LCA Food 2012 in Saint Malo, France! - Manifestations et colloques ...

GROUP 2, SESSION A: CARBON OR WATER FOOTPRINTS, SOIL, BIODIVERSITY 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
57. The influence of methodology on the water footprint of selected
UK produced and consumed products
Rob Lillywhite 1 , Ashok Chapagain 2 , Tim Hess 3
1 University of Warwick, Wellesbourne, Warwick, CV35 6JQ, UK, 2 WWF-UK, Goldaming, UK, 3 Cranfield
University, Bedford, UK, Corresponding author. E-mail: robert.lillywhite@warwick.ac.uk
Water footprinting is still evolving as a discipline and various methodologies and approaches exist to quantify
the volumes of water withdrawn, used and consumed for food production and to assess any associated
environmental impacts. The choice of methodology will influence the results and interpretation, a situation
which has resulted in considerable variation in reported estimates on water use and its impacts for different
agricultural and food products. Mindful of this, the UK Government commissioned research to explore the
different approaches using selected UK produced and consumed products (potato, lamb, milk, strawberry,
sugar and winter wheat) as case studies.
The study used three approaches:
1. The water footprint accounting framework developed by The Water Footprint Network (Hoekstra et
al., 2011). This approach estimates the volume of green and blue water consumed during the different
stages of production (evapotranspiration, irrigation, crop protection, livestock drinking, cleaning
etc.)
2. The stress-weighted water footprint (Ridoutt and Pfister, 2010). This approach estimates the volume
of blue water consumed during production and converts it to an assessment of local water stress using
a water stress index (WSI) (Pfister at al., 2009)
3. The normalised water footprint, H2Oe (Ridoutt et al., 2012) This is a development of the stressweighted
approach in which the stress-weighted value is divided by the global average WSI to give
an assessment of water consumption relative to a global average.
The results show that the considerable influence that methodology has on the estimated values. The volumetric
results are not directly comparable to the stress-weighted and normalised results since they are based on
different criteria, but they are all commonly referred to as water footprints and clearly illustrate the potential
for confusion that can arise in this discipline. Table 1 shows the results for UK and Israeli potato and allows
the following interpretation.
In terms of volumetric water consumption, Israeli potatoes use one and a half times more water than UK
production. However, where the impact of that water consumption is considered, Israeli potatoes can have a
ten-fold greater impact on local water resources and a nineteen-fold greater impact at a global scale. The key
to understanding and using these results is the omission of green water from the stress-weighed and normalised
approaches which principally reflects the difference in evapotranspiration (and therefore climate) but
also of irrigation practice, between the two countries.
The volumetric water footprint has been very successful in raising awareness of the use of water and is invaluable
for water auditing purposes but we conclude that it has limited value for determining the local water
stress of globally sourced products. A more balanced approach, especially within the LCA framework, is
possible using the normalised water footprint alongside other environmental indicators, such as eutrophication
and acidification. This will provide a more consistent and robust approach for environmental and sustainability
studies.
References
Hoekstra, A.Y., Chapagain, A.K., Aldaya, M.M., Mekonnen, M.M. (2011) The water footprint assessment manual: Setting the global standard, Earthscan, London, UK.
Pfister ,S., Koehler, A., Hellweg, S. (2009) Assessing the environmental impacts of freshwater consumption in LCA. Environ. Sci. Tech 43, 4098-4104.
Ridoutt, B.G., Pfister, S. 2010. A revised approach to water footprinting to make transparent the impacts of consumption and production on global freshwater scarcity.
Global Environ. Change 20, 113-120.
Ridoutt B,G., Sanguansri, P., Freer, M., Harper, G.S. (2012) Water footprint of livestock: comparison of six geographically defined beef production systems. International
Journal of LCA 17: 165-175.
Table 1. The influence of methodology on the water footprint of UK and Israeli potato
Volumetric (liStress- Normalised
Country tres/kg)weighted (H2Oe/kg)
UK 107 10 9
Israel 147 103 171
737