Page 160 - Materials Chemistry, Second Edition

9 Life Cycle Inventory Analysis 145

specificity. A large part of the data collection therefore usually takes place online by
searching, identifying and accessing publicly available sources, such as other LCA
studies, industry association reports and national statistics. It is also possible to
identify, via online searching, data for a process that is very similar to the actual
process to be modelled, either because the reference flow of the processes is the
same (e.g. the incineration of polypropylene) or similar (e.g. the incineration of
polypropylene versus polyethylene). The strategy of extrapolation from data for
similar processes is especially useful to ‘fill out gaps’ in a preliminary unit process,
but the LCA practitioner must carefully check the representativeness of the process
used for extrapolation. For example, if the initial data collection effort has led to a
handful of high or very high specificity emission data, but no resource inputs for a
process, the remaining flows may be quantified by extrapolation from a similar
process. Such similar process can be sourced from scientific papers or other
sources, which can document sufficient representativeness (technology, geography,
time) and disclose sufficient data to check the agreement with the existing handful
of high specificity emission data for the original unit process. A special case of
extrapolation is for novel technologies that may not yet operate at industrial scale
anywhere at the point in time where the study is to be conducted. Here, an obvious
source of extrapolation is laboratory scale processes. It is, however, important to
consider how the relationships between the flows of a process changes from lab-
oratory to industrial scale. Often the technology of the process will change, not just
in size, at the upscaling from lab scale to commercial scale, and this typically leads
to increased efficiency (e.g. less input per reference flow output) and changes in the
quality of flows.
The effort required to access data via online searching depends on the expertise
of the practitioner (e.g. familiarity with the terminology of the concerned technical
domain) and on how well-studied the phenomena behind the data is. For example,
there is generally more publically available data on greenhouse gas emissions than
on emissions of synthetic chemicals used for very specific industrial purposes and
produced in low volumes. The effort also depends on the number of data points that
can be accessed from each source. A unit process is often composed of more than
100 flows (the majority often being elementary flows). Some sources, such as LCI
databases, contain data for all flows making up a unit process, while other sources,
e.g. statistical agencies, may only cover a few elementary flows.
LCI databases are used to source data for the background system and for the
parts of the foreground system where more specific data can or will not be obtained.
Table 9.5 presents a non-exhaustive list of LCI databases.