A framework for sustainable materials management

Abstract

Achieving global sustainability will require a decoupling of material consumption from economic value creation. While industrialized
societies have achieved gains in resource efficiency and waste recycling, total material through-put continues to rise. Environmental
pressures will only be exacerbated as the world's developing economies increase their consumption rates. This paper describes
an integrated framework for sustainable materials management that will help to address these critical challenges from a systems
perspective.

Full text

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2006 August • JOM
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Global RecyclingOverview
? Achieving?global?sustainability?will?
require?a?decoupling?of?material?con-
sumption?from?economic?value?creation.?
While? industrialized? societies? have?
achieved?gains?in?resource?efficiency?and?
waste?recycling,?total?material?through-
put? continues? to? rise.? Environmental?
pressures?will?only?be?exacerbated?as?
the? world’s? developing? economies?
increase?their?consumption?rates.?This?
paper?describes?an?integrated?framework?
for?sustainable?materials?management?
that?will?help?to?address?these?critical?
challenges?from?a?systems?perspective.?
IntROductIOn
? Increasing?material?flows?contribute?
to?many?of?the?world’s?environmental?
and?social?problems.?In?the?near?term,?
sustainable?development?is?threatened?
not?so?much?by?the?depletion?of?non-
renewable?resources?such?as?minerals?or?
fossil?fuels,?but?rather?by?over-exploita-
tion?of?renewable?resources?and?the?life?
cycle?impacts?or?“externalities”?associ-
ated?with?material?extraction,?transport,?
and? utilization.1? �hese externalities�hese? externalities?
include?potential?climate?change?due?to?
global?warming?emissions;?degradation?
of?air,?water,?land,?and?wildlife?habitats?
in?industrialized?areas;?and?depletion?of?
natural?resources?including?fresh?water,?
biomass,?and?topsoil.?Hence,?there?is?a?
need?to?explore?the?potential?for?achiev-
ing?sustainable?materials?management?
(SMM).
? As?the?global?economy?grows?more?
highly? connected,?more? materials?are?
being?consumed?and?transported?over?
longer? distances.? A? recent? overview?
study?of?materials?and?waste?streams?in?
the?European?Union?(E.U.)?concluded?
that?there?is?no?absolute?decline?in?the?
volume?of?the?European?Union’s?total?
resource?requirements,?and?that?a?shift?
from?domestic?sources?toward?the?use?
A Framework for Sustainable
Materials Management
Joseph Fiksel
of? imports? is? shifting? environmental?
burdens?to?other?regions?of?the?world.2?
Improvements? in? resource? efficiency?
alone?cannot?guarantee?the?sustainability?
of? industrial? societies,? and? material?
substitution?and?recycling?strategies?will?
only? delay? the? ultimate? depletion? of?
non-renewable? stocks? since? complete?
recycling?of?waste?streams?is?impossible.3?
At?the?same?time,?a?switch?to?large-scale?
energy?generation?based?on?renewable?
resources?is?likely?to?have?unacceptable?
environmental?impacts.?
? In?response?to?these?challenges,?this?
article?presents?an?integrated?perspective?
on?the?relationship?between?materials?
flow?and?sustainability,?the?options?for?
reducing?material?intensity?in?a?diverse?
and?growing?global?economy,?and?the?
available?tools?for?assessing?the?impact?
of? material? flows? on? environmental,?
economic,?and?social?well-being.?
? �o? understand? material? flows,? it? is?
helpful?to?adopt?a?conceptual?framework?
that?includes?the?sources?of?materials,?
their?pathways?through?the?natural?and?
built?environments,?and?their?eventual?
sinks.? Figure? 1? presents? a? simplified?
systems?view?that?partitions?the?physical?
world?into?three?types?of?interconnected?
systems.?
Ecological Systems
? Ecological?systems?comprise?the?bio-
sphere?and?provide?products?and?services?
to?industrial?and?societal?systems.?�hey?
contain?four?types?of?natural?resource?
stocks.?Renewable?resource?stocks?(e.g.,?
forests)?are?replenished?over?time?pro-
vided?that?the?rate?of?exploitation?does?
not?exhaust?the?existing?stock.?�hese?
are?often?described?as?natural?capital.?
