Cheers to sustainability—lifecycle analysis pits glass bottles against aluminum cans | The American Ceramic Society

Cheers to sustainability—lifecycle analysis pits glass bottles against aluminum cans

08-23 beer

[Image above] Credit: Ewan Munro; Flickr CC BY-SA 2.0


On a recent trip to my local grocery store’s beverage aisle, I spent nearly 10 minutes pondering the vast array of choices. 

Canned cocktail or hard seltzer? Dry cider or sour beer? Hoppy pale ale or fruity pale ale? IPA or DIPA? Milk stout or coffee stout? So. Many. Choices.

To try to narrow down my seemingly infinite array of liquids of choice, I thought about other parameters that could help me choose a cold beverage. This train of thought brought me to an interesting question—from an environmental sustainability standpoint, which is better: glass bottles or aluminum cans?

Well, it turns out that the answer isn’t exactly clear. Depending on what parameters you consider, glass bottles are a clear win in some regards, while aluminum cans have major advantages in other areas.

Recyclability, savings, and energy

First of all, in terms of recyclability, both aluminum cans and glass bottles get high marks. Both materials are completely recyclable and can be recycled over and over again, with no loss of the material’s quality.

In terms of savings, a EuroNews article indicates that recycling a metric ton of glass bottles saves:

  • 42 kilowatt hours of energy
  • 19 liters of oil
  • 54 ft3 of landfill space

Compare that to aluminum cans, for which recycling a metric ton saves much more:

  • 14,000 kilowatt hours of energy
  • 6,545 liters of oil
  • 270 ft3 of landfill space

However, while some European countries recycle up to 90% of their glass, America only recycles about a third of the 10 million metric tons of glass it discards annually. The problem is an economical one, partly due to the steep costs of processing a high-quality stream of glass cullet from mixed recyclables and transporting that material often across large distances. (For more information, read this recent report from the Glass Manufacturing Industry Council.)

Aluminum cans get recycled more frequently, with 2015 statistics from the Environmental Protection Agency indicating that 54.9% of aluminum beer and soft drink cans are recycled. 

Further, aluminum beverage containers contain the highest percentage of recycled content amongst all types of beverage containers, with 68% recycled material. While these numbers vary among sources—a Slate article instead cites a figure of 40% recycled content for aluminum beer cans—the amount is higher than that of glass bottles, which are reported to contain an average of closer to 20%–30% recycled content.

That difference is important because using recycled materials also saves energy—a can made of recycled aluminum requires about 95% less energy to produce than one made from non-recycled materials (compared to closer to about 25% energy savings for glass). 

But cans are not primarily made from 100% recycled aluminum. Instead, another critical component of the sustainability equation is what’s required to produce these containers from raw rather than recycled materials.

Aluminum is notably energy-intensive to manufacture from raw materials—mining, crushing, and heating bauxite to produce aluminum cans requires a huge amount of energy. 

“The environmental impact is dominated by what it takes to make it in the first place,” David Allaway, solid waste policy analyst at the Oregon Department of Environmental Quality, says in an Oregon Public Broadcasting article. “When you recycle the aluminum, you significantly reduce the impact of making it. But that doesn’t mean the aluminum can you’re buying is made from 100 percent recycled aluminum. Most of the damage is done once you buy a product.”

“To really understand the environmental impacts you have to look upstream,” he adds. “Only then can you have a decent understanding of what’s the better choice. The requirements to recycle either of these materials are so small that they’re trivial. Recycling 100 beer bottles requires more energy than recycling 100 aluminum cans, but making the aluminum cans requires a lot more energy.”

Compare to the estimated 1.09 kilowatt-hours of energy required to manufacture a glass bottle, an aluminum can requires nearly twice as much energy, 2.07 kilowatt-hours of energy, to manufacture from raw bauxite. 

Another consideration is the weight of each material, which influences transportation costs. Aluminum cans weigh much less than glass bottles, so they require less energy to transport from one place to another. Aluminum cans are also more compact and less breakable than glass bottles and thus require less packaging, adding up to additional savings in transportation costs.

So, which is better?

Perhaps a more comprehensive way to assess the glass bottle vs. aluminum can debate is to consider a complete lifecycle assessment—a combined analysis of the energy and raw material requirements, atmospheric emissions, waterborne emissions, solid wastes, and other considerations for the lifecycle of each container.

A lifecycle assessment comparing 500-mL aluminum cans and glass bottles for packaging beer shows that aluminum cans result in more depletion of fresh water resources, generation of greenhouse gas emissions, and consumption of electricity and oil than glass bottles. However, glass bottles have higher natural gas and diesel consumption that aluminum cans.

Ultimately, the lifecycle analysis considers glass bottles more environmentally friendly due to their lower greenhouse gas emissions that aluminum cans, which are estimated to result in 1.88 times more emissions. “The hot spot for the analysis is the natural gas use and electricity used during electrolysis process to prepare molten ingot aluminum,” the report concludes.

However, while relatively comprehensive, this lifecycle analysis does not consider all factors in the glass vs. aluminum debate. “Further scope of the study may include the data for transportation from beer factory to distributers, recycling flow, solid waste management and transportation for final disposal to the landfill,” the analysis indicates. And, as we saw above, recycling is a major win in the advantages column for aluminum.

So where does that leave us?

“If you can find aluminum cans made from 100% recycled materials, they should be your top choice when shopping for single-serving beverages,” according to an Earth911 article. “Their low transportation footprint and ease of recyclability make them a winner.” 

And if recycled cans aren’t an option, the next-best choice is to opt for glass bottles instead.

But perhaps the best solution overall if you are conscious of environmental sustainability is to ditch the single-serve packaging altogether—filling a reusable growler or pint glass from a keg (also reusable) generates zero waste.

Cheers to that.

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