Urban Metabolism of Paris and Its Region

The article presents the results of a research project aimed at (1) examining the feasibility of material flow analysis (MFA) on a regional and urban scale in France, (2) selecting the most appropriate method, (3) identifying the available data, and (4) calculating the material balance for a specific case. Using the Eurostat method, the study was conducted for the year 2003 and for three regional levels: Paris, Paris and its suburbs, and the entire region. Applying the method on a local scale required two local indicators to be defined in order to take into account the impact of exported wastes on MFA: LEPO, local and exported flows to nature, and DMC_corr, a modified domestic material consumption (DMC) that excludes exported wastes (and imported ones if necessary). As the region extracts, produces, and transforms less material than the country as a whole, its direct material input (DMI) is lower than the national DMI. In all the areas, LEPO exceeds 50% of DMI; in contrast, recycling is very low. The multiscale approach reveals that urban metabolism is strongly impacted by density and the distribution of activities: the dense city center (Paris) exports all of its wastes to the other parts of the region and concentrates food consumption, whereas the agricultural and urban sprawl area consumes high levels of construction materials and fuel. This supports the use of MFA on an urban and regional scale as a basis for material flow management and dematerialization strategies and clearly reveals the important interactions between urban and regional planning and development, and material flows.     

The Copper Balance of Cities

Material management faces a dual challenge: on the one hand satisfying large and increasing demands for goods and on the other hand accommodating wastes and emissions in sinks. Hence, the characterization of material flows and stocks is relevant for both improving resource efficiency and environmental protection. This article focuses on the urban scale, a dimension rarely investigated in past metal flow studies. We compare the copper (Cu) metabolism of two cities in different economic states, namely, Vienna (Europe) and Taipei (Asia). Substance flow analysis is used to calculate urban Cu balances in a comprehensive and transparent form. The main difference between Cu in the two cities appears to be the stock: Vienna seems close to saturation with 180 kilograms per capita (kg/cap) and a growth rate of 2% per year. In contrast, the Taipei stock of 30 kg/cap grows rapidly by 26% per year. Even though most Cu is recycled in both cities, bottom ash from municipal solid waste incineration represents an unused Cu potential accounting for 1% to 5% of annual demand. Nonpoint emissions are predominant; up to 50% of the loadings into the sewer system are from nonpoint sources. The results of this research are instrumental for the design of the Cu metabolism in each city. The outcomes serve as a base for identification and recovery of recyclables as well as for directing nonrecyclables to appropriate sinks, avoiding sensitive environmental pathways. The methodology applied is well suited for city benchmarking if sufficient data are available.     

Pursuing More Sustainable Consumption by Analyzing Household Metabolism in European Countries and Cities

Bringing about more sustainable consumption patterns is an important challenge for society and science. In this article the concept of household metabolism is applied to analyzing consumption patterns and to identifying possibilities for the development of sustainable household consumption patterns. Household metabolism is determined in terms of total energy requirements, including both direct and indirect energy requirements, using a hybrid method. This method enables us to evaluate various determinants of the environmental load of consumption consistently at several levels—the national level, the local level, and the household level.
The average annual energy requirement of households varies considerably between the Netherlands, the United Kingdom, Norway, and Sweden, as well as within these countries. The average expenditure level per household explains a large part of the observed variations. Differences between these countries are also related to the efficiency of the production sectors and to the energy supply system. The consumption categories of food, transport, and recreation show the largest contributions to the environmental load. A comparison of consumer groups with different household characteristics shows remarkable differences in the division of spending over the consumption categories.
Thus, analyses of different types of households are important for providing a basis for options to induce decreases of the environmental load of household consumption. At the city level, options for change are provided by an analysis of the city infrastructure, which determines a large part of the direct energy use by households (for transport and heating). At the national level, energy efficiency in production and in electricity generation is an important trigger for decreasing household energy requirements.     

Data Acquisition for Applying Physical Input‐Output Tables in Chinese Cities

The physical input‐output table (PIOT) is a useful tool for analyzing the environmental sustainability of cities. Taking Chinese statistical sources as an example in this study, we discuss data acquisition methods for applying the PIOT to cities. We propose several methods and present a case study of Suzhou City to illustrate the proposed methods. These methods can provide foundations for constructing the PIOT of cities in other countries.     

African Urbanization: Assimilating Urban Metabolism into Sustainability Discourse and Practice

Shaping sustainable, equitable African cities requires strengthened investigations into the cities’ current resource flows, infrastructure systems, and future resource requirements. The field of urban metabolism (UM) offers multiple forms of analysis with which to map, analyse, and visualize urban resource profiles. Challenges in assessing UM in African cities include data scarcity at the city level, difficulty in tracking informal flows, lack of standardized methods, and the open nature of cities. However, such analyses are needed at the local level, given that city practitioners cannot rely purely on urban planning traditions of the global North or the typically broad studies about urban Africa, for supporting strategies toward sustainable urban development. This article aims to draw together the concepts of sustainable development and UM and explore their application in the African context. Further, the article estimated resource profiles for 120 African cities, including consumption of biomass, fossil fuels, electricity, construction materials, and water, as well as emissions of carbon dioxide. These resource profiles serve as a baseline from which to begin assessing the current and future resource intensity of these cities. It also provides insights into the cities’ relative resource impact, future consumption trends, and potential options for sustainability interventions.     

