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Urban MetabolismMethodological Advances in UrbanMaterial Flow Accounting Based on theLisbon Case Study

Samuel Niza, Leonardo Rosado, and Paulo Ferrao

Keywords:

domestic material consumption(DMC)

industrial ecologymaterial balanceresource managementsustainable cityurban planning

Summary

Urban metabolism studies have been established for only a fewcities worldwide, and difficulties obtaining adequate statisticaldata are universal. Constraints and peculiarities call for inno-vative methods to quantify the materials entering and leavingcity boundaries. Such methods include the extrapolation ofdata at the country or the region level based, namely, on sales,population, commuters, workers, and waste produced.

The work described in this article offers a new methodol-ogy developed specifically for quantifying urban material flows,making possible the regular compilation of data pertinent tothe characterization of a city’s metabolism. This methodol-ogy was tested in a case study that characterized the urbanmetabolism of the city of Lisbon by quantifying Lisbon’s ma-terial balance for 2004. With this aim, four variables werecharacterized and linked to material flows associated with thecity: absolute consumption of materials/products per category,throughput of materials in the urban system per material cate-gory, material intensity of economic activities, and waste flowsper treatment technology.

Results show that annual material consumption in Lisbon to-tals 11.223 million tonnes (20 tonnes per capita), and materialoutputs sum 2.149 million tonnes. Nonrenewable resourcesrepresent almost 80% of the total material consumption, andrenewables consumption (biomass) constitutes only 18% ofthe total consumption. The remaining portion is made up ofnonspecified materials.

A seemingly excessive consumption amount of nonrenew-able materials compared to renewables may be the result ofa large investment in building construction and a significantshift toward private car traveling, to the detriment of publictransportation.

Address correspondence to:Samuel NizaIN+ Center for Innovation, Technology

and Policy ResearchIST Instituto Superior TecnicoAv. Rovisco Pais1049-001 Lisboa, [email protected]://in3.dem.ist.utl.pt

c© 2009 by Yale UniversityDOI: 10.1111/j.1530-9290.2009.00130.x

Volume 13, Number 3

384 Journal of Industrial Ecology www.blackwellpublishing.com/jie

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Introduction

Urban areas are characterized by a concen-tration of economic activities, a large popula-tion, and large material stock densities, inducinghigh levels of energy and material flows (Graedel1999). These material flows represent potentialecosystem impacts on scales ranging from localto regional to global (Bai 2007).

To promote the sustainable material flowmanagement of an urban region, it is vital tounderstand the region’s metabolism, and this re-quires a detailed knowledge of the main ma-terial flows. According to Hendriks and col-leagues (2000), this management should include,in strategic terms, the following steps:

1. quantifying material flows and the growthof material stocks;

2. assessing the consequences of flows andstock accumulation on several levels,namely environmental, economic, and so-cial; and

3. controlling and shortening material flows(namely through dematerialization strate-gies, closing of materials cycles, and ma-terials and energy source substitution) andconsidering sustainable development ob-jectives.

All this calls for the concept of urbanmetabolism, which is based on a material flowsmodel of the interrelations between the econ-omy and the environment, in which the econ-omy functions like an environmental subsystem,dependent on the ongoing throughput of materi-als and energy (Daly 1996). Therefore, raw mate-rials, water, and air are extracted from the naturalsystem, constituting inputs to the economic sys-tem, and are partially transformed into products,residues, and other material and energy flows thatmay cause environmental damage.

Material flow accounting1 (MFA) facilitatesthe assessment of the material consumption of asystem for a certain base year—corresponding to astatic analysis of material flows—but also permitsthe evaluation of trends in material consumptionof the economic system through the developmentof time series. It can thus be considered a tool pro-viding, simultaneously, the disaggregation of dataand a quick way of characterizing the dynamics

of an economy’s metabolism (Niza and Ferrao2005).

In this context, MFA can support decisionmakers in coming to understand the metabolismof their region. It allows regional processes and ac-tivities such as construction, transportation, con-sumption, and waste disposal to be linked system-atically, with consideration of the overall inputsand outputs. More specifically, MFA examinesthe materials flowing into a given system (pri-vate household, company, region, city, etc.), thestocks and flows within this system, and the re-sulting outputs from the system to other systems.Unlike many other environmental managementtools, MFA focuses on loadings rather than con-centrations and is also useful for examining therelationship between a region or city and its sur-rounding hinterland (Obernosterer et al. 1998).Nevertheless, as Binder (2007) points out in herreview of regional MFA, there is no methodolog-ical framework for this type of study, nor are theresuitable data. If we look at urban MFA this is trueas well, and the quantity of available data is evenless.

In spring 2007, the Journal of Industrial Ecol-ogy dedicated a special issue to the global impactof cities (volume 11, issue 2), which reinforcedthe importance of studying urban material flows.In this context, this article contributes newmethodological advances in quantification for ur-ban MFA, enabling the regular compilation ofinformation relevant to characterizing a city’smetabolism. Constraints that are tied to an ur-ban scale of analysis are overcome by the newmethodology developed in this article, which wasapplied to Lisbon. A material flow balance forLisbon was developed in the context of a projectpromoted by the Lisbon Energy and EnvironmentAgency (Lisboa E-Nova), aimed at supportingthe definition of performance indicators and tar-gets to be integrated into the energy and envi-ronmental strategy for Lisbon.

Lisbon is the Portuguese capital and the ur-ban center of a region that can be considered amedium-sized European metropolitan area, as il-lustrated in figure 1, comprehending accordingto the 2001 census, more than 2.5 million in-habitants. In March 2001, Lisbon city had ap-proximately 560,000 residents, about 20% of theLisbon region population.

Niza et al., Methodological Advances in Urban MFA Based on Lisbon Study 385

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Figure 1 Geographical scale levels: Portugal, the Lisbon region, and Lisbon city. The Lisbon region includesLisbon city as well as 17 surrounding municipalities.

As with several world urban regions (Hall1998), the Lisbon region shows symptoms of anevolution toward a diffuse and nonpolycentricmetropolis (CML 2005b). It is, at the nationallevel, a highly attractive pole of economic activ-ity and employment, assuming a central role inthe international activities of the country (CML2005a).

We quantified Lisbon city’s material flow bal-ance, making use of the EUROSTAT MFAmethodology (EUROSTAT 2001) wheneverpossible. The material flow balance for 2004 wasestablished, and, in addition, four variables asso-ciated with the city’s material flows were char-acterized: absolute consumption of materials andproducts per category, throughput of materialsper material category, material intensity of eco-nomic activities, and waste flows per treatmenttechnology.

The article is organized into six sections be-sides this introduction. The first section demon-

strates the need for wide research on urban ma-terial flows. The next section reviews some ofthe most important MFA-based studies of ur-ban areas available in the literature and identi-fies the main characteristics and methodologicalconstraints observed in these studies. The nexttwo sections are dedicated to describing the newmethodology developed for quantifying Lisbon’smaterial balance and showing the main resultsof the balance. We make a benchmarking anal-ysis by comparing the results obtained with theresults from a study of Greater London, both interms of material consumption data and in termsof the methodological choices made by the re-searchers. The final two sections discuss the po-tentials and constraints of urban material flowstudies and highlight the methodological contri-butions provided by this article, in that it aidsin overcoming the main constraints observed inthe urban MFA studies currently available in theliterature.

386 Journal of Industrial Ecology

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The Urgency of Urban MFA

Cities attract a growing number of people, whocome essentially from rural areas. The EuropeanEnvironment Agency (2006) estimates that morethan a quarter of the European Union territoryis actually urban-type and that by 2020 approx-imately 80% of European citizens will be livingin urban areas. As predicted by the WorldwatchInstitute (2007), in 2008, the world crossed forthe first time an invisible but momentous mile-stone: the point at which more than half of thepeople on the planet—roughly 3.2 billion humanbeings—live in cities. More than at any time inhistory, the future of humanity, our economy, andthe planet that supports us will be determined inurban areas around the globe.

