Page 197 - Design for Environment A Guide to Sustainable Product Development

176 Cha pte r Ni ne

• Total Material Requirements (TMR) measures the “rucksack”
of indirect “hidden flows,” including mining wastes and
other discards, which are carried along with direct material
inputs, but generate no economic value and may disturb the
natural environment. For the average European, TMR is esti-
mated to be about 220 kg/day. The size of the rucksack can
be significant; for example a diamond ring weighing 10 g has
a rucksack of about 6000 kg, while an average newspaper
has a rucksack of 10 kg [7].
• Material intensity can be measured as the ratio of DMC to
gross domestic product (GDP). MFA studies suggest that
the E.U. economy has become more eco-efficient, since mate-
rial intensity slowly declined from about 1.2 kg/€ in 1992 to
about 1 kg/€ in 2000 [8]. However, the absolute DMC con-
tinues to increase due to economic growth.
Similarly, by drawing the boundary around an enterprise or a
specific product system, MFA can be used to measure its material
intensity. However, reliance on mass flow indicators can be deceptive
for several reasons. First, not all materials are equal in terms of their
environmental impacts, and MFA does not try to distinguish materi-
als in terms of toxicity or other properties. Second, MFA often does
not account for the hidden environmental burdens associated with
imported materials. In an economy where global sourcing is increas-
ingly the norm, the question of allocating accountability for these
upstream material flows remains challenging.

Land Area Footprint
A technique called “ecological footprint” uses land area (hectares) as
a metric for estimating the productive capacity needed to support
both resource consumption and waste absorption for a specified eco-
nomic activity such as power generation [9]. This footprint can be
interpreted as the burden placed on the carrying capacity of ecosys-
tems, which is the maximum amount of replenishment per unit time
that they can support without impairment. The worldwide carrying
capacity is estimated to be 2.1 hectares per capita, of which 1.6 hect-
ares are land-based ecosystems, such as forests, pastures, and arable
land and 0.5 hectares are ocean areas.
The average ecological footprint per capita is estimated to be
12.3 hectares in the United States, 7.7 hectares in Canada, and 6.3
hectares in Germany. Hence the oft-quoted statement that it would
take three planet Earths to support the world’s population if they all
adopted the lifestyle of a “developed” nation. The average footprint
for all nations is estimated to be 2.8 hectares per capita, suggesting
that humanity has already overshot global capacity and is deplet-
ing the available stock of natural capital, rather than “living off