This is not your typical cork versus screw cap article. This is the only time I will use the word “oxygen” in this piece. Search for “cork vs. screw cap” and you’ll find plenty of discussions on reduction-oxidation chemistry, an increasing amount of data, and plenty of arguing. What you won’t find is much comparing corks and screw caps on an environmental footing.

Green has been, for the past few years, as important to the wine industry as red and white. Wineries are conspicuously moving to lighter bottles, biodegradable shipping containers, and energy-efficient operating systems. The cork industry publicists have begun marketing natural cork as the earth-friendly closure option, but that discussion really hasn’t hit mainstream. I searched the American Journal of Enology and Viticulture, The Australian Journal of Grape and Wine Research, The Journal of Wine Research, The International Journal of Wine Research, and Wines and Vines for articles on the environmental impact of producing cork and/or screw cap closures and found none.

Using information generated—or funded—by either cork or screw cap companies is far from ideal, but there just isn’t much else out there. Even a book published “in conjunction with The International Screw Cap Initiative,” cleverly entitled Taming the Screw: a Manual for Winemaking with Screw Caps, barely mentions issues of environmental sustainability1.

So I went searching. My goal here is to give you a comfort-food digest of the data I found.

Harvested cork.

Image via Wikipedia

Let’s begin with cork harvesting. Cork literally traces its roots to a special type of Mediterranean oak called Quercus suber L. Harvesting cork does not kill and certainly does not involve cutting down the cork tree; the life of these valuable trees is actually carefully guarded by law. Cork—a type of outer bark called cambium—is peeled off of the tree in thick layers. The tree is then left to grow a new cork layer which can be harvested again in about nine years. Each tree can be harvested for about 200 yearswith little or no recourse to fertilizers, herbicides, or irrigation2. Cork forests spread across Portugal, Algeria, Tunisia, Morocco, Spain, France, and Italy and are considered a major biodiversity hotspot.

Screwcaps are made from aluminum plus a plastic (or sometimes tin) lining to prevent the aluminum from contacting the wine. Aluminum starts off as bauxite, a mix of aluminum hydroxide and impurities lifted out of big surface mines. Aluminum hydroxide is converted to aluminum via two chemical processes, each of which invokes large quantities of water and electricity. Bauxite is mined virtually world-wide including, most famously after last year’s “red mud” disaster, in Hungary. Red mud, also known as bauxite residue, is a highly alkaline and therefore caustic and dangerous sludge that can also include toxic heavy metals like arsenic and lead. The sludge is usually sequestered and “remediated,” but accidents do happen5.

Only one systematic study has compared cork closures and screw caps head-to-head on environmental terms, it seems, and that study was conducted by PricewaterhouseCoopers/Ecobilan at the request of Corticeira Amorim, the world’s largest manufacturer of cork closures. Using “life cycle analysis,” they evaluated seven “environmental indicators:” non-renewable energy consumption, water consumption, emission of greenhouse gasses, contribution to atmospheric acidification (think acid rain), ozone depletion, production of solid waste, and contribution to surface water eutrophication (think nitrogen run-off and algae blooms)6. No proprietary information from screw cap companies was used and the screw cap analysis therefore talks only about production of component parts; the omitted steps, however, could only have increased the environmental impact of screw cap production7. The report also claims that the worst-case scenario was always assumed for cork production. Finally, the report was reviewed by several independent individuals and agencies including a plastics association, though a similar aluminum association declined to participate.

The study results put cork on top—by a very wide margin in several cases—for six out of seven environmental indicators; aluminum won out on water consumption. Now, remember that this is a study funded by the cork industry and using limited information about the production of screw caps but, in all cases, inclusion of more information on screw cap production could only have made the screw cap outcomes worse. An important question might be whether the report omitted any obvious environmental impact factors—would any environmentalists like to weigh in on that one?—but the data seem clear on the factors that were examined.

Having followed our two closures from raw materials through manufacturing and bottling, we’re left to end-of-life issues and, for both cork and screw caps, that should mean recycling. According to Portland Metro recycling, screw caps are too small and are sorted out of aluminum recycling bins and instead sent to landfills. To avoid this problem, screw caps can either be “crimped” inside a larger aluminum container (like a soda can, but you just try to fit a screw cap through the opening of a soda can) or balled up in a largish piece of aluminum foil. Ideally, the plastic lining should also be removed and discarded prior to either crimping or balling.

Cork is recyclable too (though recycled cork is only used for lower-quality cork products like cork boards, cork flooring, or insulation, never new bottle stoppers.) Of course, you probably don’t have a city-issued bin labeled “cork” sitting beside your plastic and paper recycling containers. Nor is cork approved for recycling in mixed curbside roll bins even in progressive cities like Portland and Seattle. If you live in Australia, you can hand your corks to the nearest friendly Girl Guide; the scout-like organization has recycled corks for years. In Portugal, you can take corks to a central recycling facility or drop them off at a cooperative restaurant. In the United States, “Cork ReHarvest” drop-off boxes are in Whole Foods and assorted other wine bottle-rich places. ReCORK (operated by Amorim, a major cork producer) also has drop-off boxes in many wineries – and with American Airlines, curiously. Or, as the Seattle Metro suggests, Americans might want to turn their used corks into creative home crafts. Cork holiday wreath, anyone? As for corks that end up in landfills, Amorim-sponsored research concludes that “the available information regarding cork behavior in landfill is not sufficient”9.

In my opinion, the strongest pro-green argument from the screw cap industry is that avoiding cork taint prevents a significant amount of unnecessary waste. From the Amcor website FAQ’s on Stelvin® closures:

The purpose of the packaging system (glass bottle and closure) is to protect the wine in the best possible way, to minimize or eliminate spoilage and waste. Even just a little spoilage, including spoilage due to cork taint, has a much higher environmental impact than the impact that comes from producing the bottle closure. When considering the product (wine) and the packaging (bottle and closure) together, Stelvin® aluminum screw caps are more sustainable than cork stoppers. They lead to reduced overall environmental impacts by eliminating spoilage due to cork taint.

Unfortunately, I could find no supporting data on Amcor’s website (or anywhere else.) The claim may very well be true, but I’d like to see someone attach some meaningful numbers to those statements.

While common sense is often neither common nor sensible, it seems strikingly sensible that a process involving renewable hand-harvesting from trees will win out over a process that involves mining, smelting, and toxic waste generation in a green-minded comparison. Then again, corked bottles may represent a serious resource drain in terms of water, energy, and waste as well as time, sweat, and frustration. So, which is greener: cork or screw cap? The bad news: there really aren’t enough data out there to be conclusive. The good news: that means you can decide for yourself.

102 Responses

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    […] Screwcap vs. Cork: Which is Greener? Cork is recyclable as well (however recycled cork is only used for lower-top quality cork merchandise like cork boards, cork flooring, or insulation, never new bottle stoppers.) Of course, you possibly don&#39t have a town-issued bin labeled “cork” sitting beside … Go through far more on Palate Pres […]

  3. Sondra

    Great article – my conclusion from what you wrote is that cork is far more environmentally sound than screw caps. what’s a little taint compared to all the toxicity producing screw caps. Hope this helps people rethink closures.I didn’t notice anything about financial sustainability – which costs more to produce?

    • Mark

      To purchase screw cap are about $0.15c each. Cork varies between about $0.30c and $1.00 each depending on quality.
      If approx 10% of wine is either cork tainted or randomly oxidised then that wastage must be included in the total cork equation including the water use, CO2 production in manufacture of the glass and labels, chemicals used in the production of the grapes and so on.

      • Randy Skizinski

        I am not sure that tainted or oxidized wine should be counted against corks “green” factor. Tainted or not, the wine has already been produced, and it will either be consumed or dumped.

        And, while we are talking about the aluminum caps, shouldn’t we also be talking about the foil that covers most corked bottles? More aluminum that is almost certainly not making it to the recycling plant. This, while indirect, could be the biggest mark against the greenness of cork, as it is used for most wines.

      • John Bigelow

        Your point on the tin capsules used to cover the top of the bottle after the cork is put in is something that is never included in the “green” analysis of cork versus screw top. Tin capsules are expensive, non-recyclable, and the manufacturing process includes all of the mining, processing, etc. that was the negative on screw tops. I have moved to screw tops for quality reasons, but your comment on capsules makes me feel even better about my choice from a green perspective.

      • John M. Kelly

        Tin is indeed recyclable, at rates per pound substantially higher than aluminum. We are working to raise awareness that tin capsules SHOULD be cut from bottles before recycling the glass. Tin is a glass colorant and tin contamination of glass cullet is a problem. That said, we are transitioning to using no capsule on our cork-finished bottles. Foil capsules are intended to prevent rats from nibbling on the cork – not much of a first-world problem.

