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Is Cork Sustainable or Is It Bad For The Environment?

    is cork eco friendly and good for the environment

    Cork has always seemed like a fantastic, natural and sustainable material to me.

    Cork material just feels more environmentally friendly, but what is the truth to this?

    Around my house I have a few cork-based items – coasters, place mats and I’ve also preferred red wine from a cork topped wine bottle! However, I realised that I know next to nothing about the material, where cork comes from, how it’s made, how sustainable it is and whether cork is eco friendly or not.

    After an afternoon researching, I was amazed at what I found out about cork and wondered how I didn’t know this before!?

    Don’t worry, I’ve included everything I found out about cork sustainability here in this blog.

    Is cork sustainable?

    If you’re short of time and are looking for a quick answer, then here it is:

    Differing from man-made materials, cork is a natural product that is sustainable, environmentally friendly, carbon positive, biodegradable and renewable.

    Aside from just the product itself, cork goes a step further in the environmental stakes.

    The cork oak tree is an important species within the ecosystem in which is grows. It provides a habitat that supports an abundance of biodiversity and ecological processes, as well as the people and economies where it’s grown.

    If you’ve got a little more time and want to find out why cork is such a sustainable and eco-friendly material, carry on reading – you’ll like what you read!

    What is cork made of?

    large cork oak tree
    Large cork oak tree. Source: Pixabay

    Let’s start off with the basics.

    What is cork made of and where does it come from?

    Cork is made from the bark of the cork oak tree.

    The cork that we use for wine stoppers, noticeboards, as coasters for our drinks and for flooring is all gathered from the same place – the cork oak tree.

    There’s one primary species where cork comes from, the Quercus suber, which is simply known as the cork oak.

    Where does cork come from?

    The cork oak tree, or Quercus suber, is native to southwest Europe and north Africa.

    It’s actually a member of the same family in which the chestnut oak (Quercus montana) and common oak tree (Quercus robur) are part of.

    The majority of cork that we use in and around our homes is grown from cork oak forests in Portugal and Spain, plus smaller percentages from Morocco, Algeria, Tunisia, Italy and France.

    The cork tree has evolved to grow a thick layer of bark to protect itself from the harsh conditions (lots of sun, little rainfall, bush fires) of the Mediterranean regions where it grows.

    It’s this bark that is sustainably harvested to manufacture cork-based products.

    Are cork oak trees grow native to these regions?

    Yes, cork oaks are native to the Mediterranean region and have been here for many, many thousands of years.

    In fact, fossil remnants of the cork oak have been found in the Mediterranean basin dating over 25 million years old and fossils found in Portugal over 10 million years old, demonstrating the trees ancient history in this region.

    Naturally, cork oaks grow in mixed forests alongside other oaks, pines species and olive trees, who produce olives and olive oil. Check out my article on the most sustainable cooking oil.

    On the Iberian Peninsula, cork oak landscapes are known as a ‘montado’ in Portugal or a ‘dehesa’ in Spain.

    Why is cork eco friendly?

    Many people ask is cork eco friendly?

    The answer is an unanimous yes!

    Growing cork oak trees has been an eco friendly and environmentally sustainable activity for hundreds of years.

    Cork oak landscapes have been ranked as one of the most valuable habitats in Europe. The habitats where cork oak is grown combine cork trees with high quality pastures and rotation crops.

    The cork oak is an important keystone species in these areas and is thus treated accordingly by people and communities.

    Cork trees are so important to the communities where they are grown in Portugal (where it is also their national tree) that they are protected by law and each one is identified and regulated individually.

    Here, it’s a crime to cut down a cork oak tree and they’ve been protected in Portuguese law since the year 1209!

    It’s possible to plant cork oak forests too if you live in the right part of the world. You might be interested in this blog on tree planting.

    Cork oak landscape in Portugal with young cork and olive trees, a large chestnut to the left and cherry tree to the right
    Cork oak landscape in Portugal with young cork and olive trees, a large chestnut to the left and cherry tree to the right.

    4 reasons why is cork environmentally friendly

    As you might be learning, cork is considered an environmentally friendly material for a number of great reasons.

    Here are 4 big reasons why cork is eco friendly and sustainable.

