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

PARALLEL SESSION 1A: WATER FOOTPRINT 8 th Int. Conference on LCA in the
Agri-Food Sector, 1-4 Oct 2012
Domestic crops - light forage (e.g. alfalfa/grass hay): assumed to come from within the region (of the
five defined regions) that the farm is located.
Domestic crops - heavy forage (e.g. corn/alfalfa/grass silage): assumed to come from within the state
that the farm is located.
Local crops (e.g. pasture): grown on farm
Commodity crops such as corn grain are assumed to be produced nationwide at a rate equivalent to the
production with respect to total U.S. production. This provides a “supply mix” that is considered equivalent
for all dairy cow rations. National statistics available from the USDA are used for 2007 and 2008 (USDA
NASS 2010a).
The irrigation data for all crops modeled in this study were obtained from the United States Department
of Agriculture (USDA), National Agricultural Statistics Survey website. However, this data does not include
information on the fraction of irrigation water that is evaporated, or recuperated from drainage/run-off. The
2008 Farm and Ranch Irrigation Survey (USDA NASS 2010b) was used in order to determine the irrigation
rate for each crop at the state level. Data for areas harvested and areas irrigated were used from the 2007
USDA Census of Agriculture to calculate average irrigation rates per crop per state. This represents the water
withdrawal per crop. If data regarding average irrigation rate was not available but irrigation was used, the
average irrigation rate of the region was used as a proxy for the state in question. Green water (or precipitation)
inventory was not assessed in this study.
For the water used outside of feed and dairy farms, the water footprint is evaluated based on a nonspatialised
assessment. The model was built upon the Extended LCA SimaPro model developed by Thoma
(Thoma et al., 2010). Non-spatialised contributions include lesser feed components, ancillary and upstream
processes, as well as post-farm-gate life cycle contributions (milk processing, distribution, retail, and consumption).
3. Results
3.1. Spatialised national impact assessment for feed: cradle to feed producer gate
There is a strong correlation between irrigation requirements and Pfister’s water stress index as states that
do not receive a high amount of precipitation are more likely to have higher irrigation needs. However, the
water stress index for the State of Oregon may not accurately represent the actual average water stress of the
state. In the west, the state receives a lot of rainfall but in the east of the state, it is quite dry, with high irrigation
requirements. This reflects the limitation of applying a state level regionalisation for the water stress
indices.
Moreover, the water stress assessment per kg of crop in each state needs to be weighted by the production
in order to understand the contribution to the national impact.
Water Stress Impact
L_eq deprived / kg
state corn grain
Contribution
to national
corn grain
impact
Weight by US corn grain
production:
mainly in the corn
belt!
Figure 2. Water stress assessment of corn grain production in the U.S., combined to give national corn grain
impact.
The states that have a high water stress are primarily in the west of the country while the majority of the
corn production is in the north east of the country (the Corn Belt). As a result, only states with both high corn
grain production and high water stress index are considered to be problematic, in terms of corn grain. Such
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