Don't Toss Your Wine Corks! Here's How to Turn Them Into Compost Instead

If you have wine corks leftover after celebrating with friends and family, don’t throw them in the trash. Most natural wine corks are fully compostable, but synthetic corks can also be repurposed and upcycled in various creative ways to reduce household waste.

In this guide, you’ll find quick tips on how to judge if your wine corks are compostable or not, and learn how to help wine corks break down faster in your compost pile!

What Is Cork?

Many people don’t realize that natural cork literally grows on trees; it is the exterior bark of oak cork trees. These trees primarily grow in Spain, Portugal, and other areas around the Mediterranean. Cork is harvested using a sustainable technique that carefully removes the corky exterior bark in strips while allowing the trees to keep on growing. With this technique, it is possible to harvest cork from the same tree again at 9- to 12-year intervals, and some trees live for 150 years or more.

Although wine corks are one of the most common uses of cork bark, cork is also found in other items, like:

• Bulletin boards
• Coasters
• Tile flooring
• Trivets
• Bags and wallets

Are All Wine Corks Compostable?

Whether or not wine corks are compostable depends on what the corks are made of. If the corks are made out of natural cork from oak cork trees, they’ll break down properly into compost. However, if the corks are made from synthetic foam or silicone, or have a plastic coating, they aren’t compostable and should either be placed in the trash or upcycled into creative crafts.

If you’re not sure if your corks are made from natural cork or not, inspect them and consider cutting them in half with a sharp knife. If the interior of the cork looks uneven, woody, and fibrous, it’s likely made of natural cork. But if the interior of the cork looks smooth, uniform, and foam-like, it’s probably synthetic and isn’t fit for the compost pile.

Tips for Composting Wine Corks

Although natural wine corks are fully compostable, cork is naturally water-resistant. This trait makes corks handy for stopping bottles, but it also means they take a while to break down into compost. Left whole, cork takes up to three years to fully compost; however, there are some tricks to make it decompose faster:

1. Choose the Right Composting Technique

Wine corks and other materials that are made from natural cork can be composted using hot composting, cold composting, or vermicomposting systems. Unfortunately, cork doesn’t effectively break down in bokashi composting bins, but it won’t do any harm to put cork in bokashi composters either.

2. Remove Non-Biodegradable Elements

Before composting wine corks, make sure to strip away any leftover metal foil, wax, or plastic seals and other materials left on the cork that aren’t compostable. If you’re composting other items made from cork, take the time to remove non-compostable elements too, and steer clear of composting cork that’s been painted or has come in contact with adhesives. Paint and other additives of this sort may not be safe for compost piles or vegetable gardens.

3. Chop Them Up

Like other compostable items, cork breaks down much faster if you cut or chop it into small pieces before composting. Either carefully cut corks into tiny bits with a sharp kitchen knife, grate them with an old kitchen grater, or run them through an old blender that you don’t care about.

4. Combine with Nitrogen-Rich Ingredients

In hot and cold compost piles, wine corks count as a carbon-rich or “brown” material, which needs to be blended with plenty of "green", nitrogen-rich ingredients to compost effectively. Ideally, you’ll want to add about 3 parts cork and other brown materials for every 1 part of nitrogen-rich ingredients, such as kitchen scraps.

For better results, layer carbon and nitrogen-rich materials in your composter, and then give them a good stir with a composting fork so they’re all mixed in.

5. Add Water

Once you’ve mixed chopped cork into your compost pile, keep an eye on the pile and add water if it starts to get dry. Cork and other composting ingredients break down best when compost piles are about as damp as a wrung-out sponge. Don’t get compost too wet, though—overly moist conditions make compost smelly!

6. Aerate Compost

Compost doesn’t need to be aerated if you’re using the cold composting technique. But if you want cork and other compost ingredients to break down as quickly as possible, turn your compost every 3 to 4 days. This creates a hotter compost pile and generates finished compost in a matter of weeks, rather than years. 

Other Ways to Repurpose Wine Corks

In addition to composting natural wine corks, there are other ways to repurpose both natural and synthetic corks. If you want to keep corks out of the trash and compost pile, try:

• Upcycling corks into coasters, trivets, and bath mats
• Gluing them together to create holiday wreaths
• Painting them to create plant labels for the garden
• Using them as an alternative to packing peanuts
• Chopping up natural corks for use as worm bin bedding or as a natural garden mulch
• Placing natural corks at the bottom of large pots or containers to cut down on the amount of potting mix and improve drainage 
• Recycling them through a dedicated cork recycling program