92
5.3.8 What If the Most Reliable, Accurate, and Precise
Primary Data Are Not Available?
Since there are numerous calculated values on which a study is founded and impacts
are assessed, an LCA model is only as good as the data on which it is based. Just as
the key portions of the major “impact assessment” (LCIA) phase is included in the
primary goal and scope definition phase, so too is included a preliminary “inventory
analysis” (LCI). To those new to LCA, the subtle differences in the acronyms for
these two main LCA phases with words beginning with the exact same letters can
lead to initial confusion. A reliable impact assessment relies on an inventory analysis of data that is properly collected, calculated, and allocated. Only after final LCI
results are assigned can impact category indicator results be calculated, so, in addition to being a constituent part of determining an LCA’s initial goal and scope, the
LCI is also an integral precursor to LCIA.
Heterogeneous LCI data is typical and perfectly acceptable for most LCAs.
Documented primary readings taken from in-line or process sensors that measure
compounds such as CO 2 or other indicator chemical emissions provide the most
relevant and applicable data relating to that specific process. It is unrealistic to
expect access to primary data on the energy, material, and emission flows for the
thousands of unit processes that feed into a product system. A study based on 100%
primary data today would be exceedingly time-consuming and prohibitively expensive. Secondary data, held by any of several public or private organizations, supplies
most of the rest of the quantitative detail where primary data is absent. ISO standards make allowances for a variety of data:
Such data may be collected from the production sites associated with the unit processes
with the system boundary, or they may be obtained or calculated from other sources. In
practice all data may include a mixture of measured, calculated, or estimated data. (ISO
14044 2006b).
The Swiss ecoinvent database, for example, has readily accessible process data on
numerous sectors for use in an LCA. This data is typically averaged for each process and place. Eurocentric data is less accurate for processes carried out in North
America or Asia that might, for example, each use a very different primary energy
mix to power each unit process. Continent-/nation-specific databases, however, are
growing and improving each year. As data reporting tools and requirements proliferate, data-aggregating organizations review, categorize, and incorporate new information sets to increase the utility and relevance of the services they provide
(Matthews et al. 2014).
Generic LCI data is especially appropriate to use in the goal and scope phase as
it can give a quick view of where system “hot spots” might be in order to focus on
the right priorities and avoid spending time and effort later to collect detailed data
on processes that don’t contribute a significant portion of negative environmental
impact in an LCA model.
Tools available to designers rely on these LCI data. The impact models they create draw upon the numerical values in the aggregated inventories. These values are
5 Life Cycle Assessment
5.3.8 What If the Most Reliable, Accurate, and Precise
Primary Data Are Not Available?
Since there are numerous calculated values on which a study is founded and impacts
are assessed, an LCA model is only as good as the data on which it is based. Just as
the key portions of the major “impact assessment” (LCIA) phase is included in the
primary goal and scope definition phase, so too is included a preliminary “inventory
analysis” (LCI). To those new to LCA, the subtle differences in the acronyms for
these two main LCA phases with words beginning with the exact same letters can
lead to initial confusion. A reliable impact assessment relies on an inventory analysis of data that is properly collected, calculated, and allocated. Only after final LCI
results are assigned can impact category indicator results be calculated, so, in addition to being a constituent part of determining an LCA’s initial goal and scope, the
LCI is also an integral precursor to LCIA.
Heterogeneous LCI data is typical and perfectly acceptable for most LCAs.
Documented primary readings taken from in-line or process sensors that measure
compounds such as CO 2 or other indicator chemical emissions provide the most
relevant and applicable data relating to that specific process. It is unrealistic to
expect access to primary data on the energy, material, and emission flows for the
thousands of unit processes that feed into a product system. A study based on 100%
primary data today would be exceedingly time-consuming and prohibitively expensive. Secondary data, held by any of several public or private organizations, supplies
most of the rest of the quantitative detail where primary data is absent. ISO standards make allowances for a variety of data:
Such data may be collected from the production sites associated with the unit processes
with the system boundary, or they may be obtained or calculated from other sources. In
practice all data may include a mixture of measured, calculated, or estimated data. (ISO
14044 2006b).
The Swiss ecoinvent database, for example, has readily accessible process data on
numerous sectors for use in an LCA. This data is typically averaged for each process and place. Eurocentric data is less accurate for processes carried out in North
America or Asia that might, for example, each use a very different primary energy
mix to power each unit process. Continent-/nation-specific databases, however, are
growing and improving each year. As data reporting tools and requirements proliferate, data-aggregating organizations review, categorize, and incorporate new information sets to increase the utility and relevance of the services they provide
(Matthews et al. 2014).
Generic LCI data is especially appropriate to use in the goal and scope phase as
it can give a quick view of where system “hot spots” might be in order to focus on
the right priorities and avoid spending time and effort later to collect detailed data
on processes that don’t contribute a significant portion of negative environmental
impact in an LCA model.
Tools available to designers rely on these LCI data. The impact models they create draw upon the numerical values in the aggregated inventories. These values are
5 Life Cycle Assessment