  4. Carol

    Love the article and I am so happy to see that cork is the greener option. I still haven’t gotten used to the screwcaps.

  5. Thomas

    What amazes me in this discussion is that the cork industry always leaves out the foil that covers the cork. It is usually tin, and in some cases,plastic. Tin mining would certainly tip the equation, and I think it cannot be dismissed.

  6. Paul Ahvenainen

    Good article, however there is another factor that should be taken into account. All cork sealed bottles also use a secondary seal, usually a tin or aluminum/plastic composit capsule. The screw cap does not require this secondary seal. Your analysis should consider this into the balance.

    Also, screw caps are considerably less expensive than corks; while preserving the wine much better.

      • John Bigelow

        I read the study and it does not include the tin capsule that a majority of wineries use when choosing cork as their enclosure. If you found somewhere in the write-up that the tin capsule was included, please indicate where. This is a very important point in the debate.

    • Ben

      More and more wineries do not cover the cork by an Aluminium/plastic foil. Some use way and others simply do not use anything. (Soter for exampl, Cherry Pie, etc…).



  7. Pat Henderson

    One factor in determining sustainability is that bottles sealed with cork also use a capsule made of tin or a polylaminate whereas bottles sealed with a screw cap do not. I haven’t seen any analysis, but I suspect when you factor in the additional environmental impact of the capsule, using corks might be a little less green.

  8. Brian Loring

    As others have mentioned, the foil/capsule used on cork sealed bottles needs to be considered, which (logically) must almost equal the carbon footprint of the screwcap alone.

    And don’t forget the double shipping of corks and capsules vs the single shipment of screw caps. Also, those capsules aren’t structurally sound, so they need a LOT of plastic trays as a part of their packaging. Both corks and screwcaps come loose packed in a large plastic bag inside a box.

    Additionally, screw cap sealed bottles can use less glass and therefore weigh less because they don’t need the extra space inside the bottle to account for the cork. That’s not just a manufacturing issue (amount of glass), but a shipping issue as those bottles end up being shipped multiple times – to the winery to be filled, to a distributor, to a retail shop, etc.

    I think if all factors were included, screw cap would be the clear winner when it comes to be greenest. Oh, I did I mention that screwcaps cost a winery about 15 cents, whereas a good cork and capsule cost around a dollar?

    For me, screw caps win on all fronts – cost, function, and being green. That’s why we switched to screw caps 7 years ago.

  9. Cane

    Well done. Agreed. The data is 100% inconclusive. I propose that the argument is continually oversimplified in common culture, because cork simply SEEMS so much more Eco-friendly on the surface.

    But what of the vast and entire culture built around working with cork? Corkscrews of all kinds. Manual electric, large and small, plastic metal, wood, etc.

    – What of bottle stoppers? Made of innumerable materials, in a variety of ways.

    – What about the capsule? And capsule cutters of all kinds.

    – What about the culture built around keeping a cork moist? Racks of unlimited style, crafted from all manner of materials.

    I would also argue the report of Price Waterhouse is suspect from the beginning in so much as accepting its conclusions blindly is similar to accepting blindly the argument of a lobbyist group in Washington, DC. The fact they the subsequent marketing effort refers to screwcaps as ‘artificial closures’ should tell us something.

    I do not advocate for cork or screwcap. I am not so sure it is an either/or argument. There is probably a place for both. But I do advocate for an educated understanding of the issue.

    And either way … the great cork forests need to be preserved at all costs.

    • Erika Szymanski

      In response to everyone here who has made a similar point, I absolutely agree. A great frustration in writing this piece was the overwhelming absence of data on numerous fronts. What is the environmental impact of capsules? What is the environmental impact of shipping cork and capsules versus screwcaps? To what extent does the location of the winery matter? And what percentage of the total environmental impact of producing and packaging a bottle of wine is accounted for by the closure? If I knew, I would have said so. My hope is that the growing concern for environmental sustainability in the wine industry will seep into closure issues, that someone will do these kinds of analyses, and that winemakers and consumers will pay attention. For the time being, I do believe that the jury is still out.

      • Cane Vanderhoof

        Yes. It is faulty judgement to say at this point that cork is simply more Eco-friendly. These things need far more detailed study.

        I suspect the various outlying issues, when considered carefully and in detail, paint the screw cap in a far better light than the recent cork campaign does. But there is a great deal of information to consider, and I am highly resistant to an ‘either/or’ notion. I can well imagine a wine world in which use of both closures makes sense, depending on purpose and circumstance.

        Further, it can probably be argued that as long as serious producers are THINKING about these things and paying attention to these things, and working thru the issues with intelligence and care, we’re headed in the right direction.

  10. Valerie

    Put simply: Sustainability of natural cork is its greatest ‘green’ quality. While it would definitely be a good move to eliminate the use of foil and (or) tin capsules and seals on all wine products, clearly the sustainability factor alone negates the argument that screw caps are as good or better.

    • Ex-Cork Sales

      The biggest issue with the Amorim study is the fact that these corks are being coated with paraffin and silicone to keep the closure from absorbing the wine and allow the cork to be extracted from the bottle. We aren’t talking about a piece of tree bark lying in field to decompose we are taking about a treated piece of wood that’s purpose is to shed liquid.

      The largest carbon footprint challenge when I sold cork and capsules(tin or plastic) was the wineries lack of vision when it came to purchasing these products in a timely fashion which then required these items to be sent via air freight from production facilities in Europe. There are no tin capsule manufacturers in the U.S. nor cork production. All of these items must be shipped from overseas.

  11. Tom

    The entire issue with taint and natural cork is so overblown as to be ridiculous. Anytime a wine as a flaw the cork gets the blame. What wasn’t mentioned were any of the studies that show the link to the screw-cap liners producing carcinogenic substances. I won’t buy a wine with a screw-cap and never will because of all the reasons mentioned in the article and some that weren’t.

    • John Bigelow

      Let’s say you are right and the 10% cork taint that is blamed on TCA is only 3%. Is a 3% failure rate acceptable to a winemaker? If there is something available that can provide a solution and reduce bottle spoilage from 3% to less than 1% or possibly zero defect, wouldn’t you use that product? Think about a 3% failure rate if you were manufacturing airplanes. I wouldn’t fly. I am a winemaker and I believe in both the quality screw tops provide, and the “green” they provide as I do not need tin foils anymore.

      • John M. Kelly

        I don’t know anybody who is seeing taint rates of 3%, much less 10%. Right now in our tasting room we are pouring wines bottled between 2002 and 2010. Our rate of TCA is between 0.2% and 0.5% – given all the positive organoleptics contributed to the wine by the cork, I find this rate to be acceptable.

  12. Tom

    The entire issue with taint and natural cork is so overblown as to be ridiculous. Anytime a wine as a flaw the cork gets the blame. What wasn’t mentioned were any of the studies that show the link to the screw-caps liners producing carcinogenic substances. I won’t buy a wine with a screw-cap and never will because of all the reasons mentioned in the article and some that weren’t.

  13. Rick Lundie

    First of all, I have been involved with the wine, glass and closure business for 35 years, there is alot of mis conceptions regarding anything to do with “Green” Lets make one thing very clear, some wineries have gone to the screw cap for only one reason “its cheap and saves them money” they can justify this however they want to,; cork taint comes from “Mold” keep your winery clean and you should not have an issue.
    Cork is a renewable resource aluminum is not! The aluminim closure came out in the mid 70’s called ROPP (Roll On Pilfer proof) It was only used on the less expensive wines.

    • Mick

      Rick, Cork taint does not come from dirty wineries. It comes from the supplied cork. Suggest you do some more reading.

      • Andrew

        Agree, “cork taint” definately comes from the corks, not the winery. Furthermore, the mouldy cork taint is only part of the problem. Corks can also impart a slightly dry, oaky flavour to the wine. This is generally not noticable in red wines or Chardonnay’s, but can ruin a delicate aromatic like Riesling.

      • RP

        FYI, cork taint (2,4,6 TCA) can come from a variety of sources, including corks, barrels or even winery structural materials.

        There have been several studies along the years that have successfully demonstrated this and they’re easy to find on Google:

        2004 Study by Excell Labs in France (jump to page 26, 1.6.- Contaminations attributable to the cork stopper and to the cellars):

        Quote from this study:
        “the approach of blaming the contamination almost exclusively to the cork stopper is too simplistic and needs a more rigorous analysis, since there are many different sources of contamination. In fact, it is possible to detect in some cellars,contaminated wines that never have been in contact with cork.”

        2006 Study by the Institute of Biotechnology of León (Spain)

        Quotes from this study:
        “It can be stated that the true origin of wine contamination by haloanisoles is not the presence of fungi growing on cork or wood, but the high environmental contamination by chlorophenols and bromophenols”

        “The presence of haloanisoles in wine is not always an evidence for the
        contamination by the cork stopper since in many occasions the closures
        that arrive perfectly clean to the cellars can absorb chlorophenols,
        chloroanisoles, bromophenols or bromoanisoles that are already present
        as contaminants in the cellar’s environment or installations.”

