Page 55 - Materials Chemistry, Second Edition

50 3. Life cycle thinking tools: Life cycle assessment, life cycle costing and social life cycle assessment

enough information for an engineering bottoms-up estimation model. The model could refer
to the number of operating hours a system accumulates. Different models are appropriate for
each situation, for instance it is possible to use an operating hour driven model, or a periodic
inspection, or a periodic exercise driven model. For a system or subsystem trade study, it can
be appropriate to use a bottom-up rather than a top-down model. This means that a perfect
LCC methodology/model that fits all applications does not exist. In any case, the selected
model has to be documented properly, has to be verified and validated, and has to contain
all the elements that need to be covered (Greene and Shaw, 1990).

3.2.2 Inventory

Data collection is a significant, time-consuming phase. Data can be collected from different
sources, it is possible to collect data in the plant where the product is realized or the process
occurs, directly. However, sometimes, it is necessary to make use of data from technical re-
ports, from the scientific literature, or it can be necessary to do some estimations. The input
and output data have to be checked in terms of consistency, accuracy, validity, and complete-
ness to make sure that erroneous information is not present in the analysis or that required
information has not been neglected. This step is important in order to avoid misinformation
coming out of the analysis and to improve the credibility of the analysis.

3.2.3 Calculation of LCC results
After the collection of all the needed data, the implementation of the LCC model, and the
making of the sensitivity or risk assessment, the results of the LCC study can be calculated. If
there is the need to revise some methodological choices, it is possible to revise previous
phases, such as the purpose of the study, and adjust the study. In this step, it is necessary
to evaluate possible alternatives and identify the factors that significantly affect the LCC
study. During this step, the results of LCC analysis can be inflated or discounted.

3.2.4 Interpretation
The input parameters with significant risk and high potential for impacting cost need to be
varied over a reasonable range. It is possible to use the “best case,” the “worst case,” or some-
thing in between. LCC evaluations are estimations regarding the cost range, which can be
expressed in a statistical way, or through a model with a limited number of parameters.
The results of the LCC study have to be documented, along with the information to support
the analysis.

3.3 Social life cycle assessment methodology

Social life cycle assessment (S-LCA) is a novel methodology to address the social impacts of
products and services along their life cycle. It is based on LCA methodology, with some