Recycling glass as many already do isn't pointless, of course. Crushing up old bottles creates what bottlers call "cullet," which is considerably more energy efficient than raw starting materials for making new glass (plus it can be recycled infinitely without any loss in quality). But the difference isn't that large, because you still have to carry out most of the energy-intensive melting processes — meaning an energy savings of only about 13 percent relative to new glass. Aluminum is far better in recycling terms, because smelting it from raw bauxite ore requires a tremendous amount of energy — meaning a 92 percent energy savings for recycled cans relative to new ones.
All that changes when we start talking about re-use. For every time a glass bottle is washed out and sent back, its energy cost can be spread out over another use. A British study of soda distribution found that reusing a glass bottle just once would cut its climate footprint by 40 percent, and reusing it three times would make it about equivalent to aluminum cans and plastic bottles. After 10 reuses the decline has largely tapered off, as the energy cost of washing and transport begin to predominate.