Cork is a material with which we are all already familiar. It has been used as a means of sealing wine bottles for thousands of years, even being found in the tombs of ancient Egyptians. It was also used by ancient Greeks and Romans to make sandals and as flotation devices for their fishing nets. But cork is anything but a material of the past. In fact, it could play a very significant role as a material of the future.
Incredibly sustainable, cork has a huge range of potential uses (not to mention still providing the satisfying pop of a bottle of wine being opened) thanks to its properties of being flexible, water and fire resistant, lightweight, and a good insulator. So, let’s take a closer look at cork, including where it comes from, how it is farmed, and just why it is so sustainable.
What is Cork?
Cork comes from the outer layer of bark from a cork oak tree, usually found in around the Mediterranean parts of Europe and North Africa, particularly in Portugal where it is the national tree and has enjoyed protected status since the 13th century. In fact, Portugal is home to just over a third of the world’s cork forests, with Spain at around 27%.
The part of the bark that is harvested is called the phellem layer, which possesses pyrophosphoric (water repellent) properties. It is also highly buoyant, elastic, and fire retardant (which offers an incredible degree of protection to the tree even in the event of forest fires).
How is Cork Farmed?
The bark is harvested once the tree is old enough to sustain the harvesting process and the trunk is wide enough to make the process worthwhile, usually after 25 years and at around 24 inches. The bark is stripped from the tree by hand, usually every nine years, with the tree being marked with the date to avoid premature harvesting in the future.
The thing that makes cork such a sustainable material is that the bark can be removed without causing any damage to the tree. The outer phellem layer will simply regrow over time. And with cork oaks being able to live up to 300 years, it is possible to harvest each tree as much as 20 times over a 150 period. That makes cork an incredibly productive and profitable tree, as well as a great source of sustainable materials.
Is Cork a Sustainable Material?
The harvesting process is very low impact, with just a few hand tools required to do the job. An incision is made in the bark of the tree and the outer phellem layer is simply peeled off by hand. And because cork is harvested from sustainable and established cork forests, it has zero carbon footprint, with the cork trees actually absorbing CO2 from the atmosphere.
In fact, for every kilogram of cork produced, cork oaks absorb an average of 55 kilograms of CO2 from the atmosphere. Harvested cork oaks actually absorb 3.5 times as much CO2 as non-harvested trees. And cork oaks in Portugal alone can help to offset as much as 10 million tons of carbon every year. That’s why cork is a sustainable material commonly used as:
- Wall tiles
- Bottle stoppers
- Sporting equipment
Is Cork Biodegradable?
Cork is biodegradable, compostable and recyclable. As it is made from 100% natural materials, coming from tree bark, it can be recycled without producing toxic substances. Cork can also go in most curbside recycling programs or can be added to your compost bin. Specialist cork recycling programs also grind up the corks from wine bottles to make new cork products, which significantly reduces the end-of-life impact. However, it is important to know that some corks are manufactured with plastics, so always ensure you are only recycling or composting 100% pure cork products.
How Is Cork Sustainable?
The sustainability credentials of cork are fairly obvious for all to see. First, it comes from a naturally occurring tree which grows in large numbers across large areas of Europe. More importantly, the tree does not have to be cut down during the harvest and can produce up to 30 harvests during a lifetime. Cork does not have to be treated with any toxic products to make it water repellent and fire resistant. It is lightweight which makes it easy to transport and the trees on which it grows actually absorb more CO2 once harvested than if simply left to grow. All of which makes cork one of the most sustainable materials on the planet, and explains why cork production is growing around the world.
What Are the Benefits of Cork?
Cork has a surprising number of naturally occurring benefits which help to make it an excellent choice of building material, as well as having aesthetic properties for interior design. These include:
As you might expect from a material that has been used as a bottle stopper for thousands of years, cork is naturally water resistant. That’s because it contains suberin at a cellular level. This is a fatty substance that does not allow any water retention within the cells. That means that as well as being great for keeping wine in bottles it can also be used as an external building material, for sustainable cork flooring, as well as for protective products such as bags and cases.
Cork is a natural material that possesses antimicrobial qualities, meaning that it is resistant to mold and mildew, as well as offering protection against termites and other harmful insects. The anti-static surface also means it does not attract dust, which is great for people with allergies.
The material is naturally fire resistant, something which helps cork oak trees survive forest fires. It is not fire retardant, however, so is best not placed too near open flames or heat sources. But even when cork does burn it produces less smoke and chemicals than synthetic materials.
Cork is an incredibly versatile material that can be used to insulate or clad buildings, as well as for floors and other surfaces. It is available in a choice of different shades and finishes too, which gives it great design potential. Cork is also flexible, which means it can be used to make shoes, bags, and hats.
What are the Disadvantages of Cork?
Of course, cork is not perfect and like any material has a few weak spots. These include:
Susceptible to damage
When used as a material to cover surfaces such as floors and tables, cork can be susceptible to damage. That’s because it is softer than some other types of flooring, and can be scratched by moving furniture, or even dog or cat claws. This can be countered with treatment, but this can negate some of the sustainable benefits of using cork. Cork can also be susceptible to staining if not treated.
Despite being a naturally occurring and renewable material, the cost of harvesting the cork means it is often an expensive option.
How Else Can Cork Be Used?
As well as being used as a natural material in its own right, sustainable cork agglomerates are used in ceiling, wall, and roof insulation. It can also be used in concrete structures to allow for expansion and contraction, particularly in compression joints. Because cork is so lightweight it is often used in large scale concrete structures such as tunnels and dams.
You can check out the blog for more tips and guides on going zero waste, or visit the shop to see what sorts of products are making clever use of zero waste raw materials like cork.