Biomedical Engineering Reference
In-Depth Information
alternative, which would fall onto the highly energy intensive production
of the carbon nanofibers, whereas just including some of the savings gener-
ated in the use stage (here the lighter weight causing less fuel consumption)
would lead to the opposite conclusion. Ultimately, the outcome of the decision-
making process could be deeply influenced by such misleading results.
11.2.4.2 Inventory of Emissions
For the background data, most LCA studies have relied on available life cycle
inventory (LCI) databases. However, to build inventories for nanoproduct-
specific processes, the data used are mainly computations or measurements
from laboratory-scaled studies, which have been reported in the publicly avail-
able literature; very few studies have used data from actual pilot or commer-
cialization plants (see Hischier and Walser
58
). This is paradoxical when one
considers the amount of nanoproducts already available on the market. One
cause may stem from the potential of the market for nanotechnologies, which,
along with driving their rapid development (see Figure 11.4a), has simultane-
ously raised a number of barriers from industries that are not inclined to share
process information. Facing a rapidly evolving sector where most data are kept
confidential is a difficult challenge for the creation of inventory databases, and
one that is going to be essential for the consistency of future LCA studies.
By assessing immature and nonoptimized processes, most of the exist-
ing studies on nanoproducts are thus likely to have reported overestimated
results (e.g., energy requirements for in the production of nanomaterials).
This shortcoming may have large consequences on the interpretation of the
results when the LCA practitioner compares the thus-biased performances
of a nanoproduct with those of a product already well established on the
market. A way to address this issue could be by conducting prospective LCA
studies that include a foresight of the impacts caused by nanoproducts in a
mass production context (e.g., Walser et al.
24
).
11.2.4.3 Impact Assessment
An LCA aims at addressing all relevant environmental problems related to the
product life cycle. However, as displayed in Figure 11.8, about two-thirds of
the LCA studies identified in the scientific literature have focused on energy
requirements, with some of them solely addressing this indicator. Studies
assessing environmental impacts as such have concentrated on the assessment
of global warming (accounting for nearly all the partial assessment in the non-
toxic impact categories in Figure 11.8). As a consequence of such trend, only 15
out of the 43 listed studies have conducted a complete assessment of nontoxic
impacts, and 10 out of those 15 have included toxic impacts (among which
three have addressed the toxicity exerted by the released nanoparticles).
Several reasons can be advanced for such a pattern. The most obvious
one is likely to be the paucity of available data. In an emerging and quickly
