Are Cans More Sustainable than Plastic Bottles?

Short History

Aluminium is the most abundant metal in the Earth’s crust (8.1%) but its rarely found uncombined in nature
1800 BC – earliest known production of steel
5 BC – Oldest reference of Alum by Greek Herodotus. Aluminium comes from Latin Alumen (Alum) and means bitter salt.
1808 – The name Aluminium was coined by Sir Humphry Davy. Aluminum is used in the US and Canada and aluminium is used elsewhere
1935 – Beer available in cans.
1958 – The first recyclable aluminium drinks can was made by the Adolph Coors Company
1961 – The easy-open end (or ring pull) was introduced.
1989 – The “stay-on tab” opening was launched.
1990 – Europe’s first dedicated aluminium can recycling plant opened in Warrington, Cheshire, able to recycle 8 billion cans a year!
2008 – Steel began trading as a commodity on the London Metal Exchange.

Success of Cans

Beer used to be sold in bottles or barrels before they were sold in cans. Cans had two advantages over glass bottles:

Distributors: flat-top cans were more compact for transportation and storage, and weighed less than bottles.
Consumers: cans did not require the deposit typically paid for bottles, as they were discarded after use.

What is the difference between aluminium and steel cans?

Aluminium cans are mainly used for drinks, steel cans for food.
Aluminium cans are more malleable and lighter than steel cans (aluminium is one-third as heavy as steel).
Aluminium cans do not rust or corrode.
Aluminium is an element (Al, atomic number 13), steel is an alloy made mainly of iron and carbon.
Aluminium cans are not magnetic, steel cans are magnetic.
Steel cans are made from tin-coated steel (which is why they are often called ‘tin cans’).
Aluminium is more expensive than steel.
Worldwide numbers: 75% of drink cans are in aluminium and 25% are in tin-plated steel.
Why do drink manufacturers prefer aluminium?
- Formability/workability of aluminium
- Ductility of aluminium (in terms of the container not shattering/cracking in transit)
- Inertness of the aluminium and little to no potential toxicity
- Corrosion-resistant
- Recyclability
- Branding – Aluminium is a versatile printing medium on which any novel illustration can be made

Coatings

There’s always a thin plastic layer (coating) inside drink cans to protect the food or liquid and to protect the cans from corrosion. Every soda contains phosphoric and citric acid and it’s thus necessary to add a hidden liner inside the can to prevent the beverage from reacting with the metal.

Coatings contain different additives, e.g. agents to increase surface slipping as well as abrasion and scratch resistance of can coatings, lubricants, anti-foaming agents, adhesives, scavengers for hydrochloric acids, and pigments.

Epoxy-based coatings have the highest market share (>90%). The problem is that epoxy contains bisphenol A (BPA) and leaching of BPA into the can’s contents has been recognised as a potential health hazard

Epoxy Alternatives

Acrylic and polyester coatings are currently used as first generation alternatives to epoxy coatings and, more recently, polyolefin and non-BPA epoxy coatings were developed.

Further inventions include BPA capturing systems and top coatings. Most of these alternative coatings are more expensive than epoxy coatings and may not display the same array of characteristics with respect to their stability and universal applicability yet.

Remarks

Initially I though that in some cases, aluminium and steel cans were more sustainable than plastic bottles.

I asked an Aluminium and Steel Can Association to publish an article or LCA to proof that aluminium and steel cans were more sustainable than plastics bottles. I was expecting to receive an enthusiastic reaction. However, they kindly refused. I found it a bit weird to refuse such an offer.

I’ve discovered why. There’s plastic in aluminium and steel cans. I’ve published another article on this There’s a Plastic Film in Every Can

Why would beverage cans use plastic? Well, plastic is a champion material.

Even aluminium and steel can producers cannot (1) compete with plastics or (2) pretend their packaging is more sustainable than plastics …. because they need plastic!

I’ve learned another trick. If they’re not ready to pay for the promotion of their technology or product sustainability …. it means that they’re not ready to put their money where their mouth is; and that tells us something about how they feel about their product or technology. Follow the money.

The truth, the whole truth and nothing but the truth.