46
3 Exploring Some Fundamentals of Environmental Footprints
(a) Each of the investigated footprints performs an inventory analysis, whereby data
of wastes emitted to and/or resources extracted from the environment are tabulated and compiled specifically for defined system boundaries. The inventory
can be LCA-based, and can be non-LCA-based as well. Alternatives to LCA
include (parts of) IOA, MFA, NFA, and so on.
(b) Some of the footprints further characterize the inventory results with characterization factors to yield single-score impact indicators expressed in equivalent
units (e.g., kg CO 2 -eq., m
3 H 2 O-eq.), which is common to all contributing
substances within each single impact category. This practice builds on
the premise that environmental mechanism underlying the characterization
modeling of the impact exists and can be modeled in a linear approximation
as simple multiplication and addition.
(c) In other cases, the inventory results are aggregated with weighting factors
reflecting the relative importance based on expert-based judgments that contain
social, political, or ethical value choices in the study. It can be equal weighting
in case that all factors are assigned with the same score, as is the case for the
WF class and for the MF class . Unequal weighting is observed in the cases of the
CF class and LF class . Whichever the weighting scheme, we consider this as part
of inventory analysis, as no impact assessment has been done.
(d) While the operational formulas are similar in style (both categories of footprints do multiplication and addition), inventory weighting and impact characterization play different roles in bringing together various inventory results
into a footprint. Weighting is value-based, typically using expert knowledge to
express stated or revealed preferences and judgments. In contrast, characterization models are developed on the basis of recent scientific evidence, even though
subjective choices cannot be completely avoided. The CF clim , for instance, has
substantially benefitted from the use of GWPs and had a much broader appeal
than many other footprints, despite the arbitrary choice of time horizon.
(e) Although the dichotomous framework for contrasting inventory weighting and
impact characterization reveals valuable insights into the similarities and differences between these footprints, we admit that there is no sharp boundary between
value-based weighting and science-based characterization. One example is the
confusion surrounding the nature of the LDF used in the LF disturb . This can be
primarily attributed to the fact that a recognized consensus on land use characterization modeling is lacking (Hauschild et al. 2013). In view of the difficulties
in assessing land use impacts, the LF disturb shows a relatively good performance
on scientific robustness by tracing the causal linkages between biotic resource
extraction, soil degradation, and biodiversity decline.
3 Exploring Some Fundamentals of Environmental Footprints
(a) Each of the investigated footprints performs an inventory analysis, whereby data
of wastes emitted to and/or resources extracted from the environment are tabulated and compiled specifically for defined system boundaries. The inventory
can be LCA-based, and can be non-LCA-based as well. Alternatives to LCA
include (parts of) IOA, MFA, NFA, and so on.
(b) Some of the footprints further characterize the inventory results with characterization factors to yield single-score impact indicators expressed in equivalent
units (e.g., kg CO 2 -eq., m
3 H 2 O-eq.), which is common to all contributing
substances within each single impact category. This practice builds on
the premise that environmental mechanism underlying the characterization
modeling of the impact exists and can be modeled in a linear approximation
as simple multiplication and addition.
(c) In other cases, the inventory results are aggregated with weighting factors
reflecting the relative importance based on expert-based judgments that contain
social, political, or ethical value choices in the study. It can be equal weighting
in case that all factors are assigned with the same score, as is the case for the
WF class and for the MF class . Unequal weighting is observed in the cases of the
CF class and LF class . Whichever the weighting scheme, we consider this as part
of inventory analysis, as no impact assessment has been done.
(d) While the operational formulas are similar in style (both categories of footprints do multiplication and addition), inventory weighting and impact characterization play different roles in bringing together various inventory results
into a footprint. Weighting is value-based, typically using expert knowledge to
express stated or revealed preferences and judgments. In contrast, characterization models are developed on the basis of recent scientific evidence, even though
subjective choices cannot be completely avoided. The CF clim , for instance, has
substantially benefitted from the use of GWPs and had a much broader appeal
than many other footprints, despite the arbitrary choice of time horizon.
(e) Although the dichotomous framework for contrasting inventory weighting and
impact characterization reveals valuable insights into the similarities and differences between these footprints, we admit that there is no sharp boundary between
value-based weighting and science-based characterization. One example is the
confusion surrounding the nature of the LDF used in the LF disturb . This can be
primarily attributed to the fact that a recognized consensus on land use characterization modeling is lacking (Hauschild et al. 2013). In view of the difficulties
in assessing land use impacts, the LF disturb shows a relatively good performance
on scientific robustness by tracing the causal linkages between biotic resource
extraction, soil degradation, and biodiversity decline.