As mentioned by Kennedy and colleagues(2007), “cities grow in complex ways due to theirsize, social structures, economic systems, geopo-litical settings, and the evolution of technol-ogy” (44). Cities are open systems, dependenton the outside world to provide raw materialsand assimilate waste to sustain their functions(Bai 2007). The conversion of land to urbanuses, the extraction and depletion of natural re-sources, and the disposal of urban waste all indi-cate that urbanization in general is having globalimpacts. Dysfunctional urban environments havehigh costs—helping to perpetuate inequities byrequiring higher economic growth to improve liv-ing standards. With global population growthcentered largely in urban areas, cities will in-creasingly be places where human activities andtheir associated ecological impacts can be mostaptly met with policy and planning responses(UNU/IAS 2003). Urban researchers thus re-quire new methods best suited to dealing with avariety of urban trends, conditions, and impactssimultaneously to promote the more sustainabledevelopment of these areas.

One of the best ways to approach the sustain-ability of a city, a region, or a country involvesanalyzing it much as one would a living organ-ism, by characterizing its metabolism and so on—viewing it as a complex system that, to maintainits vital functions, consumes matter and energyand, after doing so, accumulates materials anddischarges residuals in various ways, frequently

creating environmental impacts. These are prac-tical reasons for studying urban metabolism.

Urban metabolism studies can be used as toolsin identifying environmental problems (and eco-nomic costs) related to the growth of inputs (re-sources) and the management of outputs (primar-ily urban wastes) and in designing more efficienturban planning policies. A city (as an organism)will never be sustainable in a strict sense, giventhat it cannot rely on the self-sufficiency of re-sources extracted in its area. Virtually all citiesrely on food, fuels, and materials from elsewhere,and all cities are marketplaces. As cities havebeen growing and transportation technologieschanging, resources have been traveling greaterdistances to reach cities. Kennedy and colleagues(2007) summarize this phenomenon well:

For heavier materials, which are more expen-sive to transport, the exhaustion of the nearest,most accessible resources may even at some pointbecome a constraint on the growth of cities. Formany goods, including food, modern cities nolonger rely only on their hinterlands; rather, theyparticipate in continental and global trading net-works. More than ever the vitality of cities de-pends on spatial relationships with surroundinghinterlands and global resource webs. (56)

They conclude that “full evaluation of urbansustainability requires a broad scope of analysis”(57).

MFA studies have demonstrated that, similarto the decrease of geogenic stocks (those origi-nating in the soil), a new stock is built up in theanthroposphere (Brunner 2004, 2007). The ur-ban stock of goods is rapidly increasing, becauseinputs of most materials into the anthroposphereexceed outputs. When compared to the billions oftonnes of raw materials exploited from the earth’scrust, the amount of corresponding materials thathave been disposed of, in appropriate final sinks,is still hardly known yet is estimated to be quitesmall.

The largest fraction of various materials islikely accumulated in the anthropogenic stock,not in landfills or other sinks. In the future,this anthropogenic stock can serve either as anew source of secondary raw materials or aswaste that has to be treated and landfilled. Thisanthropogenic resource stock is still not well


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known because it is often not included in eco-nomic analysis,2 in contrast to material flowsthat are accessible via economic accounts. Anexample is the hibernating fraction of the an-thropogenic stock, namely obsolete undergroundcables. In the future, this fraction of materialswill become important as a resource as well as apollutant (Ribeiro et al. 2007). It is clear that ifrecycling rates are not increased in the future, theamount of future wastes that have to be disposedof in sinks, such as landfills, will considerably in-crease. Thus, we need to better understand andmonitor these flows to design adequate policies tomanage this stock effectively and control flows,from stocks to sinks, in the environment.

Sustainable development implies, amongother things, that the metabolism of urban re-gions is managed in view of long-term resourceuse and environmental protection (Hendrikset al. 2000). This can be achieved through theconcept of materials management set forth byHendriks and colleagues (2000) in this article’sintroduction, summed up as follows:

1. quantifying material flows and stockswithin a given system;

2. assessing the importance and relevance ofthese flows and stocks; and

3. controlling material flows and stocks inview of certain goals, such as sustainabledevelopment.

MFA is thus an excellent tool for achievingthe first objective and constitutes a good ba-sis for the other objectives. When the materialflows of a region are analyzed, important charac-teristics of the regional metabolism can becomeapparent.

Review of Urban MFA-BasedStudies

The term urban metabolism was first used byWolman (1965) in a famous article in Scien-tific American. In his pioneering work, the au-thor quantified the flows of energy and materialsinto and out of a hypothetical American city, en-hancing the importance of the MFA approach forstudying cities. Nevertheless, since then, whencompared to the large number of MFA studiesperformed on the national level, studies focusing

on the regional or local level have still been verylimited, and a standardized method equivalent tothat presented by EUROSTAT (2001) for thenational level does not yet exist. Although theavailable studies show the importance of materialflows to regional and urban metabolism, they alsopresent a large spectrum of approaches that canbe defined through the MFA approach (Graedel1999).

Some of the studies focusing on urban areas aresummarized in table 1. The lack of available sta-tistical data at the municipal and regional levelscurrently calls for different approaches to assess-ing urban material flows. Studies tend to eitherfocus on choosing and analyzing only the mostimportant products and materials (Bunz Valley,Greater London, and Region of York) or focuson tracing a specific substance, such as lead, cop-per, or phosphorus (Bunz Valley, City of Vienna,City of Stockholm). This leads to studies thatgenerally do not explain the complete system ofmaterial flows within a region or city.

Another main constraint on the attempt tocalculate the material flows of a city is that no realborders exist. Consequently, it is hard to identifyand quantify the amounts of products crossing thecity borders that are for endogenous consumptionand not to be consumed elsewhere. This prob-lem may be amplified when the city serves asgateway for goods (e.g., via a big harbor, a trainstation, or an international airport) for the coun-try or even for other countries (e.g., Hamburg).Conversely, administratively and economicallysignificant cities are characterized by a consider-able number of commuters working in the citybut living nearby. This situation usually bringsabout the overestimation of the city’s materialflows if the phenomenon is not correctly identi-fied. Several urban metabolism studies have beenundertaken for greater regional areas, typicallycorresponding to “commuter sheds,” which henceminimizes errors associated with people movingover the boundaries on a daily basis (e.g., GreaterLondon, Region of York).

Additionally, with respect to urban materialflows, it has been observed that domestic ex-traction is null or residual (e.g., Hamburg, York,or London). Likely, local industrial productionmay also be residual, and this means that hardlyany raw materials are consumed within the city.


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Tabl

e1

Reg

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land

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mat

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FA)

stud

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Met

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FAO

ther

Obs

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tions

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ley,

Swit

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and,

1994

(Bru

nner

etal

.19

94)

XA

sses

sand

cont

rolr

egio

nal

indu

stri

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etab

olis

mPr

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dolo

gyfo

rthe

esta

blis

hmen

tofr

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nal

mat

eria

lbal

ance

s,us

ing

aca

se-s

tudy

ona

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sreg

ion

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er,e

nerg

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ater

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,and

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amel

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dph

osph

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hich

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atit

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unzV

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a,19

98(H

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2000

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tinu

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F O RU M

Tabl

e1

Con

tinue

d

Met

hodo

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ion

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(BFF

2002

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the

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this

arti

cle.


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With the exception of some construction rawmaterials, such as sand and gravel, cities mainlyconsume final products. Conversely, big citiesusually evidence a strong relationship in terms oftrade (materials or products) with the surround-ing region—the origin and destination of manyproducts to the city and from it.

