There is a lot of anti-Plastic talk these days, and for good reason. Our oceans are choking with plastic, tiny bits of plastic are in the soil, the water and the air where they are being ingested by animals and us. Microplastics are even being found in large quantities in completely uninhabited areas in the arctic. But are aluminum cans or glass bottles really better for the environment? It’s more complicated than you might think.

Defining “Better for the Environment”

It’s often difficult to definitively say, “this material is better for the environment than this one.” (Or more eco-friendly, sustainable, greener, whatever term you like to use.) There are so many different factors to consider, and most materials do better on certain measurements, and worse on others. Some of the environmental impacts of packaging include:

• How much energy is used to produce it;
• Whether that energy is renewable or fossil fuels;
• How much water is used in the process;
• How much environmental degradation occurs in obtaining the raw materials;
• How many toxins and hazardous wastes are created during extraction, manufacturing and disposal;
• How far it must be transported;
• How bulky and heavy the item is (which affects how much space it requires in transportation and storage, how much energy is used in transportation and how much space it will take up in a landfill);
• How easily recyclable it is and how often it is recycled;
• How much the overall process contributes to greenhouse gas emissions;
• And so on…

So yeah…it’s complicated. And finding trustworthy unbiased studies of these various impacts is also pretty difficult because most of them are paid for by industry associations that represent plastics, aluminum or glass, so they can be biased and often cherry-pick the data that shows their packaging in the best possible light.

Comparing Plastic vs Glass vs Aluminum

After much research, I did manage to find one study from 2013 called Life Cycle Environmental Impacts of Carbonated Soft Drinks which seems to be an unbiased scientific study that was not funded by any aluminum, plastic or glass industry special interest groups.

Please note: This study was based on drinks packaging in the U.K., and they assumed that the glass was made of 35% recycled material, the cans from 48% recycled aluminum, and the plastic was virgin. These numbers seem fairly comparable to ours in the U.S. except that I believe our glass bottles have less recycled content, so the environmental impact of our glass containers is likely a bit worse than what is reported here. Our plastic may be better when it contains some recycled content.

This Life Cycle Assessment (LCA) looked at the entire process of creating that bottle or can of soda that you purchase at the store, and analyzed all the environmental impacts, from manufacturing to transportation to disposal and everything in between.

Conclusions:

This report concluded that glass has the worst overall environmental impact. Aluminum and plastic are more of a mixed bag, each having some benefits and drawbacks. Here is how it all breaks out.

Greenhouse Gas Emissions

Greenhouse gases (GHGs) include the carbon dioxide emitted by vehicles and fossil fuel-generated electricity. We often call this the “carbon footprint” of a product or activity. GHGs also include gases like methane and CFCs. These gases are produced throughout the life cycle of a product from extraction to manufacturing to transportation to recycling to waste disposal and more and they all contribute to climate change.

Based on the LCA, here is a chart illustrating the average GHG emissions impact of these three types of drinks packaging:

As you can see, glass contributes the greatest amount of global warming impact mostly due to the energy used to melt down the glass. Aluminum and plastic are fairly comparable, with plastic being slightly less GHG emitting.

NOTE: I found another article in Reuters comparing aluminum and plastic bottles in the United States, and they showed a much larger disparity between aluminum and plastic, with aluminum being about twice as GHG emitting as plastic.

There could be a few reasons for this. They are comparing bottled water packaging and the study I am using compares carbonated drinks, which may have to use a thicker plastic due to the pressure and acidity. Or it could be because they were assuming the plastic bottles have some recycled content rather than 100% virgin plastic assumed in the report from the UK above. They also might be including refrigeration at the retail stores which I did not. (Refrigeration does create more emissions for aluminum cans than plastic, I’m not sure why, maybe aluminum cans require more energy to cool?)

Regardless, plastic currently performs the best in terms of lowest global warming impacts.

Other Environmental Impacts

Global warming isn’t the only environmental issue created by our beverages. There are plenty of other problems like toxins released into the water, soil and air, ozone depletion, health hazards to animals and humans and more. This study looked at 10 categories of environmental impacts created by these materials. Of these 10 categories, glass ranked the worst on six of them. Plastic and aluminum each ranked worst on two.

Let’s also take a look at which materials ranked best (lowest impact) for those same ten factors. Aluminum in this case had the lowest impact ratings in seven of the ten factors, plastic had the lowest impact in three of them. Glass was not lowest impact in any category.

IMPORTANT NOTE – Although aluminum scored best in seven of the pollutant/environmental impact categories and worst in only two, in one of the categories where it scored worst (HTP, Human Toxicity Potential), it was off-the-charts worst (like, 14 times worse than glass or plastic). So it would be too simplistic to say that aluminum is better than plastic when it comes to pollutants. It’s complicated and they both have problems.

Takeaways:

Glass is a bad choice for single-serving drinks.

Glass has the greatest negative environmental impacts of the three types of drinks packaging. This study calculated that if glass bottles were reused, then the environmental impacts of glass could be reduced quite a bit. But as far as I am aware, currently in the United States even if your state has a bottle bill most bottles don’t get reused, they get recycled (if anything is done with them at all).

Related: Is Your Glass Really Getting Recycled?

Aluminum is probably better than glass but it isn’t necessarily better than plastic.

Aluminum has fewer environmental impacts than glass, and it has a much better recycling rate than either glass or plastic in the U.S. It could potentially be competitive with plastic in terms of GHG emissions, but only if it is recycled at a higher rate than it is currently. (We are still under 50% of aluminum cans being recycled in the United States.) Aluminum mining and can manufacturing also creates some pretty serious pollution and toxic health hazards.

Lessen your environmental impact by avoiding drinks in coolers.

After packaging, the retailing of drinks is the next largest source contributing to global warming. Coolers in stores use a lot of energy and leak CFCs (refrigerants, aka Freon, etc.) which are powerful greenhouse gases. Most beverages aren’t perishable, so buy the un-refrigerated ones and you can reduce your global warming impact by almost a third.

The transportation of your drinks is a much smaller factor than you probably thought.

Yes, there is some energy savings when transporting lighter packaging like aluminum and plastic versus glass, but the majority of the environmental impact of your beverage is in the packaging itself (the materials used, how they are extracted and the manufacturing process). The transportation of getting those drinks to you is a very small fraction of the total impact.

Drinks in larger bottles are better…usually.

A large 2-liter bottle of soda will have less environmental impact than four single serving bottles. However, if you are buying a quantity that you won’t finish and you end up throwing out half or more, that can be worse.

Recycling does help.

When any of these materials are recycled, it lessens the environmental impact. You can help by always recycling cans and bottles whenever possible. Aluminum cans already have a strong market for recycling. Plastics and glass recycling need to be improved.

Avoiding disposable containers is always best.

Bringing your own mug and/or refillable water bottle is always the most eco-friendly option. Avoid single-use disposable containers whenever possible.

Related: Everyday Steps to Fight Climate Change

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