The water footprint of Irish meat and dairy products

The water consumption of a range of dairy and beef production systems was estimated for four locations in Ireland using the Cranfield Life Cycle Assessment (LCA) systems model. This included direct water consumption (for drinking, washing, cleaning, etc.) as well as virtual water in the diet (that is, water that had been used to grow grass and concentrate feedstuffs). This was partitioned into “blue” water that is abstracted from rivers or groundwater, or taken from mains water supplies, and “green” water that is rain water used by growing plants at the place where the rain falls. In general, intensive systems have a lower water consumption per unit of output than extensive systems as the higher water consumption per head is offset by high output. The water consumption of dairy-beef systems is lower than for suckler beef because most of the water use by the dairy cow is allocated to the dairy system, whereas for suckler systems, the water use of the suckler cow is included for the first year. It is clear that the vast majority of the total water consumption for all the systems studied is green water. It can be argued that green water use has negligible environmental impact as it has a low, or negligible opportunity cost. The rain water consumed by growing grass or feed crops could only be used for growing alternative vegetation, that is, it could not be used to substitute for water for domestic or industrial consumption for example. Therefore, there is no water benefit in saving green water. The blue water consumption is very small for both milk and beef under all systems. Drinking water accounts for almost half of the blue water used by dairy systems, and almost all of that consumed by beef systems. Therefore, technologies that reduce the wastage / leakage in on farm drinking water systems can reduce the overall water consumption. For dairy systems the remainder of the blue water consumption is associated with milk cooling and cleaning of the milking parlour and yards. The amount of blue water associated with growing feed is trivial. For dairy, twice as much blue water is consumed in the processing of milk compared to the livestock and feed systems. For dairy-beef and suckler beef, blue water consumption on the farm 2.5 and 7.4 times as much as used in the processing stage respectively. Most water use on Irish livestock farms is from groundwater (90%) and mains water (10%). Generally, widespread abstraction pressures on groundwater are not significant in Ireland and the impact of water use would be expected to be small, however, there are some localised cases where abstraction pressures are impacting on groundwater levels (EPA, 2008). This highlights the very local scale of hydrological impacts and suggests that even though the average water consumption of Irish beef and dairy production is very small, in certain places it may be contributing to depletion of groundwater resources and water conservation may be encouraged.

The Water Stress Index can be used to normalise the blue water consumption and to derive an index of water equivalent (H2Oe) that reflects both the volume of blue water consumed and relative stress on water in the producing region. For dairy systems, the normalised water footprint of milk production (at the farm gate) ranges from 0.12 litres H2Oe/litre fat and protein corrected milk (FPCM) for high yielding autumn calving systems in the south of Ireland to 0.17 for low-yielding, spring calving systems in the south-east. For beef systems, the normalised water footprint of milk production (at the farm gate) ranges from 0.24 litres H2Oe/kg for extensive dairy beef systems in the south of Ireland to 0.98 for autumn calving, extensive finishing systems in the south-east. These figures are very low compared to other livestock producing regions.