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Recycling Solid Wastes 139
● Mirrors
● Windshields and window glass
● Heat-resistant cookware (e.g., Pyrex )
● Light bulbs
● Clay garden pots
● Laboratory glass
Other contaminants include:

● Ceramic and wire caps for beer bottles
● Metal rings from wine bottles
● Metal caps, lids, and neck rings
● Food and dirt

Glass benefaction facilities (mentioned above) receive glass from community recycling pro-
grams and direct it through a sequence of steps to remove contaminants (stones, ceramics, and metal
caps). Metals are removed magnetically. Eddy current separators are used to remove nonmagnetic
metal contamination from caps and lids. An air classifier removes lightweight items such as loose
paper or plastics. These unit operations for waste separation are discussed in detail in Chapter 7.
Some contaminants are removed manually from mixed cullet; however, this is a slow and poten-
tially dangerous activity. The final product is a ground glass feedstock which is uniform in color
and free of contaminants, and readily acceptable by container manufacturers (CMI, 2002).
Preprocessors such as glass benefaction facilities provide a valuable market for recycling pro-
grams that do not produce the volume or have the ability to produce glass for direct delivery to a
mill. A clean feedstock at the outset of processing, however, is strongly preferred by the industry.

6.8.6 GLASS MARKETS
To be a competitive commodity, recycled glass must maintain a price that competes with raw mate-
rials. Crushed glass has a fairly strong and consistent market value compared with most postcon-
sumer recycling materials. Based on the discussion so far in this chapter, it is obvious that the price
paid for cullet will strongly depend on the color and cleanliness of the recovered product. Marketed
as flint (clear), amber (brown), emerald (green), or mixed color glass, the values range from $0 to
$65 per metric ton delivered to the glass plant. Clean flint cullet is the most desirable form of glass
scrap. Mixed color glass contaminated with food or ceramic fragments is the least desirable grade
of cullet and will bring the lowest price (GPI, 2002).

6.8.7 CONTAINER GLASS
Container glass is 100% recyclable, and glass containers can be recycled into new ones repeatedly.
There is no change in chemical or physical properties, and therefore no decline in quality with the
repeated recycling of cullet.
According to the Glass Packaging Institute (no date), glass collectors, haulers, suppliers, and
processors can reduce the risks and increase revenue by following some basic glass recycling
guidelines:

● Contact potential buyers for their specifications and acceptance policies, ability to
remove contaminants, transport preference (i.e., truck or rail car), and “furnace ready”
requirements.
● Ask about buyers’ capacity to remove metals.
● Conduct inspections regularly, especially before adding newly collected glass to stored
recyclables and during loading for shipment.