How green is your stopper?

Cork oaks stripped for corkk production APCOR

Which is the better stopper for wine bottles, cork or screwcap? A shorter version of this article is published by the Financial Times.

The fierce, often polarised, debate on this topic that raged in wine circles earlier this century centred on which is better for the wine.

Since then, considerable developments in the quality of both corks and screwcaps need to be taken into account. And now that many consumers as well as producers want what’s best for the planet, it has all become much more complicated. Especially since there is no truly impartial, complete comparison of corks’ and screwcaps’ eco-credentials to guide us.

Today as many as 5.9 billion aluminium screwcaps are sold each year, compared with 13.1 billion natural corks, together with a dwindling number of about one billion plastic corks. Screwcaps became much more common from about 2000, when Australian and New Zealand wine producers opted almost unanimously (there was a lot of animus) for what they call Stelvin, the dominant brand of screwcap. They were fed up with the poor-quality corks that were then being shipped to them from Portugal, home of the cork industry.

Too many of these corks were affected by the most common taint associated with them, known as TCA, which can render wine undrinkable or, worse because non-obvious, strips wine of its fruit to a greater or lesser degree. Imperfect corks also have an annoying habit of allowing a harmful amount of oxygen into the wine. Screwcaps, on the other hand, can offer producers the prospect of 100% consistency – what they put in the bottle will be what the consumer tastes – and producers can even match the screwcap’s oxygen transmission rate to the type of wine.

But screwcaps are hardly things of beauty, even if more aesthetically acceptable designs are available nowadays. And many sommeliers and consumers actively enjoy the ritual and sound of pulling a cork.

However, the Australian Wine Research Institute is respected worldwide and its detailed studies on the evils of natural cork had considerable influence so that some, both consumers and producers, have embraced screwcaps, even for quite smart wine (see some recommendations below).

Nations differ, however. Americans are generally wary of screwcaps. As are the Chinese. So when Australian wine producers exported vast quantities of their wine to China until the imposition of punitive import tariffs in 2020 (lifted at last yesterday), most of them stoppered bottles specifically destined for China with natural cork rather than with their beloved Stelvin. Some producers have replaced cork with glass Vinolok stoppers.

(Meanwhile, choosing natural cork over Stelvin has become a way for the new wave of younger producers, in Australia and elsewhere, to differentiate themselves from the bigger, more established outfits. Corkscrews, long abandoned by most Australian wine drinkers, are in use once more Down Under.) 

Screwcaps are widely accepted by those Scandinavians who buy their wine in bottles rather than the space-saving boxes that are so popular there. (The Swedish monopoly Systembolaget reports that boxes represent 60% of wine sales and that less that 30% of the wine they sell in bottle is stoppered by a natural cork.) Brits have also become well used to screwcaps, not least because all of the 41% of still wines that arrived here in bulk in 2023, for instance, is screwcapped. Until now all UK bottlers’ bottling lines are exclusively for screwcaps. At the same time many of those Brits who drink more expensive wine are well versed in the arguments in favour of a closure more consistent than a cylinder of the bark of a cork oak.

But Broadland Drinks of Norfolk, one of Britain’s busy commercial bottlers, announced recently with some fanfare that for the first time in 15 years, it was reintroducing a bottling line designed for natural corks ‘to help premium retailers and brand owners to cut their carbon footprint’.

It’s that word ‘natural’ that has come to cork’s rescue in this era of eco-consciousness. As long ago as 2010, Prince Charles, as he then was, argued that cork forests played an important part in preserving biodiversity in Iberia. The argument didn’t make much headway then, with Decanter magazine pouring scorn, claiming that ‘it demonstrates once again that the cork industry’s grasp on the realities of public relations is as shaky as ever’. But a more general and easily graspable point is that cork forests are not just a natural habitat for wildlife and provide a traditional way of living for locals but, perhaps even more importantly for many today, act as a significant carbon sink.