Approaches for Quantifying the Metabolism of Physical Economies: Part I: Methodological Overview

This article is the first of a two-part series that describes and compares the essential features of nine existing "physical economy" approaches for quantifying the material demands of the human economy upon the natural environment. A range of material flow analysis (MFA) and related techniques is assessed and compared in terms of several major dimensions. These include the system boundary identification for material flow sources, extents, and the key socioinstitutional entities containing relevant driving forces, as well as the nature and detailing of system components and flow interconnections, and the comprehensiveness and types of flows and materials covered.
Shared conceptual themes of a new wave of physical economy approaches are described with a brief overview of the potential applications of this broad family of methodologies. The evolving and somewhat controversial nature of the characteristics and role that define MFA is examined. This review suggests the need to specify whether MFA is a general metabolic flow measurement procedure that can be applied from micro to macrolevels of economic activity, or a more specific methodology aimed primarily at economy-wide analyses that "map" the material relations between society and nature. Some alternative options for classifying MFA are introduced for discussion before a more detailed comparative summary of the key methodological features of each approach in the second part of this two-part article.
The review is presented (1) as a reference and resource for the increasing number of policy makers and practitioners involved in industrial ecology and the evaluation of the material basis of economies and the formulation of eco-efficiency strategies, and (2) to provoke discussion and ongoing dialogue to clarify the many existing areas of discordance in environmental accounting related to material flows, and help consolidate the methodological basis and application of MFA.     

Urban Metabolism of Intermediate Cities: The Material Flow Analysis,Hinterlands and the Logistics‐Hub Function of Rennes and Le Mans (France)

Although urban metabolism has been a subject of renewed interest for some years, the related studies remain fragmented throughout the world. Most of them concern major cities (megacities and/or national capitals) and, more rarely, intermediate, medium‐sized or small cities. However, urbanization trends show that together with the metropolization process, another one is characterized by the proliferation of intermediate cities. We have studied the metabolism of two French intermediate cities for the year 2012: Rennes Métropole (400,000 inhabitants) and Le Mans Métropole (200,000 inhabitants). To this end, we used material flow analysis (MFA) based on the methodology developed by Eurostat, adapted to the subnational level. This has been made possible by the use, for the first time, of very precise statistical sources concerning freight. We have developed a multiscale approach in order to weigh the urban metabolism of those two cities and to compare it to other cases and larger territories. This allows a better understanding of the specific territorial metabolism of intermediate cities, their hinterlands, and their logistics‐hub function. We conclude with the “urban dimension” of social metabolism, and, thanks to the multiscale approach, to the debate regarding logistical hubs, dematerialization, and territorial autonomy.     

Assessment of the Industrial Tomato Processing Water Energy Nexus: A Case Study at a Processing Facility

Increased demand for water and energy and growing recognition of environmental issues motivate awareness of how these resources are used in industry. Industrial tomato processing consumes substantial quantities of both water and energy. To understand how these resources are used in tomato processing and what opportunities exist for improving efficiency, a water energy nexus (WEN) assessment was conducted that accounted for the various ways energy becomes embedded in water during processing by motors, pumps, fans, and boilers. The WEN assessment was conducted at an industrial tomato processing facility that processed 265 metric tonnes of fruit per hour to develop a map of water and associated energy use at each processing step. A total of 1.29 billion kilograms (kg) of water were used for the processing season, with 870 million kg routed to flumes. The analysis identified the thermal energy used to generate steam for the various heat exchangers and evaporators used during processing as the greatest source of embedded energy in process water (778,000 gigajoules per season). The electrical energy embedded in the process water totaled 4.4 million kilowatt‐hours per season, over 80% of which was attributed to pumping. Moreover, the data were used to identify opportunities to improve efficiency by adjusting water loads on equipment and developing strategies for water and energy conservation and recovery. The baseline water and energy use data provided by the WEN assessment can enable additional modeling to assess resource efficiency measures and the life cycle impact of processed tomato products.     

Global Patterns and Trends for Non‐Metallic Minerals used for Construction

Despite accounting for almost 50% of global material use, nonmetallic minerals—mostly used for construction of buildings and infrastructure—are the material flow analysis (MFA) category with the highest uncertainty. The main reason for this is incomplete reporting in official national statistics because of ease of availability and the low per‐unit cost of these materials. However, the environmental burden associated with nonmetallic minerals, which include energy use for extraction and transport, land‐use change, and disposal of large amounts of construction demolition waste, call for a thorough understanding of the magnitude of nonmetallic mineral flows. Previous estimates for nonmetallic minerals have used simplistic assumptions. This study aims to increase the precision of nonmetallic mineral accounts at national and global level using consumption of bitumen, bricks, cement, and railways in combination with technical coefficients from the engineering literature to infer the actual yearly consumption of nonmetallic minerals. We estimate the extraction of nonmetallic minerals and provide uncertainty estimates for the new accounts as well as information about consumption by different sectors. Analyzing the evolution of consumption for seven world regions, we find that, in North America and Europe, the consumption of nonmetallic minerals over the past 40 years has followed the growth patterns of population, whereas for all other regions consumption has been closely related to gross domestic product (GDP). A more accurate account of global and country‐by‐country extraction of nonmetallic minerals may provide insights into supply shortages and inform waste management strategies for construction and demolition waste.     

