Page 203 - Materials Chemistry, Second Edition

EXERGY ANALYSIS AND ITS CONNECTION TO LIFE CYCLE ASSESSMENT 189

• Normalization and weighting: Normalization and weighting
combine all environmental impacts and reduce them to a single
measure. Although optional, this LCIA step is but often helpful
for comparing alternatives.

Examples of impact assessment methods include CML 2001 (Guinee et al,
2002), Eco-indicator 95 (Goedkoop et al, 1996), EPS 2000 (Steen, 1999), IMPACT
2002+ (Jolliet et al, 2003), IPCC 2007 (Parry et al, 2007) and TRACI (Bare, 2002).
The CML 2001 method is used in the illustrative example at the end of this
chapter.
The Center of Environmental Science of Leiden University (CML) published
an "operational guide to the ISO standards" in 2001, which has a set of impact
categories and characterization methods and factors for a list of substances
(accounting for resources from and emissions to the natural environment) to
use in the impact assessment phase of LCA. Guinee et al (2002) explain these
environmental impact categories, important examples of which follow:

• Acidification Potential (AP): AP is the deposition of acidifying
pollutants on soil, groundwater, surface waters, biological organ-
isms, ecosystems and materials, and is measured in units of kg
S0 2-eq. Major contributors to this category are S0 2 , NOx and
NHx. The natural environment, the anthropogenic environment,
human health and natural resources are protection areas where
AP has notable effects.
• Eutrophication Potential (EP): Eutrophication comprises all
potential impacts of excessive levels of macronutrients. Nutrient
enrichment may cause an undesirable shift in species composition
and elevated biomass production in both aquatic and terrestrial
ecosystems. Nitrogen and phosphorus, as well as other emissions
causing similar effects, are grouped in the eutrophication impact
category. The unit of EP is kg P0 4 -eq.
• Global Warming Potential (GWP): GWP is the impact of human
emissions on the radiative forcing (i.e. thermal radiation absorp-
tion) of the atmosphere, and is measured in units of kg C0 2 -eq.
Global warming, which leads to climate change, may affect
ecosystem and human health. Most greenhouse gas (GHG)
emissions increase radiative forcing, which increases the earth's
surface temperature (the "greenhouse effect").
• Ozone Depletion Potential (ODP): Ozone depletion is the thin-
ning of the stratospheric ozone layer due to ozone-depleting
emissions. A greater fraction of solar UV-B radiation reaches the
earth's surface as a result of this thinning, which has potentially
harmful impacts on human and animal health, terrestrial and
aquatic ecosystems, biochemical cycles and materials. ODP, which
is measured in units of kg Rll-eq, influences on four protection
areas: human health, the natural environment, the anthropogenic
environment and natural resources.