Page 262 - Materials Chemistry, Second Edition

252 G. A. da Silva et al.

plant is ‘‘the generation of electricity’’. In order to measure this function, a
Functional Unit (FU) of ‘‘generation of 1 MWh of electricity’’ was selected.
Operationally, the process of boundary definition was a major challenge. The
core of the product system is the Itaipu Power Plant itself. However, the product
system’s boundaries also encompassed processes involved in delivery of materials
for the construction and operation of the plant—such as cement, steel, copper,
diesel oil, and lubricants. Moreover, it should be highlighted that the LCI
addresses the construction and operation of the plant, but not the dam dismantling.
So, in terms of temporal boundaries, the first statement was the division of the
power plant life-cycle into two phases: construction and operation. The con-
struction phase started with the beginning of the civil works. The operation step
lasts for a 100-year period—according to temporal coverage originally defined—
counted from 1984. For estimation and data collection of environmental loads of
consumed materials, the base year of 1977 was selected. The greatest part of the
materials was acquired on that period.
The spatial boundaries of the product system should include not only the dam
and its related structures, but also the residential and construction site, which
demanded energy and materials to be built. However, after a first screening, it was
possible to verify that the amount of consumed materials and civil works needed to
construct the residential site was not significant in comparison with the whole civil
work conducted, and thus it was excluded (Ribeiro 2003). Moreover, it should be
considered that all of these residences and support structures were incorporated
afterwards into the city. On the other hand, the construction site equipment and
structures that were fully dedicated to the power plant construction had its envi-
ronmental burdens included within the LCI. Apart from consumption and emis-
sions occurred during the operation phase, it was decided to consider also the
consumption of steel, concrete and electricity to build the dam, and their life
cycles.
The definition regarding inclusion of other unit processes within the system’s
boundaries was much more complex. This adjustment was initially made by taking
a boundary definition from international studies (Brännstrom-Norberg et al. 1996;
Swedish Environemntal Management Council 2002a, b, 1999; Vattenfall 1999),
which was modified through a screening process, based on an extensive literature
review, complemented by a personal interview with the professionals who took
part in Itaipu’s construction.
Figure 2 presents the final boundary for the product system.
No allocation procedure was conducted, due to the consideration of only one
product and one function for the dam. Also, considering that only the ‘‘Definition’’
and ‘‘Inventory’’ phases of LCA were conducted, no impact assessment criteria
definition was made.

4.4.2 Life-Cycle Inventory

Data collection