These constraints and peculiarities call for in-novative methods to quantify materials enteringand leaving the city. Methodological solutionsinclude extrapolation of data from the country orthe region and estimations based on sales; num-ber of inhabitants, commuters, or workers; or pro-duced waste.

Lisbon is a case that “suffers” from the pecu-liarities described for other cities, so new methodswere developed for quantifying Lisbon’s mate-rial balance. The results obtained were comparedwith those presented for the other cities cited intable 1.

MFA of Lisbon: Methodology

The main purpose of this study is to establisha smart methodological framework for depictingurban areas, relying on published statistical dataand based on the EUROSTAT (2001) methodol-ogy. A significant effort has been made to extendthat method, given that it was originally designedto quantify economy-wide material flows, and the

Figure 2 Material flows of an economic system.

current work is focused on Lisbon city, exclud-ing all of the surrounding municipalities of itsmetropolitan area.3

One of the major constraints to the quantifi-cation of material flows at regional or urban scaleshas to do with the availability of data for the es-tablished boundaries, as the structure of statisticalrecords does not include data at a city level. Dataneeded to quantify the material flows of a givensystem are represented in a simplified mode4 infigure 2 and include

• inputs (domestic extraction of resources,imports of raw materials and products) and

• outputs (emissions and wastes, exports ofraw materials and products).

Urban areas are regions wherein smallamounts of material extraction take place. Bycontrast, at the end of the 1970s, material extrac-tion within Lisbon still constituted an importantactivity for the construction and development ofthe city. Currently, however, there is no activequarry in the municipality (Sousa Pinto 2005).The same is true for agricultural activity, exceptfor some small private grounds.

As a consequence, it can be assumed that allmaterials consumed in the city come from out-side its limits, including its surrounding munici-palities. It may thus be considered that domestic


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extraction in Lisbon city is residual and may bedefined as nonexistent in MFA terms. This is con-sistent with results reported in similar studies (seethe Review of Urban MFA-Based Studies sectionof this article).

Consequently, import and export categoriesassume higher relevance in the quantification ofthe city’s material flows. It is therefore crucial toquantify the goods exchanged between Lisbon,the rest of the country, and the rest of the world.5

Lisbon harbor, for instance, is an input andoutput gateway for a large number of commoditiesto and from the country. It processes more than 13million tonnes6 of commodities per year.7 Con-sequently, a large number of commodities reach-ing the city only pass through it and should notbe counted as part of the city’s material flows,to avoid the overestimation of the material con-sumption associated with Lisbon residents’ eco-nomic activities.

Conversely, data related to the distributionof the labor structure and economic activitiesclearly indicate that Lisbon city has little indus-trial activity. Industrial employment representedonly 9% of total employment in 2000. Addi-tionally, this sector registers a concentration oftechnologically intensive industries, which is anindicator of a specialization in knowledge-basedeconomic activities (CML 2005a). To assess theaccuracy of these assumptions, we estimated theamount of materials used for local industrial pro-

Figure 3 Lisbon city material flows.

duction, which was approximately 1.7% of thetotal amount of material inputs.

As domestic extraction is almost nonexistentand local production is quite low, exports of ma-terials derived from Lisbon are residual or nonex-istent, in terms of material flows. Figure 3 summa-rizes flows we considered when quantifying Lis-bon’s material flows.

Material inputs to Lisbon consist of productsfor internal consumption and raw materials for lo-cal production. Outputs are emissions and wastes,to be processed in the surrounding municipalities.The remaining flows, which may constitute con-siderable amounts, are products that just crossthrough the city en route to their destination.

From the previous paragraphs, it may be in-ferred that the main catalyzer of material flows ina city is consumption and, to a much lesser degree,local production. Consequently, imports intotown (when the imports that just pass throughit are subtracted) are a proxy for the city’s con-sumption. According to EUROSTAT’s method-ology, the material consumption indicator of aneconomy is provided by domestic material con-sumption (DMC), which equals the domestic ex-traction plus imports minus exports. From ourfindings in the Lisbon case study, the city’s DMCequals imports.

The methodology developed allowed for thecharacterization of the following variables asso-ciated with Lisbon city material flows:


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1. absolute consumption and final disposal ofmaterials, per material category;

2. throughput of materials, per material cate-gory;

3. activity sectors’ material consumption; and4. waste treatment per material category and

treatment type.

We calculated each variable by making use ofa matrix built up with the data described in thefollowing paragraphs: The materials matrix pro-vides the input and output flows of materials, thethroughput matrix provides the materials that areadded to the city materials stock, the waste treat-ment matrix distributes wastes according to threetreatment categories, and the activity sectors ma-trix is intended to distribute materials consump-tion through different economic sectors. The firsttwo variables allowed for the quantification ofLisbon’s material balance for 2004, and the othertwo indicators were useful in characterizing thecity’s material consumption.

Data

The data available for this study includedvarious scales, including an urban scale, a re-gional scale (Lisbon region), and a national scale(Portugal). The most important data sources usedreferred to 2004, but for some cases, the absenceof the most recent data led to the use of a set of2003 data. The main data sources used were asfollows:

• International trade: in the Lisbon region,2004. Source: INE (National Statistics Of-fice).

• National freight transport: within the Lis-bon region and between the Lisbon regionand the other Portuguese regions (as de-lineated by the European Union NUTS IIstandard), 2004. Source: INE. It must benoted that according to INE information,the National Freight Transport statistics donot record the data of goods transported invehicles with less than 3 tonnes capacity.This may result in the undercounting ofmaterials that enter the city by this meansof transportation.

• Number of establishments per economicactivity and number of employees per eco-

nomic activity: in Lisbon city, the Lis-bon region, and Portugal, 2003 and 2004.Source: Studies, Statistics and PlanningGeneral Directorate of the Labor and SocialSecurity Ministry.

• Purchasing power: in Lisbon city and theLisbon region. Source: INE.

• Industrial Production Annual Survey(IPAS): Portugal, 2003. Source: INE.

• Fuels sales: in Lisbon city, 2003. Source:Geology and Energy General Directorate.

• Packaging waste production: in VALOR-SUL5 area, 2004. Source: Portuguese GreenDot Society.

• Fisheries (main species unshipped): in theLisbon region, by harbor, 2003. Source:INE.

• Industrial wastes: in Lisbon city, 2003.Source: INR (Waste Affairs Institute).

• Municipal solid waste: in VALORSULarea, 2004. Source: VALORSUL.

Materials Matrix

The consumption and disposal accountabilitywas formulated as a materials matrix, which wasdesigned as a product of three matrices:

• the products composition matrix, Aij;• the mass flow matrix, Pjk; and• the Lisbon quota matrix, Ljl.

M = Ai j × Pj k × L j l (1)

The products’8 material composition matrix,Aij, where i is material categories and j is products,determines the composition of each product (in-put flows) and wastes (output flows) per materialcategory, in mass percentage. Material categoriesconsidered were biomass, fossil fuels, metals andnonmetallic minerals.

The mass flow matrix, Pjk, where j is prod-ucts and k is mass amounts, is a diagonal matrix.Whenever j = k, Pjk defines the mass of prod-ucts entering the city, in a given period, and theamounts of wastes leaving it. When j �= k thenPjk = 0.

Finally, the Lisbon quota matrix, Ljl, wherej is products and l is mass percentages, is alsoa diagonal matrix. When j = l, then Ljl defines


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the fraction of each product and waste that isconsumed and produced within the city. Whenj �= l, then Ljl = 0.

Products Composition MatrixWe mainly characterized the material compo-

sition of products by making use of the AnnualSurvey on Industrial Production, as this databasepresents data in a disaggregated way, allowing anassessment per product. Composition was definedaccording to EUROSTAT’s aggregated materialcategories: biomass, fossil fuels, metals, and non-metallic minerals.