      • Tim Keller

        it is true that compounds recognized as cork taint CAN indeed come from the winery. And the point that saying that the taint comes EXCLUSIVLEY from the cork is wrong is totally valid.

        However, while systemic TCA infections can and have happened, it is only in a few isolated instances. The vast majority of cases of cork taint are, in fact, caused by the cork.

        Both extreme arguments are wrong, but the bulk of the problem does lie with the cork. And that cannot be denied.

      • RP

        Agreed, but this also goes to show that SOME winemakers dismiss off-flavours (due to poor winemaking practices or winery conditions) to a cork-related issue… it’s always easier to say “the butler did it”.

      • Andrew

        What an interesting debate. Yes, TCA can be derived from sources other than cork, but whn it comes from other sources (ie in the winery) it will affect an entire batch of wine, which the winemaker can blend away or hope that the level is low enough not to be noticed (a dangerous assumption!!). However when there is bottle variation of the same batch of wine, then the TCA is definately from the cork.

  14. Tim Keller

    Im definitely a partisan in this conversation since I’m a winemaker who has started a company making oxygen regulating cap liners for screwcaps. So take my comments with a grain of salt if need be, but I do need to add a couple of comments about that lifecycle analysis that Amorim commissioned.

    1) Some people have pointed out already the fact about the capsule not being included. The report actually did include the capsule, but assumed that they were all unprinted, clear PVC. Which still doesn’t paint an accurate picture at all of their impact. Tin production is especially environmentally taxing and my estimate is that Tin is 20-30% of the market.

    2) If you read the peer review part of their report, the expert on lifecycle analysis says that it is “abusive” to claim credit for even part of the carbon sequestration of the cork forrest. The report writer for Price Waterhouse responded that they would only take credit for the portion of the effect related to the activities of Amorim

    That is like going into a bank, saying, “give me all the money” They say, no. and you say, “ok, I’ll just take what is in the cash drawers – forget about the vault”

    The point is that a lifecycle analysis is supposed to compare environmental options. If we use screwcaps how does that change the environment as opposed to cork? What is the apples to apples difference?

    The fraud here is bold-faced if you understand what is being measured. Ask yourself: What will happen to the cork forests if I use a screwcap instead of a cork? Will the amount of carbon sequestration change?

    The answer is NO. The cork trees will go on sequestering just as much carbon, whether or not people strip the bark to make cork. The only way to stop that sequestration is to cut the trees down and then pave over the land so that no other plant grows in it’s place. Is that what Amorim is threatening? Probably not.

    Yes those forests should be protected, and they already are by Portuguese law. What is at stake is not the environment, but the livelihood of the owners of those forests. The larger economic concern is that if they cant make large margins from cork, they might illegally cut down the cork trees and instead plant eucalyptus trees for use in paper production.

    While that is certainly something the Portuguese should be concerned about, those fast-growing eucalyptus trees would sequester even MORE carbon.

    So the link between those trees and global warming is based on bad science at the very best, or at the very worst, is a deliberate fraud.

    3) Finally, if you read the report, the consumption of electricity and the environmental impacts associated with it is based on the assumption that all power is sourced based from a standard mix of european power plants, natural gas, coal, nuclear etc.

    That is fine for calculating the electricity to keep the lights on in a cork processing plant, but it heavily biases the report against screwcaps.

    Aluminum is refined using a LARGE amount of electricity. So this calculation counts for the lions share of the environmental impact of the screwcap. The problem however, is that because Aluminum uses so much electricity in it’s refining, most aluminum smelters co-locate with hydroelectric plants to provide them with copious amounts of cheap electricity.

    We can debate the environmental impacts of a hydroelectric dam and fish populations. But in terms of greenhouse gas emissions, there is none. For the caps my company is making, 100% of the aluminum is made via hydro power.

    Correct the bias of the report and I’m willing to bet that the screwcap comes out on top.

    Again, I’m disclosing my bias – I have a personal stake in the issue. But it is because of that stake that I bothered to read that huge environmental report with an analytical eye. As a winemaker, I was a fan of screwcaps well before I thought of the product we are introducing now – because the problems of cork taint, and the random oxygen performance of corks ruin a percentage of wine that is totally unacceptable in any other industry.

    Do the Portuguese cork forests need protection, Sure. Is Cork a sustainable product? Yes. Does any of that justify the $10 Billion dollars worth of wine ruined by cork every year? Not even close.

    Why should we be guilted by the cork industry into using a fundamentally flawed closure for a high-value product? Cork is for floors, shoes, and a variety of other uses, it is a great material for those applications. Just don’t put it in a wine bottle.

  15. Vino

    I agree with Brian. When you take ALL the considerations of the entire package there’s more waist with a bottle using a cork. The wine still will have a tin or plastic capsule. I love the people who talk about not buying a wine with a screwcap based on their belief that the “screw-caps liners produce carcinogenic substances.” Look around your house people! those same plastic liners are in everything from your herbal suplements to your BBQ sauce!

  16. Nicolas

    Lots of emotion on this topic. We happen to use screwcap here at our winery, not because it is less expensive, but because it preserves our wines better than cork. The average taint on cork has been between 2 and 5% and as winemakers we cannot accept that.

    I think the environmental impact of screwcap is not huge compared to glass (something like 60% of wine’s carbon footprint comes from glass), so really not a high priority for many wineries. I have worked a lot with our suppliers and I understand that aluminum recycling is very advanced in Europe but not as much in the USA (to your comment about recycling in Portland) – that being said aluminum is a highly valued waste because it is infinitely recyclable (70% of all aluminum ever produced is still in use today), so my guess is that in the long run our domestic aluminum recycling rate will rise.

    Last comment about cancer and aluminum capsule. The claim that liners have carcinogens came from a study in the 60’s that has been proven wrong several time since then. It is a bit of a urban myth and, to my knowledge, there are no carcinogen compounds in screwcap liners. I would welcome any study that would point to the contrary.


  17. Tim Keller

    Regarding screwcap liners and carcinogens? There are no such studies. Please feel free to link them if they exist.

    The concerns with plastics are things like Bisphenol-A – which is found in polycarbonate plastics – like sports bottles etc. BPA is NOT used in the production of PET, which is what is used in our cap liners.

    It’s a bad attempt at a red herring.

    Regarding TCA / Cork taint being actually from the winery? Again, a distorted claim. There have been a few cases of a winery having a systemic TCA (or TBA) infection, but it is totally false to attribute all TCA to that source.

    If TCA came from the winery environment, then ALL wines from that winery would be infected, as was the case with two california wineries I am aware of before they fixed the problem.

    But that is NOT what we see with cork taint in the real world. What we see is one bottle from the case is corked, but open another and it is fine.

    The only difference between the two bottles is the cork. Claiming that TCA is not the cork’s fault is completely ignorant.

  18. Chris

    Worthwhile article.
    What is not mentioned here is how much CO2 is taken in by these cork forest?
    Cork forest are one the of the larger CO2 sinks in the world? When you strip the cork off the trees, the trees convert even more CO2 into oxygen. There have some some studies on the cork industry that suggest that when you factor in the C02 piece, this industry might even be carbon negative.

    When you factor in all the CO2 that is converted into oxygen, the social equity piece of supporting family businesses abroad, and all the mining it takes to produce the metal for screw-caps, I think you will find that cork is a far more sustainable business.

    • Tim Keller

      Wrong. See my above comment. The CO2 absorbed by the forrest is the MAIN cited factor for the purported environmental benefits of cork. Even though doing so is fraudulent since that CO2 is captured by the cork trees whether or not you harvest the bark.

      And no, the trees do not capture more CO2 if you strip the bark. They might grow bark faster, but at the expense of limbs and branches. It is a zero sum gain.

  19. Tom


    What a string on half-truths and misdirects. There is one reason and only one reason to use screw-caps – they are cheap. Winemakers like you use smoke and mirrors to justify it, but those who use them are doing so just to make more money on each bottle they sell. Granted it’s just a few cents a bottle, but multiply that by 100,000, or more, and that’d pure profit that goes right into their pocket. I won’t buy a wine with a screw-cap or a plastic plug. When I see them it tells me the winemaker is concerned more with profit then with quality or the enviroment.

    • Nicolas


      Could you let me know what piece of Tim’s comment you judge being a half truth?

      I use screwcap myself with no intent on being cheap – I actually truly believe it is a superior closure for wine. I don’t even look at price of corks what so ever. I just refuse to deliver 5% defect to my clients when I have a better option available.

    • Tim Keller

      I have disclosed the source of my bias. What is yours?

