Page 48 - Materials Chemistry, Second Edition

3.1 Life cycle assessment methodology 43
– product system;
– functions of the product system;
– functional unit;
– system boundary;
– allocation procedures;
– impact category and methodologies of impact assessment;
– data requirements;
– assumptions;
– limitations;
– initial data quality requirements;
– type of critical review; and
– type and format of the report.

The main item is the functional unit, which allows quantifying of the identified functions of
the system or product, is the reference unit for the calculation of the inputs and outputs, and
ensures comparability in case of comparative studies. An LCA study has to be conducted by
defining product system and the system boundaries, which are necessary to establish the
functions to be considered. Ideally, inputs and outputs should be elementary flows. However,
the choice of the elements of the system depends on the goal and scope of the study, the
intended application, the audience, the assumptions made, data, cost and cut-off criteria
(ISO, 2006a), namely the criteria to establish the threshold under which it is possible to ex-
clude not significant environmental burdens.

3.1.2 Life cycle inventory (LCI)
This stage covers data collection and calculations to quantify the relevant inputs and out-
puts of the system. It is an iterative step and thus, further data requirements or limitations
may be identified to meet the goal of the study during the conduction of the analysis. The
main data required to conduct an LCA study are (ISO, 2006b):
– consumption of inputs;
– products, co-products and waste flows;
– emission to air, water, and soil; and
– other environmental aspects.
Input and output data have to be organized as usage of raw material, water usage, energy
consumption, emission into water, air, and soil, and waste. In addition, the following items
have to be indicated (ISO, 2006a):
– data sources;
– reference process
– reference technology
– geographical area;
– monitoring details;
– measuring methods; and
– specific units of measurement.