The most representative material categoriesin terms of weight were estimated for each set ofproducts (grouped by the Classification of Eco-nomic Activities [CEA]9 and designated accord-ing to the Combined Nomenclature [CN]10). Weassumed an average composition for products ofthe same CEA, avoiding a case-by-case analysisof about 3,000 different products.

Whenever possible, we consulted manufac-turers’ information about product composition(e.g., chemical products). For some cases, infor-mation provided by specific waste managemententities was used (e.g., VALORCAR11 for the av-erage composition of a car or AMB3E [2005] andIN+/IST [2002] concerning electric and elec-tronic products).

This material composition was then used foreach input (products from international trade,national freight transport, and local industrialproduction) and output (industrial waste and mu-nicipal solid waste). Due to the aggregation de-gree of international trade and national freighttransport databases, we used average composi-tions of similar products previously estimated forindustrial production. For industrial waste, thecomposition per material category was based onthe European List of Wastes.12 Lisbon’s consump-tion of electricity was converted into the amountof fossil fuel needed to produce it.13

Mass Flow MatrixThis matrix characterizes the amounts (in

tonnes) of products imported and transported inthe Lisbon region and the wastes produced in theVALORSUL area, during 1 year.

Lisbon Quota MatrixData sources used for calculations included

different geographic scales, so we had to pro-cess data to characterize only urban flows. Themethodology developed consisted of producing adiagonal matrix, Lii (i is products), that quanti-fied the fractions of products and wastes that wereconsumed and produced in the municipality, inpercentage. This matrix was quantified given thatthe city’s consumption is a function of the num-ber of workers, the number of inhabitants, or theirpurchasing power.

Both international trade and national freighttransport refer to the Lisbon region. To obtainthe Lisbon municipality share, we produced adistribution of materials and products importedor transported regionally per destination activ-ity. Wholesale and retail activities were consid-ered, together with some other specific activities(e.g., activities connected to jewelry manufactur-ing or optical material, photographic material,and cinematographic material manufacturing).For wholesale and local industrial production, itwas assumed that the number of workers was thelimiting factor for consumption. For retail, it wasconsidered that, in addition to the number ofworkers, another limiting factor was the inhabi-tants’ purchasing power. As a consequence, thevalue obtained by the estimation made throughthe ratio based on the number of workers wasmultiplied by the ratio of the purchasing powerin the Lisbon municipality and the purchasingpower of the Lisbon region.

For each import category, destination activ-ities were grouped. Imports to the municipality(in percentages) were obtained from the ratiobetween the number of workers doing these ac-tivities in the municipality and in the region.

The assessment of the uncertainty associatedwith this methodology was based on the compar-ison of the results obtained when the method wasapplied to a specific product, for which data wereavailable at a city level. A relevant product forwhich real data were available was gasoline, andthe comparison between the estimation from thedeveloped method and real data is presented intable 2.

This example shows a 5% difference betweenreal available data (from the Energy General Di-rectorate) and the methodological extrapolation,


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Table 2 Comparison between real consumptionand extrapolated consumption of 95 octane gasoline(2004)

MatrixDGEG extrapolation

Area data (t) (t) Difference

Lisbon region 428,506 - -Lisbon city 140,036 133,399 5%

Note: One tonne (t) = 103 kilograms (kg, SI) ≈ 1.102short tons. DGEG = Directorate General for Energy andGeology.

which can be viewed as an estimate of the uncer-tainty of the mechanism in calculating the Lisbonmunicipality share. Values of the same order ofmagnitude were obtained for other products forwhich Lisbon-specific data were available.

We estimated local production in the munic-ipality by defining for each IPAS activity a rela-tionship between the national number of workersand the municipal number of workers.

If we assume that no products are exported,exports equal wastes produced in the city. Forindustrial wastes, it was assumed that productionin 2004 was similar to 2003. For municipal solidwastes, the fraction of the Lisbon municipality’sresidents in the total number of residents servedby VALORSUL was calculated.

Throughput Matrix

Throughput, as referred to here, is the prod-uct life span within the city. These figures werecalculated from the following:

1. the product material composition—namely, whether it is composed of fast-degrading materials (less than 1 year)—and

2. the kind of use, or function. For instance,certain kinds of products become unusableafter their first use (e.g., food packaging orcleaning products packaging), and otherslast decades (e.g., buildings).

This classification is important for the estima-tion of materials added to Lisbon city materialstock. The material flows’ life span was dividedinto four categories:

1. flows leaving the economy within 1 yearafter their input (e.g., food, packaging, oilas fuel),

2. flows leaving the economy after 1 year butwithin 10 years after their input (relativelydurable goods, e.g., toys, computers),

3. flows leaving the economy between 11 and30 years after their input (durable goods,e.g., machines, cars, or home appliances),and

4. flows remaining in the economy for morethan 30 years (long-duration goods, e.g.,buildings or communication infrastruc-tures).

Distribution of products according to theirthroughput velocity was computed as the productof two matrices:

• the materials matrix, M; and• the products life span matrix, Rlj .

T = M × Rl j (2)

In Rlj, l represents life span categories, and jrepresents the products. Literature with informa-tion about product life span is scarce, with theexception of the work by Cooper (2005) and Hsuand Kuo (2005). Distribution of products accord-ing to the four life span categories was thereforebased on these references and resulted from spe-cific research by us.

Waste Treatment Matrix

The waste treatment matrix was designed as aproduct of three matrices:

• the waste composition matrix, Vim, wherei is material categories and m is wastes, de-termines the composition of each waste permaterial category, in mass percentage;

• the waste flow matrix, Xmn, where m iswastes and n is mass amounts; and

• the treatment category matrix, Tms, wherem refers to wastes and s to the kind oftreatment.

W = Vi m × Xmn × Tms (3)


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In Tms, industrial waste and municipal solidwaste data were distributed according to the fol-lowing treatment categories: recycling, incinera-tion (waste-to-energy recovery), and controlledlandfill. Distribution by the mentioned categorieswas based on the Waste Affairs Institute andVALORSUL databases.

Activity Sectors Matrix

Distribution of products per sector was com-puted as the product of two matrices:

• the materials matrix, M, and• the products per sector matrix, Sih .

S = M × Si h (4)

In matrix Sih, i represents products, and h rep-resents sectors. Materials were distributed accord-ing to three activity sector categories: (1) restau-rants, hotels, and services; (2) housing; and (3)industry and construction. Again, distribution ofimports to Lisbon per sector (in percentage) wasbased on the number of workers in wholesale, re-tail, and specific industrial activities in Lisbon.

Closing the Balance

We calculated emissions from fossil fuels com-bustion, wastewater solid fraction, and construc-tion and demolition wastes (C&DW) to com-plete the balance among material inputs, additionto stock, and outputs; Niza and Ferrao (2006) pre-viously calculated the average per capita amountsof these parameters when developing Portugalmaterial’s balance. These factors were then mul-tiplied by the Lisbon city population (see table 3).Given that dissipative flows are largely due to fer-tilizer and pesticide use (Matthews et al. 2000),they were considered as nonexistent in the citywhen compared to the national scale.

These results, as one can see in the next sec-tion, mean that to completely close the balance,only about 225,000 tonnes remain unknown, rep-resenting only about 2% of the total materialsthat enter the city. It may then be considered thatresults obtained with this methodology matchedand closed the balance, partially contributing to

Table 3 Output parameters estimated to close thebalance

Portugal Lisbonper capita city values

Category valuesa (t/cap) (Mt)

Emissions (without O2) 2.1 1.2Wastewater solid fraction 0.026 0.0145C&DW 0.6 0.335Total 2.73 1.52

Note: t/cap = tonnes per capita. One megaton (Mt) =106 tonnes (t) = one teragram (Tg, SI) ≈ 1.102 × 106

short tons. O2 = oxygen; C&DW = construction anddemolition waste.aNiza and Ferrao (2006).

the validation of the methodological approachdescribed.