      If there is ANYTHING in what I have written that is not supported by fact, or even the “other half” of the truths that you claim I have omitted, please let me know.

      “cheap” is what the synthetic corks are, and I think we all agree there is no reason for them.

      Saying that the ONLY reason one might use a screwcap is because it is cheap, and to sweep all of the well documented facts about how very flawed corks are is simply false and out of touch with reality.

    • Brian Loring

      I’m sorry Tom, but you’re incorrect. The reason I decided to switch to screwcaps 7 years ago was soley due to the percentage of bottles we found that had TCA. I couldn’t in good conscience put out a product that I knew had a failure rate of ~5%. So the intial impetuous was due entirely to QUALITY. And given how the screwcaps have performed, it’s one of the best things we could have done for our wines and the consumer.

      The BONUS was that since screwcaps cost less, I was able to put off raising prices for a couple of years since I’d cut some costs. And I was convinced at the time, and I still am, that screwcaps are no worse and may possibly be better for the environment that cork.

      You may not agreee with my reasoning or conclusions. But that’s the truth about how and why I considered switching from screwcap to cork. Claiming anything else about my motives would be wrong.

      • jim peck

        I very much agree with Tim Keller. I would invite all to read the article in Wine Business Monthly regarding the closure test at Hogue winery over a long period of years. They tested all closure on the market and selected the screw cap with Saranex cap liner because it is simply the best closure for controlled ageing and fruit retention in their wines.

      • Tom

        The Hogue test was very flawed is that it only used corks from one provider, thus proving my point. You get what you pay for.

      • jim peck


        Evidently you have never spent years testing and tasting cork (in wine)as I have – (40 yeasr in the wine business – winemaking, applied research, developmental research, package testing). If you had, you would be aware that as a natural product, there are large flavor differences between each cork that overshadows whatever variation there might be between cork suppliers. The flavors derived from cork exclusive of TCA or mold taint run the gammut from very neutral to pleasant wood, eucalyptus, almost minty, to strong unpleasant cork. In addition, a large supplier like Amorim would be sourcing corks from all parts of Portugal and likely also Italy and Sicily. So you cannot say that a single supplier invalidates the test.

    • Ken Sloan

      Please see the following letter sent to Wine Business Magazine Australia and Amorim August 8th 2008.
      I am writing in response to the Amorim , emotive, “Save Miguel” campaign.
      They make not one mention of the millions of bottles of cork sealed wines laid to waste each year due to cork taint, or random oxidation!
      What cost is this to the environment? In terms of waste alone it is shameful!
      Its impact on the environment must be considered in any rational discussion on this issue.
      Think about the greenhouse effect of the production of all those bottles, labels,cartons and not to mention corks,oh,and of course,the wine,all being wasted!
      Add in ,the transport,harvest costs and manufacturing inputs all with no good result.
      According to my reading of research into this matter the world wine industry allows up to 10% spoilage of all wine bottled under cork.
      The waste attributable to cork sealed wine is ginormous and must have a substantial effect on the environment.
      Then there is also the great emotional stress that cork causes winemakers and also the end consumer, who has purchased,treasured,loved and cellared a special wine, for a special occasion,
      and then finds it buggered by a little piece of mould affected wood.
      No thanks!
      We are a small winery and we produce Australian Hunter Valley Semillon which, as we all know, shows to its best advantage with extended bottle age.
      We have put wine away from 1999 onwards for mature release. Until 2004 vintage all these wines were sealed with cork.
      After a recent assessment of this cork sealed museum stock we likened finding a really sound example to playing Russian Roulette.
      We know it is not a wine problem as the sound bottles are bloody brilliant.
      We are now faced with the prospect of dumping thousands of bottles of wine.
      We are not the only Hunter producer to encounter this situation.
      The Amorim campaign tells us that if the world stops using cork, the cork trees will have to be culled, upsetting wildlife and the ecological balance.
      That sort of defies logic doesn’t it? Cull something that is home to endangered wildlife and flora?
      I would call that environmental vandalism.
      If you view the video Amorim have commissioned with Rob Schneider you will see it is at its very best misleading, at its worst dishonest, when it says that putting screwcaps on wine was borne out of
      “ our obsession to do things cheaper and quicker” .
      This statement is outrageous! I think most wineries that seal their wine with screwcaps have done so for the same reason that we have –
      i.e. to ensure our product reaches the consumer in perfect condition and will age as best it can.
      Anyway, they won’t convince me,I will not ever,ever,put another wine under cork! I am perfectly happy with the results we are achieving using screwcaps.
      However, I do have an open mind about alternative closures that may have “greener” credentials, and await future developments in sealing wine bottles.

    • John Bigelow

      You are wrong. I am a winemaker who is using screw tops for improved quality. You won’t buy my wines because they are in screw tops and frankly it is your loss; definitely not mine.

  20. Tom

    Over the years I’ve talked to a lot of winemakers about their grapes, their barrels and their corks.
    When it comes to grapes they can practically tell me which clusters of grapes came from each part of their vineyard.
    When I ask about their barrels they are very proud of the cost of their barrels and how much time they take to select just the right barrels to go with their wines.
    And when it comes to the corks – the just say, “I get the cheapest corks I can when it’s time to bottle.”
    It’s winemakers like that that kept/keep the bad cork providers in business. And yes there were a lot of very bad cork providers, who were kept in business by winemakers just wanting to get the cheapest seal they can. And now that those winemakers have found screw-caps, they are sealing with those.
    Any winemaker with taint wouldn’t have the problem if they took just as much care to select their corks as they did to select their grapes and barrels.

    • Tim Keller

      WOW, that is funny.

      I have NEVER met a winemaker who doesnt obsess over the quality of their closures. EVER.

      Even the best corks suffer from taint. It cannot be screened out unless you test every single cork by soaking it and analyzing it with a Gas Chromatograph.

      You are again demonstrating only a casual relationship with the real world.

      What cork producer do you work for again? You failed to mention it.

      I founded VinPerfect ( so yes I am biased, but I will put my company’s reputation on the line if you can prove that anything I have written here is untrue.

    • Brian Loring


      I can’t comment on the winemakers you’ve talked to – since your experience is your experience. But I can tell you we were very selective in the corks we used when we started. As are a number of my friends in the biz. Our reasoning was that trusting a $50 bottle of wine to a cheap cork to save what, 50 cents?, was about the silliest and thing you could as a business person. So we always paid a lot for the corks we sourced. And even though they all climed to have extremely low rates of TCA (and had data to “prove” that) we still saw at least a 5% TCA rate.

      And it wasn’t just our wines. Over the years I’ve gone thru my phases of collecting and drinking First and Second Growth Bdx, Grand and Premiere Cru Bugundy, high end Champagne, etc. And those wine have all had similar TCA issues. Something tells me those guys weren’t cutting corners on cork.

      • Ex-Cork Sales

        Tom…your comment also does not make sense from the cost standpoint. The least expensive cork does not mean it has taint issues. As an ex cork sales rep we tested our corks for taint by using a military testing standard and the quality if the corks had little to do with how the corks tested from a taint percentage. The cost is linked to the visual quality not the sensory quality.

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  22. Co Dinn

    At Hogue Cellars our conservative estimate is that 1.5% of all cork finished wine is ruined by cork taint. By ruined I mean that if your glass of milk or soda had as much of an off flavor you would likely not drink it. This reflects testing of multiple lots of cork for purchase as recently as 2009. This does not include a larger percentage affected to a lesser extent.

    In spite of extensive testing over many years, we have never found a taint-free lot of corks for sale. We assume that 1.5% of our production is damaged and can rightly be returned for money back by the consumer.

    The environmental cost of a guaranteed 1.5% damage to all wine made includes the carbon footprint of all the glass, grapes, production and transportation of that percentage of the production. When I get a corked bottle at home I typically pour it down the drain and open another. Normally I do not return it for my money back, but if I did I could add the transportation back to the place of purchase to the environmental cost. Everyone loses when a bottle of corked wine is poured down the drain. Especially the environment.

    Aluminum is recyclable. It is possible to get it into the recycling stream. I realize that there are some who will always want a cork in their wine. But for everyone else the screwcap is a responsible, green alternative.

    • Neil Larson

      Sorry Tom, in over 20 years in the wine business (growing, winemaking, packaging) I have never heard a winemaker say that they buy the cheapest corks they can, rather the opposite, they buy the best htey can possibly afford.
      Winemakers currently using screwcaps do so because of the issues with cork – not just TCA which runs at 2-7%, but also oxidation.
      We release both a 5 year old and a 10 year old super premium white wine, and with cork closures (the best we could buy) we would cull out over 30% of our stocks by dark colour alone. This oxidation rate will be the same in red wines, we just can’t see it as easily because of the anti-oxidant effects of the tannin and anthocyanin.
      Can you honestly say that you’re happy to wear a 30% failure rate in your business?