Non-renewable? resource? stocks? (e.g.,?
petroleum)?can?be?exploited?at?any?time,?
but?once?the?finite?stocks?are?exhausted?
they?cannot?be?replenished?and?need?to?
be?replaced?by?other?forms?of?capital.? ?
Environmental? media,? including? air,?
water,?and?land,?are?finite?and?cannot?
be?depleted,?but?their?quality?may?be?
Figure 1. A systems view of material flow cycles and policy frameworks.

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JOM • August 2006
16
degraded.?For?example,?land?area?may?
be?left?unexploited,?used?for?agriculture,?
degraded?due?to?soil?erosion,?or?rendered?
“sterile”? by? commercial? or? industrial?
use.?Last?are?sources?of?energy,?includ-
ing?solar,?geothermal,?and?tidal?energy,?
which?are?effectively?infinite?but?may?be?
influenced?by?human?activities.
Industrial Systems
? Industrial?systems?utilize?ecosystem?
services?and?extract?or?“harvest”?mate-
rials,?drawing?upon?the?described?types?
of?ecological?resource?stocks?in?varying?
degrees.?Industrial?wastes?that?cannot?be?
re-used?are?deposited?back?into?the?bio-
sphere.?�here?are?two?major?categories?
of?industrial?systems.?
? Supply? chain? systems,? actually?
networks,? are? sequences? of? supplier-
customer?links?that?begin?with?primary?
resource? extraction? and? end? with? the?
delivery?of?a?finished?product?or?service?
to?fulfill?a?societal?demand.?Energy?pro-
duction?systems?are?similar?to?supply?
chain? systems,? except? that? the? end?
product?is?energy?utilized?either?within?
the?industrial?systems?or?to?fulfill?soci-
etal?demands,?including?residential?and?
transportation?uses.
Societal Systems
? Societal?systems?consume?the?prod-
ucts,?services,?and?energy?supplied?by?
industrial?systems,?and?generate?waste?
that? is? either? recycled? into? industrial?
systems?or?deposited?back?into?the?bio-
sphere.?Societal?systems?may?also?con-
sume?ecosystem?services?and?resource?
stocks?directly?(e.g.,?through?farming).?
Product?use?can?be?separated?into?two?
categories.? Durable? consumer? goods?
(e.g.,?automobiles)?are?used?repeatedly?
over?an?extended?period,?possibly?requir-
ing?ongoing?consumption?of?supplies?
and?energy.?At?the?end?of?their?useful?
lives?the?products?become?waste,?which?
is?potentially?recyclable.?Non-durable?
consumer?goods?(e.g.,?food?items)?are?
used?once?and?either?wholly?or?partially?
consumed,?with?the?remainder?becoming?
potentially?recyclable?waste.
? Mirroring? these? physical? systems?
is? an? economic? system? that? mediates?
most? transactions? involving? flows? of?
materials,?goods,?and?services,?although?
ecological?flows?are?often?ignored.?Eco-
nomic?growth?will?typically?correspond?
to?increased?“throughput”?in?terms?of?
the?total?amount?of?materials?flowing?
through?the?three?systems,?and?may?be?
a?consequence?of?population?growth?or?
growth?in?material?demand?per?capita.?
deFInInG SuStAInAble
MAteRIAlS MAnAGeMent
? It?is?clear?that?negative?environmental?
impacts? (i.e.,? externalities)? related? to?
increasing? material? flows? represent? a?
threat?to?ecological?sustainability.?How-
ever,?there?is?an?opposite?pressure?from?
socio-economic? systems:? population?
growth?and?economic?development?tend?
to?increase?the?demand?for?materials.?A?
lack?of?adequate?material?goods,?includ-
ing?food,?water,?and?medicines,?afflicts?a?
large?proportion?of?the?world’s?popula-
tion,?which?is?growing?at?the?rate?of?about?