Lisbon MFA: Results

Material Balance

The use of the methodology developed in theprevious section made possible the quantificationof Lisbon’s material balance for 2004, schemat-ically represented in figure 4. The material in-puts for Lisbon city totaled 11 million tonnes in2004, about 7% of Portugal’s material consump-tion.14 In the same year, industrial and municipalwaste summed 625,000 tonnes. Additionally, ta-ble 3 estimations show that C&DW productionwas around 335,000 tonnes, wastewater solid frac-tion was 14,500 tonnes, and the amount of sub-stances in air emissions was 1.2 million tonnes.Total outputs, then, were 2.149 million tonnes.Table 4 shows the main inputs and outputsobtained per material category.

Nonrenewable material resources representedalmost 80% of the total material consumption.Nonmetallic minerals (mainly construction ma-terials) made up 64% of the nonrenewable frac-tion, and 11% were fossil fuels. The remain-ing 4% referred to metals. Renewable resourceconsumption (biomass) made up only 18% ofthe total consumption, and the remaining por-tion was made up of nonspecified materials. Thislarge gap between renewable and nonrenewableresource consumption may reflect two socioe-conomic phenomena that occurred in Portugalduring the 1990s and the beginning of the 21st


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Figure 4 Lisbon’s material balance, 2004. Mt = megatons; MSW = municipal solid waste; IW = industrialwaste; C&DW = construction and demolition waste.

century. Since the beginning of the 1990s, Por-tugal has had one of the highest growth rates innew housing in the European Union and, at thesame time, the lowest rate of building rehabilita-tion.15 For instance, in 2000, the investment inrehabilitation in Portugal was 6%, against 33% inthe EU-15 (MOPTH 2004). Lisbon followed thistrend with high rates of construction, mainly forbuildings in the service sector, at the same timeas it faced the widespread deterioration of olderbuildings.

During the same period, there was a sig-nificant shift toward private car travel, to the

detriment of public transportation. In 1991, themain means of transportation used by Lisbonregion commuters was public transportation,which carried 51% of the people, against 26%who used private cars. By 2001, commutersalready principally used private cars—46%,against 36% who used public transport (CC-DRLVT 2007). Conversely, a large number ofcommodities pass through the city en route toother destinations, as previously mentioned.The transport of these products inevitably hasconsequences for Lisbon’s fossil fuel consumptionlevel.


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Table 4 Lisbon total material flows, 2004 (1,000 tonnes)

InputWastes output

Material category Consumption Local productiona and emissions

Biomass 2050 23 432b

Agriculture 1,499 7 117Forestry 540 16 300Fishery 11 0 0

Fossil fuels 1,190 72 1,219c

Metallic minerals 434 34 14Nonmetallic minerals 7,261 54 380

Construction 7,168 51 335d

Industrial 85 3 34Industrial and construction 8 0 11

Nonspecified 289 3 105Total 11,223 187 2,149

Note: Bolded figures throughout the table are subtotals of the various flow categories.aLocal production is presented in this table to illustrate that its value was residual in Lisbon—only 1.7% of consumption.bIncludes wastewater solid fraction.cIncludes air emissions from fossil fuel combustion.dConstruction and demolition waste.

The amount of materials added to Lisbon’smaterial stock totaled about 9 million tonnes.Table 5 presents the materials accumulated instock in the city. Quick consumption materi-als, not added to stock, represented about 21%(2.4 million tonnes) of the total input materi-als into Lisbon and mainly included biomass andfossil fuels, such as food products, gasoline, andelectricity.

Table 5 Lisbon materials’ life span (1,000 tonnes)

Material category 0–1 years 2–10 years 11–30 years >30 years

Biomass 1,318 275 457 0Agriculture 1,292 207 0 0Forestry 15 69 457 0Fishery 11 0 0 0

Fossil fuels 1,019 132 40 0Metallic minerals 4 23 407 0Nonmetallic minerals 21 26 56 7,158

Construction 0 0 10 7,158Industrial 21 23 41 0Construction and industrial 0 3 5 0

Nonspecified 13 274 2 0Total 2,375 729 962 7,158Addition to stock 8,849

Note: Bolded figures throughout the table are subtotals of the various flow categories.

In the 2-year to 10-year life span productcategory, biomass and fossil fuels also predomi-nated. Here they mainly referred to wood andtextile products (of natural and synthetic fibers).In the 11-year to 30-year life span product cat-egory, biomass prevailed (now associated withfurniture), together with metals (associated withequipment, e.g., home appliances and cars). Fi-nally, the over 30-year life span product category


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Table 6 Treatment of waste produced in Lisbon (1,000 tonnes)

Incineration ControlledMaterial category Recycling (waste-to-energy recovery) landfill

Biomass 195.42 183.77 37.55Agriculture 0.60 98.96 17.31Forestry 194.82 84.80 20.24Fishery 0.00 0.00 0.00

Fossil fuels 14.71 24.79 5.03Metallic minerals 5.77 6.81 1.49Nonmetallic minerals 12.53 18.06 14.22

Construction 0.10 0.00 0.01Industrial 12.41 18.06 3.14Construction and industrial 0.02 0.00 11.07

Nonspecified 42.31 46.79 15.99Total 270.74 280.23 74.29

Note: Construction and demolition waste (C&DW) is not included. Bolded figures throughout the table are subtotals ofthe various flow categories.

was essentially related to construction materials,as it may be distinguished by the significant ac-cumulation of nonmetallic minerals. Construc-tion materials made up more than 95% of thiscategory.

Waste Treatment

Table 6 shows the amount of waste per mate-rial and treatment category. These results do notinclude C&DW, as it was not possible to obtaininformation about its destination.

Of the total waste produced, 43% (about270,000 tonnes) was recycled and 45% (about280,000 tonnes) was incinerated, producing en-ergy. The remaining 12% (74,000 tonnes) wasconfined to a controlled landfill. Biomass valuesconstituted an important amount of the declaredwastes—around 67%.

When we considered C&DW estimations, theamount of waste totaled 960,000 tonnes, and thenonrenewable fraction of waste with recyclingpotential was about 57% of the total productionof waste. The renewable fraction decreased to43%.

In this respect, recent Portuguese legislation16

regulating C&DW management mandates thateach construction project must have a manage-ment and prevention plan for C&DW. As a con-sequence, it will be easier in the near future to as-

sess the amounts of waste produced and to assessthe reuse and recycling potential for this categoryof waste.

At this stage, it is possible to achieve a bal-ance among inputs, outputs, and stocks, accord-ing to the law of conservation of mass in anMFA context (EUROSTAT 2001): Input = out-put + net accumulation. Inputs to Lisbon totaled11.223 million tonnes, outputs totaled 2.149 mil-lion tonnes, and stocks (net accumulation) to-taled 8.849 million tonnes. Therefore, the differ-ence between the two sides of the equation is 225thousand tonnes—the fraction of materials thatremain unknown. Of the total materials that areestimated to enter the city, this fraction repre-sents only about 2%.

Economic Activities

Table 7 shows the materials consumed per ac-tivity sector, according to three activity classes.The results obtained show the considerableweight of industry and construction, representingalmost 70% of the material consumption in 2004.For each of the other sectors—(1) housing and(2) restaurants, hotels, and services—materialconsumption totaled about 3.5 million tonnes.Fifty percent was biomass, including productssuch as textiles, wood, and paper, and about 30%was fossil fuels, used in transports and electricity


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Table 7 Consumption per activity sector in Lisbon (1,000 tonnes)

Sector

Restaurants, hotels, Industry andMaterial category and services Housing construction

Biomass 442 1,253 355Agriculture 425 1,064 10Forestry 15 179 346Fishery 2 10 0

Fossil fuels 556 608 25Metallic minerals 102 128 204Nonmetallic minerals 9 102 7,149

Construction minerals 0 78 57Industrial minerals 7 21 3Construction and industrial minerals 2 3 7,090

Nonspecified 49 240 0Total 1,158 2,331 7,734

Note: Bolded figures throughout the table are subtotals of the various flow categories.

production. Metals, included in products such ascars and home appliances, totaled 7% of the con-sumption related to services and households.

