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4 Life Cycle Assessment: Nice to Have or Essential …
material footprint indicator expressed in absolute terms, one can be clearly aware of
the total resource needs of an economy.
However, we argue that computing the material footprint in this way is misleading
from a life cycle perspective because in the goal and scope definition of an LCA,
material is treated as an upstream process before the manufacture of a product. This
means that the material footprint is an analogous but different concept from product
environmental footprint (PEF)—an ongoing European Commission policy initiative
(EC 2015b) assessing a broad set of impact categories to provide a comprehensive
picture of the life cycle environmental performance of products, for the sake of
product labeling. The material footprint, therefore, is expected to encompass a variety
of environmental impacts associated with material extraction through the processing,
distribution, storage, use, and disposal or recycling stages.
Rather than furthering the discussion on approaches to a veritable material footprint that has not come up, we call for a shift in focus to scarcity—a critical issue
which, in our view, the material footprint practitioners were intended to address.
The failure to address scarcity is due to summing up the mass of raw materials with
equal weights. To cite an example, we assume that Economy A and B both have a
material footprint of 100 kg. This, however, does not mean anything except the total
mass, because the truth might be that Economy A consumed 1 kg of Au and 99 kg of
sands, and Economy B conversely consumed 99 kg of Au and 1 kg of sands! In that
case, misleading decisions can be made as a consequence of neglecting the varying
importance of different resources in terms of scarcity.
There are several ways to quantify the scarcity of resources, such as exergy (available energy), surplus energy, and market price approaches. In life cycle impact assessment (LCIA), the impact of resource scarcity is evaluated by so-called resource
depletion potential (RDP), a form of characterization factor derived from characterization models reflecting the environmental mechanism of depletion in natural capital
stocks (Hauschild et al. 2013). In theory, there are two branches of RDP, namely,
abiotic depletion potential (ADP) and biotic depletion potential (BDP) (Guinée and
Heijungs 1995). However, the BDP is normally excluded from LCIA as most biotic
resources can be reproduced by a production process. This is why deforestation, for
example, would not be regarded as a depletion problem but a production process
with its particular environmental impacts such as soil erosion, land degradation, and
global warming.
We herein propose a resource depletion footprint (RDF) aimed at addressing
abiotic resource depletion. The rationale is that abiotic resources, such as minerals
and fossil fuels, are a dominant contributor to the depletion of natural stocks. The RDF
is calculated by multiplying the ADP by the extraction of resources, where ADP is
specified as the ratio between two estimates, indicating how fast the remaining stocks
of resources would be exhausted in comparison to a reference resource (such as Sb),
both at the current rate of use. Figure 4.1 compares resource categories for which
characterization factor ADPs are derived from Van Oers et al. (2002), which serves as
an updated version of the baseline method proposed by Guinée and Heijungs (1995).
4 Life Cycle Assessment: Nice to Have or Essential …
material footprint indicator expressed in absolute terms, one can be clearly aware of
the total resource needs of an economy.
However, we argue that computing the material footprint in this way is misleading
from a life cycle perspective because in the goal and scope definition of an LCA,
material is treated as an upstream process before the manufacture of a product. This
means that the material footprint is an analogous but different concept from product
environmental footprint (PEF)—an ongoing European Commission policy initiative
(EC 2015b) assessing a broad set of impact categories to provide a comprehensive
picture of the life cycle environmental performance of products, for the sake of
product labeling. The material footprint, therefore, is expected to encompass a variety
of environmental impacts associated with material extraction through the processing,
distribution, storage, use, and disposal or recycling stages.
Rather than furthering the discussion on approaches to a veritable material footprint that has not come up, we call for a shift in focus to scarcity—a critical issue
which, in our view, the material footprint practitioners were intended to address.
The failure to address scarcity is due to summing up the mass of raw materials with
equal weights. To cite an example, we assume that Economy A and B both have a
material footprint of 100 kg. This, however, does not mean anything except the total
mass, because the truth might be that Economy A consumed 1 kg of Au and 99 kg of
sands, and Economy B conversely consumed 99 kg of Au and 1 kg of sands! In that
case, misleading decisions can be made as a consequence of neglecting the varying
importance of different resources in terms of scarcity.
There are several ways to quantify the scarcity of resources, such as exergy (available energy), surplus energy, and market price approaches. In life cycle impact assessment (LCIA), the impact of resource scarcity is evaluated by so-called resource
depletion potential (RDP), a form of characterization factor derived from characterization models reflecting the environmental mechanism of depletion in natural capital
stocks (Hauschild et al. 2013). In theory, there are two branches of RDP, namely,
abiotic depletion potential (ADP) and biotic depletion potential (BDP) (Guinée and
Heijungs 1995). However, the BDP is normally excluded from LCIA as most biotic
resources can be reproduced by a production process. This is why deforestation, for
example, would not be regarded as a depletion problem but a production process
with its particular environmental impacts such as soil erosion, land degradation, and
global warming.
We herein propose a resource depletion footprint (RDF) aimed at addressing
abiotic resource depletion. The rationale is that abiotic resources, such as minerals
and fossil fuels, are a dominant contributor to the depletion of natural stocks. The RDF
is calculated by multiplying the ADP by the extraction of resources, where ADP is
specified as the ratio between two estimates, indicating how fast the remaining stocks
of resources would be exhausted in comparison to a reference resource (such as Sb),
both at the current rate of use. Figure 4.1 compares resource categories for which
characterization factor ADPs are derived from Van Oers et al. (2002), which serves as
an updated version of the baseline method proposed by Guinée and Heijungs (1995).