Stuff versus Stuff: Which water bottle?

Plastic bottles bad, reusable bottles good…right? Disposable plastic bottles have gone from being portrayed as the miraculously light and hygienic water container of choice to a chemical-laden, beach-choking nightmare. On the other hand, the reusable water bottle is back and comes in stylish forms from plastic to aluminium to hardwood-printed stainless steel.

Stuff versus Stuff is our mini-series where we explore the sustainability impact of our everyday product choices. In this edition, we investigate the secret lives of both types of water bottle. Is the decision as clear-cut as we think?

We’ll be focusing on two main aspects of our drink bottle choices: the impact of the materials across the lifecycle and the health implications of each.

What goes into a disposable plastic bottle?

The most common material for disposable plastic bottles is polyethelyne terephthalate (PET), a sturdy plastic which originates from crude oil and natural gas. A resin is synthesised and blow-molded into the cylindrical shape that we all know. A 2014 study of bottles produced in Thailand estimated that each bottle used 16.26g (0.57oz) of PET material and contributed approximately 69g of carbon dioxide equivalents to the atmosphere – roughly equivalent to the emissions from fully charging your phone 32 times. Around 60% of those emissions came from the process of synthesising the PET from raw materials and nearly 30% from the energy-intensive molding process.

It’s worth noting that not all emissions are created equal. Carbon dioxide equivalency is helpful for potential climate impact, but in this case the emissions also include sulfur oxides and nitrogen oxides. Both are highly toxic to human health and put factory workers and surrounding communities at risk.

With more and more pressure from customers to reduce the environmental impact of their products, manufacturers are starting to look at re-designing the disposable bottle to use less material or to utilize new innovations in plastics made from natural materials such as sugarcane, corn or cassava.

What about reusable bottles?

Reusable options range from plastic (polycarbonate or copolyesters) to metal (18/8 stainless steel or aluminium). In terms of materials, virgin aluminum is the worst offender in the greenhouse house stakes at 5.705kg carbon dioxide equivalents per pound of material.

If we compare this ‘worst case’ aluminium bottle to a disposable bottle that’s been engineered for lower impact we get interesting results. In 2007, Nestle launched a disposable PET bottle called ‘Ecoshape’ that uses 19.5% less material than previous bottles from the brand. The company commissioned a peer-reviewed study from Quantis to compare the impact of Ecoshape bottles with reusable aluminium water bottles. After considering the entire lifecycle of the bottles – including the source of the water, the energy required to manufacture the bottles, chemical usage from raw materials, regular washing and likely end of life of the bottles – they found that you would need to use an aluminium bottle approximately 50 times before the impact per serving of water is comparable to that of the Ecoshape.  

When the source of water it taken out of consideration, the reusable bottle becomes comparable somewhere between 10 and 20 uses, depending on the material, with plastic coming in as the lowest impact per use followed by steel then aluminium. However, these differences become barely distinguishable per use the more you use the bottle. So the good news is…if you used a reusable water bottle every working day for a month you would reduce its environmental impact per serving to a level that’s below disposable bottles. (If you read the Stuff versus Stuff feature on coffee, your disposable paper coffee cup has a greenhouse gas equivalent impact of 125g which is roughly equivalent to the Ecoshape.)

What happens when you’re done with the bottle?

Your actions mean a lot when it comes to disposal too. PET is relatively easy to recycle by crunching it up and melting it (or with newer chemical recycling processes), but just because a material can be recycled, doesn’t mean that it is. Only 29.1% of PET bottles and jars were recycled in 2017 according to the EPA – despite the fact that recycled PET attracts a higher price by weight than virgin PET. The problem is that the incentive does not reach the people who have the biggest capability to impact where bottles end up: individual consumers like you and me. We can improve the recycling rate of plastic bottles by making sure that they end up in the recycling bin.

Your stainless steel and aluminium bottle are also fully recyclable in theory, but harder to recycle in practice. Both materials need to be taken to a scrap metal recycler as they won’t be handled by a regular recycling plant (they can’t be crushed for processing). If the bottle has several different materials fused together, for example plastic embedded within a metal cap, they may be difficult to take apart and be sent straight to landfill.

The unfortunate truth is that often is it not the intrinsic properties of materials that define the impact of a product, but the choices we make when we manufacture, use and dispose of those materials.

What about the health impacts?

There are two main chemicals which have given plastic bottles a bad reputation. The first is bisphenol-a (BPA), which is known to disrupt the endocrine system leading to changes in the production of hormones. BPA is a stabiliser and plasticiser for plastics like polycarbonate and there was significant backlash about its use when it was found to be in commonly-used products such as baby bottles.

You might be surprised to find out that BPA is not used in the manufacture of PET, but it does contain multiple types of phthalates, which have been seen to affect the reproductive systems of laboratory animals. Storing water in PET bottles for a long time in a warmer environment, particularly if the PET has been recycled using thermal processes, can increase the level of phthalates released. While it’s still within acceptable levels for the amount of water you are likely to drink, this does mean that bottles which end up in the ocean are releasing these chemicals into the environment.

BPA may still be present in polycarbonate plastic reusable bottles, or aluminium bottles which have been lined with a resin coating, so when choosing a reusable bottle it’s worth looking for a BPA-free label even if the bottle is metal!

The other health concern is the hygiene of the bottle. A disposable bottle that’s only used once will have been handled hygienically at the factory, but a bottle you are using again and again can collect germs. A study from a gym in Brazil found E Coli bacteria on five out of 30 bottles tested. You can reduce this by cleaning your bottle regularly and choosing products which are easier to clean and don’t scratch easily.

In summary, the best bottle for you and the environment is the bottle that you pick once and stick with.

Recommendations:

• Pick a bottle you love and stick with it – even if that means saying ‘no’ to a free bottle you’re not going to use!

• Be efficient with cleaning by choosing an energy-efficient dishwasher

• Put your name on your bottle so you don’t lose it!

• Choose reusable bottles which are easy to take apart, ie. each part is made of one material.

• Reuse or donate your old bottles instead of sending them to landfill or recycling

With thanks to Jeremy Gregory for his advice.

Sources:

Cooper J E, Kendig E L, Belcher S M (2011) ‘Assessment of bisphenol A released from reusable plastic, aluminium and stainless steel water bottles’, Chemosphere

Keresztes S, Tatár E, Czégény Z, Záray G, Mihucz V G (2013) ‘Study on the leaching of phthalates from polyethylene terephthalate bottles into mineral water’ Science of the Total Environment

Papong S, Malakul P, Trunkavashirakun R, Wenunun P, Chom-in T, Nithitanakul M, Sarobol E (2014) ‘Comparative assessment of the environmental profile of PLA and PET drinking water bottles from a life cycle perspective’ Journal of Cleaner Production

Quantis (2010) ‘Environmental Life Cycle Assessment of Drinking Water Alternatives and Consumer Beverage Consumption in North America’