International Benchmark

The comparison between Lisbon city’s over-all results and results obtained in studies held forother cities or urban areas was found to be diffi-cult. This was essentially due to the inexistenceof a standard methodology to quantify materialflows at this scale. Each author makes differentassumptions based on available data and specificcharacteristics of the studied area. These differ-ent assumptions involve estimation methods, ma-terials included, indicators aggregation, and theadopted nomenclature.

In the following passage, Lisbon city’s MFAamounts are compared to Greater London’samounts (BFF 2002). This study was used becauseit turned out to be the one with the most fullyexplained methodology and the base year closestto the Lisbon study’s base year, which allowed forbetter comparison. Lisbon and Greater London’smaterial consumptions are represented in table 8.

The methodology developed for Greater Lon-don (BFF 2002) followed a MFA model devel-oped in an English study (Linstead and Ekins2001). It was devoted to identifying large con-sumption categories, such as construction mate-

rials, as well as the European Commission prioritywaste streams.

Compared to Lisbon, Greater London’s percapita material consumption was much lower.This is probably due to methodological differ-ences. Nonetheless, lack of awareness about thefull list of materials included in the Greater Lon-don study precludes a detailed identification ofthe differences. One aspect, however, may jus-tify them: Many values about products consumedin London were estimated according to a ra-tio between wastes produced in Greater Londonand wastes produced in the United Kingdom,with the assumption that London’s per capita

Table 8 Material consumption in Lisbon andGreater London (t/cap)

GreaterLisbon Londona

Material category (DMC 2004) (2000)

Biomass 3.67 1.65Fossil fuels 2.13 2.05Metallic minerals 0.78 0.13Nonmetallic minerals 12.99 3.91Nonspecified 0.52 0.73Total 20.08 8.47

Note: t/cap = tonnes per capita; DMC = domestic materialconsumption.aSource: BFF 2002.


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consumption of products was the same as theUnited Kingdom’s per capita consumption ofproducts. If Lisbon results may be overestimatedbecause it is assumed that more establishmentsor employees per economic activity in the cityusually means more consumption, in the Lon-don case, the results may underestimate actualamounts in the case that there are any undetectedwaste flows.17

In the particular case of nonmetallic minerals,London’s values were about one-third of Lisbon’svalues per capita. Part of this difference may bedue to the structure of investment in the con-struction sector. In Portugal, the investment inbuilding rehabilitation is around 6% of the to-tal investment in building construction, whereasin the United Kingdom, investment in rehabil-itation is around 40% of the total investment(MOPTH 2004). Conversely, whereas perhaps45% of the C&DW in the United Kingdom isreused or recycled, reuse and recycling of C&DWin Portugal makes up less than 5% of the mate-rials (Symonds Group Ltd. 1999). On the ba-sis of these numbers, it is possible to argue thatconstruction in London may be less material-intensive than in Lisbon, even if the oppositemight have been expected; according to Weiszand colleagues (2005), countries with a higherpopulation density, such as the United Kingdom,potentially have lower per capita consumptionvalues compared to less densely populated coun-tries, such as Portugal. But the disparities betweenthe two studies’ results are so large that method-ological differences certainly prevail.

Table 9 compares Lisbon residents’ averagematerial consumption with Portugal residents’

Table 9 Material consumption, Lisbon and Portugal(t/cap)

Lisbon PortugalMaterial category (DMC 2004) (DMC 2000)

Biomass 3.67 4.23Fossil fuels 2.13 2.24Metallic minerals 0.78 9.19Nonmetallic minerals 12.99Nonspecified 0.52 -Total 20.08 15.66

Note: t/cap = tonnes per capita; DMC = domestic materialconsumption.

Table 10 Material/water ratio for Lisbon andVienna

Lisbon ViennaInputs (2004) (1998)

Water inputs (WI) 227 kg/cap/yr 150 kg/cap/yrMaterial inputs (MI) 20 kg/cap/yr 14 kg/cap/yrMI/WI 0.087 0.093

Note: One kilogram (kg, SI) ≈ 2.204 pounds (lb).

average material consumption. Differences ofabout 24% between Lisbon city and Portugal’s percapita material consumption were due basicallyto the characteristics inherent in a capital city:Namely, Lisbon holds many companies’ head-quarters and government offices, and the numberof commuters is significant.18 Material consump-tion in the city is then a natural consequence ofthis daily flow of people.

Fossil fuel results were very similar at bothscales, mainly because they were quantified atpractically the same life cycle stage (“factoryexit”—meaning that materials are incorporatedin products acquired in the city or locally pro-duced and are therefore easily detected becausethey are part of the economic circuit). Differ-ences in biomass values were essentially due tothe fact that for Lisbon city this category did notinclude some materials that were included at thenational scale, such as pastures for animal feed-ing. Finally, when we compared material inputsto water inputs in Lisbon (Lisboa E-Nova 2006),the materials/water ratio proved to be equivalentto Vienna’s (Obernosterer 2002), another confir-mation of the reliability of the method developedin this article (see table 10).

Policy Implications

Lisbon’s material balance was developed un-der phase 1 of the proposal for the Energy andEnvironmental Strategy for Lisbon.19 This strat-egy, defined by the Lisbon Energy and Envi-ronment Agency, Lisboa E-Nova, includes re-duction targets for materials, energy, and waterconsumption.

Concerning materials, the strategy proposesan increase in building rehabilitation activity(retrofitting and renovation), complemented by


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a promotion of C&DW reuse and recycling. In2013, Lisbon should achieve levels of rehabilita-tion near the average European levels, in termsof investment and the number of rehabilitationprojects.

Another target for materials focuses on thereinforcement of municipal and industrial wastemanagement. A 30% increase is proposed in theper capita volume of waste recycling by 2013 ascompared to 2006.

Lisboa E-Nova is cooperating with the mu-nicipality in developing a set of local programsthat will involve activities such as sustainablebuilding and sustainable mobility projects. Oneof those projects involves promoting good prac-tices for sustainable rehabilitation of buildings,aiming for an optimization of the environmentaland energetic performance of buildings. As men-tioned, the MFA methodology designed in thisarticle allows for a regular compilation of datacontributing to the assessment of the fulfillmentof these targets.

Conclusions

MFA may provide decision makers an im-proved understanding of the functioning of theirregion or city so that they can prepare for andreact to present and future material stocks andflows issues. Urban metabolism analysis has beenperformed for only a few cities worldwide, how-ever, and these studies raise interpretation issuesdue to lack of common conventions.

Limits to the current applicability of MFAto lower scales are associated with the availabil-ity of “adequate” statistical data, constrained bythe fact that in a city there are no real bound-aries, which makes it hard to quantify the prod-ucts crossing the city’s borders that are for en-dogenous consumption. This problem usually isamplified when the city serves as a gateway ofgoods for the country or even for other coun-tries (e.g., through a big harbor, a train sta-tion, or an international airport). Additionally,administrative and economically relevant citiesare places with a considerable number of com-muters who work in the city but live nearby.As a consequence, urban material flows may beoverestimated if the phenomenon is not correctlyidentified.

Some peculiarities are also generally observedat this scale of analysis: When researchers dealwith city material flows, they usually observe thatdomestic extraction is null or residual. The samehappens with local industrial production. Withthe exception of some construction raw materials,such as sand or gravel, these systems mainly con-sume final products. Conversely, big cities usuallyevidence a strong trade relationship (of materialsor products) with the surrounding region (cities,villages, farms, etc.).

