Glass
has the least volatile pricing of all the post consumer
recycling commodities. Composed of sand and potash; bottle
glass is made from readily available and inexpensive raw
materials. To be competitive, recycled glass must maintain a
price that competes with these abundant raw materials. Traded
as flint (clear), amber (brown), emerald (green) or mixed
color broken glass the value ranges from $0 and $65 US per
metric ton delivered to a glass plant.
The
price depends on the cleanliness and color of the recycled
product. Clean flint cullet (another
word for broken glass) is usually the most desirable form of
recycled glass scrap. Mixed color broken glass with ceramics
or stones mixed in it is the least desirable grade of cullet
bringing the lowest price. Most Recyclers will color sort and
break or crush and screen bottles before selling their
product.
Modern,
high production bottle manufacturing requires very clean and
uniform feedstock. Over the past decade there has been a
growth in the glass benefaction sector. These are intermediate
processors that receive glass from recycling programs and run
it through a series of steps to remove any contaminants
(rocks, ceramics, metal caps, etc.) and provide a uniform
feedstock to the bottle manufacturers. These preprocessors
provide an excellent market for recycling programs that do not
have the volume or ability to produce glass for direct mill
delivery.
Glass
beneficiation plants use sophisticated optical sorting
machines to separate the glass into the three color types.
They may also x-ray the glass to detect any rocks or ceramics
which are then removed. Magnets and eddy current separators
are used to removed magnetic and non-magnetic metal
contamination from caps and lids. The end product is a
uniformly sized load of ground glass that is free of
contaminants readily acceptable by bottle manufacturers.
Lower
grades of recycled glass that are too mixed or contaminated,
may be used in concrete or in road paving material called "Glassphalt".
In some areas where there is an overabundance of low grade
glass it is used to cover over the rubbish in the land fill in
place of sand. This is not truly recycling and it is hoped
that better sorting technology will soon make this material
usable for new bottles.
Glass recycling saves energy because
recycled glass can be processed at a lower temperature than
blending new glass from raw materials. Also, recycled glass is
usually closer to the bottle plants than the sources of
potash, the most expensive component in glass bottles and
jars.
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