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[greenyes] More on Single Stream and Related Issues
On 4/14 (I'm just catching up), Wayne Turner asked a number of questions
concerning glass breakage during collection and in relation to single stream

One of the things that's happening in this discussion is that many distinct
collection program elements are being mixed together under the single stream
umbrella.  These include the issue of semi-automated and fully automated
collection and the concept of compaction on recycle vehicle, or more
particularly, light (or is it "lite")-compaction -- and all in relation to
glass breakage.

It must be understood that each of these may or may not be included in
single stream, and similarly, may or may not be included in two stream
programs. (There are two areas where single stream is unique, described
below, but they are not on the list that has been discussed to date).

The only place where they tie together is that single stream -- when done by
national garbage companies whose economic interests are antithetical to
recycling -- seems to pick the worst combination of them all when operated

There are three ways that all of these things can impact collection
efficiency for good or bad:

    1.  PICKUP RATES.  The speed with which recyclables can be loaded onto a
truck tends to increase when (a) automation is used, and (b) the number of
different receptacles that the recyclables are set out in are reduced (this
is the only element in all of this discussion which is limited to single
stream).  Of course, all of this, the ensuing discussion amply described, is
at the expense of much higher contaminant levels, LA being an unfortunate
graphic case in point, especially for full automation.

    2.  COMPARTMENTS.  Single stream reduces the number of compartments on
the truck from two to one.  Since each compartment will tend to fill at a
different rate on different days and routes, when one tops out and requires
the vehicle to go off route to empty, the other will not be full, lowering
overall truck utilization, probably to 80% of the nominal capacity. This is
unique to single stream.

    3.  COMPACTION.  This is very important and has not been explicitly
mentioned yet.  Recycle trucks have topped out at less than 5000 pounds,
while trash trucks carry 15,000-20,000 when they off-load, which is a key
indices of collection efficiency.  Light compaction,which is almost always
utilized with single stream, but can be added by two-stream programs as
well, can nearly double recycle payloads.  However, although we have run
sophisticated field tests that demonstrated that lite compaction need not
increase glass breakage if done correctly, if overpacking is resorted to,
all bets are off.  We have two major data filled studies on this for anyone
interested that were reported in:

"The Impact of Light Compaction on Curbside Recycling Collection," Resource
Recycling (May 1996).
"Glass Compaction: Defining the Possibilities," Resource Recycling (May

I hope this helps refine the discussion.


Peter Anderson
4513 Vernon Blvd. Suite 15
Madison, WI 53705
Ph:    (608) 231-1100
Fax:   (608) 233-0011
Cell    (608) 438-9062
email: anderson@no.address

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