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Analysis Methods for Design Decisions 177

the interest.” While it has been used primarily at a national level,
ecological footprint analysis can be applied at any level of granular-
ity, from an entire nation to a single individual. Thus, it offers a
method for estimating the ecological burden associated with eco-
nomic enterprises, supply chains, or communities [10].

Water Footprint
The water footprint of a product or an entire enterprise can be
defined as the total annual volume of fresh water that is used directly
in operations and indirectly in the supply chain [11]. Some indus-
tries, such as food processing, use a great deal of water. Even busi-
nesses that use very little water for manufacturing may still have a
substantial supply-chain water footprint if their raw materials come
from agricultural sources; for example, the footprint for cotton gar-
ment manufacturers includes a large amount of irrigation water.*
In addition, consumers that launder those garments use a consider-
able amount of water over the product life cycle, and this can be
considered as part of the footprint from an extended producer
responsibility perspective. In the United States, nearly 25% of all
fresh water use is process water for steam turbines in electric power
generation, and this is often the largest component of a company’s
water footprint. The water footprint of common foods can range
from about 1000 liters per kg of grain to about 16,000 liters per kg of
beef [12].
Water use can be measured in terms of water volumes con-
sumed, i.e., evaporated, and/or polluted per unit of time. Thus, water
that is simply “borrowed,” as in hydroelectric power generation,
does not count as usage. The water footprint can be split into three
elements:
1. Blue water: the volume of fresh water that was evaporated
from surface water or ground water resources.
2. Green water: the volume of fresh water that was evaporated
from rainwater stored in the soil as soil moisture.
3. Grey water: the volume of polluted water, calculated as the
volume of water that was required to dilute pollutant dis-
charges in order to meet water quality standards.
Unlike greenhouse gases, the ecological or social impact of a water
footprint depends not only on the volume of water use, but also on
the geographic locations and timing of the water use. Water-stressed
or arid regions are more vulnerable to water use, especially during
dry seasons.

*The total water footprint associated with a product is sometimes called “virtual
water.”