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Issues in Inventory Analysis
Even though the methodology of inventory analysis seems Even though the methodology of inventory analysis seems relatively straightforward, it is – in fact – complicated by two relatively straightforward, it is – in fact – complicated by two important issues:important issues:
• Defining Defining boundaries for the systemboundaries for the system under analysis: under analysis: Which processes to include and which to exclude? Which processes to include and which to exclude?
• Allocation of elementary flowsAllocation of elementary flows if the process has more than one if the process has more than one economic output:economic output:
unitprocess
materialsenergy
wastesemissions
product A product B
AllocationAllocationConsoli et al, (1993) identify 3 types of processes where allocation is necessary:
co-production, waste treatment,
recycling and reuse in an open loop.
A hierarchy of preferred approaches has been defined in ISO14044, Section 4.3.4:1. Avoiding allocation by dividing the unit process2. Avoiding allocation by system expansion3. Allocation on the basis of physical relationship4. Allocation on the basis of other relationship, i.e. economic value
unitprocess
materialsenergy
wastesemissions
product A product B
unitprocess
materialsenergy
wastesemissions
waste A waste B
LifeCycle
B
LifeCycle
A
closed loop open loop
Avoiding allocation by dividing the unit processAvoiding allocation by dividing the unit process
materials & energy
wastes & emissions
product A product BSub-
processA
Sub-process
B
Problems: - It may not be possible, realistic or desirable to run sub-processes independently- Many processes are inherently multi-functional (e.g. separation processes)
The unit process to be allocated is divided into sub-processes and data are collectedseparately for these sub-processes.
Multi-function process M
Avoiding allocation by system expansionAvoiding allocation by system expansionThe system is expanded to include the co-products in the reference flow (i.e. additional functions in the Functional Unit - FU).
Problems: - Usually means that more processes need to be included in the LCI- More complex FUs makes comparison of different product systems more difficult
co-producingprocess a
primary product A
process bintermediate
process i
Boundaries of original system
co-product Cproduct B
Boundaries of expanded system
Reference flow: A + BElementary flows: Ea + Ei + Eb
Reference flow: A + CElementary flows: Ea + Ei
Boundaries of expanded system
Allocation on the basis of underlying physical relationshipAllocation on the basis of underlying physical relationship
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
unitprocess
Emissions E(A,B)
product A product B
allocatedprocess
product A
allocatedprocess
product B
The environmental interventions are partitioned between the co-products in a way that reflects the physical relationship between products and interventions.
Emissions αE
Emissions (1-α)E
Allocation on the basis of mass relationshipAllocation on the basis of mass relationship
unitprocess
20 kg product A 80 kg product B
allocatedprocess
20 kg product A
allocatedprocess
80 kg product B
Example:
Emissions 0.2 kg
Emissions 0.8 kg
Emissions 1 kg
On a mass basis, product A is allocated 20% of the emissions.
Allocation on the basis of economic relationshipAllocation on the basis of economic relationship
unitprocess
20 kg product A$900
80 kg product B$100
allocatedprocess
20 kg product A$900
allocatedprocess
80 kg product B$100
Example:
Emissions 0.9 kg
Emissions 0.1 kg
Emissions 1 kg
On an economic basis, product A is allocated 90% of the emissions.
Chlor-AlkaliElectrolysis
1 ton of chlorine ($90)
1.1 tons of caustic soda ($262)
0.28 tons of hydrogen ($10)
1.7 tons of salt
3.8 MWh of electricity
Example of Co-productionExample of Co-production
The system is expanded to include additional burdens of co-product processingand the avoided burdens of any avoided processes
Vehicleproduction v
Vehicle
Primaryproduction p
Buildingproduction b
Recyclingprocess r
Ev + Er – Ep
Vehicle life cycle
Building life cycle
Building
Environmental burdens of the vehicle:
Allocation by system expansion (avoided burden approach)Allocation by system expansion (avoided burden approach)
scrap
A closer look at the avoided burden method
Vehicle
600 kg
EAF (0.6 kgCO2/kg)
BF/BOF(2.2 kgCO2/kg)
Building
600 kg
600 kg
BF/BOF (2.2 kgCO2/kg)
600 kg
€
600 ⋅2.2 + 600 ⋅0.6 − 600 ⋅2.2
= 600 ⋅2.2 − 600 ⋅(2.2 − 0.6)
= 600 ⋅0.6
Vehicle:
A closer look at the avoided burden method
Vehicle
600 kg
EAF (0.6 kgCO2/kg)
BF/BOF(2.2 kgCO2/kg)
Building
600 kg
600 kg
BF/BOF (2.2 kgCO2/kg)
600 kg
6.0600
)6.02.2(6002.2600
2.26006.06002.2600
⋅=−⋅−⋅=
⋅−⋅+⋅Vehicle:
600 kg
EAF (0.6 kgCO2/kg)
BF/BOF(2.2 kgCO2/kg)
600 kg
600 kg
600
2.26002.1600
2.26006.06006.0600
−=⋅−⋅=
⋅−⋅+⋅Building:
Credit for scrap generation requires debit for scrap use!