90?million?people?per?year.?According?
to?the?World?Bank,?roughly?2?billion?
people?lack?potable?water?and?sanitation,?
leading?to?proliferation?of?both?viral?and?
bacterial?infectious?diseases.4?Close?to?3?
billion?people,?more?than?half?the?devel-
oping?world’s?population,?live?in?extreme?
undeRStAndInG MAteRIAl FlOw PAtteRnS
? As?a?baseline?for?sustainable?materials?management?(SMM),?one?must?understand?
the?relative?magnitude?of?material?flows?in?the?global?economy.?Material?flow?analysis?
(MFA)?and?the?associated?methods?of?material?flow?accounting?are?important?tools?for?
quantifying?these?flows.13?Essentially?a?mass-balance?approach,?MFA?calculates?the?mass?
of?materials?entering?and?leaving?a?defined?system?boundary?(Figure?A).?A?key?indicator?
used?in?MFA?is?domestic?material?consumption?(DMC),?calculated?by?subtracting?exports?
from?direct?material?inputs.?Domestic?material?consumption?accounts?for?the?direct?trans-
boundary?flows?of?materials,?but?not?for?the?indirect?material?flows?associated?with?the?
product?chains?of?imports?or?exports.?A?fraction?of?annual?materials?input?is?sequestered?
in?capital?stocks?of?durable?assets,?mainly?buildings,?while?a?fraction?of?these?stocks?
enters?the?output?stream?as?durable?assets?are?retired.
? Another?useful?indicator?is?total?material?requirements?(�MR),?which?considers?the?
“material?rucksack”?of?indirect,?hidden?flows,?including?mining?wastes?and?other?discards,?
which?are?carried?along?with?direct?material?inputs?but?generate?no?economic?value?and?
can?disturb?the?natural?environment.?�he?size?of?the?rucksack?can?be?significant.?For?
example,?a?diamond?ring?weighing?10?g?has?a?rucksack?of?about?6,000?kg,?while?an?
average?newspaper?has?a?rucksack?of?10?kg.14?Since?these?hidden?wastes?do?not?enter?the?
economic?system,?they?represent?a?true?environmental?externality,?but?the?significance?of?
�MR?in?terms?of?actual?environmental?impacts?is?difficult?to?assess.
? A?recent?MFA?study?indicates?that?the?E.U.?economy?has?become?more?eco-efficient?
in?terms?of?material?intensity,?since?the?ratio?of?DMC?to?gross?domestic?product?(GDP),?
or?resource?efficiency,?has?slowly?declined?from?about?1.2?kg/€?in?1992?to?about?1?kg/€?
in?2000.15?However,?the?absolute?DMC?has?slightly?increased,?so?that?actual?decoupling?
of?material?use?from?economic?growth?has?not?been?achieved;?that?is,?DMC?continues?
to?grow?with?GDP.?�he?study?concluded?that?the?average?DMC?per?capita?for?the?EU-
25?in?the?year?2000?was?approximately?16.5??t,?although?individual?countries?ranged?
from?less?than?10?t?to?more?than?30?t?per?capita.?Similarly,?another?study?showed?that?
between?1980?and?2000?EU-15?DMC?per?capita?declined?from?16.2?t?to?15.6?t,?while?
overall?material?efficiency?increased?by?52%?and?GDP?grew?by?about?70%.16?�hus,?it?
can?be?asserted?that?to?support?the?lifestyle?of?the?average?European?resident?requires?
Figure A. An overview of national material flow accounting model (Source: World
Resources Institute [WRI]).
ImportsExports
Domestic Environment
Economic
Processing
Direct
Material
Input
T otal
Material
Requirement
W ater
Vapor
Air
and
W ater
Foreign
Hidden
Flows
Stocks
Domestic
Extraction
T otal
Domestic
Output
Domestic
Processed
Output to
Air, Land,
W ater
Domestic
Hidden
Flows
Domestic
Hidden
Flows

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2006 August • JOM
17
poverty,?earning?under?$2/day.?Many?of?
these?populations?are?suffering?social?
disintegration?due?to?the?displacement?
of?their?traditional?lifestyles?by?rapid?
industrialization?and?urbanization.
