The Elusive Search for the Perfect Eco-Friendly Wine Closure

The proliferation of closure options in recent years has complicated the choice for winemakers—especially when it comes to sustainability

Cork carved from stave. Photo courtesy of Amorim..
Photo courtesy of Amorim.

Winemakers are increasingly looking for closures that complement their environmental philosophy as well as their stylistic needs and budget. As a winemaker myself, that meant a biodegradable, plastic-free closure with a low carbon footprint and zero TCA (2,4,6-Trichloroanisole, a chemical compound found in cork that causes taint). But if you scour the web for this stopper, you’ll soon discover, as I did, that it does not exist. 

“It’s the easiest attack in the world to say: ‘Don’t use, it’s plastic.’ But micro-agglos [corks which use plastic as a binder to cork dust] can be up to 50 percent polyurethane; screw caps use a plastic liner; and even natural corks use a silicone coating,” says Mike Clayton, the brand manager, North America, at Vinventions, a global provider of closure solutions.

Plastic has found its way into almost every closure, but as with many questions of sustainability, nothing is that clear cut. Just because a product contains plastic doesn’t mean it should be written off; some plastics are made from fossil fuels, while others come from biological sources. From an environmental perspective, there’s a real difference—biologically-derived plastics can have lower carbon footprints than their peers. Similarly, just because something is plastic free, or mostly so, doesn’t mean it gets a free pass. 

A Centuries-Old Closure Solution

Cork has been wine’s best friend for centuries, and its sustainability credentials are well documented. Cork forests are carbon sinks, pulling CO2 out of the atmosphere and storing it for generations. They are crucial to their ecosystems and provide habitats for endemic species, like the endangered Iberian Lynx. “Each natural cork sequesters 309 grams of CO2,” says Patrick Spencer, the executive director of the Cork Forest Conservation Alliance. “If demand doesn’t stay strong for cork forests, farmers will be forced to plant other crops, which could be invasive and change the ecosystem and biodiversity in those forests.”

When cork is processed, every part is utilized and whatever remains can be burned to generate power for the production line. “Cork generates, literally, no waste,” says Carlos De Jesus, the director of marketing and communications at cork producer Amorim. “Every little bit of cork harvested is used in countless applications. Even the dust generated during [cork stopper] production is captured and used to generate zero-emissions energy. At Amorim, over 66 percent of our energy needs are met this way.”

Cork forest. Photo courtesy of Amorim.
A cork forest. Photo courtesy of Amorim.

Natural cork closures are tried and true, but not without their flaws. They allow air in, but at inconsistent rates. They’re aromatically neutral, except for when TCA taints the wine. Ultimately, their unpredictability led to the development of technical cork, or cork composites, and other closures. 

New Kids on the Closure Block

“Cork is an amazing material but it is inconsistent when used as punched corks [natural cork],” says François Margot, the sales manager at Diam North America. “Technical micro-granulate corks made using suberin [the part of the bark used to make corks] bring consistency, a choice of oxygen transfer rates—which winemakers didn’t have the option of before—and no TCA.”

Both micro-granulate and micro-agglomerate corks are made by grinding and treating cork. However, micro-granulate corks are ground more finely. 

“Granulation is intelligent to get consistency but only if the cork is completely clean, otherwise it spreads any contamination including TCA in the granules,” says Yoann Canovas, the technical sales manager at Diam North America. “So, we use a cleaning process similar to how you decaffeinate coffee to get rid of TCA, which doesn’t require any chemicals.” The granules are then compressed and bound together. Some binding agents are derived from fossil fuels, such as polyurethane, but others, like those used in Diam Origine or Vinvention SÜBR, come from biological sources, which can be less environmentally damaging. 

Screw caps also give winemakers the ability to control rates of oxygen ingress and are free from TCA. They’re made of aluminum, and producers can use recycled aluminum when making new ones. However, they take a lot more energy to make than cork closures, according to International Wineries for Climate Action

Origine by DIAM corks. Photo courtesy of DIAM North America.
Diam Origine corks. Photo courtesy of Diam North America.

