Put a Cork in It: Is Real Wood Still the Best Bottle Stopper? | Civil Eats

Put a Cork in It: Is Real Wood Still the Best Bottle Stopper?

Photo by Martin Sharman

When my phone rang two months ago, a stranger invited me to visit a Portuguese cork-oak forest. I’d never seen one, so I was intrigued. My caller, Patrick Spencer, executive director of an Oregon-based nonprofit called the Cork Forest Conservation Alliance, explained why seeing and understanding this landscape was so important: the forests are fragile, among the most biodiverse in Europe, and threatened by people who buy wine closed with screw caps and plastic. That’s me, I thought, beginning to feel a little defensive.

Spencer went on: choose wine with a cork, and you help preserve a unique ecosystem, habitat for endangered endemics like Iberian lynx—of which only 150 remain—and imperial Iberian eagles. And don’t forget the adorable and threatened Barbary deer, wild boar, skinks, spade-foot toads, genets, and more than 160 bird species that reside or annually alight in these woodlands.

Originally published at OnEarth

I heard Spencer out, told him I’d consider his proposition, then walked down the street to my wine store, and then a bit further to two others. Hardly any of the bottles in a freelance writer’s price range seemed to be closed with cork. That didn’t bother me: I had decoupled the word ‘plonk’ from aluminum closures long ago (and realized you can’t easily tell whether a bottle is stoppered with a plastic or natural cork). Asking around, I realized that very few people connected those little wooden plugs with an ecosystem half a world away, and many still believe that cork trees die to make bottle stoppers (false!).

Next, I started looking into the state of the montado, as the Portuguese call their cork-oak forests. Surprisingly they’re in fairly good shape. In fact, they are expanding. And all the best wines have natural corks. So why was Spencer giving me the hard sell? Why was the cork industry starting a Real Cork Inside campaign and inviting journalists to witness the transformation of bark into bottle stoppers?

The answer had less to do with lofty conservation goals than with a lingering public-relations hangover from a nasty-smelling chemical called 2, 4, 6-trichloroanisole, or TCA. This compound had, more than a decade earlier, blackened cork’s name, allowing alternative wine closures—made of plastic and aluminum—to grab a large share of a market that used to be exclusively cork’s. Now, it seemed, the biggest player in the cork industry, a company called Amorim, was playing the environment card to win that business back.

* * *

Cork oak forests occur throughout the Mediterranean basin, dotting nearly 12,000 square miles of Portugal, Spain, France, Italy, Tunisia, Morocco, and Algeria. But these woodlands are the most extensive in Portugal, which also produces more wine stoppers than any other nation in the world. Portuguese law has, since 1929, protected that nation’s cork oaks. Quercus suber is the national tree, and the government issues steep fines for cutting it. (Other E.U. countries also protect their cork oaks; the northwest African nations have similar laws in place, but their governments can’t actively enforce them, which leaves these forests vulnerable to overgrazing, cutting for firewood, and black-market acorn collection.)

For nearly 400 years, cork was the default wine bottle closure. The material compresses easily, expands to fit irregular openings, and allows wine to breatheBut when wine production began to boom some 20 years ago, wineries looking to improve their bottom line, and meet growing demand, began buying cheaper cork from smaller producers—garage operations—with little quality control. The incidence of TCA—which forms when naturally occurring fungal spores interact with chlorophenols in cork bark, wooden barrels, beams, or pallets—began to rise. At best, the compound mutes flavors; at worst, it makes wine smell like a dirty, wet dog, when most wine drinkers consider their bottle “corked.” The cork industry was slow to respond to the problem, admits Spencer. “But because no one else was making closures, it didn’t have to do much about it. It’s like being the only restaurant in a desert: you’re not that worried about quality.”

Makers of aluminum screw tops and plastic corks—which are not vectors for TCA—were quick to pounce, grabbing 40 percent of the wine-closure market by 2009. It took several years and $8 million dollars for the cork industry, working with academia and private labs, to characterize, synthesize, and begin to vanquish TCA. The largest companies now test soil around trees, trim the lower part of each cork-bark plank, avoid wooden pallets, and boil off the volatile chemical, among other preventive and curative measures. Amorim, which makes two thirds of the world’s cork stoppers, claims that TCA occurs in less than 1 percent of its natural corks, and in 0.5 percent of its “technical” corks, made from cork granules.