These constraints and peculiarities call for in-novative methods in the quantification of thevarious materials entering and leaving the city.These include the extrapolation of data fromthe country or region and estimations, basednamely on sales, number of inhabitants, com-muters, workers, and produced waste.

This article develops an MFA methodologyfor urban metabolism quantification allowing fora regular compilation of information about a city’smetabolism. Constraints that pertain to an urbanscale of analysis are overcome by the methodol-ogy developed, which was applied to Lisbon cityfor 2004.

Results show that annual material consump-tion in Lisbon city totaled 11.223 million tonnes,which means 20 tonnes of materials per capita.Material outputs from Lisbon were wastes andemissions and summed to 2.149 million tonnes.Finally, the accumulation to stock totaled 8.849million tonnes. The nearly 80% of total mate-rial consumption composed of nonrenewable re-sources consisted of nonmetallic minerals (64%of total material consumption), fossil fuels (11%of total material consumption) and metals (4% oftotal material consumption). Renewable resourceconsumption (biomass) made up only 18% of thetotal consumption, and the remaining amountwas nonspecified materials.

A seemingly excessive consumption of non-renewable materials may reflect socioeconomicphenomena that occurred in Lisbon in the 1990sand at the beginning of the 21st century: a largeinvestment in building construction and a sig-nificant shift toward private car travel, to thedetriment of public transportation.

Data used for calculations were statistical andtherefore inherently reliable. The errors associ-ated with the methodology are then linked to


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the use of some considerably aggregated classesof data and to the extrapolations based on vari-ables such as the number of workers and the pur-chasing power of consumers. To quantify errormargins, we made an effort to validate the resultswith other available information (or data). In thiscontext, a 5% difference was estimated betweenextrapolations and real available data for severalproducts together, with an uncertainty of around2% in balance closing. These numbers show themethod to be sufficiently reliable to perform anurban MFA, making use of publicly available sta-tistical data.

Acknowledgements

We would like to acknowledge ArchitectLıvia Tirone from Lisboa E-Nova, who supportedthe development of Lisbon Materials Matrix, atool to be included in the Energy and Environ-mental Strategy for Lisbon.

We would also like to thank Claudia Guer-reiro from INE, the Portuguese statistics office,and Eng. Ricardo Furtado and Dr. Jose Amaralfrom VALORCAR (end-of-life vehicles manage-ment society), who provided information vital tothis study.

Finally, we would like to thank both anony-mous reviewers for their valuable suggestions andconstructive critiques.

Notes

1. MFA is used in the research literature for both ma-terial flow analysis and material flow accounting.In this article, it is used to refer to the latter.

2. Progress has been made in this regard, however,by Tom Graedel’s research group at Yale’s Cen-ter for Industrial Ecology. See http://research.yale.edu/stafproject.

3. Note that since 2002, the boundaries of the Lisbonmetropolitan area have corresponded exactly tothe boundaries of the Lisbon region.

4. This simplification excludes, for instance, the hid-den flows.

5. In this context, Lisbon somehow suffers the “Rot-terdam effect” phenomenon. The notion refersto the role of huge harbors (e.g., Rotterdam orAntwerp) serving as European gateways for inter-national trade (Weisz et al. 2005).

6. One tonne (t) = 103 kilograms (kg, SI) ≈ 1.102short tons.

7. Data are from Lisbon Harbor internationaltrade statistics, at www.porto-de-lisboa.pt (March2008).

8. Although the term product is generalized here, thematrix also includes waste composition. As wasteterminology is directly linked to the original prod-uct (e.g., end-of-life vehicles, plastic packaging, orcardboard waste), the estimation of wastes’ mate-rial composition was based on the material com-position of those products.

9. The CEA refers to the classification and groupingof the production statistical units of goods and ser-vices, according to economic activity. It involves719 categories of economic activities, of which226 were used to characterize the material com-position of materials in the scope of the study. Ex-amples of categories are manufacture of perfumes,cosmetics and hygiene products; manufacture ofsynthetic or artificial fibers; manufacture of plainglass; and manufacture of ceramics products.

10. This involves 19,253 categories, of which around3,000 were used in the scope of the study.

11. Data are from VALORCAR, the end-of-life vehi-cles management society.

12. The List of Wastes, formerly the European WasteCatalogue, is a catalogue of all waste types gener-ated in the European Union. The different typesof waste in the list are fully defined by a six-digitcode, with two digits each for chapter, subchapter,and waste type. The list is used to categorize itemsand substances when they become waste but doesnot itself define items and substances as waste.

13. First, the fossil fuels mix used in electricity pro-duction in Portugal was calculated from the Por-tugal Energy Balances of the Directorate Generalfor Energy and Geology (DGEG, 2006). Electric-ity consumption for Lisbon city, in terms of pri-mary energy, was calculated from the electricityconsumption per type (DGEG 2006) and the ef-ficiency of the Portuguese electricity productionsector (Lisboa E-Nova 2005). From fossil fuels’specific heat values, the amount of fossil fuelsburned to produce electricity for the city was thencalculated.

14. Portugal’s DMC was 158 Mt in 2000, according toan MFA study on the Portuguese economy (Niza2007).

15. As used throughout this article, building rehabilita-tion includes both retrofitting and renovation.

16. Decree-law 46/2008, 12 March 2008.17. Examples are materials that are informally reused

or products that are acquired in the Greater Lon-don area but taken outside of this area and dis-posed of there. In both circumstances, institutions


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responsible for recording waste management pro-cesses would hardly detect these flows.

18. This figure is estimated as 2.1 million people perday, according to the municipality (www.cm-lisboa.pt/index.php?id_categoria=26&id_item=48, June 2007).

19. See www.lisboaenova.org.

References

AMB3E (Portuguese Association for the Manage-ment of Waste From Electrical and ElectronicEquipment). 2005. Caderno de encargos para aconstituicao do sistema integrado de gestao de resıduosde equipamentos electricos e electronicos [AMB3E’scontract specification toward the development ofa WEEE integrated management system]. Lisbon,Portugal: AMB3E.

Bai, X. 2007. Industrial ecology and the global impactsof cities. Journal of Industrial Ecology 11(2): 1–6.

Barrett, J., H. Vallack, A. Jones, and G. Haq. 2002.A material flow analysis and ecological footprintof York. Technical report. Stockholm, Sweden:Stockholm Environment Institute.

BFF (Best Foot Forward). 2002. City limits: Aresource flow and ecological footprint analysisof Greater London. www.citylimitslondon.com/downloads/Complete%20report.pdf. AccessedMarch 2007.

Binder, C. 2007. From material flow analysis to materialflow management Part I: Social sciences modelingapproaches coupled to MFA. Journal of CleanerProduction 15: 1596–1604.

Brunner, P. H. 2004. Materials flow analysis and theultimate sink. Journal of Industrial Ecology 8(3):4–7.

Brunner, P. H. 2007. Reshaping urban metabolism.Journal of Industrial Ecology 11(2): 11–13.

Brunner, P., H. Daxbeck, and P. Baccini. 1994. In-dustrial metabolism at the regional and locallevel: A case-study on a Swiss region. In In-dustrial metabolism: Restructuring for sustainabledevelopment, edited by R. U. Ayres and U.E. Simonis. Tokyo: United Nations UniversityPress.

Burstrom, F., B. Frostell, and U. Mohlander. 2003. Ma-terial flow accounting and information for envi-ronmental policies in the city of Stockholm. Pa-per presented at the workshop Quo vadis MFA?Material Flow Analysis—Where Do We Go? Is-sues, Trends and Perspectives of Research for Sus-tainable Resource Use, 9–10 October, Wuppertal,Germany.