      One issue not mentioned in detail, although Jim did touch on it, is that even fault free corks impart a ‘cork bark’ flavour to wine. Now that we bottle a large proportion of our production in screwcap, we can now smell and taste the clean ‘cork bark’ taste in cork closed wines. Producers who only use cork will be oblivious to this. It’s not a flavour we categorise as positive.

      The issue of the cork forests is also a red herring. Cork industry insiders admit that less than 5% of cork production is used for wine closures, so the change to screwcaps will have a minimal effect on cork production.

      Screwcaps may not be the best long term solution, but at present they are viewed as the best option by many progressive winemakers. Here’s hoping an even friendlier closure will be developed in future.

  23. scott stephens


    Interesting article, good follow up discussions !

    Besides TCA, which is reputed to contaminate 3 – 7% of all wines (depending upon whose research you read) the major concern for me is the failure rate of cork as a seal over time. I live, and make wine, in a region that produces a classic style of white wine that has the potential to age for up to 30 years. Unfortunately cork seals allow random oxidation of wine, and when you look at a dozen 5 year old white wines sealed by cork on the tasting bench, you often have 12 different wines ! When we release a museum wine, we have to colour sort the wines, and 10 – 30% would typically be discarded due to excessive browning. Not so with screwcap.

  24. Fabio (Vinos Ambiz)

    Great post and comments. I hope the issue becomes widely debated in the mainstream. I’d like to say straight off that I also have a bias, as confessed by some of the previous commenter above. I’m a producer of ‘organic’ wine and I don’t use any environmentally harmful chemicals in the vineyards or in the winery. And my philosophy also applies to the packaging and closures. I believe that we can argue the numbers till the cows come home, and proponents of both sides will stick to their opinion – even when more and more reliable data becomes available.
    I think here you just have to go with your heart, instict, intuition, whatever it’s called! Beyond the impact numbers, there must be a reason why winemakers really choose one option over the other.
    In my case, I go with natural cork. Which I buy from a reputable quality producer. And in 8 years of winemaking I’ve had 0% spoilage due to cork taint. For me the overriding factor is that I will not support an industry that produces toxic waste, and I will support an industry that is sustainable, environmentally beneficial, and supports numerous families in a rural environment. I also ask myself if we really need yet more products made of aluminium or plastic; the environment is already suffering from the effects of pollution, and people go an invent new closures that add to the problem.

    • Nicolas


      Love your prospective and completely understand it (I use screwcaps myself and we are producing organic and biodynamic wines). I feel that as winemakers we are being forced to choose a camp – sounds like Washington politics. This should really not be a big deal, let the winemakers decide for heaven sake – we are talking about 4% of the carbon footprint of a whole bottle of wine!

      The whole conversation about corks vs screwcaps is now centering on the environmental impact of the closures. This is where the cork manufacturers want to take the debate (and they do a great job at it). Aluminum has a handicap since it appears (and probably is) as a more manufactured closure than cork – the aluminum folks need to figure this out. I would love for aluminum manufacturer to increase the percent of aluminum recycled in this country so as to make aluminum the most sustainable, long term proposition that it can and should be (my opinion). Could we not incentivize cities to recycle aluminum – give a $50,000 prize to cities that come up with the best aluminum all inclusive recycling concept – that is the right thing to do. Also, aluminum manufacturer could plant trees in Portugal to replace or enhance oak trees, that would build a carbon sink restoring many acres to their natural beauty and providing many jobs to the local population for eco-tourism.

      • Valerie

        This is the most level-headed, logical suggestion I’ve seen in the entire string of comments. Nicolas for President! haha! Seriously though, that would be an excellent ‘middle ground’ and way to improve the carbon footprint on all sides.

      • Fabio (Vinos Ambiz)

        Winemakers ultimately make their own decision on what closures to use based on their own personal (or corporate) criteria. I know some that go both ways, ie cork for Europe and screwcap for exporting to the US.
        You (like everyone else) are of course free to choose your closure, but I have to say that I dont understand how you could go for aluminium being a producer of organic and biodynamic grapes! Your website even says “We believe that making beautiful wines should not compromise the beauty of our planet.” Open-pit mining? Landfills full of toxic waste?
        For me, the environmental impact of closures has always been the most important factor, more than the cork taint percentage game, and I’m glad that the cork industry is playing that card at last.

  25. Nancy Hawks Miller

    So many comments! Has anyone mentioned that Cork Supply USA has developed a system that purges TCA and other impurities out of cork through a steam distillation? Note: I don’t work for them, I interviewed them a few years ago for Napa Valley Wine Radio. I have no idea of how succesful it’s been. They also said that the ETS wine lab in St. Helena has a devised a way to do much better quality control regarding TCA.

    Does anyone have any actual experience with this? If so, it could take the wind out of the screw cap argument’s sails.

    • Tim Keller

      I’ll take this one.

      There are several approaches to removing TCA from corks. The one you have referenced is Innocork from Cork supply USA. Here is a link to that process

      They basically cook the corks with steam and alcohol to try to extract the TCA. I havent used this product but I think that it is a rational process for reducing TCA. Can it eliminate it? I dont know. The website states that their limit for TCA is less than 1.5ng/L of extractable. That is 1.5 parts per trillion, and the human threshold for smelling it is 3 parts per trillion.

      Sub-threshold TCA is still known to adversley affect the aeromatics of a wine, but if you are going to use a cork, that is the least I would buy.

      Another approach is what is used by DIAM which is where they grind up the cork and then extract the TCA with super-critical CO2. They then glue the cork back together into a cork shape.

      My suspicion is that this process gets rid of more of the TCA, since it cannot hide out in the little lenticels and crevices of the cork. I HAVE used that product myself and I have only heared aesthetic complaints and complaints about difficulty of removing the cork from the bottle neck.

      So the TCA issue with cork is indeed getting better with these processes, but lets get back to the whole point of this article: Environmental benefits. The energy used to steam the corks in the innocork process, and certainly the energy used to create liquid CO2 and the CO2 released from the DIAM process are definatley not figured into the price waterhouse report.

      So are these “better” cork technologies still the “green” alternative? Probably not. Especially if you correct the anti-screwcap biases of the report.

      Oh, and if you are worried about plastics in contact with your wine, the DIAM is not an option for you either, since a large percentage of that product is the binders that hold the cork bits together.

      And with the Innocork? There is still no protection from the huge bottle-to-bottle variation in regard to oxygen. As a natural product, cork will always have uncontrolled levels of oxygen coming into the bottle. Since a picture tells a thousand words, here is an illustration
      A screwcap is on the left, and a number of corks array to the right, ranging from just as little oxygen as the screwcap, to enough to ruin the wine in even the 28 month timeframe.

      End of the day, my money is still on the screwcap for coming out ahead environmentally and on the basis of wine quality.

  26. Tom

    * What’s needed to produce an aluminum screw-cap
    Open pit mines, use of heavy equipment, extreme electrical power use, production of toxic wastes, and a petroleum based seal it order for it to work properly. Just visit a bauxite mine and you’ll see what I mean – I did about 6 years ago in Australia.

    * What’s needed to produce a nature wine cork
    Tree covered foothills, sprinkled with a few grazing cows, low impact harvest using some light equipment. And at the same time creating wildlife habitats.

    Need I say more.

    PS – Screw-caps do ruin wine through reductive taint, improper seal and seals that are prone to damage during shipping (stacking).

    And I can’t see how anyone can use a screw-cap to seal their wines and still call themselves organic or biodynamic! Geezzz….

