Wine closures: the facts

Environmental impact

With a growth in demand for sustainably sourced products, the environmental impact of wine is under increased scrutiny, meaning that the eco-friendliness of the different closure types has become a factor in which stopper to select.

Consequently, closure manufacturers have undertaken carbon footprint and other analyses to see which is the greenest stopper. When it comes to CO2 emissions alone, Nomacorc was the first to release a comparative study when it published the results of a Greenloop audit in April 2008. Having analysed the CO2 released during the production of the raw material for the closures and their packaging, then the manufacture of the stoppers, and distribution, as well as disposal, it showed that the cork had the lowest carbon footprint and screwcaps the highest (see bar chart), with the Nomacorc synthetic stoppers producing double the amount of carbon dioxide equivalent (CO2e) on average than a natural cork, although the plastic stopper was shown to be 30% less polluting than micro-agglomerated corks.

A few months later, in November 2008, Amorim released its peer-reviewed PriceWaterhouseCooper/Ecobilan study, called Analysis of the life cycle of Cork, Aluminium and Plastic Wine Closures. This incorporated seven indicators (see table, bottom). In terms of Carbon Dioxide emissions, the results were similar to the Nomacorc study – cork was the least polluting, screwcaps the most – although natural cork was shown to have a much lower output, under 2 grams of CO2 per unit, compared with 8g/CO2 in the former producer’s analysis. The Amorim study also showed that, in comparison to the aluminium and plastic closures, the cork stopper is the best alternative in terms of non-renewable energy consumption, contribution to atmospheric acidification, and production of solid waste, although screwcaps are the best alternative in terms of consumption of water, followed by cork stoppers.

Finally, the Cork Quality Council has also pointed out that the Portuguese cork forest, aside from being a diverse natural habitat, acts as a carbon sink for 4.8m tons of CO2, representing an offset of 113.2g of CO2 per cork.

As for recycling rates among the different closure types, it is assumed that 100% of the corks produced go to landfill, where they will slowly biodegrade, while around one third of aluminium closures are recycled and less than one quarter of plastic stoppers (see table, right).

Aware of the higher environmental impact of screwcaps, Alupro (Aluminium Packaging Recycling Organisation) in the UK has launched the ‘Leave Your Cap On’ campaign, part-funded by Guala Closures, encouraging residents to recycle aluminium screwcaps along with the glass bottles on which they came.

Meanwhile, Nomacorc created “the world’s first zero-carbon-footprint wine closure” in 2013. Called Select Bio, it is partly made with plant-based polymers derived from sugar cane, and, according to the manufacturer, the bio-plastics contribute a negative carbon footprint value that fully offsets the positive emissions originating from conventional raw materials in the product.

Little has been said so far on the topic of energy use in micro-agglomerated corks, although this closure type did feature in the initial Nomacorc study, and came out with a higher Carbon Footprint than the synthetic closure. This is no doubt due to the processing of the cork granules – Amorim for example wash them using water at 70ºC and then put them through a steam distillation process called ROSA. This is to remove any potential wine spoilage compounds, above all trichloroanisole (TCA). Diam treats cork granules for the same reason, but uses the Diamant procedure, in which “supercritical CO2” extracts the unwanted compounds. Needless to say, both these processes are energy-intensive.

9 Responses to “Wine closures: the facts”

  1. Bruce Devlin says:

    No one ever considers the fact that cork type closures usually come with a capsule, and its impacts on the environment. Weather Tin, Poly, or plastic. It is part of the closure choice, and I’m pretty sure it would skew the environmental results in a different manner. It is rare you find a cork/synthetic bottle without some sort of capsule. An advantage of the screwcap is that it performs both jobs in one unit.

  2. Bottom line is there is no one closure that is perfect for all wines. Research has shown that most wines retail for under $20 per bottle and will be consumed within a week of purchase. No need to use a closure that is expensive or not easily recycled. Consumers do not buy a bottle of wine based on the closure! They buy a wine because it tastes good, is in their budget and is easy to open. Newer consumers are not adept at using a cork screw so why make opening a bottle of wine so complicated? Do you think Coke or Pepsi would enjoy the sales volume they have today if it required a special tool to open each bottle? When will the wine producers learn to simplify the package and get rid of the “mysticism” that surrounds wine.

