[Sparkologist]

Irrespective of what has previously been in any returned bottle they are sterilised before being re-used, if they are in fit condition to do so. If any glass is melted down to be recycled, the expense is for heating the furnace and running the casting machinery, natural resource in the form of raw product is not used. I have seen this in operation whilst working at Beatson & Clark's bottle plant in Rotherham.

Even if a shop retailer were to add the cost of a deposit to the price of a bottle of pop or beer, it would add an incentive to return the bottles. When I was a kid, I used to take my dad's Crystal Ale bottles back to the off-licence on Commercial St in Ossy, to collect the deposit which was mine to keep.
The deposit system was alive & kicking whilst we were on holiday in New Zealand earlier this year.