Page 278 - Materials Chemistry, Second Edition

262 4 Life Cycle Impact Assessment

considered in the impact assessment with geographically highly resolved inventory
data. Without doubt phosphor and nitrogen are the highest contributors to the
impact category eutrophication.
The former impact category ‘chemical oxygen demand’ has been integrated as an
indicator for nutrients into the impact category ‘eutrophication’. As a matter of fact,
organic compounds that are biologically degradable under consumption of oxygen
are better characterised by the biochemical oxygen demand (BOD) but the data
availability of COD is much better and the BOD is included in the COD. As a result
of aerobic bacterial degradation of organic compounds (particular or dissolved)
the oxygen concentration decreases, CO concentration and the concentration of
2
inorganic nutrient salts increase. The impact of an increased entry of these organic
compounds into the waters is therefore comparable to an over-fertilisation with P-
and N-containing compounds followed by increased growth of algae.
Heat released by power plants into waters can have a qualitatively similar impact:
bacterial degradation processes of organic matter are speeded up. Furthermore
different species compared to those of cooler waters are favoured. Keywords like
eutrophication, BOD and heat have been comprised into one impact category by
SETAC Europe 255) (see Table 4.2).
An attempt can be made to comprise eutrophication and BOD or COD as one
indicator; however, heat cannot be included. It has to be assigned and assessed
separately, if relevant, in the study under consideration, as for instance for thermal
power plants. Experience shows that heat is never an impact category of its own
nor nearly ever integrated as indicator into the eutrophication category.
Following the precautionary principle for a calculation of the aquatic eutrophica-
tion potential (EP) or nutrification potential (NP) it is presumed that every unintended
nutrient supply to the environment, contrary to targeted fertilisation in the tech-
nosphere, can imply over-fertilisation. Neither the local situation nor pre-existing
pollution loads of the site are considered. As a basic idea behind the scenes it is
presumed that loads caused by humans, no matter whether by nutrient or pollutant
overload can have a damaging or at least an unintended impact on the environment.
This is in accordance with experience: eutrophic lakes, unrestricted growth of algae
in the estuaries and over-fertilisation of forests in case of terrestrial eutrophication
(forest soils are generally nutrient-poor). Oceans are also very nutrient-poor. Only
in upwell regions where nutrient rich water from the deeper layers drifts to the
surface, under natural circumstances and based on an increased growth of algae
(primary production) high amounts of biomass are observed at all trophic levels.
Also in the marine ecosystems, an increased entry of nutrients can imply
undesirable, and above all (in contrary to many limnic ecosystems), uncontrollable
changes. Many eutrophic lakes of anthropogenic origin could be remediated by
strict regulations with respect to discharge of waste water and the implementation
of waste water sewage plants (i.e. prevention of the input).

255) Udo de Haes (1996).