What if there was a naturally occurring material that could easily replace plastics while remaining carbon negative? Even better, what if this material could feed an industry that provides a lucrative living to everyone involved in its production?
There is. Cork.
As a sustainable material for a wide variety of products from flooring to furniture, from clothing to insulation, cork is now reaching all-time highs in use for major industries. Cork exports from Portugal, the world’s largest cork producer, reached 670 million euros ($728 million) in the first half of 2023—more than it ever made from this ancient product.
But—and here’s the cool part—the trees are not cut down to harvest the bark. They remain in place as a sustainable crop that can be harvested every nine years. So, while they’re providing jobs, income, and a GDP for the countries where they thrive, they’re also still growing, sequestering CO2, and providing food and shelter for animals throughout the 150+ years they typically live.
Wait. There’s more. Part of the carbon absorbed by the cork oak while the bark is still intact is carried in the cork products produced from the bark. Production of the source material into its various products does not release the carbon. And since those products can be used for long periods of time, or even repurposed, recycled, and reused for other purposes, cork is carbon-negative, meaning it stores more carbon than was used to produce it.
Harvesting
While the outer layer of bark on just about every tree is considered cork bark, the product we think of as cork comes from the evergreen cork oak, native to the Mediterranean region. There, these trees evolved their thick outer bark specifically to protect them from harsh conditions in the region—droughts, brush fires, and fluctuating temperatures. What’s more, most trees, if stripped of their outer bark, would die. Not cork. That outer sheath can be stripped from up to ¾ of the tree, since it will completely regenerate within nine years.
Cork cutters train for years to get the swing of their axes just right—deep enough to cut through the outer bark but not deep enough to nick the inner bark and damage the tree. But because of this, cork cutting is one of the best-paying agricultural jobs in Portugal. Harvesting takes place between early May to late August and is done entirely by hand. No mechanical stripping devices are used for this part of cork production.
Once the nicks are cut, the bark is pried away from the bole and set aside to dry for six months. The planks are then cleaned and sorted, and the rough outer surface is scraped away by hand. The choicest planks are usually selected for products like wine bottle stoppers, while the lesser quality cork can be used for many other things. In addition, any cork left over after the stoppers are cut is combined into other items or used in several ways. In addition, all chemical by-products from the process, like tannins, hard wax, and phonic acid, are used by a variety of other industries, so they don’t go to waste.
Properties
Cork is believed to be one of the most versatile materials on Earth. Why?
It’s elastic. The cell membranes of the material are flexible and compressible.
It’s water-resistant because of the presence of suberin, a waxy rubbery substance, in the cork cells. The suberin keeps water out and prevents the growth of mold and mildew.
It’s fire-retardant. Cork oak trees developed this thick bark in part because of the frequency of natural wildfires. The material doesn’t easily catch fire, even when it encounters high temperatures. If/When it does burn, it does not produce flames, only a non-toxic smoke.
It’s durable. Materials made from cork age well, and don’t lose flexibility and durability over time.
It’s resistant to friction and abrasion.
It’s lightweight because of its low density.
It’s hypoallergenic, because it doesn’t absorb dust.
It’s a great sound insulator because of the gas between the cells of cork material, which makes it a poor conductor of noise and vibrations.
Products
Of course we’re all familiar with cork bottle stoppers. But industries are now putting this amazing material to new uses. Because it’s comprised of air-filled, watertight, flexible cells, cork is lightweight, which adds to its desirability in many cases.
- Stoppers. Of course.
- Insulating material. The cork oak’s bark is especially thick, adapted to protect the tree from fire. Thus, it’s now being used to shield the fuel tanks on NASA spacecraft, as well as electric car batteries, even home insulation. It’s resistant to water and oil, as well as termites. It retains its springiness while being able to stand up to compression.
- Cork tile flooring.
- Cork message/note boards.
- Shoe soles.
- Cork fasteners in musical instruments.
- Life vests and floats.
- Purses, wallets, jewelry, and an assortment of other fashion accessories.
- Fabrics that are easily sewable on any standard sewing machine.
- Leftover materials are ground and pressed into cork sheets or blocks.
- Cork dust is used to fuel boilers and thus this resource even powers its own processing facilities.
Other cool facts
Cork is a completely vegan product. In addition, because of its versatility and endurance, cork is becoming popular as an alternative to animal leather or plastic. And in the wild, the trees provide habitat for wildlife, some of which are in danger of extinction. Even rare plant species and fungi grow on, among, or because of these trees. And since they aren’t ever cut down, the habitat they provide is reliable, and long-lasting.
Image credits
Cork Oak Tree Image by Jörg from Pixabay
Cork Bark Image by Jörg from Pixabay
Cork Stopper Photo by Renzo D’souza on Unsplash
Research sites
This ancient material is displacing plastics and creating a billion-dollar industry – https://www.washingtonpost.com/climate-solutions/2024/02/03/cork-sustainable-material/
Cork: Plant anatomy – https://www.britannica.com/science/cork-plant-anatomy
Where does cork come from? – https://home.howstuffworks.com/question550.htm
What is cork? – https://www.wecork.com/benefits-of-cork/what-is-cork/
The Ultimate Referenced Guide to Cork Material — https://www.lafloreparis.com/blogs/laflore-blog/the-ultimate-reference-guide-to-cork-material?tw_source=google&tw_adid=&tw_campaign=21161138092&gad_source=1&gclid=Cj0KCQjwztOwBhD7ARIsAPDKnkB1XdiJoyCkYwUoJ3g8j9qTR0jo67HxvZy9Z9MFvLEbTTpnmFQzhVoaAnmkEALw_wcB
One of Nature’s most extraordinary materials — https://amorimcorkcomposites.com/en-us/why-cork/what-is-cork/
Cork Fabric — https://fabricfunhouse.com/pages/cork-fabric