  27. Keith Stewart

    For those claiming there is no research into endocrine disruptors leaching into wine try; New concepts in sorption based sample preparation for
    chromatography / by Henricus A. Baltussen . – Eindhoven:
    Technische Universiteit Eindhoven, 2000. – Proefschrift. – ISBN 90-386-2971-0
    NUGI 813
    The fact is that public health was never a factor considered by winemakers when adopting screwcaps, because it compromised their profitability. Screwcaps are a cheap option, and consumers know it. The two national wine industries that have been leading the adoption of screwcaps, New Zealand and Australia, have subsequently suffered dramatic declines in the value of their wines on international markets.
    In the heightened value-added world of wine marketing, whatever the industrial winemakers say about TCA taint (not just of corks) and TBA taint (what do agriculture authorities fumigate imported wood products with in Australia and New Zealand – bromide, a source of TBA taint)consumers know that fine wine comes under cork, cheap wine comes under screwcap or plastic.
    I am amazed that all this talk of science avoids recognition of the above paper, which has been well publicised. If the industrial wine industry wants to prove that screwcaps are free from taint, they should be obliged to commission research to prove their case.
    Those who still prefer to obfuscate the issue should consider some reading of published research on the health impacts of p-nonylphenol, a substance found leached out of screwcap closures into wine.
    If we are considering an open debate on the real issue here, which winemakers pretend is the case, why was it that when I wrote about the threat of endocrine disruption leaching from screwcaps in the New Zealand magazine, “”The Listener”, Winegrowers New Zealand lobbied to have me fired.Hardly the actions of a wine industry confident in the science behind their argument and so much for a free and open debate on a matter as important as public health, the argument for screwcaps has always been a PR campaign to reduce the cost of mass produced (industrial) wine. Winemakers claiming otherwise are deluded by their own pseudo-science.
    Finally, for those who pose the fatuous arguments that not using cork will not impact on the biodiversity of Iberia’s cork forests is not living in the “real world” they claim to represent. Surely to have a commercial basis for one of the oldest sustainable natural/human environments in the world, that is, cork harvest for wine closures, is the soundest argument in support of corks. Identify one part of the aluminium process that provides a sustainable haven for Iberian lynx or Imperial eagles.
    But this is not about being green, it is about food safety. How is it that a global industry providing a food product to millions can change its packaging without any consideration for public health? If wine companies are concerned for public health, where is the research to back up the safety of their new closures?
    Yes, the use of saranex and other plasticised barriers in screwcap closures is no worse the the same barriers being used in cans and other food grade packaging, but surely there is a responsibility on the producers to make change that do not further compromise human health.
    The frightening answer to all this debate about closures is that winemakers have improved their profitability apprently without care for their customers’ health. Under the United States’laws on carcinogens this is illegal, and it is time a screwcap user was charged by the FDA.

    • Nicolas


      Thank you for pointing to the nonyl phenol leaching. I have read the paper, and it referred on page 206 to one red wine from south africa and yes the contamination was linked to NP. NP is heavily regulated so I am puzzled how this got into that cap. I am going to dig a bit into this and report.

      I am not on a crusade, yes discussing what we are doing and why. I do spend a lot of time on those issues either at our winery and on industry committees. Thank you for the passion and the information.

    • Neil Larson


      I’ll quote you here: “the argument for screwcaps has always been a PR campaign to reduce the cost of mass produced (industrial) wine. Winemakers claiming otherwise are deluded by their own pseudo-science”.

      All of the winemakers I know who use screwcaps did so after much research, testing, debate and intelligent discussion. To proscribe other motives to them is ridiculous and insulting. When we changed to screwcaps it cost us MORE per bottle for 3 years until screwcap prices fell with increased availability.

      To quote you again: “Finally, for those who pose the fatuous arguments that not using cork will not impact on the biodiversity of Iberia’s cork forests is not living in the “real world” they claim to represent.

      Sorry but that really is quite untrue. As I stated above, less than 5% of cork production goes to bottle closures. So the lynx and eagles will continue to have their wonderful habitat.

      Also, please look about your home and count the number of food and beverage containers which have saranex or similar seals. Please lobby those producers with the same fervour – they have been using these seals for much longer than the wine industry.

      Screwcaps are not perfect, and winemakers aren’t suggesting they are. Just a better option than ruined wine. Neither are automobiles, airplanes, ball point pens, computers or any of the other paraphenalia of our modern lives.

      • keith stewart

        What research. Cite a paper, or at least point me in the direction of a serious organoleptic study of the differentials in percieved characteristics. Well researched would mean that before making the decision, winemakers like you would be well informed, so that you would know that the cork industry relies on wine closures to be profitable. Have you read any of the papers on the redox capacity of wine and its influence on development of bottle age characters?
        Just because other producers use dangerous packaging components does not make it acceptable for winemakers. Especially when the existing packaging does not pose health problems. Are you saying that you are providing a better product for your customers by eliminating TCA from their wine, but they must accept their fertility and other aspects of their health will be compromised as a consequence. Would you be happy to put that detail on your labels?

      • Neil Larson


        I’ll just chime in one last time to correct a couple of your assertions.

        You should be aware of one of the world’s most comprehensive closure trials, initiated in 1998 by the Australian Wine Research institute. Refer: The AWRI Closure Trial: sensory evaluation data 36 months after bottling by Francis, Field, Gishen, Coulter, Valente, Latty, Hoj, Robinson and Godden. Australian & New Zealand Grapegrower & Winemaker August 2003.
        Please Google it, or request a copy from the AWRI.

        There were some issues with a reduced ‘rubber like’ compound from the screwcaps in this trial, but winemaking practice rather than the closure has proven to be the culprit here. Correct preparation of the wine for bottling (as is required with cork) ensures that these reduced compounds do not occur.

        Cork profitability.
        My discussions with cork suppliers were to the contrary of your assertion. I would like to see some independent data on this but in this area the cork industry has been reticent to disclose detailed profitability figures.

        Health problems from screwcaps.
        Food and beverage regulatory bodies the world over do not share your concerns, evident by the number of similar closures used for many years in the food industry. If the problems are as serious as you state then there should be extensive patient data readily available.

        Redox capacity.
        Oxygen ingress through the cork closure has been demonstrated to be another red herring of the cork industry. Subsequent research by the AWRI using glass sealed ampoules concluded that oxygen transfer is not necessary for bottle age characters to develop. After 10 years of real world trials our wines under screwcap show very similar bottle development to cork closed bottles, but they are fresher and far more consistent. Wine judges and journalists agree.

        Again, screwcaps are not necessarily the long term answer to wine bottle closure, but they are preferred by many winemakers for many sound reasons, and are welcomed by many consumers who are open minded and heartily sick of faulty wine.

        I’m afraid we will have to agree to disagree, but I appreciate your lively debate.



  28. Tom

    Wait a minute, someone said there were NO studies showing the connection between screw-caps liners and cancer. So how can this be?? 😉

    It is also interesting the right here in the comments there are winemakers reporting 8-percent corked to zero-percent corked. Sounds like someone is a bit smarter in their cork purchasing.

    A couple of years back I read about one of the most definitive studies on taint levels that was conducted by the British Wine & Spirit Association (WSA). Their research involved nearly 14,000 bottles of wine sealed with natural cork. They were opened and tasted over 18 months by respected wine retailers and importers in Great Britain, followed by independent verification of suspected faults by trained quality control panels. Keep in mind this involved wines from all over the world with corks supplied by hundreds of different providers. Only 0.07 percent was found to have been affected by their cork seal – a far cry from 8 percent stated here.

    Keith – you should keep an eye out for any letter bombs that might come your way from any of those screw-cap zealots. 😉

  29. Sarah Crowe

    At the end of the day my choice to use screwcaps as a closure is to ensure wine quality and nothing else.

    Any mention of reductive off-flavours under screwcap is a result of poor winemaking rather than using a more forgiving closure which is actually oxidising the wine to varying degrees.

    Are we the only industry utilising screwcaps to seal our product? How about the thousands of bottles of olive oil, sauces etc that line the supermarket shelves. For some reason the wine industry is the only bad guy in this argument!

    • Tim Keller

      Well said.

      Reduction is indeed a winemaking problem that can be avoided by good practice. My company makes oxygen regulating screwcaps and people always assume my our goal is to eliminate reduction – but that isn’t totally accurate.

      A wine that is reductively inclined will reduce no matter what closure you pick. There is no substitute for good winemaking practice in this regard. However, there are anti-reduction insurance steps such as proactive copper fining that many screwcap users employ that will not be necessary with our liners, and I am happy about that.

      Nicholas pointed out above the studies that state that wine aging will occur with or without oxygen from the outside. This is true, but those reactions are still oxidative, and oxygen is still being moved from one molecule to another. To make a Riesling like PRV makes the oxygen that is in the bottle at bottling is probably all it ever needs. Get heavier in phenols however, and you will have problems. Maybe not reduction, if you make the wine well, but the aging will indeed slow down, the wine will taste more closed, and the wine will not get any of the benefit of aging that consumers expect.

      As a winemaker myself, I don’t want to change my wine style to fit the packaging. I want the packaging to complement my wine style. And to do so without a significant chance of defects. THAT is what I have spent the past 4 years of my life pursuing.

      While there is a benefit of some insurance against reduction with our product, the aspect I am most excited about is that we will be able to craft a wine that is open, approachable, and in it’s best condition when it reaches the consumer – without worrying about having a short shelf life.

      THAT a level of quality control that we have never had before as winemakers, and that we will NEVER get from cork.

  30. Erika Szymanski

    Fifty-five comments and this makes fifty-six. Wow. Nothing like corks vs. screwcaps to get people riled up, it seems, even if the vast majority of the arguing has nothing to do with sustainability data. But heck, if whatever particular angle is important to you — and it obviously is — then have fun.

  31. Tai-Ran Niew

    Who is “Tom”? And “Keith Stewart”? Would be grateful for some disclosure! They do make interesting points. But not sure why they have to be so insulting?

