In the problem-oriented approaches, flows are classified into environmental
themes to which they contribute. Themes covered in most Life Cycle Assessment
(LCA) studies are: Greenhouse effect (or climate change), Natural resource
depletion, Stratospheric ozone depletion, Acidification , Photochemical ozone
creation, Eutrophication, Human toxicity and
Aquatic toxicity. These methods aim at simplifying the complexity of hundreds of
flows into a few environmental areas of interest. The EDIP or CML 2000 methods
are examples of problem-oriented methods.
The damage-oriented methods
also start by classifying a system's flows into various environmental themes,
but model each environmental theme's damage to human health, ecosystem health or
damage to resources. For example, acidification - often related to acid rain -
may cause damage to ecosystems (e.g., in the Black Forest in Germany), but also
to buildings or monuments. In essence, this method aims to answer the question:
Why should we worry about climate change or ozone depletion? EcoIndicator 99 is
an example of a damage-oriented method.
Problem-oriented methodologies
are based on internationally and scientifically accepted approaches when
possible. But some categories, such as human toxicity or aquatic toxicity,
remain difficult to model and are currently under development and require
careful evaluation when used. Even more difficulties with scientific relevance
exist with damage-oriented methods, hence careful evaluation is necessary.
An important issue with problem-oriented methodologies is the
communication aspect of the results. For example, the human health indicator for
EcoIndicator 99 uses the concept of "Disability Adjusted Life Years (DALY)."
When assessing the life cycle of drinking water production, how do you
communicate that producing drinking water constitutes a certain number of
Disability Adjusted Life Years?
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Interpretation of Impact AssessmentImpact assessment methods have been
developed as tools to broaden the information and context of Life Cycle
Inventory (LCI) data, which refer mainly to mass and energy. The fact that LCI
indicates that certain emissions are associated with certain environmental
themes or impact categories does not imply that the studied product or system
actually causes effects. It means, however, that in the course of the life
cycle, emissions are generated that contribute to a pool of similar emissions
known to be associated with these environmental themes or impact categories.
Used this way, Life Cycle Assessment is the appropriate tool to help
determine to what extent a particular product, process or ingredient's emissions
may be associated with a particular impact category.
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LCIA: An Indicator SystemThese Life Cycle Impact Assessment categories
are what we consider "indicators." Indicators are unlike quantitative inventory
data that measure weights of materials or emissions and joules of energy or heat content.
Indicators are conversions of these inventory data.
It is important to
understand both the advantages and limitations of the conversion in order to
interpret the indicators properly and reach sound conclusions.
Most
indicators are "directional" to a greater or lesser degree. P&G is cautious
to keep in mind that the use of numbers for the value of an indicator may
incorrectly imply that it is quantitative and that any differences are absolute
and meaningful.
This is not true in all cases. Indicators differ widely
in how they relate to the environment and the assumptions used to derive them.
In all cases, the assumptions may not be fully scientific. Some indicators take
on the nature of judgmental scores or even opinions.
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