Page 433 - Solid Waste Analysis and Minimization a Systems Approach

POTENTIAL TECHNOLOGIES, STRATEGIES, AND APPROACH 411

31.4 Potential Technologies,

Strategies, and Approach

In all of the processes used to convert plastic raw materials into end products there is
an inevitable arising of some scrap material. This results from the start-up and shut-
down periods of the processing machinery, from out of specification products, and
from quality-control samples. Material of this type is termed industrial scrap. Almost
all molding companies recycle their own plastics waste, or scrap, in house. The spe-
cialist plastics recycling industry also recycles material of this type, mostly skeletal
waste from thermoforming and off-specification moldings.
Mechanical recycling is where the plastics, which soften on heating, are,
reformed into molding granules to make new products. The process involves col-
lection, sorting, baling then size reduction into flake (film and sheet) or granules,
which may then need washing and drying. This is then recompounded with addi-
tives and/or more virgin raw material, extruded and chopped into pellets ready for
reuse. Feedstock or chemical recycling is where the plastics are broken down into
their chemical constituents usually by heat and pressure. Good design for recycling
should:

■ Allow for easy disassembly of a product into its component parts
■ Avoid the use of too many different types of plastic

Markets for some recycled plastic resins, such as PET and HDPE, are stable in most
geographical areas in the United States and are expanding in many others. Currently,
both the capacity to process postconsumer plastics and the market demand for recov-
ered plastic resin exceed the amount of postconsumer plastics recovered from the
waste stream. The primary market for recycled PET bottles continues to be fiber for
carpet and textiles, while the primary market for recycled HDPE is bottles, according
to APC.
In the future, new end uses for recycled PET bottles might include coating for cor-
rugated paper and other natural fibers to make waterproof products like shipping con-
tainers. PET can even be recycled into clothing, such as fleece jackets. Recovered
HDPE can be manufactured into recycled-content landscape and garden products,
such as lawn chairs and garden edging.
The plastic lumber industry also is beginning to expand. New American Society for
Testing and Materials (ASTM) standards and test methods are paving the way for use
of these materials in decks, marinas, and other structural applications for both resi-
dential and commercial properties.
Source reduction is the process of reducing the amount of waste that is generated.
The plastics industry has successfully been able to reduce the amount of material
needed to make packaging for consumer products. Plastic milk jugs weigh 30 percent
less than they did 20 years ago. Plastic packaging is generally more lightweight than
its alternatives, such as glass, paper, or metal.