  3. Michael Quirk says:

    In reference to people not buying wine due to the closure sounds like a the cork industry trying to redeem itself, or simply call it for what it is “Bull”. Ignorance is the biggest issue but as people around the world become more wine savvy and aware of what they do choose (mostly retail) for the easiest and best option available. As for the environmental aspect besides the capsule you also has to consider all the wine that has had to be tipped down the sink due to oxidation, TCA and poor storage all closures may be exposure but the majority of the time it’s the cork closure as the major culprit.
    The inconsistency of the each wine due to the cork quality and being a natural product that it effects every bottle of wine differently so a case of wine has a huge variation of flavours both good and bad. Ordering wine by the glass in a bar or restaurant shows clearly how different each bottle is and very annoying for the bar and the customer.
    As a natural product they degrade and crumble and annoyingly you only remember that when trying to remove the cork. So out come all the tools to try and get rid of all the cork floating in the bottle and the mess all over the bench.
    Even being TCA free and guaranteeing the cork doesn’t mean getting the damn cork out of the bottle any easier. Really we just what great wine not effected by the closure and the Screwcap is the best option at present.

  4. Martin Thompson says:

    Just to present a counterpoint, as I live in Portugal and love wandering the montado – cork oak forests – when I get the time. Aside from the significant environmental benefits, (very fair point regarding the need for a capsule though!) there are multiple downstream social benefits associated to the extraction and processing of cork.

    As a ’79 vintage, I still appreciate pulling a cork and honestly the risk of a tainted bottle doesn’t bother me much but it reminds me that wine still does have some mystical allure, hence the fantastic prices fetched per litre versus a soft drink.

    To be sure there is a market for fast consumption wines that is well served by screw cap closures, they are not to my taste but it has nothing to do with the practicality or technical supremacy of the stopper or even the wine itself. I guess I just really like to hear that pop!

  5. Angeliki Tsioli says:

    Very interesting reading and facts on a controversial subject.
    Just wanted to mention a false number in page 5 of the article, where the detection level of TCA is mentioned to be 0,5 ng/l. Of course this is correct in the previous page, so by 5 ng/l or just 5 ppt.
    I enjoyed reading this,
    Angeliki Tsioli

  6. Angeliki Tsioli says:

    In relation to my previous comment, I admit to have confused the two different kinds of thresholds:

    1. The threshold of detection by humans is about 5 ng/l, while
    2. the threshold of detection by a machine or technique, like that of ND (developed by Amorim) lies far lower than that at 0,5 ng/l.

  7. Tim Keller says:

    What is also missing from this discussion is the topic of VARIANCE in OTR. I developed the first oxygen controlling screwcap closure (the VinPerfect Smartcap ) focusing not just on the oxygen rate – but on how consistent it is. Cork proponents are correct in the fact that some oxygen is needed for higher quality – but the problem is just how wide the range is in terms of OTR performance with cork – it spans several orders of magnitude.

    The other thing to understand is that different suppliers offer oxygen control – but in widely different ranges. My screwcaps go from 0.11 ppm of oxygen per year for the light to 0.27 ppm for the medium+. And you can tell the difference in the aromatics of those wines with that little bit of difference within 6 months.

    By contrast, the tightest oxygen controlling synthetic cork is about 1ppm per year. Wine is pretty resilient and can take that, if not be improved by that in the very short term. – and yes, most are consumed young – but the problem is that the consumer does not see wine as perishable – instead they expect to to hold up if not improve with age. So if you use a closure such as a synthetic cork that is guaranteed to oxidize the wine in 1-2 years, then the responsible thing for producers to do is to add an expiration date to the label.

    Also – one needs to be careful when producers talk about oxygen. Many producers including Diam and the vinolok are very vague when they talk about their oxygen rates. Quality closure producers should not be afraid to publish OTR data in mg or ccO2 units including variance data – yet few do. So I would not take them at their word when they say vague things like “will last 30 years”

  8. Neil Monnens says:

    In 2009, 2012 and 2015 I surveyed my audience about their closure preference for red vs white wines. Most studies I have seen ask their audience their wine closure preference without discerning between red and white wines. Results are consistent among the years and in 2015 77% preferred natural cork for red wine and 52% preferred screw cap for white wines. Full study is available in the “other” section of (questions 17 and 18).

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