Do you buy your water in PET or glass bottles?

Monomere of Polyethylene terephthalate (PET)

For a long time drinks and other liquids were filled in glass bottles. Glass is a very suitable material for this application: it does not release carbon dioxide, it is acid-resistant, it leaves no residue in the liquids and it is relatively easy to process. In contrast, however, it is heavier than the plastic PET (Polyethylene terephthalate) which is used today for beverage bottles. Furthermore it is fragile and more energy is required for the production of bottles.

E.g.  Coca Cola supplied its product of the same name exclusively in glass bottles, until in 1978 ( the company decided to bottle its drinks in plastic (PET) bottles as well.

If one compares the glass and plastic bottles in terms of their environmental impact, one should consider a few other points:

  • resource consumption in production
  • energy expenditure during transport
  • resource and energy consumption for multi-purpose bottles
  • the impact on the climate over the entire life cycle
  • the burden on the environment caused by pollution or careless throwing away

In summary, the returnable PET bottle performs better than a returnable glass bottle. But why?

Due to the lower weight of the plastic, it is more efficient in transport because no beverage crates have to be used. The density of PET is approximately 50% lower than that of glass (density PET: 1.38g/cm³, density glass: 2.5 – 2.6 g/cm³). This also means that a truck can be loaded with more plastic bottles than glass bottles in terms of weight, and the savings in deliveries in turn affect the amount of CO₂ emitted by the truck during transport.

An undeniable advantage of glass is it is 100% recyclable and could be recycled endlessly without loss in quality or purity – theoretically. In practice only 33 percent of waste glass is recycled in America. When you consider 10 million metric tons of glass is disposed of every year in America, that’s not a very high recycling rate. Mostly glass put into the recycling bin is used as a cheap landfill cover to keep costs low.

Glass takes a very, very long time to break down. In fact, it can take a glass bottle one million years to decompose in the environment, possibly even more if it’s in a landfill. Because its life cycle is so long, and because glass doesn’t leach any chemicals, it’s better to repurpose and reuse it over and over again before recycling it.

Due to the lower energy requirement of plastic bottles during production, it also conserves resources. Even with the higher refilling of glass bottles (glass up to 40 times, plastic up to 25 times), however, the advantage of PET bottles cannot be eliminated. Around 500 billion plastic beverage bottles are produced worldwide every year, over 100 billion of them by Coca Cola alone, which is around 190,000 bottles per minute (!). The demand for lightweight packed beverages is not stopping, and the question is: Which packaging to choose?

ALPLA Packaging Report 2019

According to Alpla (a manufacturer of plastic bottles and closures) which published the Alpla Packaging Report 2019, performance of the returnable PET bottle is overall better in the following categories:

  • Climate change [equivalent to kg CO₂]
  • Acidification potential [equivalent to kg SO₂]
  • Summer smog [equivalent to kg Ethylene]
  • Water consumption [liter]

The comparison in these categories of different bottle types (glass and plastic (PET and recycled PET (rPET), one way (OW) and more way (MW)) for mineral water is shown in the charts below.

As expected, the disposable glass bottle shows the worst result with a value of 324 g CO₂ equivalent. The returnable PET bottle with 100% recyclate (rPET) content has the lowest environmental impact.

In acidification, the disposable PET bottle with 100% rPET performs best, followed by the returnable PET bottles. The worst values are again for the glass bottles, with the disposable glass bottle having a significantly higher value than all other bottles.

The comparison with summer smog shows a similar result. All three PET returnable bottles are slightly behind the PET non-returnable bottle with 100% recycled content, followed by the other PET non-returnable bottles, followed by the glass returnable bottle. The value of the non-returnable glass bottle is approximately four times higher than that of the PET bottles.

In terms of water consumption, the PET disposable bottle (< 0.6 liters) is ahead of the PET returnable bottles (0.84 liters), followed by the glass returnable bottle (1 liter) of water per packaging system. The glass non-returnable bottle is again the worst performer with a water consumption of 1.57 liters of water per package.

You can download and read more comparisons about milk, lemonade and detergents as well as these results in detail in the ALPLA report 2019.

Alpla Packaging Report 2019 (c7 consult)


Glass bottles for beverages are still part of our daily use and for water bottling it can be an option when the water source and processing as well as the distribution is not too far away. For longer distant transports, PET based packaging is more resource efficient.

Moreover, glass bottles have still an appearance advantage for beverages such as wine, beer and other alcoholic liquors, which is driven by customers.

Which packaging do you choose? Leave us a comment!

Hopefully we were able to give you some new inputs. Don’t hesitate to share your thoughts and join the hubbub.

Peter & Herwig

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