Biomedical Engineering Reference
In-Depth Information
should be explored further if it leads to a relatively high impact or if the
system is sensitive to this value (i.e., small changes in the factor lead to
large variations in calculated impacts). To determine these factors, the
interpretation stage involves a systematic look at each stage of the assess-
ment (inventory and impact assessment), each life cycle phase (manufac-
turing, use, and disposal), and each product component (e.g., boots and
shoelaces), identifying the dominant processes, substances, and impact cat-
egories. Interpretation can be taken further by looking at cost-effectiveness
or ease of acting see Cost-effectiveness and Rebound Effects. Processes that
have small impact contributions but can be easily improved should also be
identified, as reducing many of these small contributions can lead to large
benefits.
Many of the assumptions made during an LCA are consistently applied to
all scenarios, yielding valuable comparison results; however, these assump-
tions can yield large uncertainties, so the field has developed methods for
estimating uncertainty for individual scenarios and for scenario compari-
sons. Parameter uncertainty propagation has mainly been studied using
Monte Carlo
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or Taylor series expansion
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techniques to evaluate the distri-
bution of outcomes (impacts, in this case) given uncertainty distributions for
the input parameters (e.g., amount of formaldehyde emissions per kilowatt-
hour of electricity used).
LCA only deals with the environmental impacts of a product, but sus-
tainability also refers to economic and social aspects, which can be com-
pared with and balanced against the environmental aspects. To address
the economic aspects, LCA could be complemented by performing a life
cycle costing to calculate the costs to the consumer associated with each
step in the life cycle of a product and to guide a decision maker to make
more cost-effective decisions. For example, the construction costs of a
well-insulated and energy-efficient building may be higher than those
of a conventional building, whereas its energy consumption costs will
be reduced during operation. To address the social aspects, social LCA
is being developed, which quantifies various social indicators associated
with goods and services, such as wages, gender equality, child labor, and
health insurance.
11.1.3 A Short LCA Example
As an example, polystyrene packing peanuts are made with nonrenewable
raw materials (oil) and are not biodegradable; therefore, popcorn has been
proposed as a substitute packaging material.
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To compare the two, the dif-
ferences in environmental impacts must be quantified and the responsible
key variables must be determined.
Using LCA techniques, the emissions over the life cycle of each option
can be inventoried to quantify the subsequent environmental impacts in a
manner consistent with the product function. Many materials are compared
