Environmental Engineering Reference
In-Depth Information
Figure 8.2
The energy use and GWG emissions associated with the
production of material and fabrication of containers for milk (~1 l). The
first segment of bar is for material production, and the second is for
manufacturing. Drawn from data in Ghenai (2012).
This clear LCA picture changes, however, when reuse of containers or
material recycling is included in the calculation. Using realistic end-of-life
options, including recycling (as well as all the related transport costs), is
critical in meaningful LCA studies on packaging as the findings are
especially sensitive to these variables. For instance, using recycled
aluminum in place of the virgin metal results in a 36% saving in energy
(making it competitive with glass) and a 40% saving in GHG emissions, in
the previous data. Reusing glass bottles recaptures approximately 97% of
the original embedded energy.
Another study (Franklin Associates Study, 2008) compared glass bottles,
paperboard cartons, HDPE jugs and biodegradable polylactic acid (PLA)
containers for packaging of milk. The reusable glass bottles were shown
to have the least energy cost and the biodegradable PLA containers, the
highest. Despite the high transportation energy (given the relatively higher
weight of glass containers), a low energy value is found for the glass bottle
because once fabricated, these were assumed to be reused eight times. The
energy costs of cleaning to enable reusability, however, were not fully taken
into account, in the analysis. A recent packaging study comparing PET
vs. glass found that half the environmental impact of glass bottles was
in fact associated with the bottling process (Doublet, 2012). Given the
approximations in the methodology used, paperboard carton and the HDPE
milk jug were estimated to have about the same energy cost. However, the
energy for HDPE is almost entirely derived from nonrenewable fossil fuel,
while only about 40% of the total energy cost of paperboard is derived from
fossil fuel.
The lowest GHG emissions were also associated with the HDPE milk jug,
whereas both glass and PLA package showed relatively higher values (both
about the same within the margin of error.) With heavier glass bottles,
it is the transportation cost that is responsible for most of the emissions.
Milk production itself accounts for only approximately 4% of global GHG
emissions (FAO, 2010; Gerber et al., 2010), and producing half a gallon of
milk results in emission of approximately 4.3 kg CO
2
equivalent. Though
the study included estimates of waterborne emissions as well, these were
