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percentages of greenhouse gas in the atmosphere increase the potential for global
warming and the resulting negative climate change impacts (Masson-Delmotte
et al. 2018). When specifying metals, it is likely that “climate change” will be an
important environmental impact category to focus on. This is mainly due to the high
temperatures used in the refining process requiring a high exergy fuel source, typically coal. “Global warming” may be the term used depending on which modeling
system is used, but in either case radiative forcing, caused by the increasing concentration of CO 2 and other greenhouse gasses, is the universally accepted indicator.
Agricultural products specified in a design including wood, vegetable fibers, and
natural dyes that depend on fertilizer and pesticides will likely consider the negative
effects of nutrient loading on freshwater and marine ecosystems. In these cases,
“eutrophication” is a likely impact category to include with several impact indicators including the relative amounts of dissolved oxygen, chlorophyll a, phosphates,
and nitrates in streams, rivers, lakes, and oceans.
In these two impact category examples, climate change is a global impact, and
eutrophication impacts are typically local or regional. The scale of the impacts is
determined by how the indicator substances are released and travel into and throughout the ecosphere over time. The relationship between specific emissions, effluents,
and solid wastes and their negative environmental impacts are represented through
models that multiply the amounts of one substance by a characterization factor (CF)
to produce a value that can be added to others in order to estimate the total impact.
This can either be expressed as an attributional (midpoint) or consequential (endpoint) impact. A model that translates many contributing greenhouse gas emissions
into single equivalency impact score would take gasses such as carbon dioxide
(CO 2 ) x 1, methane (CH 4 ) x 28, nitrous oxide (N 2 O) x 265, and sulfur hexafluoride
(SF 6 ) x 23,500 and typically express them as total single midpoint characterizations
score in kg CO 2 e or kilograms of carbon dioxide equivalents over a certain time
period. This example uses published 100-year global warming potential (GWP) factors for specific GHG emissions. There are different factors available for each gas’s
20-year GWP time horizon (US EPA 2016). This points to the importance of which
time element or duration is included in a study. Characterization factors are commonly used to model the various heterogeneous substances in all environmental
impact categories, and LCA studies will clearly state which characterization models
will be used. This will be discussed in more detail in the section covering life cycle
impact assessment.
As important as the impact assessment phase is to a full LCA, depending on the
study’s overall goal and scope, it may or may not even be included. Most LCAgenerated documents that designers would use, however, will include the impact
assessment phase. The study may be limited to only focus on what the data inventory of material and energy that comprises a product system tells about it. Either
way, the goal and scope will make explicit what major subsequent phases are
included.
5.3 Goal and Scope Definition
percentages of greenhouse gas in the atmosphere increase the potential for global
warming and the resulting negative climate change impacts (Masson-Delmotte
et al. 2018). When specifying metals, it is likely that “climate change” will be an
important environmental impact category to focus on. This is mainly due to the high
temperatures used in the refining process requiring a high exergy fuel source, typically coal. “Global warming” may be the term used depending on which modeling
system is used, but in either case radiative forcing, caused by the increasing concentration of CO 2 and other greenhouse gasses, is the universally accepted indicator.
Agricultural products specified in a design including wood, vegetable fibers, and
natural dyes that depend on fertilizer and pesticides will likely consider the negative
effects of nutrient loading on freshwater and marine ecosystems. In these cases,
“eutrophication” is a likely impact category to include with several impact indicators including the relative amounts of dissolved oxygen, chlorophyll a, phosphates,
and nitrates in streams, rivers, lakes, and oceans.
In these two impact category examples, climate change is a global impact, and
eutrophication impacts are typically local or regional. The scale of the impacts is
determined by how the indicator substances are released and travel into and throughout the ecosphere over time. The relationship between specific emissions, effluents,
and solid wastes and their negative environmental impacts are represented through
models that multiply the amounts of one substance by a characterization factor (CF)
to produce a value that can be added to others in order to estimate the total impact.
This can either be expressed as an attributional (midpoint) or consequential (endpoint) impact. A model that translates many contributing greenhouse gas emissions
into single equivalency impact score would take gasses such as carbon dioxide
(CO 2 ) x 1, methane (CH 4 ) x 28, nitrous oxide (N 2 O) x 265, and sulfur hexafluoride
(SF 6 ) x 23,500 and typically express them as total single midpoint characterizations
score in kg CO 2 e or kilograms of carbon dioxide equivalents over a certain time
period. This example uses published 100-year global warming potential (GWP) factors for specific GHG emissions. There are different factors available for each gas’s
20-year GWP time horizon (US EPA 2016). This points to the importance of which
time element or duration is included in a study. Characterization factors are commonly used to model the various heterogeneous substances in all environmental
impact categories, and LCA studies will clearly state which characterization models
will be used. This will be discussed in more detail in the section covering life cycle
impact assessment.
As important as the impact assessment phase is to a full LCA, depending on the
study’s overall goal and scope, it may or may not even be included. Most LCAgenerated documents that designers would use, however, will include the impact
assessment phase. The study may be limited to only focus on what the data inventory of material and energy that comprises a product system tells about it. Either
way, the goal and scope will make explicit what major subsequent phases are
included.
5.3 Goal and Scope Definition