Disposable drink bottles: Plastic vs glass vs aluminium

G Magazine

Buying a drink on the run has worked its way seamlessly into our hectic lifestyles, and despite best intentions is sometimes unavoidable. But does one of the packaging options come out trumps environmentally?


Credit: sxc.hu

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Bottled and canned drinks are big business in Australia. The soft drink industry generated total revenue of $8.9 billion in 2008, and while we all may try to avoid non-disposable products, sometimes buying a drink on the run is tough to avoid.

For many soft drinks and juices, the same product comes packaged in a variety of different containers. So, what’s the best environmental option from the array of bevies facing you from the fridge – glass or plastic bottle, or aluminium can?

Building a bottle or can

Most plastic drink bottles are made from polyethylene terephthalate (PET). Like all plastics, PET is sourced from non-renewable petroleum and its extraction and manufacture leave yeti-sized carbon footprints. Although bottles containing recycled plastic are becoming more widely available, the majority are still formed from virgin plastic.

Glass is also made from non-renewable resources – sand, silica and limestone. Although these are more plentiful and less environmentally damaging to extract than petroleum, glass bottles still swing the eco-cost meter to high during manufacture because the elements require energy to heat them to 1200°C
in a furnace.

Aluminium cans also have a less-than-auspicious source. Aluminium is made from bauxite, mined from open-pit or dredging mines that have damaging environmental impacts. Australia is one of the world’s biggest exporters of bauxite, and bauxite mining threatens sensitive ecosystems, while aluminium processing is water and energy hungry and produces a variety of pollutants.

For all three options, the extraction and manufacture process have the largest environmental impact. Primary aluminium production accounts for more than 90 per cent of the total environmental footprint of making aluminium cans, according to an industry study. A life-cycle analysis by researchers in Mauritius finds a similar figure for the assembly phase of PET bottles.

However, most glass bottles and aluminium cans in Australia are manufactured with 40-70 per cent recycled materials, significantly cutting energy and environmental costs associated with production. The manufacture of cans with recycled material uses 90–95 per cent less energy than virgin aluminium, while recycled content in glass bottles has energy savings of 75 per cent due to lower production temperatures.

In a study from the United States, disposable glass bottles had a higher environmental impact than aluminium cans, including 23 per cent greater climate change potential, and 43 per cent greater use of fossil resources.
In a comparison of all three options, conducted by the plastics industry, the plastic PET bottle has the lowest global warming impact, while aluminium cans and glass bottles had 23 and 40 per cent greater global warming potential, respectively. The analysis included materials and processes for production and transportation.

A weighty issue

After manufacturing, the greatest environmental impact comes from transportation, and our three contenders weigh in with considerably different masses – impacting on truckload size and thus fuel use.

For a 335 ml container, the aluminium can is the featherweight at 11 g. The middleweight PET bottle weighs 24 g, while the heavyweight champ of the drink container world, the glass bottle, weighs a comparatively colossal 200 g.

The additional 176-plus grams holds a sizeable environmental punch, as fewer bottles can be loaded onto trucks due to weight limits, meaning more trips, and a heavier load uses more fuel. In a German study, researchers calculate that a recycled glass bottle could be the cause of 20 per cent more greenhouse gas than a virgin aluminium can due to its added weight on a cross-country truck journey.

The R factor

All three materials, glass, PET plastic and aluminium, are inherently recyclable, but whether or not we actually do recycle them varies considerably. Australia has relatively good rates of aluminium recycling with almost two of every three cans being recycled, but only 40 per cent of glass bottles and a dismal 24 per cent of PET bottles are recycled.

Neither glass nor aluminium degrades during the recycling process, meaning they can be recycled indefinitely. For both, the process is essentially a closed-loop; meaning bottles and cans become new bottles and cans.
For every tonne of recycled aluminium, 5 tonnes of bauxite is conserved, and every tonne of glass saves 225 kg of carbon dioxide.

Plastics however can degrade during the recycling process and, although some plastic bottles are turned into new bottles with 25 per cent recycled material, the majority is open-loop recycled into products including wheelie bins or eco-fleece. According to an American study, for every kilogram of PET recycled, primary energy demands decrease by 54 per cent and global warming potential by 23 per cent.

Professor Richard Thompson, from the University of Plymouth in England, led a published study that reviewed the potential benefits and problems of plastics for the environment and believes lack of recycling is a major obstacle. “Single trip convenience packaging, such as plastic drink bottles, accumulates in landfill and the environment,” Thompson explains. “The full environmental benefits of plastic can only be realised together with end-of-life recycling to produce new plastic items in a closed loop so a bottle becomes a bottle again.”
If not recycled, glass and plastic take more than 400 years to break down in the environment, and aluminium cans around 80 years.

The verdict

Determining a winner is no easy task. Although plastics are regarded as environmental harbingers of doom,
they come out on top in terms of being lightweight and easily portable and potentially recyclable into other useful products.

The can kicks it at the bauxite mine – the eco-cost of destructive mining and aluminium production can’t be undone by recycling or the fact that it is the most lightweight option to transport.

The heavyweight glass bottle, though beloved by many, is let down by its comparative bulk during transportation, although does gain some eco-points for being forever recyclable back into new bottles.

What is clear is that quaffing a beverage from a disposable container is an environmentally costly activity, so avoid it where you can. A reusable bottle filled with juice or iced tea from home will win every time.
If you do find yourself having to grab a drink on the run, make sure you recycle, even if it means taking the bottle or can home for your kerbside collection.