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Life cycle assessment, technical and economical analyses of jatropha biodiesel 527

24.4 Methods and assumptions

24.4.1 Life cycle assessment
24.4.1.1 Method
LCA is the most common method for analyzing the environmental impact of a
product, service, or system throughout its life cycle (Belboom, 2012; Beloin-Saint-
Pierre, 2012). It is widely used to help design and/ redesign evaluated systems in
order to identify areas for the improvement (Belboom, 2012; Beloin-Saint-Pierre,
2012). In particular, it is generally used to compare different products or services
responding to the same functions throughout their life cycle. The harmonization
work that led to ISO 14040 structured the implementation of a LCA in the follow-
ing four steps or mandatory phases (Belboom, 2012; Beloin-Saint-Pierre, 2012):
Objectives and scope study definition. This step is necessary to target and clarify the
purpose of the study. It justifies the realization of the LCA. The definition of the
objectives of a LCA must indicate without ambiguity the intended application, the reasons
leading to the study, the public concerned, that is, the persons to whom it is intended to
communicate the results of the study. The scope of study takes into account the product to
be studied, the product function, the functional unit, and the boundaries of the product.
The functional unit translates the characteristics and performances of the evaluated
product. In this step the reference flow is also determined that is the number amount of
product needed to respond to the function (Benoist, 2009).
Inventory analysis. Following the definition of the objectives and scope of the study, the
boundaries of the system are known as well as the data to be collected. This is the stage that
consumes the most time because it requires the collection of all flows relevant from an
environmental point of view, involved in the studied product, previously cut into elementary
processes. The inventory therefore consists of carrying out the material and energy balances
of all incoming and outgoing flows for each elementary process (Benoist, 2009).
Life cycle impact calculation. Once the material and energy balances data are obtained for
each subprocess of the studied system, the environmental impact can be calculated. This
consists of describing the environmental consequences of the emissions and consumption
obtained during the inventory. The ISO 14040 standards impose mandatory steps during
this phase. It concerns the definition of the impact categories, the classification of the data
obtained during the inventory between the different impact categories, and finally
the characterization that allows the calculation of the environmental impact by category.
The characterization is carried out using characterization factors linking the inventory
data with their environmental impact. Scientifically, recognized methods have been devel-
oped over the years to facilitate the use of the LCA method. These methods are not fixed,
and there are differences between them. Indeed, the transition from the inventory analysis
to the impact calculation is not obvious for each category, and this can lead to a great var-
iability of the results. Impact 2002 1 , ReCiPe 2008, CML 2001, and Eco-Indicator 99 are
very often used for LCAs (Benoist, 2009).
Results interpretation. ISO 14040 defines the results interpretation as the step in which
the results obtained in the impact calculation are combined with the purpose and scope of
the study in order to obtain adequate and relevant conclusions and recommendations.
Three substeps are considered when interpreting the results, namely, the identification of
significant issues, the verification of the study, and the expression of conclusions, limits,
and recommendations (Benoist, 2009).