42
3 Exploring Some Fundamentals of Environmental Footprints
tables. Once such inventory choices have been made, the characterization aspect
runs smoothly.
3.2.2.2 Classical Carbon Footprint (CF class )
Although the carbon footprint is generally referred to as the CF clim , the classical
version of the carbon footprint (CF class ) was introduced about two decades ago by
Wackernagel and Rees (1996), who convert carbon emissions from fossil energy
into the emissions of CO 2 and then into the area of forest required to achieve carbon
neutrality. This is why people also call it “energy footprint” (Fang et al. 2014).
The CF class premises that all carbon emissions are ideally emitted in the form of
CO 2 . Carbon contents (CCs) and carbon sequestration rate (CSR) are employed
as parameters to make the two phases of conversion come true. Since the CSR is
practically assigned with a fixed value of 970 kg/(ha · yr) for all cases (Blomqvist
et al. 2013), the aggregation of multiple CCs can be seen as rough inventory analysis,
in which the ratio of energy-specific carbon contents to the CSR serves as weighting
factors for different types of fossil energy. It is not surprising that the scientific
reliability and accuracy of its estimate have been debated (Blomqvist et al. 2013;
Kitzes et al. 2009), thus preventing the CF class from mainstream acceptance.
3.2.3 Water Footprint
3.2.3.1 Classical Water Footprint (WF class )
The classical water footprint (WF class ) has received great popularity in past years,
and its applications have been extended to a wide range of fields, in particular to
the arena of basin water resources management (Hoekstra et al. 2009; Hoekstra and
Hung 2002). It measures and sums up the volumetric consumption of green, blue,
and gray water within an investigated system at the inventory level. The former two
water components refer to the cubic meters of freshwater evaporated from the soil
and ground surface, respectively, and the latter is expressed as the cubic meters of
freshwater needed to dilute pollution below an acceptable standard (Chapagain and
Hoekstra 2008). The WF class in general can be interpreted as an inventory analysis
with regard to H 2 O. However, its gray component is, to some extent, committed to
an impact assessment because of the large similarity between the dilution approach
used and certain characterization approaches (Kounina et al. 2013). Finally, the green,
blue and gray components are aggregated without a clear characterization principle,
signaling an inventory weighting aspect (even though the weighting factors are 1,
i.e., equal weighting).
3 Exploring Some Fundamentals of Environmental Footprints
tables. Once such inventory choices have been made, the characterization aspect
runs smoothly.
3.2.2.2 Classical Carbon Footprint (CF class )
Although the carbon footprint is generally referred to as the CF clim , the classical
version of the carbon footprint (CF class ) was introduced about two decades ago by
Wackernagel and Rees (1996), who convert carbon emissions from fossil energy
into the emissions of CO 2 and then into the area of forest required to achieve carbon
neutrality. This is why people also call it “energy footprint” (Fang et al. 2014).
The CF class premises that all carbon emissions are ideally emitted in the form of
CO 2 . Carbon contents (CCs) and carbon sequestration rate (CSR) are employed
as parameters to make the two phases of conversion come true. Since the CSR is
practically assigned with a fixed value of 970 kg/(ha · yr) for all cases (Blomqvist
et al. 2013), the aggregation of multiple CCs can be seen as rough inventory analysis,
in which the ratio of energy-specific carbon contents to the CSR serves as weighting
factors for different types of fossil energy. It is not surprising that the scientific
reliability and accuracy of its estimate have been debated (Blomqvist et al. 2013;
Kitzes et al. 2009), thus preventing the CF class from mainstream acceptance.
3.2.3 Water Footprint
3.2.3.1 Classical Water Footprint (WF class )
The classical water footprint (WF class ) has received great popularity in past years,
and its applications have been extended to a wide range of fields, in particular to
the arena of basin water resources management (Hoekstra et al. 2009; Hoekstra and
Hung 2002). It measures and sums up the volumetric consumption of green, blue,
and gray water within an investigated system at the inventory level. The former two
water components refer to the cubic meters of freshwater evaporated from the soil
and ground surface, respectively, and the latter is expressed as the cubic meters of
freshwater needed to dilute pollution below an acceptable standard (Chapagain and
Hoekstra 2008). The WF class in general can be interpreted as an inventory analysis
with regard to H 2 O. However, its gray component is, to some extent, committed to
an impact assessment because of the large similarity between the dilution approach
used and certain characterization approaches (Kounina et al. 2013). Finally, the green,
blue and gray components are aggregated without a clear characterization principle,
signaling an inventory weighting aspect (even though the weighting factors are 1,
i.e., equal weighting).