Environmental Engineering Reference
In-Depth Information
the goals also specify the audience expecting to use the findings
(Winkler and Bilitewski, 2007). Scope identifies the functional unit of
product being studied and establishes the boundaries (Eriksson et al.,
2002) of the study.
2. Building the life cycle inventory (LCI). This includes the collection of
data, assigning data to different processes, and calculating, converting,
and aggregating the data in relation to functional units of the product
(Consonni et al., 2005). A complete set of data covering all phases of the
value chain is essential for a good LCA (Hassan, 2003).
3. Impact assessment. The collected data analyzed for physical, chemical,
and biological impacts on the environment. These are generally
quantified in different units and therefore need to be normalized
(Tugnoli et al., 2008) into dimensionless values. Only the comparable
impacts are aggregated together to reduce the number of parameters
involved in the analysis. For instance, data relating to resource
depletion, ecosystem degradation from externalities, and human health
impacts might be aggregated and normalized, separately.
4. Interpretation of findings. Conclusions are drawn from the LCI analysis
and impact analysis. Where products are compared, this provides a
comparative ecoprofile. The attributes of a product that needs to be
changed to make it more sustainable are identified in the analysis. The
limitations and weaknesses of the LCA are addressed usually via a series
of iterative executions of these four steps.
LCA models may synthesize environmental indicators using data from LCI
or by using midpoint or endpoint indicators. LCI results can compare
different products on the basis of energy costs, resource demand, and the
externalities generated. But they do not describe impacts on the
environment completely or even substantially. Midpoint indicators use
models to determine the impact of flows on a selected environmental
predictor such as the global warming potential (GWP). Endpoint indicators
show the final impact of the flows from LCI and not only are more complex
and more difficult to model but also have a high level of uncertainty. Tool
for the Reduction and Assessment of Chemical and Other Environmental
Impacts is a midpoint indicator model by the USEPA and recognizes 12
impact areas including ozone depletion, global warming, acidification,
eutrophication, tropospheric ozone (smog) formation, ecotoxicity, human
particulate effects, human carcinogenic effects, human noncarcinogenic