? At? the? same? time,? income? gaps? in?
society?are?growing.?�he?ratio?between?
income?earned?in?countries?with?the?rich-
est?20%?of?the?population?compared?to?
the?poorest?20%?widened?from?30:1?in?
1960?to?60:1?in?1990?to?74:1?in?1997.?�his?
gap?is?reflected?in?the?disproportionate?
share?of?materials?consumption?among?
global?nations.?�he?richest?20%?of?the?
world?population?accounts?for?86%?of?
total?private?consumption?expenditures;?
consumes?58%?of?the?world’s?energy,?
45%?of?all?meat?and?fish,?and?84%?of?
paper;?and?owns?87%?of?cars?and?74%?
of?telephones.?Conversely,?the?poorest?
20%?consumes?5%?or?less?of?each?of?
these?goods?and?services.5?�hus,?contin-
ued?economic?growth?and?resilience?are?
important?elements?in?assuring?quality?
of?life?not?only?for?affluent?societies,?but?
also?for?disadvantaged?populations.??
? �he?adverse?environmental?impacts?
of? economic? growth? might? be? miti-
gated?by?decoupling?the?rate?of?material?
throughput?relative?to?economic?growth,?
yet recent empirical studies questionet? recent? empirical? studies? question?
whether?the?shift?to?new?technologies?
in?the?information?age?leads?to?reduced?
materials?intensity.6?It?has?been?hypoth-
esized? that,? in? developed? countries,?
rising?resource?intensity?will?flatten?out?
and?begin?to?decrease?as?income?rises,?
but?some?economists?argue?that?a?new?
phase?of?“rematerialization”?or?re-link-
ing?can?occur.7?Establishing an efficient Establishing?an?efficient?
level?of?decoupling?ideally?would?require?
that?all?external?environmental?costs?are?
reflected?in?material?and?product?prices,?
allowing?the?market?to?determine?the?
appropriate?level?of?material?use.8?How-
ever,?it?is?unlikely?that?environmental?
resource?protection?will?be?a?priority?as?
long?as?these?resources?are?perceived?to?
be?free?and?limitless,9?thus,?in?the?absence?
of?perfect?markets,?more?active?interven-
tions?appear?to?be?necessary.
? �he?following?definition?is?intended?to?
help?both?government?policy-makers?and?
business?decision-makers?to?develop?pro-
active?strategies?for?managing?material?
flows.?Sustainable?materials?manage-
ment?(SMM)?is?an?integrated?approach?
toward? managing? material? life? cycles?
to? achieve? both? economic? efficiency?
and? environmental? viability.? Material?
life?cycles?include?all?human?activities?
related?to?material?selection,?exploration,?
extraction,? transportation,? processing,?
consumption,?recycling,?and?disposal.
? It?follows?that?SMM?practitioners?will?
seek?to?reduce?the?material?throughput?
required?for?sustained?economic?prosper-
ity?and?to?minimize?the?adverse?impacts?
of?material?usage?upon?environmental?
and? social? well-being.? Strategies? for?
SMM?can?be?separated?into?two?catego-
ries:?dematerialization?and?detoxifica-
tion.?
Dematerialization
? Dematerialization? refers? to? the?
reduction?of?material?throughput?in?an?
economic?system,?and?can?include?the?
following?approaches:?increase?of?mate-
rial?efficiency?in?the?supply?chain,?thus?
reducing?waste;?eco-design?of?products?
to?reduce?mass,?packaging,?or?life-cycle?
energy?requirements;?reduction?of?trans-
port?in?the?supply?chain,?thus?reducing?
fuel?and?vehicle?utilization;?recovery?and?
a?direct?material?consumption?of?about?44?kg/day.?�he?majority?of?these?materials?are?
construction?minerals,?fossil?fuels,?and?biomass?from?agriculture.?(�he?�MR,?including?
the?material?rucksack,?is?estimated?to?be?about?five?times?greater,?or?about?220?kg/day.)
