Biomedical Engineering Reference
In-Depth Information
Goal
definition
Inventory of
extractions and
emissions
Interpretation
Impact
assessment
FIGURE 11.1
General scheme of four stages of LCA (ISO 14040). (From International Organization for
Standardization ISO 14040 International Standard. In
Environmental Management—Life Cycle
Assessment—Principles and Framework
. Geneva, Switzerland, 2006.)
this is particularly important to initially identify the hot spots by location and
process and then find more location-specific data where necessary.
The four steps of LCA are further defined as follows (adapted from Shaked
and Jolliet
2
).
11.1.2.1 Goal and Scope Definition
In this initial step, the problem is described, and the objectives and the scope
of the study are defined. A number of crucial elements are determined at
this point. Because the goal of LCA is to assess the environmental impacts of
the function of the product, it begins by defining the main function and the
main service offered by the system. Products or systems can only be com-
pared on the basis of a similar specific function.
On the basis of the determined function, it is possible to define the
functional
unit
of all scenarios, which is the common unit representing the function of
the system (the offered service), serving as the basis for scenario comparison
(e.g., a single use of 1 m
3
of packaging material for a filling material or 100 days
of use of a T-shirt). The functional unit is the same for all scenarios, and it is
a quantified and additive value (i.e., not a ratio). This is an important choice
because inventory emissions are calculated and compared per functional unit.
A low-quality T-shirt (scenario 1) can then be compared with a high-quality
T-shirt (scenario 2) by determining the type and number of products needed
to be purchased to achieve the functional unit. Assuming a low-quality T-shirt
lasts for 50 days of use and a high-quality one lasts for 200 days of use, the
reference flow for scenario 1 is 2 low-quality T-shirts, whereas the reference
flow for scenario 2 is only 0.5 high-quality T-shirt. In addition, assuming that
T-shirts are washed every 2 days of use, 50 washing/drying are accounted for