But even one tainted bottle in 100 is too many for most wine merchants. Besides, the vast majority of wines don’t need the slow exchange of gases that cork allows. Eighty-five percent of wine, globally, costs less than $10 a bottle, which consumers usually empty within two days of leaving the store. “It’s a waste to use [cork] for wine you’ll drink in its first year,” says Amy Louise Rommier, the buyer at Brooklyn’s Prospect Wines. Cork, she says, should be reserved for expensive, aging vintages.

So where does that leave the green-minded wine drinker? It’s complicated. Each wine-closure industry promotes its product’s reliability and environmental bona fides. Aluminum screw caps are recyclable, but only if people actually put them in their recycling bins. They also require bauxite, mined ore that requires smelting, an energy-intensive and polluting process. Producing aluminum screw tops emits 24 times the carbon dioxide equivalent of cork stoppers, according to a PriceWaterhouse Coopers lifecycle study of all three closure types (funded by Amorim but independently validated).

We’ll bring the news to you.

Get the weekly Civil Eats newsletter, delivered to your inbox.

Plastic corks, made from fossil fuels, aren’t nearly as recyclable as aluminum tops, but they could, theoretically, be made of recycled plastic. And they have a lower carbon footprint than screw tops. Neither cork nor synthetic closures can be reused as stoppers, but cork can be, and increasingly is, ground up and used in flooring and other products. This works only if you can efficiently get the material to a recycler. Spencer is working with nine Whole Foods Markets to collect corks for such “downcycling,” while Nomacorc is piloting a collection program in Texas that converts its plastic stoppers into bumpers and floor mats.

Considering only environmental factors, cork wins in six out of seven categories studied (water use is cork’s weak point). On economics alone, cork loses: plastic corks and screw tops are way cheaper. But of the three closure types, only cork is integral to a sustainable silvicultural history that stretches back several hundred years and continues to this day.

* * *

I saw that in person on a hot June morning in the rural province of Coruche, where a dozen men in flat black caps drifted through the montado’s widely spaced oaks, part of a landscape that has the golden, grassy look of California chaparral. The men adroitly worked the cutting edge, butt edge, and end knobs of their axes into theQuercus suber’s outer skin, using their hands and feet to pry loose five-foot-long planks of curved bark. The outside is gnarly and gray, the interior—or belly—is roseate and redolent of oak. After reaching 25 years of age, cork oaks can be stripped like this every nine years: trees thus harvested can live for roughly 250 years.

The montado is a mosaic of grasses, cedars, wildflowers, and shrubs. Some landowners pasture cattle among their trees, others run brush hogs over the hillsides, which also produce mushrooms, honey, medicinal and aromatic herbs, berries, game animals, and acorns—some of which turn into new cork-oak trees and some of which become fodder for livestock and wild boar.

Clearly, the environment supports rural livelihoods (and diets). But it also provides substantial ecosystem services. By resisting both fire and drought, cork oaks stabilize the region’s sandy soils and hold a line against creeping desertification. The trees, which are neither irrigated nor treated with herbicides or fertilizers, store carbon. (Because a harvested tree needs to regenerate its bark, it absorbs up to five times more carbon than an unharvested tree.) They also provide plant and animal habitat, absorb rainfall and prevent soil erosion, thus protecting the watershed that supplies two thirds of Lisbon’s drinking water.

Working in teams, the men stacked cork planks into piles 10 feet high and 100 yards long. The wood that passes Amorim’s muster goes to one of its vast factories to be seasoned, outdoors, for another nine months. After that, the company boils, steams, and dries the planks indoors. After trimming and grading, the bark is granulated or punched or stamped into stoppers or discs. Next comes optical scanning, pressure testing, chemical analysis, polishing, chamfering, peroxide washing, fire branding, paraffin coating, bagging, and shrink wrapping onto pallets for worldwide distribution. Yes, it’s an energy intensive process, but 63 percent of Amorim’s power comes from burning cork dust (which counts as an alternative energy source but puts carbon dioxide into the atmosphere).