? Material?flow?analysis?can?be?used?to?focus?on?particular?substances,?geographic?areas,?
or?industries.?More?in-depth?investigations?may?be?necessary?to?support?policy-making?
regarding?intervention?in?particular?material?flow?pathways.?Figure?B?depicts?a?substance-
specific?analysis;?it?shows?that?arsenic?use?in?agricultural?applications?has?declined,?but?
its?use?as?a?wood?preservative?has?risen?nearly?25-fold?in?the?United?States,?which?may?
pose?a?threat?to?soil?and?water?quality?when?wood?products?are?discarded.?In?2001,?the?
U.S.?Environmental?Protection?Agency?adopted?a?stricter?standard?for?arsenic?in?drinking?
water?and?reached?agreement?with?the?wood?treatment?industry?to?phase?out?arsenates.
? Obviously,?not?all?materials?are?created?equal?in?terms?of?their?environmental?impact;?
for?example,?sand?and?gravel?represent?a?large?proportion?of?material?flow?by?weight,?but?
are?much?less?significant?than?other?materials?in?terms?of?their?adverse?effects.?Similarly,?
while? metals? and? fossil? fuels? are? often? lumped? into? the? category? of? non-renewable?
resources,?the?elemental?structure?of?metals?means?that?they?are?perpetually?recyclable?
and?not?subject?to?the?degradation?that?occurs?with?materials?composed?of?complex?
molecules.17? Generally? speaking,? variations? in? toxicity,? reactivity,? flammability,?
environmental?fate,?bioaccumulation,?and?persistence?will?alter?the?ultimate?impact?of?
different?substances?that?are?released?to?the?environment.?In?addition,?the?geographic?
location,? flow? rate,? and? medium? of? discharge? can? introduce? uncertainties? about? the?
environmental? impacts? associated? with? such? releases.? Accounting? for? all? of? these?
differences?at?a?national?or?global?level?appears?to?be?an?intractable?problem.?�herefore,?
aggregated?economy-wide?material?flow?indicators?should?be?utilized?with?caution.?
? Finally,?a?reliance?on?mass?flow?indicators?can?be?deceptive?because?of?the?hidden?
environmental? burdens? associated? with? manufactured? products.? For? example,? the?
miniaturization?of?electronic?products?gives?the?appearance?of?dematerialization,?yet?a?
more?careful?analysis?reveals?that?large?quantities?of?chemicals,?materials,?and?energy?are?
required? as? inputs? to? the? manufacture? of? these? products.18? In? the? case? of? imported?
electronic?devices,?these?hidden?flows?will?not?be?counted,?not?even?as?part?of?the?
ecological? rucksack? associated? with? the? products.? Instead,? they? will? appear? in? the?
domestic?material?flows?for?the?nations?that?manufacture?the?components.?In?an?economy?
where?global?sourcing?is?increasingly?the?norm,?the?question?of?allocating?accountability?
for?these?upstream?material?flows?remains?challenging.?
Figure B. Potential arsenic outputs to the U.S. environment, 1975–1996 (Source: WRI).
Other
Glass
Wood Preservatives
Coal Fly Ash
Agricultural Chemicals
25
20
15
10
5
0
19751980 198519901995
Thousand T onnes

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JOM • August 2006
18
beneficial?recycling?of?post-industrial?or?
post-consumer?wastes;?substitution?of?
electronic?services?for?material-inten-
sive? services;? substitution? of? services?
for?products.
? Dematerialization?has?been?popular-
ized?in?proposals?such?as?Factor?4,?which?
suggests? doubling? global? economic?
wealth?while?halving?material?resource?
use.10?Some?argue?that?for?industrialized?
nations?to?reach?long-term?sustainability,?
a? Factor? 10? transformation? is? neces-
sary.11
Detoxification
? Detoxification?refers?to?the?preven-
tion?or?reduction?of?adverse?human?or?
ecological?effects?associated?with?mate-
rials?use,?and?can?include?the?follow-
ing? approaches:? material? substitution,?
replacing?toxic?or?hazardous?materials?
with? benign? ones;? cleaner? technolo-
gies,?reducing?the?toxic?or?hazardous?
properties?of?waste?streams;?reduction?
of?greenhouse?gas?emissions?associated?
with? fossil? fuel? combustion;? material?
regulation,?placing?restrictions?on?the?
use?of?specified?materials;?waste?modi-
fication? through? chemical,? energetic,?
or?biological?treatment;?waste?contain-
ment?or?isolation?to?prevent?human?and?
ecological?exposure;?and?in-situ?waste?
treatment,?reducing?the?effective?con-
centrations?or?adverse?impacts?of?wastes?
that?have?previously?been?discharged?into?
the?environment.?