Each Closure’s Recycling Capacity 

Despite the energy used to make them, screw caps are fully recyclable, with programs available worldwide. That said, sometimes the caps are too small for a local recycler to recover the aluminum, or they may struggle to process the metal skirt on the neck of the bottle. “Screw cap liners are generally melted out during the remelting process,” says Don Huffman, the director of sales and wine quality at Vinventions. “The bigger issue is the portion of the cap that remains on the bottle can be difficult to sort and recycle.”

Natural or technical corks placed in a home recycling bin generally won’t get recycled; natural cork can be composted, but technical corks will be sent to landfill. Corks can also be sent to a recycler like Cork Reharvest, ReCork, or CorkClub, which will turn them into other products. “Recycled corks can be used in applications as varied as aerospace materials, footwear, and floor coverings,” says De Jesus. “In addition to using [dedicated recycling networks like] ReCork, you can also use corks in an enormous variety of home-made applications that can range from doormats to placemats to mulch for potted plants and bird houses.” 

Cork recycling bins are conveniently located in several retail outlets, too. “We have recycling programs in Total Wine & More stores nationwide, and Spec’s stores throughout Texas,” says Huffman. “Through those collection programs, we get a mix of all cork types in our recycling bins and manually sort and separate them. Natural corks can be re-ground into other products. Vinvention (Nomacorc) corks are picked out, re-ground, and re-purposed in a multitude of other products.”

What is pretty clear is that when most closures are tossed, they don’t compost and turn into flowers overnight, if at all. “[Unlike micro-granulate or natural corks], micro-agglomerate corks have no ability to be recycled except for [in] home art projects through sites like Etsy,” explains Huffman. “The polyurethane binder in micro-agglos gums up all the grinder parts and can’t be broken down. If you heat it up, it turns into something like peanut brittle.”

Cutting cork trees. Photo courtesy of Amorim.
Cutting cork trees. Photo courtesy of Amorim.

Steps Towards a More Sustainable Future

Consumer recycling programs are readily available, but while some trade recycling programs exist, they’re still not universal. Collecting corks and screw caps at restaurants, bars, and tasting rooms would vastly improve closure recycling rates and ensure they don’t waste away in landfills. Improving recycling and upcycling rates are two areas closure producers are working on, but they’re also looking into new, biologically-derived binders and how to incorporate more recycled plastic into their processes. 

“Normacorc is made from bio-polymers that come from sugarcane and can be recycled into other products,” says Vinventions’ Clayton. “In Europe, we use 50 percent recycled plastic for our Blue Line, and we plan to launch the Blue Line in the U.S. in 2023. Our 2025 to 2030 plan is to have recycled Normacorcs make up 25 percent of our business.”

The wine industry is getting closer to that ideal, but for now, no closure is perfect. However, I am cautiously optimistic. Closure manufacturers are actively looking for more environmentally friendly binders, and while some technological advances aren’t here yet, they are on the horizon. 

For now, as winemakers, we can focus on recycling more cork and screw caps by connecting restaurants and tasting rooms to existing recycling programs or encouraging them to start their own. Recycling gets a lot of flak, but every incremental step is crucial to arriving at a sustainable future.


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Diana Hawkins is a Certified Sommelier with an MSc in Wine Science who’s worked at top Chicago restaurants, including the James Beard Award-winning Lula Cafe and three-Michelin-star Alinea. In 2017, she traded in her wine key for a pair of work boots and moved to Aotearoa New Zealand to pursue a winemaking career. She works as an assistant winemaker and as head winemaker for her own wine brand, Responsible Hedonist. She completed her WSET Level 3 Award in Wine with Distinction and dreams of becoming a Master of Wine. When not exploring the wine world, Diana loves listening to music, kayaking around Waiheke Island, and practicing yoga.

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