Save Energy and Don't Trash That Can

Embedded energy in Aluminum form | Photo: Ishikawa Ken/Flickr/Creative Commons License

Let's take a few minutes to celebrate the people on the front lines of the Clean Energy revolution: the people who climb on your tall roof to put up those solar panels. The activists who lobby for better renewable energy policies. The scientists and engineers working to make solar panels more efficient, and LED lightbulbs cheaper. The people protesting against mountain top removal mining. The guy on the streetcorner pulling aluminum cans out of the trash.

Wait, what?

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We mainly think about energy use when we're the ones using the energy directly: turning light switches on and off, paying our heating bills, driving the H2 down the block to buy a candy bar. But almost everything we encounter in our lives comes with its own energy footprint. We use energy to gather and process raw materials, manufacture goods, and ship them to where the end-users are. Some people call this "embedded energy," a helpful image: each thing we own has energy embedded in it, an energy footprint that the object carries around with it like the chains Jacob Marley's ghost carried around in "A Christmas Carol."

And one of the most energy-intensive things we encounter in a typical day is the common aluminum can.

Aluminum is an extremely common substance: it's the third most abundant element in the earth's crust. The problem is that aluminum as found in nature, usually in the form of bauxite, is very tightly bonded to the most abundant element in the earth's crust, namely oxygen. (Silicon is number two, if you're wondering.) In order to get metallic aluminum out of aluminum oxides like bauxite, we have to break the chemical bonds between the aluminum and oxygen atoms.

That process takes energy -- a lot of it. Averaged worldwide, the typical amount of energy it takes to refine a kilogram of aluminum is about 15 kilowatt-hours of electricity.

A typical beverage can weighs about 13 grams these days. That's about 15 percent lighter than the aluminum cans your grandparents drank out of in the 1990s: it takes 77 modern soda or beer cans to make a kilogram.

Even with less aluminum in them, beverage cans still represent a significant amount of embedded energy: just under 200 watt-hours each.

If you throw that can away, in other words, the smelters use 200 watt-hours of electricity to refine enough aluminum for a new can. That's not counting the energy spent mining, transporting the ore, and shipping the raw aluminum to the can factory.

If you recycle it, though, the can merely needs to be melted down and reformed, which takes about 5 percent as much energy as refining the same amount of metal from Bauxite.

Which means that that 30-pack of PBR you neglected to recycle after your party wasted enough energy to leave your 75-watt incandescent black light bulb burning for three days.

Another way to look at it: not recycling an aluminum can wastes energy equivalent to filling that can halfway with gasoline, then pouring the gasoline on the ground. Which ReWire doesn't recommend.

So here's to the clean energy heroes who pull those energy-intensive cans out of the trash and haul them off to the recycling center. We really should pay them better.

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For ongoing environmental coverage in March 2017 and afterward, please visit our show Earth Focus, or browse Redefine for historic material.
KCET's award-winning environment news project Redefine ran from July 2012 through February 2017.

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