Environmental Engineering Reference
In-Depth Information
Even with the most rigorous environmental controls in place, the use of
plastics, in common with other materials, still leaves its footprint on the
ecosystem. Societal benefits of plastics need to be appreciated to be able to
assess if this environmental footprint is justified. Externalities are for the
most part associated with the production phase of a plastic product and
perhapsduringitsdisposal.Societalbenefitsgenerallyaccrueduringtheuse
phase as apparent from the discussion that follows.
5.1 TRANSPORTATION APPLICATIONS OF PLASTICS
Plastics, particularly polymer-based composites (both thermoplastic and
thermoset composites), have been exploited in transportation applications
for decades. The use of common composites such as glass or carbon fiber
reinforced unsaturated polyesters, epoxy, and poly(vinyl ester) matrices is
well known. The unique advantage of composites is their strength (tensile
strength 4-6 times that of steel) and stiffness, despite their lightweight.
5.1.1 Passenger Cars
by 2050, this number is expected to grow to 5.0 billion. 0.8 billion of these
are already in use in China where car ownership is growing at the rate
of >25% a year. Internal combustion engines, however, are both wasteful
and polluting. Automobiles, especially larger vehicles used in the United
States, are a particularly energy-inefficient (as well as polluting) means of
transport or delivery of goods. Less than 12% of the energy in the fuel
is actually used for transportation, the rest being lost as heat (about a
third in hot exhaust gases and about the same in cooling and braking).
A single-occupant light automobile still consumes approximately 80 kWh
per 100 person-km of travel, nearly double that for a passenger in a full
Boeing 747 (~42 kWh 100 person-km) (MacKay, 2009.) Also, 30% of the
US contribution to GHG emissions is from transportation with each (US)
gallon of gas burnt emitting about 24 pounds of CO
2
into the air. About 75%
of this fuel consumption relates to vehicle weight (McWilliams, 2011). Any
decrease that can be achieved in the weight of a vehicle (without reducing
its functionality) would result in very significant savings in fossil fuel use
and avoided GHG emissions, provided it could be achieved without
compromising passenger safety. This has driven automobile makers to
