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Re: [greenyes] The big picture on glass
Sharon Gates posted:

"There is a piece of the "big picture" that nobody has mentioned in
this 
recent discussion of glass:  energy costs/savings."

A few months ago, when the issue of glass recycling was being discussed
on this list, Jeff Morris made a case to keep glass on the recycling
truck through an analysis of the internal/external costs/benefits.  I
thought I'd kept that post but can't put my hands on it.  Maybe he will
jump into this discussion thread and refresh our memory.

"The issue is how to recycle glass in such a way that it doesn't
contaminate other 
materials in the recycling stream."

In my experience with single-stream, fully automated collection program
using large carts (which was one of the factors that Peter initially
pointed out), glass breakage is almost impossible to control under
current circumstances.  First, it breaks when it is dumped into the
truck - suffering from a 6 - 8 foot drop onto the hopper floor.  The
hopper isn't always carpeted with other recyclables if the driver packs
the load.  This brings up the next issue of breakage.  Many drivers are
simply not trained or allowed to run their routes without packing up
frequently.  Packing up does two things.  It breaks more glass but keeps
the hopper clear and thus reduces the amount of paper that flies from
the truck during transit.  Next, when the truck tips the load onto the
concrete floor at the MRF, there is more glass breakage.  There was a
study several years ago about a MRF in Illinois (I think) that used a
ramp for tipping the load.  The load 'rolled' downt he ramp, thus
reducing the glass breakage.  I don't know if that tipping method is
still in use and has spread or not.  Anyone have any knowledge?

The rubber tired loader at the MRF is the next threat to glass.  As it
is being pushed from the tipping area to the infeed conveyor, breakage
occurs yet again.  Once on the conveyor, glass is relatively safe from
breakage, but how many whole glass containers are left to sort?  As I
pointed out in my last post, a conservative estimate is that no more
than 50% is left to sort.

So, even if we all agree that it is economically worth it to keep glass
on a single-stream, fully automated recycling truck, system-wide changes
will have to be made to keep the glass in a state that will allow it to
be recoverd at its highest value.  It seems to me that a redesigned
truck could hellp a great deal since during collection and transit most
of the breakage of glass occurs.  To my knowledge, most fully automated
recycling trucks are simply garbage trucks that are pressed into service
to collect recyclables.

One other point.  How many jurisdictions out there pay their MRF
operator per ton to process their materials?  And how much of the glass
is recovered?  Every ton of non-recovered glass is a ton for which the
processing fee was paid without the benefit on any revenue being
returned, unless there is some form of credit from the MRF for residue. 
MRFs that accept single-stream loads with glass delivered already broken
probably would not be willing to issue a credit for the fraction of
residue composed of broken glass.

"I have heard of places that have single-stream-except-glass collection
and have drop-off locations for 
glass."  

This certainly sounds like a viable alternative.  Are there many
jurisdictions doing this?  I think Orange County, NC has a special glass
recycling drop-off system for bars and restuarants.  This kind of system
may reduce the total amount of glass recycled in a single-stream program
but it would probably not reduce the total amount processed for markets.
 In fact, it may bring in the bar and restaurant crowd, large consumers
of glass containers.




B. Wayne Turner
City of Winston-Salem
Utilities Division
phone: (336) 727 8418
email: waynet@no.address

"Experience is what allows us to recognize repeated mistakes."





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