What Is Cork Made of?

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Iberian lynx peeking out from behind a tree
An Iberian lynx peeks out from behind a tree. Photo: Iberian Lynx Conservation Program.

What is cork?

A number of times, I’ve been asked the question, “What is cork made of?” Most recently, my dental hygienist and I started talking about cork when he asked me what I do for a living. I showed him my cork wallet as an example of some of the products I write about on UniGuide, and he said his mother had just gotten back from a trip to Portugal where she bought a cork bag. Then, he said, “But what is cork exactly?” My dental hygienist isn’t alone when it comes to not knowing what this mysterious material actually is. I certainly didn’t before I started UniGuide.

A 100% Natural, Sustainable, and Biodegradable Material

Most of us are familiar with cork, as it’s used in all kinds of products, from wine corks to shoes, flooring, purses, bulletin boards, and more. And besides being an incredibly versatile material, cork is a superstar natural and sustainable material. Plus, it’s biodegradable.

 

Cork Trees

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Cork comes from the inner bark of cork trees (Quercus suber), a species of oak tree that is evergreen and can grow to about 66 feet, or 20 meters. And cork trees are native to southwestern Europe and northwestern Africa.
Harvesting Cork Bark

 

Cork Forests

Cork trees grow in cork oak forests. Portugal is home to 34 percent of the Earth’s cork forests and Spain is home to another 27 percent. In addition, cork forests can be found in France, Italy, Morocco, Algeria, and Tunisia. Cork oak trees thrive in warm, humid environments. In all, there are about 6.6 million acres of Mediterranean cork forests.
Harvesting Cork Bark

 

Cork Forest Biodiversity

Spanish imperial eagle
Spanish imperial eagle (Aquila adalberti). Photo: José Antonio Lagier Martin.

Cork forests support a wide variety of species, including:

  • 24 species of reptiles and amphibians, including spiders, spadefoot toads, geckos, skinks, and vipers (São Marcos da Serra)
  • 160 species of birds, including kestrels, tawny owls, black storks, Spanish imperial eagles, kites, black vultures, robins, thrushes, chaffinches, woodlarks, woodpeckers, hoopoes, bee-eaters, skylarks, starlings, jays, magpies, nightingales, blackcaps, robins, chiffchaffs, nuthatches, sparrows, yellowhammers, and grey herons, which migrate from northern Europe
  • 37 species of mammals, including hares, weasels, wolves, genets, wild boars, deer, and Iberian lynxes (Apcor)
  • 135 species of plants, including other species of oak trees, stone pines, maritime pines, wild olive trees, and more (Rainforest Alliance)

Many of the species of plants and wildlife that live in cork forests cannot be found anywhere else in the world.

Cork Forest Endangered Species

Barbary stag and deer
Barbary deer and stag (Cervus elaphus barbarus). Photo: Ayoub Chaabi.

Cork forests are home to a number of endangered species, including the:

  • Black vulture (Spain)
  • Black stork (Spain)
  • Barbary stag (Tunisia and Algeria)
  • Spanish imperial eagle (Portugal and Spain)
  • Iberian lynx (Portugal and Spain) (Amorim)

Iberian Lynx

Iberian lynx cubs
Iberian lynx cubs. Photo: Iberian Lynx Conservation Program.

According to the World Wildlife Fund, the Iberian lynx (Lynx pardinus) is the world’s most endangered species of feline. Intense conservation efforts have brought the population to above 400, but they are still gravely endangered.

Thus, preserving cork forests protects vital habitat for endangered and critically endangered animals that cannot be found anywhere else in the world.

In addition to providing natural habitats to endangered species, cork oak forests support life by preventing desertification, a process that destroys fertile land.

They also support many human families whose livelihoods depend on the production of cork for products.

Cork Forest Alliance

The Cork Forest Conservation Alliance (CFCA) has a wealth of information about the many wonders of cork.

And if you haven’t seen it yet, be sure to check out CFCA Founder Patrick Spencer’s TED Talk about cork.

 

The Oldest Cork Tree

The Whistler Tree
The Whistler Tree, the oldest living cork tree. It was planted in 1783. Photo: Union of the Mediterranean Forest.

The oldest living cork tree is called The Whistler Tree. Located in the Alentejo region of Portugal, The Whistler Tree was planted in 1783, making it 236 years old at the time of the writing of this post. When The Whistler was planted, the U.S. and Great Britain were signing the Treaty of Paris, which ended the Revolutionary War.

The Whistler Tree is about 46 feet tall (14 meters) and its trunk has a diameter of 13 feet, or 4 meters. It still produces cork for harvest to this day. And besides being a help to humans, The Whistler is home to many songbirds who live in its canopy, thus the inspiration for the majestic tree’s name. (The Treeographer)

 

Cork Tree Bark

Harvested cork bark
Harvested cork bark. Photo: Video Podlahy.