The system is expanded to include additional burdens of co-product processingand the avoided burdens of any displaced processes
Vehicleproduction v
Vehicle
Primaryproduction p
Buildingproduction b
Recyclingprocess r
Vehicle: Ev + Er – Ep = Ev – (Ep – Er)
Boundaries of original system
Boundaries of expanded system
Building
Building: Ep + Eb = Er + Eb + (Ep – Er)
The avoided burden principle: credit = debit
Vehicle + Building: Ev + Er + Eb
Environmental burdens:
Credit
Debit
Sec
Sec
Prim
Prim
Prim
1
0.750.25
0.250.75
1
A
B
C
Material Recycling: Recycled Content vs. Avoided Burden
22=AE
13
1075.02225.0
=⋅+⋅=BE
13
1075.02225.0
=⋅+⋅=CE
Recycled Content(no allocation)
( )13
102275.022
=
−−=AE
( )
( )13
102275.0
1075.02225.0
102275.0
=
−−
⋅+⋅+
−=BE
( )
22
1075.02225.0
102275.0
=
⋅+⋅+
−=CE
Avoided Burden
22MJ/kg
10MJ/kg
More allocation methods for material recycling :
22=AE 13
1075.02225.0
=⋅+⋅=BE
13
1075.02225.0
=⋅+⋅=CE
( )13
102275.022
=
−−=AE
( )
( )13
102275.0
1075.02225.0
102275.0
=
−−
⋅+⋅+
−=BE
( )
22
1075.02225.0
102275.0
=
⋅+⋅+
−=CE
( )5.17
1022375.022
=
−−=AE
( )
( )13
1022375.0
1075.02225.0
1022375.0
=
−−
⋅+⋅+
−=BE
( )
5.17
1075.02225.0
1022375.0
=
⋅+⋅+
−=CE
16=AE 16=BE 16=CEAverage (n=3,r=0.75)
50 / 50
100% Avoided Burden
100% Recycled Content
Allocation method:Avoided burden
Problem:Product system A has same environmental burdens as product system B
Allocation methods for material recycling :
Product A
Product B
Product C
Primaryproduction
Recycling
Recycling
0% recycled content100% end-of-life recycling
100% recycled content100% end-of-life recycling
100% recycled content0% end-of-life recycling
Disposal
Allocation : Recycled content
Problem: Product system B has same environmental burdens as product system C
Allocation methods for material recycling :
Product A
Product B
Product C
Primaryproduction
Recycling
Recycling
0% recycled content100% end-of-life recycling
100% recycled content100% end-of-life recycling
100% recycled content0% end-of-life recycling
Disposal
Allocation methods for material recycling :
Product A
Product B
Product C
Primaryproduction
Recycling
Recycling
0% recycled content100% end-of-life recycling
100% recycled content100% end-of-life recycling
100% recycled content0% end-of-life recycling
Allocation : Average burden
Problem: Product systems A, B and C have same environmental burdens
Disposal
A closer look at the avoided burden approach
Production ofthe necessary
material
Futurecollection &reprocessing
Avoided materialproduction & disposal
Factual Probabilistic Counterfactual
+ –
Type of causality
Observation 1: There are three types of causality involved in the approach
Involved processes
Observation 2: Recycling does not automatically displace primary production
Collected scrap can
1. displace metal from primary production
2. displace scrap collection and recycling elsewhere
3. displace other materials (primary or secondary)
4. increase market demand (i.e. not displace anything)
LCA Process (review)
Where RERP is the “Environmentally Responsible Product Rating”
Define Scope
Manufacture RERP
Inventory Analysis
Improvement Analysis
Impact Analysis
Feedback
Life Cycle Inventories (LCIs)Life Cycle Inventories (LCIs) by themselves do not characterize the environmental performance of a product system.
Impact Assessment (IA)Impact Assessment (IA) aims at connecting, to the extent possible, emissions and extractions listed in LCIs on the basis of impact pathways to their potential environmental damages.
Impact Assessment Impact Assessment is aimed at understanding and evaluating the magnitude and significance of the potential environmental impacts of a product system (ISO14040).