    1. Positive impact on local biodiversity

    Cork oak landscapes have a major positive impact on other plants and animals and can sustain a rich mix of biodiversity.

    In such landscapes plant diversity levels can reach 135 species per square metre. The polar opposite of a monoculture and a brilliant form of sustainable agriculture.

    The cork oak woodlands are also home to a high diversity of animals, including a number of threatened species such as the Iberian lynx, Iberian imperial eagle, barbary deer, black vulture and black stork.

    The woodlands also temporarily support millions of migratory and wintering birds.

    2. Big carbon dioxide store

    All plants absorb CO2 from the atmosphere in order to live and grow.

    This captured carbon is then stored inside the plant. This is why deforestation is such a problem as all that trapped carbon gets released quickly into the atmosphere.

    In the Andalusian forests, it’s estimated that cork trees store over 15 million tonnes of CO2 alone.

    3. Help protect important ecological processes

    The cork oak landscapes also play a vital role in protecting the physical environment and sustaining crucial ecological processes.

    If you haven’t been before, the Mediterranean is a hot, dry region, particularly in the summer. The cork trees help protect against soil erosion through wind and lowers the water erosion and run off rate.

    The environmental services don’t stop there.

    The tree tops create a microclimate which prolongs the growing session by creating less extreme environments. The trees also produce a large amount of organic material which rots and enriches the soil, as well as bringing nutrients up from the lower to upper soil levels, which the local vegetation can also access.

    All these facts are backed up by scientific reports cited in a 2006 published by the World Wildlife Fund looking at the importance of cork oak trees to the environment and local economies. Have a look at my blog which discusses if WWF are a good charity to donate to.

    4. Support local people and communities

    Another incredible important aspect about cork oak forests is that they support and benefit local people and livelihoods.

    The trees and their bark have a high economic value. Because of cork’s sustainable nature, plenty of jobs in rural locations are created and kept over the long term.

    The cork oak woodlands almost single-handedly guarantee the survival of local communities. This is sustainability in a nutshell – true harmony of nature and people.

    It’s also a reason why I’m a huge fan of sustainable agroforestry.

    5. A renewable resource

    Unlike some forms of agriculture, cork is a renewable resource.

    This is thanks to the way it’s grown and harvested. A cork oak tree can stay in the ground for hundreds of years whilst being sustainably harvested on a rotational basis for the bark.

    This sustainable production takes place over the timescale of years and decades rather than months, which help to make cork the renewable material it is.

    Let’s find out how cork is made and harvested.

    How is cork made?

    skilled worker stripping away bark from cork oak tree
    Skilled worker stripping cork from the Cork Oak between May-August. Source: Apcor

    We know about the benefits of cork for the environment, but how is cork harvested and produced?

    Cork trees are grown naturally in their native environment and are left untouched and without interference for their thing for the first 25-30 years of life.

    Once the cork on the outside of the tree reaches a certain thickness, the bark is harvested by stripping away layers in late Spring or early summer.

    It’s done at this time of year as the tree is physiologically active, meaning the cork can be stripped off without damaging the underlying tissue layer. Another reason why cork is sustainable.

    Does cork grow back?

    Once harvested the trees are marked with a date and left to regrow and regenerate over many years. Yes, the cork bark grows back.

    On average the tree won’t be harvested again for another 9-12 years whilst the bark grows back. This is why cork is renewable and highly sustainable.

    Producing and harvest cork requires no trees to be cut down. No deforestation or habitat destruction at all. Zero.

    Once the layer of cork is taken, the tree continues to live and grow. This is similar in the way that latex from rubber trees is harvested, without the need to chop the tree down. You can read if rubber is bad for the environment here.

    “The harvesting of the bark of the cork oak offers one of the finest examples of traditional, sustainable land use.”

    World Wildlife Fund

    Is cork sustainably produced?

    As the cork oak lives between 100 and 300 years, this cycle can be repeated many times and the benefits can be continually reaped.

    The average cork tree usually yields 40-60kg of cork when harvested but older, larger trees can yield 100s of kilograms.