When most of us think about tree bark, we think of the hard substance that chips off the tree in pieces. But the cork bark that’s harvested is the underlayer of the hard bark, which is referred to as the phellem layer, and it’s quite spongey.

Cork bark is a renewable and biodegradable material, and it can be obtained through a sustainable harvesting process. In addition, it’s easily recyclable.

Special properties make cork bark super versatile. It’s impermeable, elastic, and buoyant, so it can be used in a variety of applications. In addition, it’s naturally fire retardant.

Is there such a thing as cork wood?

While cork trees can be cut down for their wood, the saving grace for these special trees is that the cork bark itself is valuable to humans, and we don’t have to cut down the tree to harvest it.

 

Cork Harvesting

Harvesting cork bark
Harvesting cork bark in Santa Margarida da Serra, Portugal.

Cork is a sustainable resource that can be harvested every nine years, once the tree is about 25 years old. And the cork tree can be harvested for its bark roughly 16 times in its lifespan, which is about 200 years. Many cork forests have been in families for generations.

The cork harvest season spans from early May to late August. During this period, the cork can be separated from the tree trunk without causing permanent damage to the tree.

The first time cork is harvested from the tree, it yields a lower quality cork, which is used in products like the insoles of shoes and flooring. Subsequent harvests produce softer cork, which can be used for wine and champagne bottle stoppers and other products.

The Art of Harvesting Cork

Harvesting cork is a skilled trade because the harvesting process takes significant force, but the harvesters must ensure they don’t injure the underlying layer of the tree, which could make it more susceptible to pests and diseases.

To this day, the art of harvesting cork requires the work of two people; the process has not been able to be replicated by machines. It’s delicate work that’s also physically demanding, requiring a lot of strength. Hence, it’s usually men who do the job.

Once the cork is harvested, it’s removed in large planks, usually by people on foot as cork forests are not easily accessible by vehicles.

Here’s a video from Great Big Story about how cork bark is harvested:

Increased CO2 Absorption

In addition to the variety of products that can be made with cork, another positive about harvesting cork is that it enables the tree to absorb even more CO2 from the environment, which helps to fight climate change.

 

Are cork trees endangered?

Currently, cork trees and cork forests are not endangered, and a big part of this reason is that humans have a monetary reason for keeping them alive. Buying products that are made from natural cork helps to keep cork forests alive, and therefore helps to protect the natural habitats of the species who live there alive.

Right now, cork is a plentiful resource, according to the CFCA. There is enough cork in the cork forests of Portugal and Spain alone to last more than 100 years. And with the introduction of composite cork and granulated cork, which is obtained from smaller, leftover pieces of raw cork, there is now better utilization of existing cork resources than ever before.

 

Cork Recycling

Wine corks
Wine corks. Photo: Elisha Terada.

While cork is usually not accepted by regular curbside recycling programs, it can be recycled. In addition, if you have items that are made only with natural cork, such as wine corks or coasters, you can put them in your compost bin.

Although standard curbside recycling programs don’t recycle cork, there are some programs that will. You can either ship your used cork to them or leave it at drop-off locations.

Where can I recycle cork?

Here are some resources that recycle cork:

Cork Forest Conservation Alliance

TeraCycle

ReCork

Cork Club

 

Things Made out of Cork

Cork backpack by Corkor
Cork backpack by Corkor.

Cork isn’t just for wine bottles and laundry room bulletin boards anymore. Like hemp and bamboo, it’s a rockstar sustainable material because of its multi-faceted, good-for-people-planet-and-animals qualities. Today you can find a variety of eco-friendly products made from cork.

Cork stoppers for wine and champagne bottles represent about 60 percent of the cork industry.

In addition, cork is used in shoes and accessories, such as cell phone cases, cork leather purses and wallets, hats, and even cases for sunglasses.

Cork grease is used in woodwind and reed instruments, such as saxophones, clarinets, bassoons, and oboes.

Other uses of cork include gasket material for carburetors.

If you like to play badminton, you should know that cork is used in the shuttlecocks.

And you’re probably familiar with bulletin boards and coasters, as well as cork flooring.

Cork also makes great insulation for homes. It has natural fire retardant properties, and it works well for sound proofing and thermal insulation. It’s also hypoallergenic, making it a safer alternative to petrochemical-based insulation products.

In addition, granules of cork can be mixed into concrete to make it less dense.

Here are some cork products on UniGuide:

Eco-friendly and Vegan Backpack Brands

Women’s Vegan Sandals

Recycled and Eco-Friendly Flip Flops

Cool Laptop Cases and Sleeves

Eco-Friendly Phone Cases Guide

iPad and Tablet Cases and Sleeves Guide

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