Issues in Inventory Analysis Even though the methodology of inventory analysis seems relatively straightforward, it is – in fact – complicated by two important

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


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)


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)


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


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



Disposal

Allocation : Recycled content

Problem: Product system B has same environmental burdens as product system C


Product A

Product B

Product C

Primaryproduction

Recycling

Recycling




Disposal


Product A

Product B

Product C

Primaryproduction

Recycling

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

Documents

Issues in Inventory Analysis Even though the methodology of inventory analysis seems relatively straightforward, it is – in fact – complicated by two important