Life Cycle Assessment

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Life Cycle Assessment
?
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Goal and scopedefinition
Interpretation
Inventoryanalysis
Impactassessment
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Inventory analysis
In the inventory analysis the elementary flows
associated with the life cycle of the product
system that generates the reference flow are
quantified. These are the material and energy
inputs and waste and emission outputs of all
economic processes that are within the system
boundaries.
Functional unit
Reference flow
Initial flow diagram
Detailed flow diagrams
Unit processes
Inventory table for each unit processes
Aggregate inventory table for reference flow
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Inventory Analysis Initial flow diagram
Definition The flow diagram provides an outline
of all the unit processes to be modeled,
including their interrelationships, which are
intermediate product flows. Starting with an
initial diagram at the level of aggregated
processes for each life cycle stage
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Inventory AnalysisDetailed flow diagram
The initial diagram is followed by detailed
diagrams, at the level of unit processes(processe
s of the system for which individual data are
collected).
Styrene production
naphta gas
styrene
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Inventory Analysis Description of unit processes
Process data
Flow data
Unit process
Intermediate output flows
Intermediate input flows
Elementary input flows
Elementary output flows
Source and collection data
Collector data
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Inventory Analysis Description of unit processes
Process data

• Includes information like
• Function of the process (typically given as its
  economic outputs)
• Name of the process
• Technical description of the process and all
  sub-processes
• Geographical coverage
• Time-period covered
• Technology coverage
• Representativeness

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Inventory Analysis Description of unit processes
Collector data

• Includes information like
• Person or organization that collected the data
• Contact information

Source and collection data

• Includes information like
• Data collections methods (sampling
  measurements techniques)
• Description of models used
• Bibliographic information for secondary data
  sources
• Cut-off criteria and screenings
• Allocation method (if any)

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Inventory Analysis Description of unit processes
Flow data
INPUTS
OUTPUTS
Goods Services Materials Energy Waste (for
treatment)
Goods Services Materials Energy Waste (for
treatment)
Unit Process
Intermediate flows
Intermediate flows
Chemicals to air Chemicals to water Chemicals to
soil Radionuclides Sound Waste heat Casualties Etc
.
Biotic resources Abiotic resources Land
occupation Land transformation Etc.
Elementary flows
Elementary flows
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Inventory Analysis Inventory table
Inputs
Outputs
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Inventory Analysis

• Even though the methodology of inventory analysis
  seems relatively
• straightforward, it is in fact complicated by
  two important issues
• Defining boundaries for the system under
  analysis
• Allocation, which is the partitioning of input
  and output flows for multi-functional unit
  processes (also a boundary issue)

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Inventory AnalysisSystem boundaries
In LCA inventory analysis 3 types of boundaries
can be distinguished 1. the boundary between the
product system and the environment system 2. the
boundary between Flows and processes that are
relevant and irrelevant for the product
system (cut-off) 3. the boundary between the
product system under consideration and other
product systems (allocation) Ad 1. Human
control over processes is the main criterion for
regarding a process as a unit
process, hence including it in the product system
(how about landfills?). Ad 2. - Cut-off is
necessary mainly for reasons of lack of data,
time and money - Cut-off is more than
simply ignoring certain parts, the estimation of
lacking data is essential.
- Possible guideline Processes that contribute
less than X of the total inputs
or outputs can be excluded from the
study (ISO14041, Section 3.1) -
Example In many LCAs production and maintenance
of production equipment
is omitted (how about agricultural
machinery?) Ad 3. Allocation is the result of
the multi-functionality (also called
co-production) of an economic process
and is performed at the unit process level
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Inventory AnalysisAllocation
(Consoli et al, 1993) identify 3 types of
processes where allocation is necessary
co-production, waste treatment, recycling and
reuse in an open loop. The 3 are treated on the
basis of the same allocation rules.
open loop
closed loop
materials energy
wastes emissions
waste A
waste B
Life Cycle B
Life Cycle A
unit process
materials energy
wastes emissions
unit process
product A
product B
A hierarchy of preferred approaches has been
defined in ISO14041, Section 6.5.3 1. Avoiding
allocation by dividing the unit process 2.
Avoiding allocation by system expansion 3.
Allocation on the basis of physical
relationship 4. Allocation on the basis of other
relationship, i.e. economic value
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Inventory AnalysisAvoiding allocation by
dividing the unit process
The unit process to be allocated is divided into
sub-processes and data are collectedseparately
for these sub-processes.
materials energy
Multi-function process M
Sub- process A
Sub- process B
product B
product A
wastes emissions

• Problems
• May not be possible, realistic or desirable to
  run sub-processes independently
• Many processes are inherently multi-functional
  (e.g. separation processes)

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Inventory AnalysisAvoiding allocation by system
expansion
The system is expanded to include the co-products
in the reference flow (or additional functions
in the FU).
co-producing process a
primary product A
Boundaries of original system
process b
intermediate process i
co-product C
product B

• Problems
• Usually means that more processes need to be
  included in the LCI
• More complex FUs makes comparison of different
  product systems more difficult

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Inventory AnalysisAvoiding allocation by avoided
burden approach
The system is expanded to include additional
burdens of processing of the co-product and the
avoided burdens of any displaced processes
co-producing process a
primary product A
Boundaries of original system
co- product C
intermediate process i
displaced process d
process b
product B
Boundaries of expanded system
Reference flow A Environmental burdens Ea Ei
Ed
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Inventory AnalysisAllocation on the basis of
underlying physical relationship
The environmental interventions are partitioned
between the co-products in a way that reflects
the physical relationship between products and
interventions.
allocated process
Intervention aE
unit process
Intervention E(A,B)
product A
allocated process
Intervention (1-a)E
product A
product B
product B

• Problems
• - Ignores relationship between co-products A and
  B
• Assumes linear relationship between
  environmental interventions and product outputs
• - Ignores the downstream impacts of the excluded
  co-product

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Inventory AnalysisAllocation on the basis of
mass relationship
Example
allocated process
Intervention 0.66 kg
unit process
Intervention 1 kg
20 kg product A 900
20 kg product A 900
10 kg product B 100
allocated process
Intervention 0.34 kg
10 kg product B 100
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Inventory AnalysisAllocation on the basis of
economic relationship
Example
allocated process
Intervention 0.9 kg
unit process
Intervention 1 kg
20 kg product A 900
20 kg product A 900
10 kg product B 100
allocated process
Intervention 0.1 kg
10 kg product B 100
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Homework for Wedesday, 24 January Assignment 1
(will be posted on course website on Thursday, 18
January )Reading for Monday, 22JanuaryEkvall
Weidema (2004) System boundaries and input data
in consequential life cycle inventory analysis,
Int J LCA 9(3) 161-171Hendrickson et al.
(1998) Economic Input-Output Models for
Environmental Life-Cycle Assessment,
Environmental Sci. Tech. 32 184A-191A. (will
be posted on course website on Thursday, 18
January )