The most thorough waste characterization study in Texas to date -- the
Cal Recovery Systems study for San Antonio, Texas in 1990 -- found
that glass containers made up 5.5% of the total materials destined for
area landfills that were sorted in this study. 3.3% was clear glass, 1.7%
was brown, and 0.5% was green. That means that of the glass
containers entering landfills, the proportions were about
60% clear glass
31% brown glass
9% green glass
For comparison, the report cited 3 other local studies which found glass
containers to be 7.6%, 3.3%, and 4.9% of the waste, respectively. None
of these other studies sorted glass containers by color.
Regarding the effort to estimate the composition of discards on the basis
of front-end sales or manufacturing data:
The widely circulated EPA national waste characterization data
generated by Franklin Associates are based on manufacturing and trade
data, attempting to estimate how much material actually is consumed in
the U.S. There are many difficulties with this approach, including:
1. Trade data rarely reflect tons of manufactured materials imported and
exported across national boundaries. They are generally in terms of
dollars.
2. Tonnage of materials going into products is only accessible at the
manufacturing stage, and not very precisely. Where the products go in
terms of tons rather than dollars is almost impossible to track to the state
or local level. As the variation in glass containers as a % of waste in
different cities shows, a per capita estimate is unlikely to be as accurate
as a waste sort.
3. Another big uncertainty is lag time -- how long materials stay "in use"
or in storage before being discarded. What % of today's discards were
manufactured in 1995, 1985, 1925? How much of that material has been
around the recycling block 2, 3, 4 times as different manufactured
products before ending up in a landfill?
4. EPA figures for waste characterization exclude several categories of
materials that end up in municipal landfills, such as construction materials
and "transportation equipment" materials.
5. There are also non-manufactured materials such as yard trimmings
and land clearing debris going into landfills for which there are no
production figures of any kind.
There are, nevertheless, some interesting categories of products, such
as alcoholic beverages by specific container type, that are tracked at the
state level (at least in Texas). They do not, however, add up to a
complete picture of even one recyclable commodity, much less the
universe of materials destined for landfills.