2.3 Elaboration of a Footprint Family
21
(b) The origin of the energy footprint can be traced back to a subset of the ecological
footprint (Wackernagel and Rees 1996) in reply to the question of how much
forest area is required to absorb CO 2 emissions from energy consumption. The
energy footprint, in many cases, makes up a dominant proportion of the entire
amount of ecological footprint at a regional or global level (Kitzes et al. 2009).
(c) The carbon footprint is rooted in the indicators of GWP which represents
the quantities of GHGs that contribute to global warming when considering
a specific time horizon such as 100 years (Wiedmann 2009b). It is concerned
with the question of how much (CO 2 -eq.) weight of the total GHG emissions is
over the life cycle of products or activities.
(d) The water footprint is derived from the concept of virtual water equal to the
volume of freshwater used to produce a commodity (Allan 1998; Hoekstra
2009). It aims to address the question of how much volume of the cumulative
virtual water is needed to provide products or activities.
2.3.3.2 Components and Units
(a) The ecological footprint is built upon a tradition of seeking alternatives to the
appropriated carrying capacity which is related to the maximum population size
that can be supported by a given set of resources (Dietz and Neumayer 2007;
Ehrlich 1982). It is intended to deal with the question of how much area of
biologically productive space is required to produce consumed resources and to
absorb generated waste.
(b) The energy footprint can be classified into concrete components such as the fossil
fuel footprint, the hydroelectricity footprint, and the nuclear footprint (Browne
2009; ˇ
Cuˇ cek et al. 2012a; Stöglehner 2003), all of which are expressed as the
area of forest that is necessary to compensate for human-induced CO 2 (Van
den Bergh and Verbruggen 1999). The unit of measurement can be gha or local
hectares with a specific carbon sequestration estimate (Walsh et al. 2010).
(c) The components of the carbon footprint include a variety of GHGs such as CO 2 ,
CH 4 , and N 2 O. The use of GHG characterization factors as determined weightings dependent on the 100-yr GWP has a broad base of acceptance (Ridoutt and
Pfister 2013) because the greater the GWP of a GHG, the more responsibility
it should take on for increasing global temperatures. The metric is expressed in
CO 2 -equivalent mass units such as kilogram or ton, indicating the impact unit
of time-integrated radiative forcing.
(d) The water footprint consists of three components in volume-based units: the
blue, green, and gray water footprints. The blue and green footprints correspond
to the demand for freshwater resources (from surface or ground water, and from
rain, respectively), while the gray footprints refer to the waste assimilation by
water and are defined as the volume of freshwater required to assimilate load of
pollutants based on the existing ambient water quality standards (Chapagain and
Hoekstra 2008; Hoekstra 2009). Although Hoekstra (2009) has declared that no
weighting is involved, equal weighting is also a form of weighting. It fails to
21
(b) The origin of the energy footprint can be traced back to a subset of the ecological
footprint (Wackernagel and Rees 1996) in reply to the question of how much
forest area is required to absorb CO 2 emissions from energy consumption. The
energy footprint, in many cases, makes up a dominant proportion of the entire
amount of ecological footprint at a regional or global level (Kitzes et al. 2009).
(c) The carbon footprint is rooted in the indicators of GWP which represents
the quantities of GHGs that contribute to global warming when considering
a specific time horizon such as 100 years (Wiedmann 2009b). It is concerned
with the question of how much (CO 2 -eq.) weight of the total GHG emissions is
over the life cycle of products or activities.
(d) The water footprint is derived from the concept of virtual water equal to the
volume of freshwater used to produce a commodity (Allan 1998; Hoekstra
2009). It aims to address the question of how much volume of the cumulative
virtual water is needed to provide products or activities.
2.3.3.2 Components and Units
(a) The ecological footprint is built upon a tradition of seeking alternatives to the
appropriated carrying capacity which is related to the maximum population size
that can be supported by a given set of resources (Dietz and Neumayer 2007;
Ehrlich 1982). It is intended to deal with the question of how much area of
biologically productive space is required to produce consumed resources and to
absorb generated waste.
(b) The energy footprint can be classified into concrete components such as the fossil
fuel footprint, the hydroelectricity footprint, and the nuclear footprint (Browne
2009; ˇ
Cuˇ cek et al. 2012a; Stöglehner 2003), all of which are expressed as the
area of forest that is necessary to compensate for human-induced CO 2 (Van
den Bergh and Verbruggen 1999). The unit of measurement can be gha or local
hectares with a specific carbon sequestration estimate (Walsh et al. 2010).
(c) The components of the carbon footprint include a variety of GHGs such as CO 2 ,
CH 4 , and N 2 O. The use of GHG characterization factors as determined weightings dependent on the 100-yr GWP has a broad base of acceptance (Ridoutt and
Pfister 2013) because the greater the GWP of a GHG, the more responsibility
it should take on for increasing global temperatures. The metric is expressed in
CO 2 -equivalent mass units such as kilogram or ton, indicating the impact unit
of time-integrated radiative forcing.
(d) The water footprint consists of three components in volume-based units: the
blue, green, and gray water footprints. The blue and green footprints correspond
to the demand for freshwater resources (from surface or ground water, and from
rain, respectively), while the gray footprints refer to the waste assimilation by
water and are defined as the volume of freshwater required to assimilate load of
pollutants based on the existing ambient water quality standards (Chapagain and
Hoekstra 2008; Hoekstra 2009). Although Hoekstra (2009) has declared that no
weighting is involved, equal weighting is also a form of weighting. It fails to