Even for glass it takes less energy to recycle it than to make it.
Remember, it takes more than just melting sand to make glass. Like for
metals, there is a lot of background work involved. Only very fine sand
is used to make glass, and there are people who make their profession
out of finding that sand. So in order to make glass, we have to provide
the energy to feed and take care of everything for those people. Then
we have to collect the sand. This also takes people and machines, and
the energy to support them.
Then the sand has to be transported to wherever it's going to be
used. (Remember - sand is usually found near the coast.) It takes a lot
of energy to support the people and vehicles that will move the sand to
where it will be used. With recycled glass, you still need to support
people to do the recycling, but not to go out and find the recyclables.
You don't have to transport the glass as far as sand.
There are so many different little things that use energy that go
into everything we do that it's easy to forget about a lot of them. For
example, it takes energy to transport the trees that will be made into
paper that will be printed into money that will be distributed to banks
so that it can go to pay the person who writes the paychecks for all
the employees of the company that makes the lunches for the company
that digs up the sand. ;)
Even at the simplest level, though, it takes less energy (less
heat) to melt glass back into liquid glass than it does to melt sand
into liquid glass.
Hope this answers your question.
(republished on 07/18/06)