Environmental Engineering Reference
In-Depth Information
Definition of goal and scope
Life cycle inventory (LCI)
LCI analysis
Life cycle impact assessment (LCIA)
Step 1: Selection of impacts
Step 2: Classification
Step 3: Characterization
Step 4: Presentation of data
Step 5: Optional elements of LCIA
Normalization
Grouping
Weighting
Life cycle interpretation
Figure 4.3 Steps of a life cycle assessment.
declarations that will be disclosed to the public. The definition of the scope comprises the
product or system to be studied, the functional unit, the system boundary, the allocation
procedures, assumptions, limitations, and so on.
LCAs are conducted on a base, which is called a functional unit . For instance, a six-pack
of beer, 1L of beer, or a beer keg all represent functional units that can be used to conduct an
LCA on the production of beer. Commonly used functional units in food and agricultural
products are mass of final product (kg), content of energy (kJ), protein content per serving,
and so on. In some instances, multiple functional units are used when dealing with food
products (e.g., 1 gram of protein and 1 kJ of energy [Roy et al., 2009]).
Once the functional unit is defined, the next step is to define the system boundaries,
which will depend on the goal and scope. If the goal is to study the environmental impact
of beer production from ingredients cultivation to disposal of used containers, then the
boundary has to encompass all steps in the process (see generic diagram on Fig. 4.2) in
addition to other subsystems such as electricity generation, water purification, waster treat-
ment, and so on.
However, if the interest is only limited to understanding the impact of the processing part,
then the boundaries are set just around the brewery ( gate-to-gate analysis). Figure 4.4 is a
generic diagram that illustrates this point. Boundary 1 includes only production of raw materi-
als that may include the subsystem's cultivation of cereals and hops and production of support-
ing materials, such as bottles, caps, and labels. Boundary 2 encompasses only the processing
plant. So, for instance if the goal is to know the environmental impact of the processing plant
with the purpose of improving the process, comparing with alternative processes, and making
claims about the process, then the boundaries need to be set right around the factory. If the
objective is to study the impact of commercialization distribution, and consumption, then
analysis needs to be restricted to Boundary 3.
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