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
ods, addressing major issues related to water use in Life Cycle Assessment (LCA). An up-to-date and exhaustive
scheme can be sent upon request, including all inventories flows, characterisation factor methods,
etc.
Water is withdrawn, either in the form of surface water or renewable groundwater, and used for various
purposes such as crop irrigation. In this study, this is represented as water “input”. On the other hand, “outputs”
may be represented as surface and/or renewable groundwater that are released unaffected or as water
consumed (or dissipated) by evaporation or incorporation into the product or another watershed. Depending
on the type of water, different impact methods are applied in order to evaluate the stress on human health,
ecosystem quality, and resources for future generations (see Figure 1). In addition, a simplified water stress
assessment is performed by weighting the water inventory by a water stress index, represented in m3 equivalent,
which is used for assessing the competition for water.
Figure 1. General framework for water use impact assessment for feed production and on farm water use
(grey water is not included in the water use part of the study).
The simplified water stress assessment applies Pfister’s water stress index (Pfister et al., 2009) which is
used to assess the competition for water as a function of withdrawal to availability. The Water Stress Index
(WSI) indicates the portion of water consumed by different users (i.e. industry, agriculture and households)
that deprives others of freshwater. In this study, the level of resolution used is at state level. Therefore, water
consumed is multiplied by a water stress index and the result is expressed as litres of water “in competition”
or “deprived”, as shown in the Equation 1:
52
Water in competition= 0 . 05WSI
LCI WSI
Eq. 1
LCI withdrawal blue,
consumed
The WSI varies widely across the United States and is related to precipitation, as well as water use and
availability. State level data were provided by Pfister (Pfister et al., 2009) and were calculated by weighting
the values at the watershed level by the area and water withdrawal of each state.
2.2. Description of the life cycle data
For a water use impact assessment of milk production in the U.S. it is important to take into account the location
of the feed production as water use impact can vary significantly across the country. The crop type, the
irrigation requirements and the type of water used (e.g. groundwater withdrawal vs. surface water withdrawal)
are all important factors to consider when evaluating water impacts. In order to model the crops, the
average rations in terms of amount of crops consumed per cow are used. Crops are all assumed to be obtained
from within the United States and are separated into four different types:
Commodity crops (e.g. corn grain and soybean): assumed to come from anywhere in the country,
custom modeling based on literature data (Fruin et al., 1989; Larson et al., 1990)