Page 107 - Materials Chemistry, Second Edition

Life Cycle Assessment: Principles, Practice and Prospects
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represents all the uses of water over the life cycle of a particular system being analysed. In
general, the water indicator is interpreted as an environmental impact that should be mini-
mised. This interpretation can have its flaws, some of which are discussed below. Second, LCA
can be used to assess the environmental impacts of water delivery and management systems
(e.g. water treatment, stormwater management). LCA used in this manner aggregates a vector of
environmental impacts over the life of a water system and then typically allocates impacts to a
unit of consumption or disposal (e.g. global climate change impact per unit of water used or
eutrophication impact per unit of wastewater treated). Incidentally, water use is often one of the
environmental indicators considered (e.g. water used per unit of water delivered).
Although data collection and modelling may be complex and time-consuming, LCA has
proved to be effective for assessing the sustainability of water systems and is increasingly used
by water users and suppliers to maximise the sustainability of synthetic water systems. The
following sections indicate elements of importance when using water as an indicator of envi-
ronmental impact (see Section 8.2), and when undertaking an LCA of a water system (see
Section 8.3). In Section 8.4, challenges and limitations in LCA for water assessment are dis-
cussed. Conclusions are drawn in Section 8.5.

8.2 Water as the indicator: a flawed measure?
As with any LCA, the goal and scope defines the objectives and desired outcomes of the study.
Usually, the goal will be to determine potential environmental impacts associated with a par-
ticular system of interest. In determining impacts, the life cycle inventory is reviewed and
indicators of environmental impact are calculated based on widely accepted scientific under-
standing. For example, the aggregation of carbon dioxide emissions may be undertaken as an
indicator of the climate change effect of a system. In general, indicators typically used in LCA
are measures of environmental damage or adverse affect, such as ‘photochemical smog
produced’, or ‘fossil fuels depleted’. Water as an indicator is used in a similar fashion to the
latter – principally as a resource depletion measure.
Hence, the typical water indicator used in an LCA is constructed from the life cycle inven-
tory by adding all water inputs to the system during its life cycle. The indicator provides an
accurate measure of water inputs needed by the system, but not necessarily an indication of
environmental damage. For instance, a system that accepts a given amount of water and dis-
charges this water unchanged (such as a pipeline) will attract the same impact assessment in
the water indicator as a process transforming a given amount of water into unusable sludge.
Where the inventory of water consumption is presented as an indicator of impact, this indi-
cator also fails to deal with issues of local scarcity and site specificity. For example, the water
impact of growing rice in southern New South Wales in Australia may be presented as similar
to the water impact of growing rice in Bali in Indonesia, yet the local scarcity and implications
of removal of this same quantity of water from different local systems may be quite different. It
is therefore important to differentiate between inventory quantities (load, use or depletion)
and effects (impacts of these quantities of use in a temporal and spatial context).
The potential for confusing an inventory quantity with actual environmental damage is not
unique to water indicators. Other indicators meet with similar problems. For example, eutroph-
ication describes nutrient disposal to the environment, with the potential to over stimulate bio-
logical growth in waterways. In some cases eutrophication will be limited by the phosphorous
content of a waste stream, and in others it will be limited by the nitrogen content of a waste
stream. The element that determines the eutrophication outcome depends on the geography of
the locale. Nonetheless, eutrophication impacts typically do not incorporate spatiality, so the
indicator may assume a worst possible eutrophication impact, which in reality may not occur.

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