Page 80 - Solid Waste Analysis and Minimization a Systems Approach

58 BACKGROUND AND FUNDAMENTALS OF SOLID WASTE ANALYSIS AND MINIMIZATION

squeeze out more water, some heated cylinders, which dry the paper, and an iron
roller, which irons the paper. Next, the paper is wound into a giant roll. One roll can
be as wide as 30 ft and weigh as much as 20 tons. The roll of paper is cut into smaller
rolls, or sometimes sheets, before being dispatched for use.

2.8.6 PLASTIC RECYCLING

Plastic recycling can be separated into six steps

1 Sorting
2 Shredding
3 Cleaning
4 Melting
5 Extrusion
6 Pelletizing

Plastics are synthetic polymers made from oil and natural gas and are one of the
world’s most used raw materials. Plastics are blended in different formulas and mod-
ified with additives to create the 40 categories of plastic and the several specific grades
within these. All plastics are labeled with an identification code, a number from 1 to 7.
Before plastics are processed, they are sorted into seven different polymer types. The
polymer type indicates both the properties and characteristics of the material, such as
the melt temperature and its suitability for recycling. The symbols used to classify the
different polymer types can be found on the plastic bottles. The seven different poly-
mer types have been listed in detail in Chap. 1.
Once sorted, the plastics are baled before being transported to a plastics reprocess-
ing plant. Once at the reprocessing plant, the plastic is shredded into small pieces
which are then washed. After washing, the plastic pieces are passed under a metal
detector to remove any metal, and a de-dusting unit, which removes any lighter
particles.
The clean plastic pieces are dried and melted so they can be made into new
shapes. The melted plastic is then filtered to remove any remaining contaminants
and extruded to form fine spaghetti-like strands. The plastic strands are then cut
into pellets, cooled in water, then dried and stored ready to be processed and
molded as new plastic items.

2.9 Common Problems and the

Human Factors of Recycling Systems

There are many common problems involved in creating a successful recycling pro-
gram. The two biggest problems found in the duration of this research were material
misplacement and hindrances inherent in the company itself.