Aluminium cans

"manufacturing aluminum cans is so challenging, and requires such a vast amount of study, design, and precise machining, that many consider cans the most engineered products in the world." Jonathan Waldman - Wired

I walked from the main road to home this morning, and inevitably as I walked I saw the occasional discarded aluminium can. Mea culpa - I did not pick them up. Note to self, when going for a walk always take a plastic bag so that you can pick up cans and bottles discarded along the way. Although, carrying a heavy bag would be a pain. Although if you just stuck to cans and plastic they wouldn't be that heavy. That's one of the pluses of the aluminium can. Actually I did not see that many cans. In fact, by the time I had decided to write about them and thought I would photograph some, I saw no more.


They're tricky aren't they - aluminium cans? They are, after all, eminently recyclable, and indeed it turns out they are the most recycled thing in the world. Apparently 69% of cans worldwide are recycled - more in some places than others of course, but still, that's a lot. And yet to produce aluminium is one of the most energy hungry and emission producing things we can do.


So why don't people recycle them? Why do they just throw them away wherever they happen to be? My son's building site had several scattered around the site, left by the various workers. I mean it's easy to recycle them these days isn't it? You jut put them in your recycle bin. And yes I know that at the moment we can't actually be sure that what goes into those bins will be recycled because of China's ban on importing our waste, but eventually I imagine we will be doing it ourselves. It's got to be a business opportunity for some forward thinking company surely?


In times gone by we used to get paid for recycling them. I remember when our kids were small they would collect them and keep the (very small) bounty they got for them for themselves. If you went to a big public event there would be quite a competition to collect the cans. Not so now. But then, I guess we have those recycling bins, which we didn't have then.

The cans are then compressed and sent away for recycling.

Aluminium cans are not really that old. They were invented back in 1957, and then in 1962 Alcoa created the 'easy open' can - which I guess means that pull tag thing on the lid. And they're great aren't they? They are light, the shape is pleasing and you can cool your drinks down. It is also much nicer to drink from a can than a plastic bottle. Not that aluminium cans are only used for drinks of course. Food is also put into aluminium cans, although I have to say I cannot think of any food that comes in an aluminium can. Food seems to most come in steel cans.


It's not as simple as just making a can from a sheet of aluminium though. They have to be coated inside because otherwise the cans would corrode and eventually explode, or at the very least leak. And it turns out that different foods and beverages corrode differently. Rhubarb is the worst, beer is the best - which is why beer is so often in cans.


"It turns out that cans were made for beer, and beer was made for cans. In fact, the only reason beer cans have a coating at all is so that the carbon dioxide doesn’t escape at once. The coating smoothes out the surface of the metal, so that the gas has no microbumps from which to propagate." Marc Gunther - The Guardian


Products with a lot of sugar do not corrode as badly as acidic ones. In fact:


"some beverages are so corrosive that no amount of coating will protect their cans. (Roughly one in seven new energy drinks are too corrosive to put in cans.)" Marc Gunther - The Guardian


Those coatings are thin but, of course, made of some kind of chemical - epoxy resins I think. Sorry I didn't really understand all of this, but if you read Jonathan Waldman's and Marc Gunther's articles all will be made clear. And a lot of research has gone into it.


"for nearly every variety of food or beverage, there’s a coating that’s been devised just for it." Jonathan Wladman - Wired


It is not a case of one coating does for all. It turns out there are at least 15,000 different coatings! Which would lead to complexity in manufacturing. You don't just have to change the pretty picture on the outside.


Nevertheless aluminium cans are recyclable, and indeed are potentially infinitely recyclable. A recycled can can be recycled again. The Guardian article explored one particular company Novelis, which apparently has set up an enormous plant in Germany. I mean enormous. Billions of dollars involved. They claim that 90% of each can is made of recycled material. And yet, at the time of the writing of the article, they could not persuade the big users - Coca Cola, Pepsi Cola and Buddweiser to use their cans. From the cagey answers the reporter got from Coca Cola and Pepsi it sounded as if the reason was either price - in which case there is probably bargaining still going on, or the fact that the buyers would need to commit to just one supplier. Not a good idea as Australia's current problems with China shows.


On the plus side though, at the moment most of the aluminium that Novelis produces is used by car makers, who apparently have all sorts of interesting ideas for what to do with it.


I did also see another article that posed the dilemma between recycling plastic and recycling aluminium. Plastic (and glass) cannot go on being recycled, and is usually recycled into some other kind of product. So you have to go on making new plastic bottles and containers. However it produces less carbon emissions and is more energy efficient. So I guess this is yet another example of the old adage - you just can't win. Well until somebody either solves the problems or finds another reusable, environmental friendly product altogether. Or we stop drinking beer and Coca-cola. No that's not going to happen.


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