> I really don't know what people objecting to this imagine typically happens to old, unwanted books.
In the UK at least, people usually take them to a second hand / charity shop, who sort through them and send the valuable ones to auction (typically early editions, 100+ years old) and then either sell them themselves (for recent books that are easy to get rid of) or sell them to specialised second-hand bookshops.
Most of the specialised second-hand bookshops rarely throw books away, usually if nobody buys them after a couple of years they end up in the extreme discount piles (20p, 50p etc) and probably only trashed if they still don't sell from there.
In the UK at least, people usually take them to a second hand / charity shop, who sort through them and send the valuable ones to auction (typically early editions, 100+ years old) and then either sell them themselves (for recent books that are easy to get rid of) or sell them to specialised second-hand bookshops.
Most of the specialised second-hand bookshops rarely throw books away, usually if nobody buys them after a couple of years they end up in the extreme discount piles (20p, 50p etc) and probably only trashed if they still don't sell from there.