CCDRLVT (Coordination and Development Com-mittee for Lisbon Region and the Tagus Valley).2007. Lisboa 2020: Uma Estrategia de Lisboa para aRegiao de Lisboa [Lisbon 2020: A Lisbon Agendafor the Lisbon Region]. Lisbon, Portugal: CCDR-LVT.

CML (Municipal Council of Lisbon). 2005a. Di-agnostico Socio-urbanıstico da Cidade de Lis-boa. Uma perspectiva censitaria (2001) [Lis-bon’s socio-urban diagnosis. A census perspective(2001)]. Coleccao de Estudos Urbanos [UrbanStudies Series]—Lisboa XXI—4. Lisbon: CML.

CML. 2005b. Desenvolvimento Economico e Com-petitividade Urbana de Lisboa. [Lisbon Eco-nomic Development and Urban Competitive-ness]. Coleccao de Estudos Urbanos [Urban Stud-ies Series]—Lisboa XXI—2. Lisbon: CML.

Cooper, T. 2005. Slower consumption, reflections onproduct life spans and the “throwaway society.”Journal of Industrial Ecology 9(1–2): 51–67.

Daly, H. E. 1996. Beyond growth: The economics of sus-tainable development. Boston: Beacon Press.

DGEG (Directorate General for Energy and Geology).2006. Estatısticas: Balancos energeticos 2004–2005[Portugal energy balances, 2004–2005]. www.dgge.pt/?cn=6891700270677156AAAAAAAA.Accessed November 2006.

European Environment Agency. 2006. Urban sprawl inEurope: The ignored challenge. Report No. 10/2006.Copenhagen, Denmark: European EnvironmentAgency.

EUROSTAT. 2001. Economy-wide material flow ac-counts and derived indicators: A methodological guide.Luxembourg, Luxembourg: Statistical Office ofthe European Union.

Graedel, T. E. 1999. Industrial ecology and the ecocity.Bridge 29(4): 4–9.

Hall, P. 1998. Cities in civilization. New York: Pantheon.Hammer, M. and S. Giljum. 2006. Materialflussanal-

ysen der Regionen Hamburg, Wien und Leipzig.[Material flow analysis of the regions of Hamburg,Viennaand Leipzig.] NEDS Working Papers #6(08/2006), Hamburg, Germany.

Hammer, M., S. Giljum, and F. Hinterberger.2003. Material flow analysis of the city ofHamburg: Preliminary results. Paper presentedat the workshop Quo vadis MFA? MaterialFlow Analysis—Where Do We Go? Issues,Trends and Perspectives of Research for Sustain-able Resource Use, 9–10 October, Wuppertal,Germany.

Hendriks, C., D. Muller, S. Kytzia, P. Baccini, and P.Brunner. 2000. Material flow analysis: A tool tosupport environmental policy decision making.


F O RU M

Case-studies on the city of Vienna and the Swisslowlands. Local Environment 5(3): 311–328.

Hsu, E. and C.-M. Kuo 2005. Recycling rates of wastehome appliances in Taiwan. Waste Management25(1): 53–65.

IN+/IST (Center for Innovation, Technology, andPolicy Research of the Technical Univer-sity of Lisbon). 2002. Producao de resıduos deequipamentos electricos e electronicos em Portugal,no contexto da Uniao Europeia. Relatorio interno[WEEE production in Portugal. Internal report].Lisbon, Portugal: IST.

Kennedy, C., J. Cuddihy, and J. Engel-Yan. 2007. Thechanging metabolism of cities. Journal of IndustrialEcology 11(2): 43–59.

Linstead, C. and P. Ekins. 2001. Mass balance UK:Mapping UK resource and material flows. London:Forum for the Future.

Lisboa E-Nova. 2005. Matriz energetica de Lisboa [Lisbonenergy matrix]. Lisbon, Portugal: Agencia Munic-ipal de Energia e Ambiente.

Lisboa E-Nova. 2006. Matriz da agua de Lisboa [Lisbonwater matrix]. Lisbon, Portugal: Agencia Munic-ipal de Energia e Ambiente.

Matthews, E., S. Bringezu, M. Fischer-Kowalski, W.Huetller, R. Kleijn, Y. Moriguchi, C. Ottke, E.Rodenburg, D. Rogich, H. Schandl, H. Schuetz,E. Van Der Voet, and H. Weisz. 2000. Theweight of nations: Material outflows from industrialeconomies. Washington, DC: World ResourcesInstitute.

MOPTH (Portuguese Ministry of Public Works, Trans-portation and Housing). 2004. O sector dahabitacao no ano 2003 [The housing sector in2003]. Lisbon, Portugal: MOPTH.

Niza, S. 2007. Uma avaliacao do metabolismo daeconomia Portuguesa atraves da contabilizacaodos fluxos de materiais [An assessment of the Por-tuguese economy through material flow account-ing]. Doctoral thesis at Universidade Tecnica deLisboa [Technical University of Lisbon]. Lisbon,Portugal: Technical University of Lisbon.

Niza, S. and P. Ferrao. 2005. Material flow accountingtools and its contribution for policy making. Paperpresented at the International Conference of theEuropean Society for Ecological Economics, 14–17 June, Lisbon, Portugal.

Niza, S. and P. Ferrao. 2006. A transitional economy’smetabolism: The case of Portugal. Resources, Con-servation and Recycling 46(3): 265–280.

Obernosterer, R. 2002. Urban metal stocks: Futureproblem or future resource? Substance flow andstock analysis as a tool to achieve sustainable de-

velopment. Paper presented at the InternationalConference Regional Cycles: Regional EconomyTowards Sustainability, 31 October–2 November,Leipzig, Germany.

Obernosterer, R., P. Brunner, H. Daxbeck, T. Gagan, E.Glenck, C. Hendriks, L. Morf, R. Paumann, and I.Reiner. 1998. Materials accounting as a tool for de-cision making in environmental policy: MAcTEmPocase study report. Urban metabolism, the city of Vi-enna. Vienna, Austria: Institute for Water Qualityand Waste Management, Technical University ofVienna.

Ribeiro, P., S. Niza, and P. Ferrao. 2007. Material flowaccounting and waste production forecasting: Atool for decision-making. Paper presented at theISIE Conference, 17–20 June, Toronto, Canada.

Schulz, N. B. 2007. The direct material inputs into Sin-gapore’s development. Journal of Industrial Ecology11(2): 117–131.

Sousa Pinto, M. J. 2005. Levantamento Cartograficode Locais de Pedreiras no Concelho de Lisboa[Mapping of quarry sites in Lisbon City]. Lisbon:Camara Municipal de Lisboa [Municipal Councilof Lisbon].

Symonds Group Ltd. 1999. Construction and demoli-tion waste management practices, and their economicimpacts. Report to DGXI. Luxembourg, Luxem-bourg: European Commission.

UNU/IAS (United Nations University Institute ofAdvanced Studies). 2003. Defining an ecosys-tem approach to urban management and policy de-velopment. UNU/IAS report. www.ias.unu.edu/publications/reports.cfm. Accessed April 2007.

Weisz, H., F. Krausmann, C. Amann, N. Eisenmenger,K. Erb, K. Hubacek, and M. Fischer-Kowalski.2005. The physical economy of the European Union:Cross country comparison and determinants of ma-terial consumption. Social Ecology Working Paper76. Vienna, Austria: IFF Social Ecology.

Wolman, A. 1965. The metabolism of cities. ScientificAmerican 213: 179–190.

Worldwatch Institute. 2007. State of the world 2007:Our urban future. A Worldwatch Institute reporton progress toward a sustainable society. New York:Norton.

About the Authors

Samuel Niza is a postdoctoral researcher,Leonardo Rosado is a doctoral student in sus-tainable energy systems, and Paulo Ferrao is anassociate professor, all at the Instituto SuperiorTecnico, Lisbon, Portugal.


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