Summary literature Toolbox I
Week 46: A survey of unresolved problems in life cycle assessment. Part 1: Goal and scope and
inventory analysis - Reap J, Roman F, Duncan S, Bras B. (2008)
Abstract Life cycle assessment (LCA): Tool for estimating environmental effects
caused by products and processes from ‘cradle to grave’ or ‘cradle to
cradle.’
Problems with LCA arise from decisions about inclusion and exclusion.
Introduction Four interdependent phases of LCA:
Goal and scope definition: Set the scope of the inquiry and
specify the methods used to conduct it in later phases.
Life cycle inventory analysis: Defines and quantifies the flow of
material and energy into, through, and from a product system.
Life cycle impact assessment: Converts inventory data into
environmental impact estimates using a two-step process of
classification and characterization.
Life cycle interpretation: Draws conclusions and formulates
recommendations based upon inventory and impact assessment
data.
Goal and scope Problems in goal and scope definition occur as a result of three
problems methodological choices:
Functional unit definition: Selecting a functional unit is of crucial
importance because different functional units could lead to
different results for the same product systems.
Potential sources of error related to the functional unit:
Step 1: Identify and prioritize functions
- Potential error: Missing or mispecified functions
Step 2: Define functional unit
- Potential error: Assigning functional units to multiple
functions.
, Step 3: Define reference flow
- Potential error: Different ways of handling multiple
functions
Unit process boundary selection: Boundary selection determines
the processes and activities included in a LCA study. A well-
justified and transparent selection of boundaries is warranted to
add credibility or confidence to the LCA results. Increasing
confidence in selecting appropriate boundaries might require a
great deal of data, which might increase the costs and time of the
LCA study with very little to no value added. Two type of
problems:
o Problems with ISO 14041’s approach to boundary
selection: Many researchers have criticized the amount
of subjectivity allowed by the ISO standards, which could
lead to less confidence in comparative LCA study results.
o Problems with Input- Output (IO) approaches to
boundary selection: The approach assumes that the
amounts of imported commodities can be neglected.
Data can be outdated for some sectors. Many IO LCA-
based methods do not seem to consider the recycling.
Life cycle costs and social impacts: Product systems cause
environmental, economic and social impacts during their life
cycles. LCAs focus only on environmental impacts, it fails to
address social and economic concerns.
Difficulties in integrating social aspects in LCA:
- No consensus on how to integrate and calculate social
impacts
- More than 200 societal indicators
- Most social impact is independent from product process
- Lack of data
Difficulties in integrating LCC in LCA:
- No consensus in terminology, methodology, data etc.
- Disagreement on how to handle externalities (taxes etc.)
- Disagreement on how to assign costs to different
stakeholders
- How to align data per functional unit with financial data
Life cycle inventory Life cycle inventory problems:
problems Allocation: Determining how much of the environmental
burdens caused by the multi-functional process should be
apportioned to each product or function even though other
researchers have suggested a different definition. Could lead to
incorrect LCA results and thus less preferable decisions. To deal
with the allocation problem, ISO recommends the following
steps:
o Avoid allocation when possible (by dividing the unit
processes into sub-processes or by expanding product
system boundaries to include additional functions
related to co-products
o Allocate the environmental burdens of each product
, based on their underlying physical relationship (if
allocation cannot be avoided)
o Allocate environmental burdens of each product based
on relationship (if allocation based on physical
relationship cannot be done)
- Problems with avoiding allocation by subdivision or system
expansion
Subdivision can help reduce, though rarely eliminate, allocation
problems because these processes are not likely to consist of
physically separate single-function sub-processes.
Regarding two system expansions (direct system enlargement
and avoided burdens approach), but they rely on the existence of
alternative production systems and reliable inventory data for
these production systems. If those two conditions could be met
in LCA, then the allocation problem could be avoided.
System expansion should occur if we know that it has a
significant influence on LCA results.
- Problems with allocation procedures based on physical causality
If the allocation problem remains after subdivision and/or system
expansion, the allocation of the remaining environmental
burdens should be carried out using causal, physical
relationships.
- Problems with allocation procedures based on non-causal
relationships
If the allocation problem remains after subdivision or system
expansion and if causal, physical relationships have not been
used to allocate the remaining internal functions, then non-
causal relationships should be used. Several reasons for using
these relationships instead of causal relationships are:
- Lack of data or scientific knowledge
- Convenience, the data is readily available or easier to get
- The relationship may coincide with causal, physical
relationships
Negligible contribution criteria: Not all physical flows associated
with an activity are modelled, but people try to justify this by
arguing that they make a negligible contribution to a product’s
environmental profile. We should also take these ‘cut-off’ criteria
into account because they still cause noticeable impacts and the
sum can be significant.
Local technical uniqueness: Becomes problematic when average
or generic data or models are used to represent processes that
significantly differ from the norm.
Week 46: International Reference Life Cycle Data System (ILCD) Handbook: Recommendations for
Life Cycle Impact Assessment in the European context
, 5.3 Classifying Two aspects of different decision-context:
the decision- LCI/LCA study is used to support a decision: the extent of changes that the
context as decision implies in the background system and in other systems and that are
Situation A, B, caused via market mechanisms (LCI model should reflect the consequences)
or C LCI/LCA study is not used to support a decision: study is interested in
interactions of the depicted system with other systems (LCI model should
describe the system, without including any market consequences)
Two subtypes of studies for an LCI model which will describe the system:
Studies that are interested in including any existing benefits the analysed
system may have outside this system (e.g. benefits of recycling)
Studies that analyse the system in isolation without considering such
interactions.
Three archetypal goal situations:
Situation A: Micro-level decision support
Decision support directly or indirectly related to inform the purchase of
products (good/service) that are already offered in the market or to
products that will enter the market. Produced as consequence of the
decision supported by an LCA/LCI study. "Micro-level" referring to changes
that are caused via market mechanisms with small-scale consequences
beyond the system. Situation A also covers the development of LCI and LCIA
data that are meant to be used in LCA-based decision support.
o Key Environmental Performance Indicators (KEPI)
o Design for recycling
o Green Public Procurement (GPP)
o Weak point analysis of a specific product
Situation B: Meso/macro-level decision support
Life cycle based decision support with consequences that
will via, market mechanisms, change parts of the rest of the economy by
having large-scale structural effects.
o Policy development
Situation C: Accounting
Descriptive documentation of the analysed system of the past, present or
forecasted future, and without implying a decision-context that would
account for potential additional consequences on other systems. No direct
decision is made based on the results of the LCA, because the life cycle has
already been decided before the analysis takes place.
o Situation C1: Accounting, with system-external interactions
Existing interactions with other systems are included in the LCI
model. These interactions refer to existing interactions with other
systems only. Life cycle based monitoring of e.g. all products of a
