Within the requirements of ISO 14040 and 14044, the LCA must consist of the following steps:
Goal^ and scope definition which defines the goal and intended use of the LCA, and scopes the
assessment concerning system boundaries, function and flow, required data quality, technology and
assessment parameters,
Inventory analysis which consists in collecting data on inputs (resources and intermediate
products) and outputs (emissions, wastes) for all the processes in the product system.
Impact assessment, phase during which^ inventory data on inputs and outputs are translated into
indicators of potential impacts on the environment, on human health, and on the availability of
natural resources.^
Interpretation of results where the results of the LCI and LCIA are interpreted according to the
goal of the study and where sensitivity and uncertainty analysis are performed to qualify the results
and the conclusions.^In addition, the ISO standards require that LCAs disclosed to the public are submitted to a critical review
performed by independent LCA experts to ensure that the methods and results are scientifically and technically
valid. The fulfilment of the ISO standards is thus a guarantee for quality and transparency. Except for some
studies published by recognised organisations (US EPA for example), the fulfilment of the ISO 14040-series was
required for the publication selection.
2.2.2 The study included a comparison of two or more end-of-life scenarios for the material
under study
In order to be able to conduct a comparison between various end-of-life scenarios, the systems compared must
have the same functional unit and equivalent system boundaries, data quality and impact assessment
methodologies. In practice, it is thus very difficult to compare LCA results for scenarios from different studies. In
the present study, the choice has thus been made to conduct numerical comparisons only for scenarios analysed
in a single publication. This implies that each selected study must include a comparison between at least two
end-of-life options for a given fraction. This criterion was the most restrictive one and some studies of
high quality and interest had to be excluded with respect to this criterion. Nevertheless, it ensured
the overall coherence of the study.
2.2.3 Transparency in the assumptions made......................................................................
The variability of the results from one LCA study to another is often very high since results are highly dependent
on the assumptions made. It is also common for studies on similar systems to lead to different conclusions. When
conducting comparisons across various studies, it is therefore essential to be able to identify the key parameters
that can explain why conclusions differ from one study to another. The transparency of the assumptions made
was thus considered as an important criterion for the publications selection step. Most identified studies satisfied
this criterion fully but a lack of information in this area was sometimes observed when the study was only
reported in a journal article without an associated report. Requests were made to authors for further information
but this was very difficult obtain, in particular for studies over two years old.
2.2.4 No ambiguity in the way impacts are ascribed to materials ..........................................
The objective of the study was to come up with an evaluation of the environmentally preferable end-of-life
options for the range of considered fractions. The selected LCAs were thus required to present material-specific
results. High quality LCAs comparing end-of-life options for municipal solid waste as a whole were therefore not
suitable for selection.