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How eco-friendly is cork? Is it sustainable or not?

Written by: Hendrik

Category: News, Sustainability

Updated on:


What comes to your mind whenever cork is mentioned? A wine stopper, right? Cork is a versatile material that has many uses besides wine stoppers. You have probably come across other cork products such as yoga mats, coasters, shoes, handbags, etc. But how eco-friendly is cork, after all?

As various industries continue seeking ways of becoming more eco-friendly, we are seeing a breed of new sustainable materials now and then. And now, we have cork.

But is cork eco-friendly, or is it just another form of greenwashing? Does it live up to the hype? Let’s find out.

What is cork?

how eco-friendly is cork
Photo by Mathis Jrdl on Unsplash

Cork is a naturally occurring material derived from the outer bark of a tree, especially the cork oak tree (the Quercus Suber).

Cork is one of the most sustainable materials on earth. It has many uses but is most commonly used in the wine industry as a wine stopper.

Recent developments have taken cork to another level, now used in the fashion industry as a vegan fabric, an alternative to traditional leather. You’ll find cork shoes, handbags, wallets, and clothes.

Other uses include cork tiles for flooring and insulation for walls, ceilings, and roofs.

Check out this article about eco-leather!

How is cork made?

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Photo by Jude Infantini on Unsplash

Cork is harvested from mature cork oak trees, which are common in the Mediterranean and Iberian regions. The cork oak trees take approximately 20-25 years to mature, which is when cork harvesting begins. At this age, cork bark can be harvested every nine years again until the tree’s end of life.

The cork oak trees have a productive life of around 200-300 years.

The cork oak tree has a thick bark (up to 20 cm thick) with a unique cellular structure that acts as a defense mechanism against external forces such as forest fires. This thick bark is sustainably harvested as cork, and the cork oak regrows the bark again.

To harvest cork, skilled laborers use a specially designed hatchet to carefully cut through the bark horizontally and vertically. This is usually done on the tree trunks, but they may also use branches in giant trees.

The layers are gently removed to ensure the living part of the tree is not damaged.

Once harvested, the barks are dried for about four months, after which they are taken to the factories, at the factories, the dried barks boiled in pallets, leaving them clean, soft, and flexible. Poor quality cork is removed at this stage, and the good quality is left to cure and dry.

Once dry, it is flattened and cut into workable sizes, ready for use.

Notably, over 60% of cork goes into the manufacture of cork stoppers, while the rest is used for other purposes.

Characteristics of cork

cork tree

Cork exhibits specific unique characteristics that make it such a versatile material.  It is waterproof, fire resistant, buoyant, and has a unique appearance. Other common features include;

  • Elastic

Cork comprises flexible and bouncy membranes that allow it to regain its original shape and size when compressed. This characteristic allows it to be molded into different shapes, which is why cork stoppers can adapt to oddly shaped bottlenecks.

  • Impermeable

The cork bark is a thick and buoyant cellular structure that contains a high percentage of fatty substances and is filled with air. This makes cork a hydrophobic material that resists water.

Cork’s resistance to water means it does not deteriorate with time; hence perfect for stoppers.

  • Good with insulation

Cork is an excellent thermal, sound, and acoustic insulator, thanks to its millions of airtight cell structures. A cork oak stopper perfectly protects wine from temperature variations.

In construction, it is used for thermal and acoustic insulation for walls, floors, and ceilings for improved indoor air quality and comfort. 

  • Inert

As a dead tissue, cork does not have any taste or odors. It is also hypoallergic as it does not absorb dust. This gives it a tremendous hygienic value.

  • Durable

Cork has a rigid cellular structure, making it an excellent vegan alternative to making long-lasting products.

Is cork eco-friendly?

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Photo by Dulcey Lima on Unsplash

Yes, cork is very eco-friendly. It has numerous benefits not only to the environment but also to the local ecosystem.

Here are the reasons why we are confident that cork is the most eco-friendly material.

1. Cork is a renewable, recyclable and biodegradable material

Cork is made from the bark of the cork oak tree, not the tree itself. Harvesting cork does not harm the cork oak tree. It is harvested by skilled laborers (no machines) who ensure that the living part of the tree is not damaged.

Cork is regenerative, making it incredibly sustainable. It is harvested every nine years, and a single cork oak tree can give at least 16 harvests as it has a lifespan of up to 300 years.

Cork is also recyclable and biodegradable. Recyclers can transform it into new products, and at its end life, it breaks down without releasing any toxic substances.

2. Low carbon footprint

Cork is a carbon-negative material; it absorbs much of the carbon dioxide in our atmosphere. Studies show that a harvested cork oak tree absorbs 3-5 times more carbon dioxide than an unharvested cork, as the bark regeneration process requires more CO2. 

Besides being a carbon sequester, growing cork trees requires minimal resources. No pesticides or fertilizers are used, which makes the cork oaks have a very minimal carbon footprint.

3. Zero waste

Cork production produces zero waste. The process does have some wastewater, but seeing that no chemicals are added, the water returns to the earth with zero damage.

Waste from the manufacturing process is often reused to make agglomerated cork products. Cork dust is used as biomass to make renewable energy.

4. Promotes biodiversity

Cork oak forests support the highest levels of biodiversity among forest habitats. Cork oak landscapes are home to many plants, with up to 135 plant species per square meter.