? While? detoxification? reduces? the?
environmental?pressure?of?materials?use,?
dematerialization?can?actually?decouple?
material? use? from? industrial? growth,?
either?by?reducing?material?requirements?
or?by?substituting?recycled?materials?for?
virgin?raw?materials.?
? Provided?that?ecological?limits?are?rec-
ognized,?decoupling?material?consump-
tion?from?economic?growth?appears?to?
be?a?reasonable?aspiration.?For?example,?
the?proven?reserves?of?non-renewable?
resources?continue?to?increase,?largely?
due?to?technology?improvements.?It?is?
estimated?that?the?present?terrestrial?stock?
of?fossil?fuels?represents?about?a?1,000-
year?supply?at?the?present?rate?of?con-
sumption,?which?is?equivalent?to?about?
7?billion?metric?Gigatons?of?oil?per?year.?
�o?sustain?the?availability?of?this?stock?
for?perpetuity?would?require?decoupling?
fossil?fuel?consumption?from?economic?
growth?and?decreasing?it?by?0.1%?per?
year,?a?realistic?goal.12?Of?course,?efforts?
to?limit?atmospheric?carbon?emissions?
may?require?even?further?reductions?in?
fossil?fuel?consumption.?
? Concerns? about? the? environmental?
impacts? of? non-renewable? resource?
consumption?will?likely?outweigh?con-
cerns? about? resource? scarcity? for? the?
foreseeable?future.?Increased?material?
consumption? presents? a? threat? to? the?
sustainability? of? renewable? resources?
such?as?forests?and?fisheries,?as?well?as?
the?quality?of?environmental?media?such?
as?arable?land?and?fresh?water.?�hus,?the?
key?to?SMM?is?to?understand?and?mitigate?
the?adverse?impacts?of?material?flows?
upon? ecological? and? societal? systems?
rather?than?simply?constraining?material?
flows.?For?example,?the?global?transport?
of?materials?from?producing?countries?
to?consuming?countries,?while?it?may?
appear?economically?efficient,?can?have?
undesirable? side? effects? upon? natural?
resources? (e.g.,? land? appropriation? or?
accidental?spills).?A?well-balanced?policy?
approach?might?internalize?these?nega-
tive?impacts?into?transport?costs.??
AnAlyzInG the IMPActS
OF MAteRIAl FlOwS
? �he?sidebar?on?page?16?describes?how?
material?flow?analysis?(MFA)?can?be?used?
to? understand? material? flow? patterns.?
However,?analysis?of?material?flows?in?
terms?of?mass?alone?does?not?account?
for?differences?in?their?environmental?
impacts.?�he?following?two?techniques?
can?augment?MFA?by?considering?envi-
ronmental?implications.?
Ecological Footprint Analysis
Ecological? footprint? analysis? is? a?
technique?for?estimating?the?amount?of?
productive?capacity?needed?to?support?a?
specified?economic?activity,?quantified?in?
terms?of?the?total?land?area?hypothetically?
required.?�his?can?be?interpreted?as?the?
burden?placed?on?the?carrying?capacity?
of?ecosystems?due?to?economic?activi-
ties?and?material?flows.?In?some?cases,?
technological?intervention?(e.g.,?use?of?
biotechnology?to?increase?agricultural?
productivity)?can?increase?the?carrying?
capacity?of?a?resource.?However,?in?prac-
tice,?renewable?resource?systems?such?as?
forests?have?an?upper?limit?on?the?amount?
of?replenishment?per?unit?time?that?they?
can?support?without?impairment.?