    Probably the most interesting comment/question comes from Nancy Hawks Miller re: Cork Supply USA. Does anyone have an answer?

    As for “greeness”, it is definitely a very slippery thing, as there are so many components and links in the chain. As a comedian once remarked: “If you take the analysis to its logical conclusion, the best thing to do for the planet is to not have any children …”

    • RP

      All major cork suppliers (at least those members of the US Cork Quality Council) have ways to reduce (not eliminate) TCA incidence in corks. Elimination can only be achieved by preventing that the two major precursors of TCA get together throughout the entire process (specifically chlorinated compounds and microbial activity). As usual, prevention always beats remediation.

    • Keith Stewart

      Fair question. I am a frelance writer who specialises in business to business food industry news. For 20 years I was the drinks columnist for New Zealand’s largest weekly news magazine, “The Listener”. I have published 14 books on various subjects, including 8 on wine, the latest being “Chancers and Visionaries” a history of NZ wine that was shortlisted for this years Louis Roederer award. Just a summary run-down of my position as follows;
      1976 first job in NZ wine industry, my new boss tells me the biggest marketing challenge facing wine in NZ is to convince consumers to accept ROPP (screwcap closures)as this will be the most significant contirbution to company profitability possible in the production area.
      In 1998 I wrote my first piece about the growing concern over TCA taint appearing in wine, calling on consumers to pressure winemakers to respond to the challenge posed.
      2001 Screwcap Initiative in New Zealand launches a PR campaign promoting the use of screwcaps. I am supportive in principle, but when researching screwcaps I find a couple of serious challenges that are brushed off as irrelevant by those running the Screwcap Initiative campaign. These are that no-one can tell me what the cause of this recent problem with TCA taint is, and secondly that the two real scientists who are committed to producing high quality NZ wine are uncomfortable with what the Screwcap promoters are claiming is their scientific basis for action. Those two, by highly regarded PhDs with a career in hard science before becoming winemaker, have proven credntials as pioneers of genuine wine quality in NZ conditions. Neither have ever used screwcaps.
      Noting that the screwcap lobby’s intellectual arguments were being articulated by winemakers with limited science literacy, most of whom had trouble even understanding the arguments from the serious science community, I decided to read through published science papers to become better informed.
      First was to find the cause of TCA. This turned out to be most likely environmental contamination by chlorophenols and bromophenols and that the largest contamination problem is not wine, but public water supplies in North America and Europe. What we have is not so much a problem with a tiny number of consumers rejecting TCA and BCA tainted wine, but a massive environment pollution problem. The next question I considered was whether the solution promoted by the Screwcap Initiative was actually a solution, or one that exacerbated the real problem.
      That was quite easy, because of the seals under the screwcaps which contribute cholorphenols to the wider environment through manufacture and waste.
      Further investigation revealed that these persistent pollutants are also implicated in human health issues, such as the diabetes and cancer epidemics, and the rapidly declining fertility of Western communities.
      So I look for what may be in the wine from screwcap use, and find just one piece of research, which is the paper I have noted.
      Rather than be a scaremonger, I approach the largest importer and supplier of screwcaps to the NZ market and provide evidence of the looming problem. When that is ignored, I approach one of the most active Screwcap Initiative winemakers, one with a doctorate, and am again ignored. When I put my concerns to fellow winewriters in New Zealand I am ridiculed. Nobody reads the paper, nobody bothers with the real science.
      I am invited to Portugal to look at the cork industry as part of their initiative in response to screwcap’s PR. I agree to go on the basis that I can talk independently to Portuguese evironmental groups about the issue, and the consequences of a move to screwcaps by the industrial wine industry. My approach is that this is not a wine consumer issue, it is an environmental one, and a public health one.
      My visit makes it clear that there is a real threat to the Iberian cork oak forests and their remarkable human/natural sustainability, as well as a serious increase through the wine industry in contamination of the global environment by persistent pollutants, specifically organic chlorophenols and bromophenols.
      On my return I write about these issues, and about the growing weight of scientific evidence that the argument in support of wine aging in the traditional manner under screwcaps is seriously flawed. I am immediately branded as being in the pay of the cork lobby, and that the Portugal trip was nothing but a pay-off. Not one of my detractors is p[repared to engage in the environmental debate, because, quite frankly, they have seen the colour of the money and see it as their salvation as the New Zealand wine industry has become beholden to supermarket trading and selling their wines at low margins.
      One of my fellow writer, Paul White, also takes up the debate on behalf of cork because he sees that the evidence is that increased sulphur contamination of wine is just replacing one taint with another. He is subsequently blackballed by the NZ wine industry, losing his wine columns in newspapers through their lobbying, and can only find publishing support outside New Zealand.
      When the Listener asks me to provide details of pollutant contamination for an article on the public health risks of sythetic spray contamination in the food chain, I provide the information from the opnly published research on the matter.
      New Zealand Winegrowers screams traitor, and lobbies the Listener to remove me from autghoring their drinks column. In effect, I am fired.
      So much for addressing the issues, taking public health seriously, or being true to their claim of being committed to sustainable winemaking.
      Given the evidence, I am amazed that anybody with any concern for the global environment can consider screwcaps, especially those sealed using PVdA film.
      Screwcaps are a closure that compromise the traditional consumer benefit of bottle aging wine, which is why the producers of wines that the French call vins de guarde, universally reject screwcaps. Note that in spite of Australia’s support for screwcaps that their most famous and highly valued wines, those of Henschke and Penfolds, are still closed with corks.
      Screwcaps as a closure increase the contamination of our environment with persistent pollutants.
      Screwcaps as a wine closure increase the risk of birth defects, infertility, cancer and diabetes for those that drink wines packaged in this way.
      TCA and BCA are not exclusive to cork, so the change in closure from cork to screwcap does not eliminate the problem. No amount of closure changes would have eliminated the TCA problem at Hanzell, what was needed was a full refurbishment of a contaminated cellar.
      Most wineries are as much at risk from TCA and BCA contamination of their wines through their barrels as they are via cork, yet no winery has yet mounted an attack on barrels. Could it be that barrels taint their wine in a way they can use to add a margin? Whatever, noboy talks of wines with “barrel taint”, even though every barrel aged wine is tainted by its exposure to oak, chestnut or hickory.
      The Screwcap initiative has no advantages for consumers in the widest sense. Winedrinkers sharp enough to identify TCA/BCA are usually those who have cellars and are prepared to accept a degree of failure. Cork, like oak, is a natural product that cannot be completely controlled by winemakers, before or after they have sold their wine. Indeed most wine drinkers cannot identify TCA/BCA taint unless it is pointed out to the by a sanctimonious wine writer.
      So what is the pressing problem that needed to be solved by increased pollution, posing a threat to established and thriving biodiversity, and increasing the carbon cost of wine through the increased bauxite mining and energy consumtion required by alimunium?
      If it is not consumer interest, could it be increased profitability for wine companys. Especially those pumping out millions of bottles of industrial wine?
      Given their pointed refusal to consider the situation by reading ALL the science and by further research into the problem they say is posed by çork taint’, I can only conclude that this is indeed the case.

      • Tim Keller

        Obviously well studied on the issues, and while most of your points are valid, I think you and I put very different weights on the various factors being discussed, and so there is not likely to be any agreement since we hold different things to be important.

        As a wine producer, it’s not about making money, it’s about SURVIVING. The average winery makes a profit by it’s 3rd owner. The marketplace is insanely competitive. It’s not greed – it’s competitive advantage, by keeping costs low, eliminating returns of tainted bottles, and making sure that everyone who tries the bottle is willing to try another. If that customer gets a bad bottle, they aren’t coming back to our brand.

        Screwcaps are indeed cheaper, but the wineries aren’t seeing that savings – the consumer does. That is just the nature of the free market.

        We do care about the environment, and despite your assertions, most of us are scientifically trained and understand the chemistry involved QUITE well thank you.

        So we aren’t being sold any BS, we aren’t ignorant, and we do care both about our product, but also it’s sustainability. You might assume the worst case for the impact of the cap, and the best for cork – that is on you, But the rational view of the choices involved shows very little environmental difference, if any, and a LARGE increase in quality and reduction of spoilage.

        I might add: If you are against aluminum or pit mining, I hope you also do not; Drive a Car, Fly anywhere, consume food other than what you grow and harvest by hand, use computers or technology etc etc.

        To say we should avoid screwcaps because pit mining is bad and live your daily life using products made from aluminum, or even worse things to mine: like coal for electricity, copper, Tin, Iron ore… just shows that we are totally out of touch with reality and the larger context of the issue.

        All of that mining DOES need to be done carefully and without accident, but we either have to tolerate and mitigate the risk of it or abandon our modern conveniences altogether. Even so, aluminum for wine closures is completely insignificant in the total picture of aluminum production, so if what you are really concerned with is reducing aluminum production, I suggest your efforts be made elsewhere where much much more aluminum is consumed. How about sports cars, building materials or aircraft?

