Sometimes it is nice to look beyond one's own subject (mechanical engineering) and find that others are getting things completely wrong: As in recycling and energy (HT: Division of Labour).
"Recycling one aluminum can will save 95% of energy rather than
extracting aluminum from a bauxite ore. This amount of energy saved can
light the city of Pittsburgh for six years." How big is this can you
Here we have some really intriguing mistakes. It'd be right if he had written it the other way round, because the recycling of aluminium is NOT saving any energy, instead we have to USE energy to change the material back into its raw shape. So, recycling aluminium is at least as expensive as extracting aluminium from ore. But as it is with all recycling methods, they are overly expensive. To generate energy out of carbon-products, we would have to sell it for a price ten times higher than just burning fresh oil. With bauxite and aluminium, we have the same problem. The recycling of aluminium is certainly an option, but it doesn't SAVE any energy. Even less will one can be enough for a whole town (it won't even be enough for a house, because it doesn't save any energy).