Ever since 2008 the dominant cork supplier Amorim has been commissioning studies to showcase the sustainability attributes of the renewable resource that is cork in comparison with those of screwcaps. The results have gradually been making their way into professional wine consciousness. Screwcap production may use much less water than cork treatments but the Amorim-sponsored studies suggest that natural corks are superior not just in terms of greenhouse-gas emissions but also non-renewable energy consumption and various other key parameters. Today Amorim provide their customers with a comforting estimate of how much carbon is sequestered by the trees responsible for the corks they order.

Aluminium’s principal sustainability credential is that it is infinitely recyclable and most of it, cans anyway, is actually recycled. Wine corks lose elasticity so they are not really suitable for reuse and in practice most of them just go to landfill. For effective recycling they generally need to be shipped back to Portugal, an energy- and emission-intensive exercise that has not so far been included in life-cycle assessments, to be repurposed into other cork products such as insulation, flooring, tennis balls and aircraft components. (The wine industry is by far the cork industry’s most important customer, however, taking about 70% of all cork products.) 

Both the UK and Australia have recently drawn up stringent packaging regulations with sustainability in mind. Along with a host of plastics, wine corks are currently classified non-recyclable in both sets of regulations. In the UK this means that special fees may in future be imposed on the use of such a naughty material – although it seems crass to impose admirable standards of packaging without offering a workable recycling system. (Alcohol monopolies such as those in Scandinavia and Ontario’s LCBO are much better placed to collect corks systematically than the UK or Australia.)

For what it’s worth, I take my used corks to a branch of Nicolas wine merchants in London who say, rather vaguely, that they send them to a recycling centre. Majestic in the UK collect corks and give mulched corks to the Eden Project to add to their soils. Recorked UK also collect and recycle used corks.

The Wine Society in the UK recently launched a cork recycling scheme whereby they will mulch corks returned to their Stevenage HQ or their delivery vans. Diam stoppers made of agglomerate cork particles are accepted. Plastic corks (which can look disconcertingly like some smooth natural corks but are even less elastic) are not. They will eventually be sent back to Portugal in suitably large consignments.

In Australia the APCO initiative is aiming to phase out packaging materials that are not reusable, recyclable or compostable by next year so there’s an urgent need to work out what to do with the relatively few corks there. Retailer Dan Murphy’s recently launched a scheme to collect them and send them to a factory where they are turned into cork mats for the wine store staff.

Interestingly, APCO has also identified the PVDC (polyvinylidene chloride) film commonly used today to line screwcaps as unacceptable after 2025. Australian wine producers are so wedded to their Stelvins that the hunt is on for a biodegradable alternative. (It may be worth noting that Australia is the world’s leading supplier of bauxite, from which aluminium is extracted.)

Some wine producers may be embracing natural cork today for qualitative rather than sustainability reasons. Amorim, for example, now offers, at a price (several euros a pop), stoppers described as ‘the world's first natural cork with a non-detectable TCA performance’ with a usefully reliable oxygen transmission rate. This is obviously a considerable improvement on a cork failure rate put as high as 5–6% by some in the early years of the century. I still come across ‘corked’ bottles horribly affected by TCA but they tend to be wines bottled more than 10 years ago.

Like many, I am convinced that screwcaps are as good for wine as a perfect cork, but for the moment can’t work out which is better for the planet.

Superior screwcapped wines

A host of Australian and NZ wines, thanks to impeccable pioneers Grosset of South Australia and Kumeu River of Auckland.

Many an Austrian and German producer such as Bründlmayer, Eva Fricke, Hirsch, Jurtschitsch, Josef Leitz, Nigl, Pfaffl, Prager, Salomon Undhof and Herbert Zillinger.

Fewer in France but Domaine Begude, Domaine des Baumard, Jean-Claude Boisset and Domaine Laroche are examples that spring to mind – in some cases for some wines only.

In Italy, Livio Felluga, Franz Haas, Isole e Olena, Massolino and Pieropan all use screwcaps for some of their wines. As do, in the US, Bedrock, CADE, Plumpjack, Red Newt, Tablas Creek – and Bonny Doon, which organised an elaborate ‘funeral’ for cork in New York in 2002 at which I gave the eulogy.

Access to all 38 articles we have published about stoppers and cork is included in membership of As are the many tasting notes on the producers listed above.

Credit for the image of cork oaks stripped for cork production: APCOR.