It is in these forests that different species of animals call home, including some of the rarest and endangered species like the Iberian lynx, Iberian imperial eagle, Barbary deer, and many others. Millions of wintering and migratory birds also find shelter in cork oak woodlands.

5. Supports local communities

Harvesting cork provides employment opportunities to the local people. Due to the extra care needed in harvesting cork, only skilled human labor (not machines) is used. According to a report by the world wildlife fund (WWF), over 100,000 people earn their livelihoods from cork forests in the Mediterranean region.

In fact, cork oak trees are so valued by the communities they grow in Portugal that they are even protected and regulated by the law. The cork oak is Portugal’s national tree, and it is a criminal offense to cut it down. 

The country has set initiatives to protect the cork oak forest to ensure its value doesn’t fade away.

6. Protects the physical environment

Cork oak landscapes help protect the physical environment by preventing soil erosion and promoting water conservation. This helps fight desertification and climate change.

The cork oaks also produce a considerable amount of organic content that enriches the soil, providing nutrients for other vegetation.

Are cork oak trees endangered?

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Photo by Jacek Ulinski on Unsplash

With the rise of plastic stoppers and screw caps, the cork industry faces reduced demand for wine corks. As a result, the economic value of cork oak forests may fall. This may result in overexploitation of the cork trees, abandonment, and even clear-cutting to provide land for other uses.

However, most of these non-cork alternatives are not as eco-friendly as cork. If environmentalists and eco champions continue to root for cork stoppers, then its demand will remain, which is good for the cork industry.

Thankfully, cork is now being used for other purposes, as cork is gaining momentum in the sustainable fashion and construction industries.

With a readily available market, cork oak trees and their forests remain preserved with no risk of exploitation.

Is cork biodegradable?

Since cork is a natural material, it is completely biodegradable. So, how does cork biodegrade? As with any other organic material, it breaks down in the presence of oxygen and moisture.

As cork is a rigid material, it can take longer to biodegrade, but it will eventually break down without releasing any toxic substances.

Is cork compostable?

Yes, Cork is compostable. You can add it to your compost pile like any other natural product. For a speedier composting process, ensure you chop it into smaller pieces and add more veg scraps and grass into your compost.

For wine corks, always confirm they are corks and not plastic closures made to look like natural corks. When cut open, you’ll notice that natural corks look woodier and have random foaminess, while plastic corks have uniform foaminess.

Also, ensure you remove anything artificial attached to the cork. These may include plastic, screw lid material, or foil covers.

Keep painted or glued cork items such as noticeboards and cork tiles away from your compost pile. Not only will they hinder the decomposition process, but they will also release toxic substances into your compost which is not cool. 

Learn more about composting and get this free PDF download.

Is cork recyclable?

Cork is 100% recyclable. It can be transformed into various products such as shoes, mats, lampshades, etc.

However, putting cork items in the recycling bin may not be a very nice idea. Chances are it won’t get appropriately recycled or recycled at all. Instead, look around for recyclers who guarantee cork recycling.

The Cork Forest Conservation Alliance has a cork recycling scheme called Cork Reharvest. They have cork collection boxes in grocery stores, wine shops, and wine tasting rooms.

ReCork are cork recycling experts who recycle wine corks into sustainable plastics or foam alternatives. They allow you to drop your corks at their drop-off locations near you for recycling.

Alternatively, you can engage the creative side of your brain with DIY cork crafts. You can make coasters, corkboards, wreaths, etc. And if crafting isn’t your cup of tea, simply compost your corks.

Wine corks vs screw caps

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Photo by pmv chamara on Unsplash

Wine corks take close to two-thirds of the total cork market share. Corks have been the most popular method for closing wine bottles since the 1400s until recent developments of other cork alternatives.

One of the never-ending debates within the wine industry is whether natural cork or screwtops are best for holding wine. The debate majorly focuses on the quality of wine rather than the environmental impact of the stoppers. Ever wondered what is more eco-friendly between a cork stopper and a screw cap?

Screw caps and plastic stoppers started gaining popularity over natural cork as a result of two things;

  1. They are cheaper than cork. Since cork requires highly skilled labor, it is quite expensive.

  2. Cork taint ruins the smell and taste of a wine due to the presence of TCA (2,4,6 trichloroanisole) chemical compound in a wine cork.

While the latter is a major concern for most people, the cork industry reports great improvements in the fight against cork taint to less than 1%.

From an environmental point of view, it is clear that corks carry the day.

Firstly, cork stoppers are manufactured from the bark of cork oak trees. The raw material is renewable and utilizes very few resources.

On the other hand, plastic stoppers and screwtops are manufactured from non-renewable resources, not to mention how their production processes emit toxic substances that harm the environment.

Secondly, though aluminum screw caps are recyclable, they are not always efficiently recycled. Additionally, it takes a lot of energy to recycle them.

Non-cork alternatives are also not biodegradable and compostable.

Final thoughts

Cork is a highly sustainable renewable resource. No trees are harmed for their production, and its numerous environmental and social benefits make it a highly sustainable material.

Next time you grab a bottle of wine, pick one with a cork stopper. You will not only be preserving the environment but also supporting the local ecosystem.

Photo of author

Hendrik Kaiser

I've studied biology and lived for 3 years on an off-grid permaculture farm. I love kitesurfing and keeping my body healthy and fit. Hence, I care so much about keeping our environment clean and being as zero waste as possible. Being a zerowasteman is a superpower everyone has inside of themselves, and I want to teach you how you can unleash it.

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