Life Cycle Inventory results
Impact categories
Category indicator results
Environmental profile
One-dimensional environmental score
Normalization
Valuation
Characterization
Classification
Life Cycle Impact Assessment
Mandatory elements
Selection of impact categories, category indicators and characterization models
Classification: Assignment of LCI results to impact categories
Characterization: Calculation of category indicator results
Category indicator results (LCIA profile)Category indicator results (LCIA profile)
Optional elements:
Normalization of category indicator results relative to reference informationGroupingWeighting
Data quality analysis
Elements of LCIA according to ISO 14044
SO2
emissions
Acidrain
Acidifiedlake
Deadfish
Loss ofbiodiversity
Increase in uncertainty for predicting the environmental impact from the initial interventions
Increase in effectiveness of communication of results (generally)
Source Midpoint Endpoint
Impact pathways consist of linked environmental processeslinked environmental processes, and they express the causalchain of subsequent effects originating from an emission or extraction (environmental intervention).
Examples:
CFCemissions
Stratospheric O3 Depletion
UVBexposure
Humanhealth
The environmental mechanism (impact pathway)
According to ISO14044, LCI results are first classified into impact categories that are relevant and appropriate for the scope and goal of the LCA study.
A category indicator, representing the amount of impact potential, can be located at any place between the LCI results and the category endpoints. There are currently two main Impact Assessment methods:
• Problem oriented IA methods stop quantitative modeling before the end of the impact pathway and link LCI results to so-defined midpoint categories (or environmental problems), like acidification and ozone depletion.
• Damage oriented IA methods, which model the cause-effect chain up to the endpoints or environmental damages, link LCI results to endpoint categories.
Carbon dioxide
MethaneCFCs
Nitrogen oxides
Sulphur dioxide
Climate change
Stratospheric ozone depletion
Photochemical oxidant formation
Acidification
Example:
Impact CategoriesImpact Categories
Human toxicity
Photochemical oxidant formation
Ozone depletion
Climate change
Acidification
Eutrophication
Ecotoxicity
Land use impacts
Species & organism dispersal
Abiotic resources deplection
Biotic resources deplection
LCIresults
Human Health
Biotic & abioticnatural environment
Biotic & abioticnatural resources
Biotic & abioticmanmade resources
Midpoint categoriesMidpoint categories(environmental problems)(environmental problems)
Endpoint categoriesEndpoint categories(environmental damages)(environmental damages)
Missing: CasualtiesNoise Source: Int J of LCA 9(6) 2004
Impact categories proposed by UNEP/SETAC Life Cycle Initiative in 2003Impact categories proposed by UNEP/SETAC Life Cycle Initiative in 2003
The chain of physical, chemical and biological events in the natural environmentthat link a particular elementary flow to a particular impact category is called an environmental process.
For each impact category, the characterization modelcharacterization model models all relevant environmental processes (to a greater or lesser extent).
How to implement classification and characterization:How to implement classification and characterization:
• for a chosen impact category, identify one or more category endpoints
• define a suitable category indicator
• identify those LCI results that contribute to the indicator
• choose characterization modelcharacterization model and characterization factor
Characterization model:Characterization model:
Classification and characterization
LCI results
LCI results assigned toImpact category
Category indicator results
Category endpoint(s)
Impactcategory
Example:
Acidification
Proton release(H+ aq)
Cd, CO2, NOX, SO2, etc.(kg/functional unit)
NOX, SO2, etc.(kg/functional unit)
In general:
- Forest- Vegetation- etc.
Characterization model
Source: ISO14044
Classification and characterization
An Approach to Product Impact
• Each product of an environmentally conscious firm should receive an LCA– Reveals whether a design is responsible– Helps the designer identify improvements
• Adapt a matrix approach to deal with all materials over a single product line (rather than a single material over all product lines)
• Display Life Stage vs. Environmental Concern– Materials choice, energy use, solid residues, liquid
residues, and gaseous residues
Auditing by Environmental Concern
• The same approach can be taken by environmental concern rather than by life stage
Per Cup
x2.5xCost
11.510Finished weight (g)
3.24.1Petroleum (g)
033Wood and bark (g)
Foam CupPaper CupRaw Materials
Per mg of material
35.500 Pentane (kg)
0.15-15 Particulates (kg)
02.0 Sulfides (kg)
00.5 Chlorine (kg)
Air Emissions
0.15-15 Metal salts (kg)
05-7 Organochlorides (kg)
0.0730-50 BOD (kg)
Trace35.60 Suspended solids (kg)
0.5-2.050-190 Volume (m3)
Water Effluent
15450 Cooling water (m3)
0.4-0.63.5 Power (GJ)
50009000-12000 Steam (kg)
Foam CupPaper CupUtilities
Recycle Potential
HighLowAfter use
EasyPossiblePrimary User
Foam CupPaper Cup
Ultimate Disposal
NoYesBiodegradable
1.510.1Mass to landfill (g)
4020Heat recovery (MJ/kg)
Foam CupPaper Cup
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