Portugal seems like a curious place to focus cork-oak forest conservation: the montado is healthy, protected, and growing by 4 percent a year. But landowners with marginal agricultural land are carefully watching the wine-closure market. Instead of planting new cork oaks—which won’t be profitable for at least a quarter century—many plant maritime pine for timber or eucalyptus for pulp. The cash is quicker, but those trees are prone to burn, provide habitat for fewer plant and animal species, and because they use a lot of water, they drastically reduce stream flow.

That’s where incentives come in. The cork industry pays Forest Stewardship Council-certified landowners in Portugal, Spain, and Italy 50 cents for every 33 pounds of cork. (Of Portugal’s 1.8 million-acre cork-oak forest, 27 percent is certified.) The European Union pays farmers about $52 per hectare to expand or improve existing cork forests and clear shrubs using approved techniques. And soon E.U. lawmakers may reward landowners who maintain and regenerate young cork oaks. But these programs’ success all depends on how much the world values cork.

Thank you for being a loyal reader.

We rely on you. Become a member today to read unlimited stories.

If cork doesn’t generate enough income to these landowners, they may abandon the land or let shrubs encroach on the ecosystem, explains Miguel Bugalho, a researcher at the Technical University of Lisbon’s Centre for Applied Ecology. Eventually, those areas will turn into non-woodland or agricultural areas. Without cutting a single tree, the forest will dwindle.

* * *

Throughout my time in Portugal, Amorim representatives repeatedly impressed upon me cork’s natural wonders. Besides keeping wine inside bottles, the bark insulates against temperature, vibration, and sound; it’s heat and water resistant, antimicrobial, elastic, and lightweight. Increasingly, cork is used in flooring, as sound proofing, to lighten subway and train cars, in aerospace, sports equipment, furniture, and as a textile. And yet 99 percent of the world’s cork is still being transformed into wine stoppers, a product whose time, if you believe cork’s competitors, is coming to a close.

Is the cork stopper destined to become an endangered species, used only for expensive wines crafted to evolve on their sides in the dark? I hope not. And if the cork industry eliminates TCA completely, which Patrick Spencer claims will happen within five years, its chances of survival will drastically improve (provided winemakers and importers get the message and revert to cork).

Whether non-wine uses of cork gain ground or not—and I hope they do—more than 31 billion wine bottles need to be safely closed each year. Aluminum and plastic can do that job, but they can’t also store carbon, protect watersheds, and provide habitat for species that occur nowhere else on earth. And that’s why, given a choice, I’ll stick with cork.

This story originally appeared at OnEarth.org.

Elizabeth Royte writes for OnEarth and the New York Times Book Review, which called her "no stranger to the pleasures and perils of chasing errant pieces of plastic and other castoffs to surprising (and often disgusting) places." She's the author of Bottlemania: How Water Went on Sale and Why We Bought It and Garbage Land: On the Secret Trail of Trash. Read more >

Like the story?
Join the conversation.

  1. gvillanie
    I still don't see how disturbing these pristine ecosystems benefits the creatures that live in them? The question of how this harvesting helps was left unanswered until almost the last few paragraphs. People being paid for harvesting the cork stay employed and thus live nearby and will continue to clear underbrush which allows the ecosystem to survive. So this is the big reason to use cork? Seems like there are still other options to preserving the habitat while allowing recycling of other materials for wine stoppers.

More from




In Brazil, a Powerful Law Protects Biodiversity and Blocks Corporate Piracy

An overhead shot of the Atlantic Forest in Brazil. (Photo credit: FG Trade, Getty Images)

Bringing Back Local Milk, Ice Cream, and Cheese

Foggy Bottoms Boys co-owner Cody Nicholson-Stratton pictured with his son. (Photo courtesy of Foggy Bottoms Boys)

Can Cooking in Community Slow Dementia and Diabetes?

The Promise and Possible Pitfalls of American Kelp Farming

an illustration by nhatt nichols showing a hand pulling a kelp line out of the sea