Page 77 - Materials Chemistry, Second Edition

62 M.Z. Hauschild

The goal definition and the ensuing scope definition are very important to
consider when the results of the study are interpreted since these definitions involve
choices that determine the collection of data and the way in which the system is
modelled and assessed. They therefore have a strong influence on the validity of the
conclusions and recommendations that are based on the results of the LCA.

6.2.2 Inventory Analysis

Following the definition of goal and scope, the inventory analysis collects infor-
mation about the physical flows in terms of input of resources, materials,
semi-products and products and the output of emissions, waste and valuable
products for the product system (see Chap. 9). The analysis studies all the processes
that were identified as belonging to the product system, and the flows are scaled in
accordance with the reference flow of product that is determined from the functional
unit. Due to the comprehensiveness of most product systems, the inventory analysis
often relies on generic data for many processes originating from databases with unit
processes or cradle-to-gate data, presenting the in- and output flows for one unit
process, e.g. for production of a material, generation of heat or electricity, trans-
portation or waste management. Environmentally extended input–output analysis
can be used to support and qualify the collection of inventory data as discussed in
Chap. 14.
The outcome of the inventory analysis is the life cycle inventory, a list of
quantified physical elementary flows for the product system that is associated with
the provision of the service or function described by the functional unit.

6.2.3 Impact Assessment

Taking the life cycle inventory as a starting point, the impact assessment translates
the physical flows and interventions of the product system into impacts on the
environment using knowledge and models from environmental science (see
Chap. 10). The impact assessment consists of five elements of which the first three
are mandatory according to the ISO 14040 standard:
1. Selection of impact categories representative of the assessment parameters that
were chosen as part of the scope definition. For each impact category, a rep-
resentative indicator is chosen together with an environmental model that can be
used to quantify the impact of elementary flows on the indicator.
2. Classification of elementary flows from the inventory by assigning them to
impact categories according to their ability to contribute by impacting the
chosen indicator.