Materials Characterization Paper

In Support of the

Advanced Notice of Proposed Rulemaking –

Identification of Nonhazardous Materials That Are Solid Waste

Secondary Glass Material - Used as ingredient in glass manufacture

December 16, 2008

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1.	Definition of Secondary Glass Material

Secondary glass material consists of both post-consumer (MSW) glass as
well as post-industrial glass (i.e., glass scrap generated in the
process of glass material manufacture. Glass in the MSW stream includes
glass containers and packaging as well as glass used in durable goods,
such as furniture, appliances, and consumer electronics. Post industrial
glass includes fiber scrap from fiber glass and fiberoptics
manufacturing processes as well as internal container glass scrap.

2.	Annual Quantities Generated and Used

Sectors that generate secondary glass material: 

Secondary glass material is generated by NAICS sector 3272, Glass and
Glass Product Manufacturing.  Secondary glass material can also be
collected as part of municipal solid waste streams (MSW), but the focus
on this paper is on the industrial product.

Quantities and prices of secondary glass material generated:   

EPA estimates that 13.6 million tons of glass packaging and other glass
scrap material was generated in 2007 (EPA 2007).

In addition, one report addressing the glass industry estimates that
more than 60,000 tons of “glass-manufacturing scrap” are generated
annually (Argonne National Laboratory). It is unclear if other process
steps in glass manufacturing generated additional quantities of scrap,
and it is also unclear whether this scrap includes or excludes scrap
that is internally reused in manufacturing.  This estimate does,
however, exclude scrap from fiberglass manufacturing, and appears to
exclude secondary glass from post-consumer sources.  

The report further estimates that an additional 200,000 tons of
fiberglass scrap is annually generated during the manufacturing of
fiberglass products (Argonne National Laboratory).

Glass pricing information is available in some cases for post-consumer
MSW glass, but is not available specifically for industrial scrap.  It
is possible that  industrial glass scrap has a different pricing
structure, due to differences in composition, quality, product
consistency, and contamination.

Trends in generation of secondary glass material:  

Differences in trends between different types of glass could not be
identified at this time.  

3.	Uses of Material/Commodity

Ingredient uses of secondary glass material in combustion processes:  

Glass-to-glass processing is generally the most environmentally
beneficial recycling option, other things being equal.  Ninety percent
of recycled MSW glass is used to make new glass containers. Today, most
glass manufacturers rely on a steady supply of recycled crushed glass,
known as "cullet," to supplement raw materials. To make glass,
manufacturers mix sand, soda ash, limestone, and cullet; heat the
mixture to a temperature of 2,600 to 2,800 degrees F; and mold it into
the desired shape. Sand is the only material used in greater volumes
than cullet to manufacture glass.

Attempts by the glass manufacturing industry to recycle secondary glass
fiber material back into fiber glass and fiberoptics production
processes have failed in the past because they have resulted in an
unacceptably high rate of filament breakage in the subsequent
glass-manufacturing processes. This breakage rate is due to the presence
of impurities in the secondary glass fiber material.   It is not clear,
however, whether these problems prevent the use of this material in
other types of products

Other uses of secondary glass material:

Other uses of high-quality cullet include use as abrasives, aggregate
substitute, bead manufacturing, kitchen tiles, counter tops, wall
insulation, frictionators (match tips), fluxes in metal foundry work,
and roadbed aggregate.

Quantities of secondary glass material landfilled: 

The recycling rate of glass in the MSW stream in 2007 was 23.7 percent. 
Of the 13.6 million tons of MSW glass and packaging generated in 2007,
10.36 million tons were landfilled and 3.22 million tons were recycled
(EPA 2007).

At this time, we have not determined landfill quantities of other glass
types, such as fiberoptic material and glass manufacturing scrap that
never enters the MSW stream.  At most, according to the report by
Argonne National Laboratory, these quantities would be roughly 260,000
tons for fiberglass and other glass manufacturing scrap.

Quantities of secondary glass material stockpiled/stored:

Estimates of the quantity of secondary glass material being stockpiled
could not be identified at this time, but because disposal of these
products is not restricted and the market for secondary materials has
generally been strong, little incentive exists to create stockpiles.

Exhibit 1:  Overview of Generation and Use of Secondary Glass Material

Commodity	Annual Quantity Generated 	Annual Quantity Used as Ingredient
Annual Quantity Landfilled	Annual Quantity in Other Uses	Total Quantity
Stockpiled



Glass Furnaces	Other





-------------------------------------- Short Tons per Year
--------------------------------

MSW Glass	13.6 million	2.90 million*	Undetermined	10.36 million	0.32
million	Undetermined

Glass manufacturing scrap	60,000	Undetermined	Undetermined	Undetermined
Undetermined	Undetermined

Fiberglass manufacturing scrap	200,000	Undetermined	Undetermined
Undetermined	Undetermined	Undetermined

*Calculated using EPA data (EPA, 2007) and the EPA estimate that 90% of
MSW glass is used to make new glass containers (EPA, 2008).  All other
ingredient uses are included in the “Other Uses” category.

Sources:

EPA 2007, 2008

Argonne National Laboratory



4.	Management and Combustion processes

Types of units using secondary glass material:

Secondary glass material can be used in glass furnaces in place of
virgin raw materials in glass manufacturing, though particular types of
scrap (e.g., from fiberglass) appear to be difficult to use in certain
applications.

