Corks vs Screw Caps

In pursuit of sustainable ‘carbon neutral’ wine: Closing a bottle with a cork significantly reduces the carbon footprint of the wines packaging and helps sustain vital ecosystems.

The observant amongst you will have noticed that our most recent still wine launches, Sussex Rose 2021 and Bacchus MV, have a cork closure rather than a screw cap.    So why have we done this when these corks cost over twice the price of screw caps and we are in the middle of a cost inflation crisis?

This is because there is only one crisis that is more significant and more pressing than the current economic one and that is the climate crisis.

As a vineyard and winery we are committed to producing ‘sustainable wines’, and we believe a fundamental element of this is being ‘carbon neutral’ as a busines.   To enable us to do this consistently we need to look at every opportunity to reduce our Carbon Footprint: from how we grow our grapes to how we package our wines.

From a packaging point of view, the standard glass wine bottle that has become the accepted norm for wine packaging has a significant carbon footprint and finding alternative other solutions is complex (although we are looking at it!).  However, we found we could do something right now about our bottle closures.

Finding data to accurately calculate the carbon footprint of a product is one of THE big challenges facing any company like us trying to ‘do the right thing’.   A few years ago, Price Waterhouse Coopers carried out a Full Lifecycle Analysis on wine closures and demonstrated that cork showed a 24-fold advantage over aluminium screw-caps in terms of their carbon footprint.  Our own analysis of data provided by our suppliers indicates that the carbon footprint of the Diam 5 corks we use is 26g CO2e per cork vs. 316g CO2e for a standard aluminium screwcap (so a 12-fold advantage).   Whatever the order of magnitude, common senses suggests that cork does have significant benefits over screwcaps.

This is because cork is a natural sustainable product harvested from the bark of cork oak trees. These evergreens, the majority of which grow in Portugal and Spain, are abundant and strictly protected. Cork oaks regenerate their outer layer of bark, which allows them to be harvested about once every decade. With a lifespan of up to 200 years, one tree can provide cork for thousands of bottles. During growth, the cork tree is sequestering carbon from the air. A study by accountants Ernst & Young estimated that a single natural cork contains up to 309 grammes of sequestered CO2, while a sparkling wine cork holds up to 562 grammes.  If these corks are reused for alternative uses…this carbon is captured for the long term.  If they are burnt or decompose, the CO2 returned will be the same as that sequestered, so the overall cork is ‘carbon neutral’ in its impact.

In addition, these cork forests are biodiversity ‘hot spots’ The cork forests are well known as a keystone species driving biodiversity in this region as well as supporting the livelihoods of thousands of local people.

In contrast, screw caps are made from aluminium, produced from bauxite, a finite resource which is highly energy intensive to mine and produce.   And whilst it is re-cyclable, this also requires energy use resulting in a net ‘carbon positive’ product.

But what about ‘cork taint’ I hear you say?

In the last 15 to 20 years there has been a mass move away from cork to screw caps for still wines due to this issue.   Cork taint, or what many refer to as ‘corked’ wine, gives wine a damp cardboard aroma and destroys the wine’s pleasurable characteristics.   This is the result of the wine being contaminated – not by the presence of the cork but by a chemical compound – TCA (2,4,6- trichloroanisole). TCA is formed when fungi (which reside in the cork) come into contact with cork and wine sanitation products such as bleach.

However, due to considerable technical advances in the understanding of the causes and new methods of producing corks, this problem is now negligible.   Corks today are very different than they were then.    Obviously, corks can vary greatly in quality (as can screw caps).   The key issue is for the winemaker to select the optimum cork for the wine to be bottled.

Screw caps are made with different plastic linings which determine the speed with which oxygen can enter the wine bottle and hence how rapidly the wine will develop and evolve.   In the same way,  corks can be selected with different permeabilities, which also effects the speed of evolution of the wine in the bottle.  The lowest cost screw caps and the lowest cost corks are for wines that will be drunk within a couple of years of bottling.

We have selected high quality Diam 5 corks for our white and rose wines, which will keep them young and fresh with just the right amount of oxygen ingress.  For our red Pinot Noir we are using the Diam 10 as this wine could potentially age and evolve for a much longer period.  But no cork lasts for ever, so premium wines that are aged for many years should have their corks replaced every 10 – 20 years to ensure they retain the optimum seal.

An important difference from a use point of view is that for prolonged storage, as for all wines under cork, the bottles should be stored horizontally so that the corks remain wet.

Keep following us on social media for further updates on our Carbon reduction initiatives.   We welcome your thoughts and feedback.

Cork Wine Bottle Closure

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