? �he?amount?of?biologically?productive?
capacity?worldwide?has?been?estimated?
Figure 2. Comparative analysis of mass flow and exergy flow for an
ammonia process.

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2006 August • JOM
19
for?the?year?2000?as?2.1?hectares?per?
capita,?of?which?1.6?hectares?are?land-
based?ecosystems?such?as?forests,?pas-
tures,?and?arable?land?and?0.5?hectares?
are?ocean?areas.19?Setting?aside?a?small?
fraction?as?protected?areas?leaves?about?
1.8?hectares?per?capita.?Ecological?foot-
print?analysis?can?be?used?to?estimate?
the?human?demand,?based?on?the?bio-
logical?capacity?required?to?support?both?
resource?consumption?and?waste?absorp-
tion.?Given?numerous?assumptions?and?
uncertainties,?the?methodology?conser-
vatively?estimates?the?average?footprint?
in?1996?to?be?12.3?hectares?in?the?United?
States,?7.7?hectares?in?Canada,?and?6.3?
hectares?in?Germany.?�he?average?global?
footprint?for?all?nations?is?estimated?at?
2.8?hectares?per?capita,?suggesting?that?
humanity’s?ecological?demands?already?
exceed?what?nature?can?supply.?�hus,?
humanity?has?arguably?moved?into?what?
is?termed?ecological?overshoot,?and?is?
effectively?depleting?the?available?stock?
of?natural?capital?rather?than?living?off?
the?interest.?
? �he? components? of? the? ecological?
footprint? are? heavily? dependent? upon?
material? consumption? patterns.? For?
example,?in?lower-income?nations,?over?
50%?of?the?footprint?is?due?to?agricultural?
and?forest?products,?and?about?18%?is?
due?to?energy?production?(mainly?fossil?
fuels).??In?higher-income?countries?only?
about?28%?is?due?to?agricultural?and?
forest?products,?while?close?to?60%?is?
due?to?energy?production.20?From?this?
perspective,?it?appears?that?decoupling?
material?consumption?and?waste?gen-
eration? (especially? CO2)? from? indus-
trial?growth?is?essential?for?the?global?
economy?to?reverse?the?overshoot?and?
return?to?a?sustainable?path.?
? Ecological?footprint?analysis?can?be?
applied?at?any?level?of?granularity,?from?
an?entire?nation?to?a?single?individual.?
�hus,? it? offers? a? method? for? testing?
the? burden? associated? with? economic?
enterprises,?supply?chains,?or?communi-
ties.21?However, it should be noted thatHowever,?it?should?be?noted?that?
the?concept?of?carrying?capacity?merely?
addresses?survivability,?rather?than?sus-
tainability?in?terms?of?quality?of?life?for?
human?populations.
Thermodynamic Analysis
? �hermodynamic? analysis? is? an?
approach?for?modeling?material?flows?
in?complex?systems?based?on?the?laws?
of? thermodynamics.? �he? underlying?
concept?is?exergy,?defined?as?the?avail-
able?work?that?can?be?extracted?from?a?
material;?for?example,?the?exergy?content?
of?a?fuel?is?essentially?its?heat?content.22?
More?generally,?exergy?tends?to?be?cor-
related?with?material?scarcity?and?purity,?
since? it? measures? the? difference? of? a?
material?from?its?surroundings.?In?fact,?
embodied?exergy?can?serve?as?a?common?
currency?for?aggregating?material?flows?
and?provides?a?more?meaningful?weight-
ing?of?waste?flows?in?terms?of?potential?
impacts.?Since?energy?(actually?exergy)?
is?the?ultimate?limiting?resource,?and?
since?embedded?energy?is?a?common?
characteristic?of?all?materials,?it?is?pos-
sible?to?measure?material?flow?patterns?
in?terms?of?exergy?flows.?