    Another plus point for local workers is that cork harvesting from the tree is done entirely by hand. The expert tiradors use a very sharp axe to make cuts on the outer layer of the tree (being extremely careful not to damage the underlying living cells) before wedging their axe underneath the strip and peeling the layer of cork off.

    Like all careful crafts, this is a skilled job. Thanks to this, cork harvesting is one of the best paid agricultural jobs in the world! It might be for this reason why cork products can be on the expensive side.

    During the regrowth period, the forest persists in all its glory as the cork oak helps to keep the local landscapes and ecosystems stable, as well as absorbing a large amount of carbon dioxide from the atmosphere.

    cork oak landscape in south portugal
    Cork oak landscape in Serra do Marvao in Portugal.

    A study in 2005 by Luis Gil et al found that a harvested cork oak tree absorbs 3 to 5 times more CO2 than one which is not harvested. How environmentally friendly is that?

    So yes, growing and producing cork is a sustainable practice.

    Cork stoppers are better than plastic and aluminium

    Let’s for a second compare a common cork wine stopper with it’s non-cork alternatives in plastic and aluminium screw tops. How does these do from an environmental and carbon footprint perspective?

    A lifecycle analysis study by PWC found that the production of a plastic stopper releases around 10 times more CO2, and even worse was the aluminium stopper that releases 26 times more carbon dioxide that a cork stopper.

    Even better, as a cork oak stopper is 100% plant material, a wine cork can be composted. However, as it’s a tough material, it’s better to chop it up into smaller pieces to speed the process up.

    Why do some people ask is cork bad for the environment?

    Let’s start with the elephant in the room. As you’re googling ‘is cork sustainable’, you’re bound to find answers telling you that cork is bad for the environment and not eco-friendly.

    How can you have two contrasting answers to a fairly simple question?

    The problem seems to stem from the harvesting. Many people believe that cork is bad for the environment because the trees need to be cut down to be harvested.

    This is not true, trees do not need to be cut down to harvest cork.

    Cork trees are harvested by stripping the bark from the lower section of the main trunk, then left to regenerate and grow its unique cork bark again, during which it is constantly absorbing carbon dioxide from the environment.  

    Some people also believe that a cork oak forest is a planted monoculture that destroys the local habitat in favour of a economic crop. This also isn’t true.

    Cork grows naturally and is a native of where it is mainly produced around the Mediterranean basin. As we discovered above, cork oak landscapes have a vast number of positive impacts and benefits to the local environment and ecosystem.

    This differs to other common household materials, such as plastic and even silicone, which is often deemed environmentally friendly but is still heavily manufactured. Have a more in-depth read here on whether silicone is better than plastic for the environment.

    Why is cork sustainable?

    As we’ve seen so far, the growing, harvesting and regeneration of the cork tree is an incredibly sustainable process.

    Even better, because the tree is native to the south and west corners of the Mediterranean where the vast majority of the world’s supply comes from, it’s not causing harm to the local environment. In fact, as we’ve seen in the section above, the cork oak landscapes actively benefit all local biodiversity, including both plants and animals.

    This contrasts to palm oil trees for example, which are actually native to Africa and were only brought to South-East Asia around 100 years ago and decimate landscapes with their over-powering, carefully managed monocultures.

    If we want to get a little bit more technical, cork has a very low embodied energy. This is a value that takes into account all the energy needed for production, extraction and transportation. Compared to a material like concrete or silicone, cork has an extremely low embodied energy.


    FAQS on Cork Sustainability

    Here are a few frequently asked questions about cork sustainability.

    Is cork biodegradable?

    Does cork biodegrade?

    Yes, natural cork is biodegradable.

    As you’ve hopefully read, cork is an eco-friendly material that is fully biodegradable.

    Cork will biodegrade into its natural constituents without producing any toxic residues. Very environmentally friendly. However, this will take a long time.

    Being on the outside of trees, cork is a tough material – there’s a reason it’s used to keep bottles of wine airtight and leakproof. To speed the process up, chop any cork up into small pieces. This is a similar situation to the biodegradability of bamboo.

    Is cork compostable?

    Yes, cork is compostable.

    It’s a 100% natural product so can be composted along with your other organic waste. This is as long as the product doesn’t contain any other non-compostable materials. As mentioned above however, cork won’t break down in a hurry.

