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128 Waste Management Practices: Municipal, Hazardous, and Industrial
required to purchase paper manufactured containing a specified percentage of recycled fibers. By the
early 1990s, most states had established regulations addressing waste recycling. As a result of such
incentives and pressures, many industrialized nations have established innovative and proactive recy-
cling strategies.
There are two primary approaches to the segregation of MSW for eventual recycling: source
separation and the MRF. Source separation includes the segregation of specific waste components
by the individual homeowner and commercial establishment. (i.e., at the source). The individual
products (e.g., aluminum cans, paper, glass, and plastics) are collected and transported to a facility
for further processing such as densifying and shredding. These slightly processed, clean materials
are then sold to and removed by brokers or manufacturers. In contrast, the MRF is a centralized and
mechanized facility which accepts either raw (“commingled”) MSW or source-separated materials.
The mixed items are placed on conveyor belts where specific recyclables are removed at various sta-
tions, either by hand or by a specialized mechanical device. Both source separation and MRF meth-
ods differ drastically in terms of efficiency of separation, capital costs, labor costs, energy use, and
other factors. The MRF will be discussed in the next chapter.

6.2 RECYCLING TERMINOLOGY
Several terms related to recycling are often misused; in order to avoid confusion, it is important at
the outset to clarify some of the relevant language.
Source separation — Removal of potentially recyclable materials from the waste stream.
Conducted by the individual consumer and commercial establishment (Figure 6.1).
Reuse — Using an item for its original purpose. A common example is refilling a returnable
soft drink bottle.
Recycling — Use of a material in a form similar to its original use. Newspapers are recycled
into cardboard or new newspaper. Plastic is shredded and manufactured into fabric. Aluminum win-
dow frames are converted into new beverage containers.
Waste-to-energy — The conversion of MSW (preferably the organic fraction only) into energy
by combustion in a controlled incinerator. Energy is recovered as heat and can be utilized directly;
however, some facilities convert the heat energy into electrical energy.

FIGURE 6.1 Drop-off centers are one means of segregation of MSW components.