? �he?energy?intensity?of?materials?is?
very?different?from?their?mass?intensity,?
and?is?arguably?more?closely?correlated?
with? the? life-cycle? natural? resource?
impacts?of?material?inputs?as?well?as?the?
economic?value?and/or?environmental?
impact?of?material?outputs.?As?a?result,?
there? has? been? a? growing? interest? in?
the? use? of? thermodynamic? indicators?
to?represent?the?impacts?of?industrial?
processes.23?In?fact,?all?of?the?factors?of?
industrial?production—energy,?materi-
als,?land,?air,?water,?wind,?tides,?and?even?
human?resources—can?be?represented?
in? terms? of? exergy? flows.? �herefore,?
exergy?can?be?used?as?a?universal?cur-
rency?to?measure?growth,?efficiency,?and?
sustainability? in? industrial-ecological?
systems.24
? Figure?2?provides?a?simple?comparison?
of?alternative?analysis?methods?for?an?
ammonia?process.?�he?top?of?the?figure?
shows?a?typical?MFA,?with?the?width?of?
each?arrow?corresponding?to?the?quantity?
of?material?inputs?or?outputs.?Due?to?the?
law?of?conservation?of?mass,?the?sum?of?
materials? entering? the? process? equals?
the?sum?of?the?materials?leaving.?�he?
bottom?shows?a?similar?analysis,?except?
that? each? material? or? energy? flow? is?
measured?in?terms?of?exergy,?including?
embodied?chemical?or?physical?energy?
(expressed?in?Megawatts).?�he?differ-
ences?are?evident.?For?example,?water?
accounts?for?over?half?the?mass?flow,?but?
has?low?exergy?content?because?it?can?
be?piped?directly?from?a?natural?source.?
In?contrast,?the?mass?inputs?of?fuel?and?
natural?gas?are?low,?yet?their?exergy?con-
tent?is?high,?reflecting?their?combustion?
potential.?Similarly,?the?exergy?content?of?
ammonia?is?high,?reflecting?its?value?for?
subsequent?processes?involving?energy?
extraction.?�he?mass?flow?of?electricity?
is?zero,?yet?the?impact?of?electricity?use?
can?be?significant.?Due?to?the?second?
law?of?thermodynamics,?some?exergy?
is?inevitably?lost?as?“waste”?energy,?and?
thermodynamic?efficiency?can?be?mea-
sured?as?the?ratio?of?exergy?produced?to?
exergy?consumed.?
buSIneSS VAlue OF SMM
? In?the?private?sector,?business?pro-
cesses?that?involve?materials?manage-
ment—including? sourcing,? inventory?
management,? warehousing,? logistics,?
and? distribution—are? increasingly?
viewed?as?strategic?levers?in?enhancing?
business?competitiveness.?�his?is?due?
partly? to? the? drive? toward? more? effi-
cient?asset?utilization,?and?partly?due?to?
increasingly?complex?supply?networks?
that?result?from?globalization?and?out-
sourcing.?At?the?same?time,?environmen-
tally?conscious?purchasing?practices?and?
increased?awareness?of?corporate?social?
responsibility?have?elevated?corporate?
concerns? about? product? stewardship?
and? waste? minimization.? Companies?
recognize? that? environmental? issues?
can?no?longer?be?addressed?in?a?reactive?
fashion.?�hey?are?increasingly?expected?
to?take?responsibility?for?the?disposal?of?
products?and?packaging?at?the?end?of?their?
useful?life,?so?that?designing?for?reverse?
logistics?has?become?a?strategic?approach?
for?converting?wastes?into?assets?and?
thus?generating?shareholder?value.24?As?
a?result?of?these?trends,?SMM?is?fully?
compatible?with?the?business?goals?of?
leading?multi-national?companies.
? Recent?research?has?demonstrated?a?
correlation?between?shareholder?value?in?
capital?markets?and?excellence?in?sustain-
ability,?including?both?social?responsibil-
ity? and? environmental? management.25?
Specifically,? there? are? two? types? of?
business?value?creation?associated?with?
improved?sustainability?performance.
Liability and Cost Avoidance
? Liability?and?cost?avoidance?is?the?
traditional? domain? of? corporate? envi-
ronmental? management,? and? includes?
compliance? with? regulations? and?
standards,?minimization?of?product?or?
process-related?risks,?and?environmen-
tal?stewardship.?Materials?management?