    To compost quicker, cut your cork up into smaller chunks and make sure there is some greenery into your compost mix too – the smaller the pieces the better as these are easier to break down by the all important microorganisms.

    Remember a good compost pile is a mix between ‘brown waste’ i.e. materials that contain a lot of carbon like cork, and ‘green waste’ such as grass or veg that contains more nitrogen and protein. The composting microorganisms will be happy.

    Are wine corks compostable?

    Yes wine corks are compostable too.

    A good wine cork will be 100% natural material straight from the cork oak bark. Once a strip of bark is off, it’s simply cut into shape.

    No need for any other ingredients or materials, just pure cork which is why wine corks can be composted.

    Is cork recyclable?

    Yes, cork is very much recyclable.

    When a product, such as a wine stopper, is no longer in use, it can be recycled into other products. Cork is technically a type of recyclable wood.

    I’m planning on recycling my own cork collection at some point and re-purposing the corks into something useful, such as a noticeboard for the house.

    If cork is accepted at your local council recycling point, get in touch with Recorked UK who offer a cork recycling scheme.

    cork oak wine stoppers in a pile
    70% of all cork oak goes into making wine stoppers

    Is cork renewable?

    Yes, cork is a renewable resource.

    The bark of a cork oak is harvested for the first time when it is around 25 years old, then after that is left for at least 9 years. During this time, the cork naturally regrows and regenerates on the tree.

    The average cork oak can be harvested around 15 times over its lifetime over between 100 and 300 years.

    The largest and most productive cork oak tree in the world is the Whistler Tree in the Alentejo region of Portugal. Planted in 1783, this exceptional tree is home to numerous birds and has been harvested every 9 years since 1820.

    In 1991, around 1,200kg of cork was harvested from the Whistler, enough to produce 100,000 cork stoppers!

    The tree is still in excellent condition, which goes to show how renewable and astounding the cork tree is. If you’re wondering, the next harvest will be in 2027.

    Is cork waterproof?

    Yes cork is waterproof – this is why it makes such a good wine stopper!

    Cork has waterproofing properties thanks to its natural structure. The tight fibres of the bark mean it isn’t very permeable to liquid or gases, which makes whatever is on the other side waterproof.

    Is cork flammable?

    It can repel water, but is cork flammable or fire resistant?

    Cork is not very flammable. It’s better to describe cork as fire resistant.

    It can withstand high temperatures and when it does burn it doesn’t go up in flames like other flammable materials thanks to the natural materials in contains.

    These anti-flame properties are why cork has been used by NASA in space-bound rockets.

    Other benefits of cork

    As if all that wasn’t enough, this exceptional natural material has even more benefits. I’ve listed some of the top benefits below that would all be great on their own, but with cork you get them all!

    • Lightweight – as cork is around 50% air, it is very lightweight. This contrasts to solid timbers which are extremely heavy due to the densely packed fibres leaving little space for anything else. This means any cork product is easy to move around and takes less energy to do so.
    • Flexible – cork is also highly flexible and can be used for a variety of products
    • Soft to the touch – great for household products
    • Hypoallergenic
    • Thermal insulator – fantastic insulating properties that keep heat in or out depending on your perspective. Another reason for NASA’s use. Also why it’s a great eco-friendly insulation for your home.
    • Acoustic insulator – in a similar way that it isn’t good at conducting heat, it’s not very good at letting sound through either.

    Even cork that doesn’t pass the quality tests for a wine stopper has another use. There is little to no waste from cork production. Lower grade cork gets collected, ground up and recycled into other cork products or at the very worst, burned for heat.


    Wrap up on eco friendly cork

    With all that in mind, I think you’ll agree that cork is an amazing, natural material.

    So, at the minimum, make sure your next bottle of wine comes with a cork stopper rather than a screw cap. You’ll not only be drinking a better quality wine (in my opinion), you’ll be helping to preserve the ancient Mediterranean cork oak forests plus all the other biodiversity and ecological benefits that come with this.

    In fact it has so many benefits to both the environment and local ecosystem over 100 of years whilst the tree is kept fully functioning and healthy, I think cork is one of the greenest, most sustainable materials on earth!

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