Yeah, I was mostly thinking along the lines of "is recycling a way to reduce energy use". Like, after Peak Oil, I doubt any recycling will be feasible because it will be too expensive to do. But really, I have no clue. I'm just curious what people think about it.
I can only speak about glass recycling but there it really makes a huge difference. To melt a glass from raw materials requires a lot more energy and higher temperatures than remelting an existing glass. Switching to a feed which partly consists of recycled material can lower your troughput times, and melting temperatures, and thus greatly reduce your energy needs.
For optical glasses recycling is not an option because you can't guarantee quality, but for containerglass it is perfectly suited. There are furnace designs which can handle an intake of 90% recycleglass.
To give you an idea on the amount of energy involved: A typical glass bath is 30 meters long 10 meters wide and 1 meter deep and running at 1600°C. It consumes as much gas and oil as a large town. A typical glass plant has 2 or 3 of these baths in operation 24/7.
Of course when you want to recycle you need to collect and transport the used glass. Moreover you have to clean it from organic debris before you can allow it in the furnace. That is going to consume some energy.
However to make new glass you need to ship quartz sand from the middle east to your furnace so there is no real transport benefit in not-recycling.