Sourcing of secondary glass material:

In terms of industrial glass production, typically the same glass
manufacturing facility that produces secondary glass material reuses it
in their glass manufacturing processes; it is not clear to what extent
this feedstock is considered scrap.  Glass manufacturers can also buy
recovered glass (cullet) on the commodity market; much of this glass is
recovered from municipal solid waste streams and traded by municipal
recycling facilities (MRFs) or by brokers.

Processing of secondary glass material:  

Although all glass is made of silica and soda, the type and quantity
vary slightly with different types of glass. These differences
frequently cause manufacturing problems due to different melting points
and chemical incompatibility. In addition, since neither brown nor amber
glass is used to manufacture clear glass, it is important to sort glass
by color. After color sorting, glass is typically crushed and travels by
conveyor belt through a series of refinements. Magnets pull out metal,
and air currents remove lightweight material such as paper (EPA 2008).

Some cullet suppliers use sophisticated equipment such as lasers to sort
colors of crushed glass and further remove small contaminants.
Scientists continue to develop mechanisms to improve materials sorting,
and, therefore, the quality of the cullet (EPA 2008).

Argonne National Laboratory is developing a technology that will enable
the glass fiber industry to recycle its glass-fiber-forming and
fiberglass-manufacturing scrap into new glass products without either
adversely impacting its operations, or the quality of its products due
to the increasing glass-filament breakage rate (Argonne National
Laboratory).

State status of secondary glass material use as ingredient:  

At this stage we have not identified any states that have approved use
of secondary glass material in glass manufacturing, but we have not
performed an exhaustive investigation of state activities and
regulations.  The practice of glass-to-glass recycling is commonplace,
although manufacturers of CRT glass are now generally located outside of
the United States. Under federal regulations, processed CRT glass sent
to a glass manufacturer is not a solid waste, and it is unlikely states
consider this a process that falls within their solid waste
jurisdiction.

5.	Commodity Composition and Impacts

Composition of secondary glass material:

Common glass contains about 70 percent silicon dioxide. In addition,
other compounds used in glass manufacturing are present in the final
glass product. Soda ash (anhydrous sodium carbonate) acts as a fluxing
agent in the melt. It lowers the melting point and the viscosity of the
formed glass, releases carbon dioxide, and helps stir the melt. Either
limestone or dolomite are sometimes used in lieu of soda ash. Alumina,
lead, and cadmium are used to increase the strength of the glass and
increase resistance to chemical attack. Various iron compounds, chromium
compounds, carbon, and sulfur are used as coloring agents (Turner
Fairbank Highway Research Center).

The major contaminants present in glass-manufacturing material from the
fiber-optics industry include:  carbonaceous material, tiny noble metal
particles, as well as trace amounts of Zr, Sr, Cr, Cu, Mg, Zn, Fe, Ba,
V, and Mn (Argonne National Laboratory).

Impacts of secondary glass material use:

Using cullet saves money and helps the environment. Cullet costs less
than raw materials, prolongs furnace life since it melts at a lower
temperature than sand, and demands less energy. Avoided energy use
results in reduced emissions of nitrogen oxide. Use of cullet also can
reduce the unit consumption of virgin glass materials (primarily sand).

The specific lifecycle impacts of cullet use as a raw material in glass
manufacturing are not evaluated here because of uncertainties in
lifecycle scenario development. For example, it is difficult to
determine the replacement ratio between cullet and other raw materials
in glass production. Thus, the correct quantity of material to be
modeled is unclear.

The ability to use recycled glass fibers in fiber optic applications
lowers energy costs by an average of $3-$8 per ton of glass fibers, when
compared to using virgin raw materials. If these glass material streams
are recycled, the glass industry will annually save over $2 million in
energy costs and over $5 million in disposal costs. Associated with the
energy savings is also a significant reduction in NOx emissions (Argonne
National Laboratory).



References

Argonne National Laboratory, Energy Systems Division, Recovery and
Recycling of Glass Manufacturing Waste and Fiberglass Scrap, accessed
at:   HYPERLINK
"http://www.es.anl.gov/Energy_systems/Process_Engineering/Technologies/D
ocuments/8-Glass%20Recycling-2003.pdf" 
http://www.es.anl.gov/Energy_systems/Process_Engineering/Technologies/Do
cuments/8-Glass%20Recycling-2003.pdf . 

Turner Fairbank Highway Research Center and the Federal Highway
Administration, User Guidelines for Waste and Byproduct Materials in
Pavement Construction, accessed at:   HYPERLINK
"http://www.tfhrc.gov/hnr20/recycle/waste/begin.htm" 
http://www.tfhrc.gov/hnr20/recycle/waste/begin.htm .

United States Environmental Protection Agency (EPA). 2008, “Municipal
Solid Waste: Glass,” accessed at:   HYPERLINK
"http://www.epa.gov/osw/conserve/materials/glass.htm" 
http://www.epa.gov/osw/conserve/materials/glass.htm .

United States Environmental Protection Agency (EPA). 2007, “Municipal
Solid Waste Generation, Recycling, and Disposal in the United States:
Facts and Figures for 2007.” Available at:   HYPERLINK
"http://www.epa.gov/epawaste/nonhaz/municipal/msw99.htm" 
http://www.epa.gov/epawaste/nonhaz/municipal/msw99.htm 

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