Cork is a hugely versatile natural material that can be fashioned into several different items. Most well known for its use in the wine industry, it has branched out (pardon the pun) into lots of industries – from yoga to vegan leather. In terms of its production, cork is sustainable – but what about after use? Will it sit in the landfill for centuries when it comes to the end of its usable life or is cork biodegradable? Thankfully, for the sake of the environment, it does biodegrade. Making composting a great, arguably the best, option for used cork.
Firstly, a bit background – what is cork and where does it come from?
Cork is a highly sustainable natural material that comes from the bark of the cork oak tree (Quercus suber). It is lightweight, waterproof and durable – making it a great material for lots of different products. Most natural cork is harvested from trees in Europe and northwestern Africa. Portugal has the largest cork oak tree population and lead the way when it comes to production of cork products.
It is particularly sustainable due to the way it is harvested. Once the tree reaches a certain maturity – at least 25 years old at least – the bark can be stripped. The bark will then renew itself and can be stripped every nine (or so) years. Whilst it renews it also absorbs even more carbon dioxide, a greenhouse gas – as well as being sustainable, it even contributes to the fight against global warming!
Is cork biodegradable?
Biodegradable materials are those that can be broken down naturally by microbes. Cork falls into this category – unlike plastics, for example, cork will not persist indefinitely. A wine cork that ends up landfill, whilst not ideal, will biodegrade eventually.
Can cork be composted?
Cork is biodegradable so it can be composted, right? Not necessarily. Materials must be biodegradable to be composted. But not all biodegradable materials can be composted! The breakdown of all biodegradable material does not contribute to a nutrient-rich compost. Luckily, natural cork brings nutrients to the end-product of the compost pile – so you can throw it in there.
Cork is rich in carbon which makes it a ‘brown’ material in terms of composting. As will all composting, it is important to incorporate both ‘green’ materials – those rich in nitrogen – and ‘brown’.
The caveats of cork composting….
When cork is made into a product it may not be in its 100% natural form. In the example of cork fabric/leather, a thin layer of cork is attached to a backing material. In some cases, this may be a totally natural material such as pure cotton, in other cases it may be a material that contains plastics such as Polyurethane (PU). It largely depends on the manufacturer. This does not necessarily make it destined for the trash though. In this case, you could pop it in the compost and sift out any parts that have not fully decomposed later.
Also, a bit of a heads-up regarding wine bottle corks – make sure they are made from natural cork before you pop them in the pile! Wine producers are turning towards synthetic corks which in some cases replicate the look of real cork. Although, you should be able to tell the difference – they tend to a have a foam-like texture. These synthetic corks will not be suitable for composting, unfortunately, and are likely to live many years in the landfill if not recycled in a specialist scheme.
You will also need to do a bit prep – or you cork might be sitting in the compost pile for a lot longer than you’d like! Cork is waterproof. And although this is ideal for your wine bottle or cork leather bag, it makes composting a bit more challenging! But this is easily remedied. Simply break down your cork into small pieces – a blender is ideal, but anything that grinds it down will do the job.
The bottom line
Cork is one of the most sustainable materials out there – the fact that after use it is biodegradable and compostable makes it even better! If you are new to composting, a few basics can be found here. Otherwise, make sure you grind down the cork sufficiently and ensure an appropriate balance of ‘green’ materials to balance the ‘brown’ cork. This should provide a good basis for successful cork composting. Good luck!