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disadvantages of plastics and other synthetic into gasoline or diesel fuel. The other main family of petrochemicals is
materials: production and recycling are energy- the aromatics family (named for its sweet cotton-candy-like odor), com-
intensive; low absolute tensile strength; soft monly referred to as BTX molecules (for benzene, toluene and xylene).
(making them subject to surface scratching); These molecules are suitable for blending into transportation fuels in
low thermal properties (heat deformation and that they have low volatility and high octane. However, environmental
melting); and the last and most detrimental prop- regulations restrict the amount of these molecules that can be blended into
erty, resistance to organic degradation making gasoline due to human health concerns and the great equalizer. . . price.
disposal highly problematic. This last property, BTX molecules typically carry a greater value (and price) as synthetic-
plastics’ resistance to environmental degrada- fiber building blocks than as an octane booster for gasoline blending.
tion, is the main societal concern with plastic Today, roughly 7.5 percent of each oil barrel consumed globally
usage and the focus of various environmental is converted into building-block molecules for plastic and synthetic
initiatives to ban or limit the use of plastic, material production—a good use for molecules that have little value for
especially plastic bags. transportation.
Although pure plastics are generally con-
sidered inert and non-toxic for human consump- HOW PLASTICS ARE CONSUMED
tion, there is emerging research indicating that See Figure 1 for a good representation of plastic demand by end
microplastics and certain plastic hardening use. In the building, construction and automotive sectors, plastics are
agents such as bisphenol A [to make the plastic primarily used as an engineering alternative to wood, concrete and
more scratch resistant] are detrimental to human metal, mostly steel.
health and development. We’ll discuss these Plastics use in automobiles is interesting from an environmental and
topics in a future article. engineering perspective. Plastics help reduce the weight of an automo-
bile, a key requirement for improved fuel efficiency and for reducing the
HOW PLASTICS ARE PRODUCED greenhouse gas emissions. Given that these plastics are designed to last
Plastic and other petrochemical production the life of the building or automobile, they don’t produce a significant
is highly integrated in the oil refining process. amount of single-usage waste compared to the alternatives. More impor-
The purpose of a petroleum refinery is to pro- tantly, they provide a variety of environmentally beneficial properties
duce environmentally compliant transportation when compared to other construction materials.
fuels, but plastic and petrochemical production Packaging presents a different challenge altogether and is likely what
fills an economically viable secondary role in most of us have in mind when we think about plastic waste and plastic
providing a use for the molecules contained in pollution. From the gadgets to the groceries, pretty much everything
the oil barrel that aren’t suitable for blending we buy today comes encased in some form of often frustrating-to-open
into transportation fuels. plastic packaging, and almost all of it is discarded after one or two uses.
Most plastics and synthetic rubber are pro- Nonetheless, much of the global supply chain is dependent on plastic
duced from ethane, propane and butane, mol- packaging.
ecules that are too light or volatile for blending The ease of application, durability and compressive flexibility of

Figure 1:
Plastic demand and end use

FALL 2020 Wise Traditions 49