        Finally, while a lot of your arguments have a basis in fact, the rant about barrels exposes an ignorance about TCA that I will help correct:

        The connection between wood and TCA is that wooden structural members that have been chemically treated contain anisoles. That compound comes from the preservative, not the wood.

        If you then use chlorinated cleansers in the winery, you can chlorinate those anisoles to create TCA which can then spread to the wine through the air. Other similar compounds like TBA arise by similar sources, or are produced by mold.

        Barrels are NOT, in any way a target for being a source of “barrel taint” because the oak is not treated with any preservative, nor to people use chlorinated cleansers to wash them. (hot water ONLY) Even if TCA was in the wood to start, the process of toasting the barrel during it’s manufacture would eliminate them.

        So that is a freebie for you lest you repeat the barrel taint thing again. It just isn’t an issue.

        I love the debate, but sadly, the importance of the various issues is a matter of opinion, and when people cant agree on which issues are most important, they will never agree on what is best.

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    […] investment, rapid growth and an influx of foreign expertise but prices remain too high (Guardian) Screwcap vs. Cork: Which is Greener? (Palate Press) In UK, wine producers enjoy good year helped by climate change (This is Money) […]

  33. Tom

    Several years ago it was reported in Wine Spectator that BV in Napa had a TCA problem with their red wines. Apparently, the source of the TCA was in the barrel room and came from a humidifier.

    About the same time is was reported by Rich Cartiere in his Wine Market Report that of the 53 other Napa County wines tested for TCA in their barrel rooms, about a quarter of them showed comparable levels of TCA. If those tests are representative of all the wineries in California, then that would mean that upwards of 250 to 300 wineries in California have TCA tainted barrel rooms.

    Wine Spectator also reported problems in the barrels rooms of a large number for French wineries. Seems the source there were preservatives that had been used on the wood there.

    And do any of you remember the massive recall of Perrier many years ago. It was because of TCA in their water. Funny – don’t they use screw-caps? Actually it was from the chlorine they used to clean the equipment.

    So how many of you winemakers use chlorinated water to clean your equipment or wash down the floors in your winery? When chlorine breaks down it leaves behind TCA.

    So as you can see TCA can come from a lot of different sources. But I’m sure will cork get the blame.

    • Tim Keller

      Again, there ARE cased of systemic TCA infections. Nobody denies that.

      But that does not get the cork off the hook for causing the majority of cork taint we actually see in wine bottles.

      Wineries used to use chlorine a lot in sanitation. Just as the cork companies used to use it to bleach corks.

      Both industries have moved away from the use of chlorine, which is probably the reason why the TCA rate is now below 5%.

      Wineries have eliminated preserved wood, changed sanitation chemicals to avoid chlorine and changed drainage systems to avoid these kind of problems, and methods for testing wineries products for systemic infection is now readily avaliable and used by winemakers.

      But the TCA problem persists. Thankfully it is at a much lower level than before, but still at a higher rate than ANY other industry would tolerate.

  34. RP

    Focusing on the environmental aspects, I also wish there was more information available to compare.
    But quite frankly, after googling “alumina production environmental impact” and “bauxite mining environmental impact” I don’t see how can a few spoiled bottles due to bad corks can compare to the environmental impact of aluminium production. Not to mention the risk for tremendous environmental disasters, like the one last year in Hungary:

    Regardless of the recycling merits of aluminum… it’s better to support the cork to keep improving its performance without any environmental compromise.

  35. Shawn Burgert

    For me when I go pull a nicely aged bottle and begin to plan my special dinner around this wine…..working many hours to get the right meal with the right wine…..then to open this aged bottle only to find that it’s been corked; this is the biggest frustration and disappointment.

    I recently interviewed a very sustainable minded winemaker highly regarded that is fully dedicated to screw caps in all of his wine (mostly all rate 90+). He shared with me that the screw cap can handle the age and mimics the perfect cork. That was all I needed to hear. How much does green matter when my 8 year old wine that I’ve been storing in a temperature controlled cellar goes straight to the garbage?

  36. Peter

    Very interesting article, thank you!
    Something else to consider is using the above mentioned closure during Bottling, I do mobile bottling in the Western Cape, approx 4.5 million bottles a year, If one takes into account production loss (Normal industry standards are between 1 and 2%), Every hour 6 bottles are taken, opened and then tested IE; Temperature, Do2,Co2, volumetric, Foreign body etc, Thats 6 bottles, 6 corks or screw caps and 4.5liters of wine thrown away every hour of production, Thats a lot of waste but a necessary evil to ensure product quality.If one had to truly have all the data surrounding the Green debate we would probably all end up drinking water. I am pro screw cap to my own horror as it is more versatile from a consumer point of view but cork is way more user friendly during production, less troubleshooting etc as opposed to screw cap which is a mechanical closure made by machine, machines always end up with problems due to maximizing production. Just my 5 cents.

  37. opium

    There is a contest running on the French web presently (
    It invites Sommeliers to post their best humorous anecdote.
    one of the sommelier posted this one (short translation) : ” a client complained on his wine : it is corked, he said. I answered : sorry, it is screwcap !”
    One thing everybody should know : TCA is everywhere and not only in CORK !!!

  38. dylan

    being a ex -bodegero and wine maker i understand totally that the form of representation is vitally important for flavour and taste however take this argument to the scottish isles and they will laugh at you why because being a whiskey country the scottish will out last any man from any country any drink at the table that i know so i guess that wheather you put a plastic , or metal or cork in your bottle doesnt sell the wine the wine sells it self on the right shelf at the right time right price can make you a millionaire catch my drift looking for a sales man well contact me on im your man …..

  39. Jose FO

    This is the most interesting discussing on wine closures I have ever seen and indeed it is a passionate subject. As some have done I also disclose my bias – as opposed to Tim I have a stake on cork business. I am not sure whether or not any blogger is directly involved in the cork industry but PR speaks as if he were and his reasoning is crystal clear. Indeed in the cork industry prevention is the key word (and practice) to provide the market with the best, safest corks. It is mandatory that cork production is vertically integrated so that you know perfectly well all steps from cork bark harvest down to the final product being supplied to the winery. By doing this you have the complete traceability of your product. Unfortunately this is not what is happening and that is where a winemaker or cork buyer must be selective. And honestly, just amongst cork users, very often price is the main factor for decision making. Pity!…
    Thanks Erika for the excellent article that prompted such interesting, long lasting discussions.

  40. Gerald Rebitzer

    In this discussion, one should come back to the following quote from the Amcor website:

    “The purpose of the packaging system (glass bottle and closure) is to protect the wine in the best possible way, to minimize or eliminate spoilage and waste. Even just a little spoilage, including spoilage due to cork taint, has a much higher environmental impact than the impact that comes from producing the bottle closure. When considering the product (wine) and the packaging (bottle and closure) together, Stelvin® aluminum screw caps are more sustainable than cork stoppers. They lead to reduced overall environmental impacts by eliminating spoilage due to cork taint.”

    It is understandable that on a first glance one looks at the packaging and not the interaction with the packaged wine, but if one examines all the facts, it is evident that the closure actually has a relatively small impact compared to the overall impact of wine consumption and that better protection (less spoilage due to reduction of cork taint) leads to reduction in impacts. There is also a scientific study available on this topic:

    And in this third party study it says:

    “….it can be concluded that
    1. the contribution of the closure itself, whatever the type, to the global impact score for a typical bottle of wine is not significant and is therefore not a key parameter;
    2. the wine loss rate induced by the type of closure is a more important parameter than the closure material to determine the environmental footprint of a bottle of wine;”

    When talking about sustainability and environmental issues, it is important to look at the overall system and not just at single aspects.

    Gerald (for full disclosure: I work for Amcor)

    • Keith Stewart

      For full disclosure you could also note that the study was commissioned by the EAFA European Aluminium Foil Association, with a direction panel of 3 that included 2 Amcor employees. Hardly independent.
      Keith Stewart.

      • Gerald Rebitzer

        sure, I think it is clear that this study was commissioned by the industry – in order to make the whole discussion a bit more objective. But I would encourage everyone to have a look at the facts – the key point is to look at the complete picture of the wine bottle system vs. just focusing on one single aspect (impact of the closure). If losses are not taken into account, the assessment is misleading.
        Sustainabilty is all about systems and overall impacts. Please feel free to contact the consultant of the study directly in case you have any doubts on the validity of the results.

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    […] Screwcap vs. Cork: Which is Greener? – Let’s begin with cork harvesting … discarded prior to either crimping or balling. Cork is recyclable too (though recycled cork is only used for lower-quality cork products like cork boards, cork flooring, or insulation, never new bottle stoppers.) […]