Page 35 - Chemical Technology

The direct operational water footprint contributed
1% of the footprint. The indirect supply chain consti-
tuted 99% of the water footprint in the production of the
0,5litre PET bottle of Coca Cola (Hastings and Pegram,
2012). The water assessment of the 0,5 litre PET Coca-
Cola bottle showed that the indirect supply chain water
footprint was the most significant component. This large
contribution was associated with the raw material pro-
duced by the agriculture sector.
Figure 5 shows the water footprint of sugar beet used in
producing some of the Coca-Cola products. The sugar beet
was produced in different countries in Europe and had dif-
ferent water footprint impacts in those countries. Greece
had the largest water footprint at almost 1 250 litres/kg
sugar and France the lowest at almost 380 litres/kg sugar.
The average blue, green and grey water footprint was 54-,
375- and 128 litres/kg sugar respectively (Hastings and
Pegram, 2012).
Fossil fuel Water Footprints
The most important primary non-renewable energy car-
rier is crude oil. Production of the oil product involves
drilling, pumping from underground sources and treating.
Gleick (1994) estimated that between 2 and 8 m3 of wa-
ter are required for every 103 GJ of oil production. Steam
injection used to improve recovery and the viscosity of
the oil requires between 100 and 180 m3 of water per
103 GJ of energy.
Open pit coal mining requires about 2 m3 of water per
103 GJ while underground operations require between 3
and 20 m3 per 103 GJ (Gleick, 1994).
Natural gas is obtained by drilling into underground
reservoirs. Gliek (1994) estimated that natural gas plant
operations require about 100 m3 of water per 103 GJ.
Uranium is harvested through open pit and un-
derground mining operations. Water is needed for
dust control and ore refining. Water requirements for
uranium mining are 0,2 m 3 of water per 103 GJ for
underground mining, 20 m3 of water per 103 GJ for
open pit mining and 20 m 3 of water per 103 GJ for the
milling, refining and enriching of uranium (US Atomic
Energy Comm, 1974).
Renewable energy Water Footprints
Hydropower requires water to drive turbines which
generate electricity. Dams are often used as sources for
hydropower. The water requirements for the dams are
caused by evaporation and seepage from the reser-
voirs and amount to between 5 and 26 m3 per 103 kWh
(Gleick, 1994).
For solar energy, it was estimated that water require-
ments of solar thermal power plants are about 1 m3
per 103 kWh. Wind energy uses kinetic energy in the
air to generate electricity via wind powered turbines.
If the land used for wind farms has no agricultural
uses, no water requirements are allocated to wind
energy. Thus the water requirement of wind energy
requires no water except during construction which is
negligible (Gleick, 1994).
Water Footprinting limitations
The water footprint concept is time- and space-depen-
dent. Unlike a Carbon Footprint, water withdrawn in Africa
and returned or used in Asia does not cancel out the
impact caused by removing that water from Africa. Simi-
larly, water withdrawn in summer does not cancel out the
impact even if the water is returned in winter (Hoekstra,
2003). The freshwater scarcity and its impacts (environ-
mental, social and economic impacts) from one region
cannot be displaced or transferred to another region that
is water-rich. Currently the water footprint concept is not
able to explicitly measure and report local environmental
impacts caused by usage of freshwater and the pollution
of freshwater (Hoekstra, 2003).
Conclusion
Notwithstanding its limitations, the Water Footprint is a
very useful tool for identifying those areas of high wa-
ter usage. It can thus assist companies and industries
in addressing and even potentially mitigating the risks
associated with high water usage. The potential also
exists for operations to use the technique to bench-
mark their water usage with a view towards achieving
on-going reductions.
Figure 4: Water footprint of a 0,5 litre bottle of Coca-Cola (Hastings
and Pegram, 2012)
Figure 5: Water footprint of sugar used in Coca-Cola products by
country of production (Hastings and Pegram, 2012)
Chemical Technology • January 2013 33
water treatment