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
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Parameters Unit Dairy Waikato Dairy Canterbury Beef and sheep NZ
Grassland area ha 94.6 200.2 245 - 8,872
Stocking rate SU 1 /ha 2.96 3.11 1.1 – 10.6
Feed supplements kg DM 2 /ha 798 1,892 0.4 - 291.5
Irrigated area % of total ha 0 71 0 – 0.5
Rainfall mm/yr 1264 677 688 - 1500
1 Stock units in dairy cows or sheep and beef cattle equivalants e.g., based on 550 kg DM intake for a mature sheep
2 Dry Matter
Although annual dry matter intake from pasture by animals on farm was similar for the two systems
(11,670 kg DM/ha for the Waikato system and 11,260 kg DM/ha for the Canterbury region), the Canterbury
dairy system used more brought-in supplementary feed (1,892 kg DM/ha vs. 798 kg DM/ha) and relied on
cows grazing off-farm over winter, which resulted in a higher annual milk production (13,183 L milk/ha vs.
10,514 L milk/ha).
Water losses associated with evapotranspiration from irrigated pasture, as well as nitrate leaching and
phosphate runoff (from all soluble and soil-adsorbed sources) were computed using the hydrological sub
model in the OVERSEER ® nutrient budget model (Wheeler et al., 2003).
We used nitrate and phosphate loss when computing the water quality indicator “eutrophication potential”
(EP), while excluding gaseous emissions, as preliminary results showed that ammonia and nitrous oxide
emissions dominated the EP which is questionable for NZ conditions. Data are expressed in phosphate
equivalents (PO4 3- -eq).
The cradle-to-farm-gate life cycle required for the production of milk, beef, and sheep meat were analysed:
for the production of inputs to products leaving the farm-gate, i.e. excluding transport or processing of
raw milk or animals. Water abstraction and consumption associated with the production of machinery, buildings,
and medicines were excluded. Economic allocation was applied when dividing the WF between milk
and meat. Biophysical allocation based on feed intake was used when dividing the WF between beef cattle
and sheep, while economic allocation was used when dividing the WF for sheep between meat and wool.
In the impact assessment, the water stress index (WSI) following Pfister et al., (2009) was applied to get a
stress-weighted WF. Data were normalised against the global WSI and expressed in H2O-equivalents (Ridoutt
and Pfister, in press).
3. Results
The stress-weighted WF of NZ beef (excluding beef from culled dairy cows) was 0.2 L H2O-eq/kg live
weight (LW) (Table 2). Blue water losses from the grazed system were low and consequently the main
losses were associated with bull calf rearing (57%) and blue water losses associated with evapotranspiration
from irrigated pasture (36%). The stress-weighted WF of NZ sheep meat was 0.1 L H2O-eq/kg LW. Table 2
shows that the stress-weighted WF was 0.01 and 7.1 L H2O-eq/kg fat-and-protein-corrected milk (FPCM) for
the Waikato and Canterbury farm systems respectively. Water consumption associated with irrigation dominated
the WF of the Canterbury dairy system, whereas water consumption associated with hydro-electricity
supply was a hotspot in the WF of the Waikato dairy system.
Table 2. The stress-weighted water footprint (WF) of beef and sheep meat (based on a NZ weighted average),
and milk produced in the Waikato and Canterbury regions respectively.
L H2O-eq/kg unit Unit WF
Beef (NZ weighted average) LW 1 0.2
Sheep meat (NZ weighted average) LW 0.1
Milk in Waikato region FPCM 2 0.01
Milk in Canterbury region FPCM 7.1
1 Live Weight sold
2 Fat-and-Protein Corrected Milk
The EP of NZ beef (excluding beef from culled dairy cows) was 12.2 g PO4 3- -eq/kg LW (Table 3). The
EP of NZ sheep meat was 4.9 g PO4 3- -eq/kg LW. Nitrate and phosphate loss at the farm (71% and 75% respectively)
and the eutrophying pollutants to waterways associated with the production of artificial fertilisers
(20% and 22% respectively) dominated the EP. Table 3 shows that the EP was 1.94 g PO4 3- -eq/kg FPCM and
1.49 g PO4 3- -eq/kg FPCM for the average Waikato and Canterbury dairy farm systems respectively. Nitrate
and phosphate loss within the dairy farm (94-98%) dominated the EP of milk in these two regions.