It takes far less energy to recycle an aluminum can than to make one from scratch – recycling 40 Aluminum cans is the equivalent of saving a gallon of gasoline. One problem is that not all of the can is Aluminum.
[R]ecycling the cans turns out to be harder than it looks, because the basic soft drink or beer can is actually made of two kinds of aluminum. The bottom and sides are made from an aluminum sheet that is strong enough to be stamped into a round shape without tearing. For the top, which must be stiff enough to help the can retain its shape and withstand the bending force when it is opened, can makers blend aluminum with magnesium.