The secrets of cork: So much more than a bottle stopper

Lisbon, Portugal — The sound of a cork popping out of the end of a bottle is known across the world. It often precedes moments of celebration, a shared meal or simply the quiet enjoyment of a glass of wine. But many who’ve taken part in the simple ritual may not realize that it’s also a synonym for sustainability, natural wonder, and even human ingenuity.

Cork, the humble material used for centuries to seal bottles, is a unique product not only for the way it’s grown, but also for the plethora of inventive uses people have found for it — which go far beyond the ubiquitous bottle stoppers. Cork is used in everything from the building of spacecraft to the insulation of homes, and it can replace rubber or plastic on just about anything that needs protection from heat or vibration.

Thanks to the unique, delicate conditions in which it grows, cork is also a powerful, natural carbon sink, meaning it absorbs harmful CO2 from the atmosphere and locks it away.

CBS News visited the southern European nation of Portugal, which produces the majority of the world’s cork, and met António Rios Amorim, who humbly rejects the title “King of Cork.”

“I’m just inheriting a huge legacy from a family that, for the last 154 years, has been dedicating itself to cork, and really trying to develop this unique product to give it new life,” he said.

Amorim Cork produces more than five billion of the approximately 13 billion cork bottle stoppers produced annually across the globe. It’s enough to give the family firm comfortable supremacy in the industry, but Amorim said finding new and innovative uses for the material, beyond sealing bottles, remained “fundamental” to his empire’s future.

Among the less-well-known applications — and one Amorim clearly relishes — is the use of cork on NASA rockets. The material is mixed into the heat shields that protect spacecraft as they leave and reenter the Earth’s atmosphere. 

Its light weight, malleability and insulating properties against vibration have made the spongy material a natural choice for some of the most important space missions, including the Apollo missions and the Mars rovers. It’s also used on Elon Musk’s SpaceX rockets.

“It’s remarkable,” said Eduardo Soares, as he gave CBS News a tour of Amorim’s eclectic showroom. “Cork has this very peculiar effect, a slow burning process. It will absorb heat without transferring it.”

As head of the unit tasked with dreaming up new ways for Amorim to profit from cork that isn’t suitable for bottle stoppers, Soares could easily identify every product in the room.

Biodegradable cork granules replace rubber in artificial turf infill, which also helps keep surface temperatures down and avoids the release of microplastics; Insulation panels that absorb vibration, making train carriages quieter and smoother; Children’s playground flooring, normally made of synthetic materials, now have a natural alternative. 

For Amorim, the list of alternative uses for cork seems endless.

“It’s very important for us that we use the raw material that we take out from nature until the very last limit,” Soares explained.

Amorim is also part of a recycling initiative, aptly named The Cork Collective, that aims to help restaurants and hotels recycle the cork stoppers from bottles they open, to give the precious material a new lease of life.

Another family-run business in the field is Sofalca, which specializes in turning cork into natural insulation for walls and floors. 

CEO Paulo Estrada gave CBS News a tour of his factory’s autoclaves, affectionately nicknamed the “popcorn makers,” which cook granules of cork at high temperatures and under intense pressure. The cork expands, and its natural resin glues it all together without the need for added chemicals. A large block rolls off the assembly line, ready to be cut into slabs, shaped into enormous walls of art or even pieces of furniture.

Estrada said the material can give an otherwise unassuming part of someone’s home a “contemplative effect.”

“If you come near a cork wall, you will touch, smell and feel it. Nobody stays indifferent,” he added.

The desire by businesses to make the most out of every single ounce of the natural material can be explained by its biggest caveat: Cork is a layer of bark that grows only on the Quercus Suber oak tree. It typically takes 25 years from the moment a tree is planted for it to be ready for its first harvest. It then takes another nine years to regrow the bark.

“You have to be patient,” said Casimiro Milheiras, taking a quick break from climbing up trees with a small axe. At 57, Milheiras is one of thousands of seasonal workers hired every summer to comb through Portugal’s scorching Alentejo region to manually strip the bark off the Quercus oaks.

“It’s almost an art form, so you only do this work if you really love it,” he said.

His 20 years of experience have taught him exactly how to strike the tree hard enough to pierce through the bark, but not so hard that he cuts into the trunk, as doing so would compromise the next harvest.

The natural landscape cork comes from isn’t just important for the industry, however. Environmental impact studies by international consulting firms EY and PricewaterhouseCoopers have demonstrated that many of Amorim’s products are actually carbon negative, which means the overall process — from growth to extraction, transportation and production — absorbs more carbon than it emits into the environment.

“There is no best example of a carbon sink in a forest like the cork oak forest, because we don’t cut the tree,” explained Nuno Oliveira, “we want them to grow [for] as long as possible.”

Oliveira is the director of Amorim’s forestry division, which is responsible for the research and practices that keep its cork oak forests healthy. His work helps secure the future of both Portugal’s cork industry, and the company.

Standing in a field of planted cork oaks that were about 100 years old on average, Oliveira explained that as long as the trees keep growing and regrowing their precious bark, they will keep sucking carbon out of the air.

His biggest challenge, he said, has been to find a way to shorten the time needed for a tree’s first cork harvest from the current 25 years, to just 10, which CEO Amorim highlighted as one of the most “fundamental” questions his business needs to answer.

“This is a gift of nature,” Amorim said. “We need to consume products with a negative carbon footprint. That means we are going to have to plant a lot more cork trees, which at the end of the day will make us live in a much better world.”