost too wet, an imbalance of green to brown ingredients, and not enough aeration.

Overly wet compost causes a smell due to the lack of air reaching the ingredients. The result is moldy, slimy, putrid contents that stink!

Related | Mold In Compost

When green ingredients overpower brown ingredients within the compost, the material not only becomes too moist but compacts down, doubling up the smell factors.

The best news is that it takes minimal effort to keep your compost processing correctly by following the tips I outline below.

How to Keep Compost from Smelling

Steps For Indoor Kitchen Compost Bins

kitchen compost bin

Indoor kitchen compost bins should not smell bad, especially when the lid is down.

Because kitchen bins tend to collect more food scraps than outdoor containers, it’s easy to “unbalance” the ingredients and produce ammonia or sewer-like smells.

Related | Best Kitchen Compost Bins

To combat foul odor, follow these steps:

Step 1 – Buy The Right Bin

Invest in the best quality countertop or floor kitchen compost bin you can afford. Check that the lid shuts tight, and any spigot for removing the compost tea does not leak.

Make sure the bin offers replaceable charcoal filters and environmentally-friendly disposal bags, which are crucial for keeping odors at bay.

Step 2 – Change The Filters

Set a reminder to replace the charcoal filters in your kitchen composter every 3-4 months.

After several months, the filters lose their effectiveness, and smells will begin to emanate from your bin.

Step 3 – Keep Moisture Down

Food scraps are wet, which means adding in more brown material will balance out the mixture and keep the microbes that are beginning to break down the contents happy.

Keep a container of brown paper bag or cardboard shreds nearby and toss in a bit with each wet food scrap addition to your kitchen composter. This trick is a great way to recycle used toilet or paper towel rolls.

The exception here is the Bokashi Composting method.

Step 4 – Empty The Bin Regularly

It takes about three days for food scraps to begin decomposition. Emptying the bin every 3-4 days will reduce the chance bad smells will permeate your kitchen space.

Step 5 – Wash And Disinfect Your Bin

Most kitchen countertop compost bins are made to pop into the dishwasher, which you should try to do every time you empty the bag.

For larger bins, wash the components weekly with a water and bleach mixture. The bleach will sanitize the parts and keep things smelling fresh.

Don’t ever add a new bag into your bin until the inside is completely dry.

Extra moisture in the composter will immediately begin to grow mildew and mold, which feeds on the food scraps and will start to stink much sooner than usual.

Steps For Outdoor Compost Bins Or Piles

outdoor compost bin

I find keeping my outdoor compost smelling good much easier than my indoor bin.

The fresh air circulation helps tremendously, and I have more space to add green or brown ingredients to balance the pile if things turn stinky.

Related | Best Compost Aerators

These steps will fix up any bad scent issues in your outdoor compost:

Step 1 – Maintain Proper Green To Brown Levels

You want to maintain a ratio of one part green waste to three parts of brown waste.

Green (nitrogen-based and “wet”) ingredients include:

Brown (carbon-based and “dry”) ingredients include:

  • Leaves
  • Pine needles
  • Hay or straw
  • Sawdust
  • Cardboard

At the first hint of bad odor, mix in a generous helping of brown ingredients to your pile. The combination of drier material and aeration from mixing will stop the stink in its tracks.

Step 2 – Keep It Light

It’s easy to compact a compost pile, especially when you let the pile get too deep or overstuff your bin. When this happens, smells will emerge.

Compost needs air so the microbes can feed on and break down the material inside.

When you smell a sulfur-like odor, get out your pitchfork or shovel and turn your compost pile well. If you have a compost bin, make it a point to turn the barrel several times a day over several days until the smell dissipates.

Related | Best Compost Tumblers

If turning the compost doesn’t alleviate the smell, add in more brown material, and keep mixing.

TIP: A good practice is to spread out grass clippings for a few hours, so it dries out a bit before adding it to your composter.

Grass clippings are a significant reason compost begins to smell. The grass blade’s heavy moisture and weight compact down quickly, cutting off the critical air supply.

Step 3 – Control Moisture

Outdoor compost bins are not airtight, so during times of heavy rain, the material gets too soggy, cools down, and begins to rot. This issue leads to some horrible smells.

Not only is wet compost slimy, but it also gets very dense. Add in loads of brown material and aerate the pile as much as possible to offset the moisture.

Keep an eye on the weather and toss a tarp over your bin or pile before it rains to prevent a soggy, stinky mess from happening in the first place.

Step 4 – Watch The Layers

Don’t ever toss a thick layer of either brown or green material into your compost.

Related | Types Of Composting Methods

Even if, in total, you add in the correct ratio of green and brown ingredients, that doesn’t mean it won’t ever smell.

If you don’t have time to mix in the additions to your compost, layer thin amounts of green and brown material together, so they are touching.

Keeping both nitrogen and carbon material together is critical in keeping those good microbes happy, which lets them digest and break it down quickly.

The faster your compost breaks down, the less chance it has to smell.

In Summary

Compost should never smell bad, and luckily, preventing this issue is not difficult.

I hope you try these simple solutions to keep your indoor and outdoor compost bins from getting stinky. There is something joyful about creating rich compost and using it to grow healthy, vibrant flowers and vegetables.

Now you know the tricks to keep your compost smelling fresh!

About Justin Micheal

Justin has always loved gardening and caring for the outdoor spaces in his grandmother's backyard. He believes everyone can enjoy the space available to them, no matter how big or small. On Backyard Digs, he shares everything he's learned about growing a successful garden and maintaining and improving the landscape of a backyard.