From the urban metabolism to the urban immune system

Urban areas face mounting risks from many sources. Cities pursue myriad tactics to resist, recover from and adapt to shocks and stresses, but little is known about how these approaches relate across the scales of a city nor how cities compare in their abilities. Part of the challenge in addressing these gaps is that the risk to cities is typically studied with an emphasis on one or a few hazards or through the lens of a singular sector. This paper proposes a framework, dubbed the Urban Immune System (UIS) to coalesce and expand industrial ecology research on urban risk management. In the same way that Urban Metabolism (UM) is a unifying framework for urban environmental sustainability, UIS can be a unifying framework for urban resilience, especially related to climate change. Herein, UIS is defined, its many capabilities are dissected and linked to disparate studies; and opportunities for application of the concept are provided. The paper concludes by examining the relationship between UIS and climate change and by identifying those attributes of the UIS that are expected to be of increasing importance under climate change.     

A Material Flow Accounting Case Study of the Lisbon Metropolitan Area using the Urban Metabolism Analyst Model

This article describes a new methodological framework to account for urban material flows and stocks, using material flow accounting (MFA) as the underlying method. The proposed model, urban metabolism analyst (UMAn), bridges seven major gaps in previous urban metabolism studies: lack of a unified methodology; lack of material flows data at the urban level; limited categorizations of material types; limited results about material flows as they are related to economic activities; limited understanding of the origin and destination of flows; lack of understanding about the dynamics of added stock; and lack of knowledge about the magnitude of the flow of materials that are imported and then, to a great extent, exported. To explore and validate the UMAn model, a case study of the Lisbon Metropolitan Area was used. An annual time series of material flows from 2003 to 2009 is disaggregated by the model into 28 material types, 55 economic activity categories, and 18 municipalities. Additionally, an annual projection of the obsolescence of materials for 2010–2050 was performed. The results of the case study validate the proposed methodology, which broadens the contribution of existing urban MFA studies and presents pioneering information in the field of urban metabolism. In particular, the model associates material flows with economic activities and their spatial location within the urban area.     

Approaches for Quantifying the Metabolism of Physical Economies: A Comparative Survey: Part II: Review of Individual Approaches

This article is the second of a two-part series that describes and compares the essential features of nine "physical economy" approaches for mapping and quantifying the material demands of the human economy upon the natural environ-ment. These approaches are critical tools in the design and implementation of industrial ecology strategies for greater eco-efficiency and reduced environmental impacts of human economic activity. Part I of the series provided an overview, meth-odological classification, and comparison of a selected set of major materials flow analysis (MFA) and related techniques. This sequel includes a convenient reference and overview of the major metabolism measurement approaches in the form of a more detailed summary of the key specific analytical and other features of the approaches introduced in part I. The surveyed physical economy related environmental analysis ap-proaches include total material requirement and output mod-els, bulk MFA (IFF (Department of Social Ecology, Institute for Interdiscplinary Studies of Austrian Universities) material flow balance model variant), physical input-output tables, substance flow analysis, ecological footprint analysis, environmental space, material intensity per unit service, life-cycle assessment (LCA), the sustainable process index, and company-level MFA.     

Regional Patterns in Global Resource Extraction

This article presents an account of global resource extraction for the year 1999 by material groups, world regions, and development status. The account is based on materials flow analysis methodology and provides benchmark information for political strategies toward sustainable resource management. It shows that currently around 50 thousand megatons of resources are extracted yearly on a global scale, which results in a yearly global average resource use of around 8 tonnes per capita. Assuming further growth in world regions not yet close to the levels of resource use in the industrial cores—such as India or China—numbers could easily double once these parts of the world come to fully incorporate the industrial mode of production and consumption. This article contributes to information on resource use indicators, complementing and enriching information from economic accounting in order to facilitate political measures toward a sustainable use of resources.     

The Direct Material Inputs into Singapore's Development

Because human population and socioeconomic activity are both increasingly concentrated in cities, an improved understanding of the environmental consequences of urbanization is needed. A 41-year annual time series of direct material flows was compiled for Singapore, representing a case of fast, export-driven industrialization. Results show that the spectacular economic growth of Singapore by a factor of 20 was associated with a similar expansion of domestic material consumption (DMC). DMC remained closely coupled to economic activity, increasing from below 4 tonnes per capita annually in 1962 to more than 50 tonnes annually in 2000. Despite economic structural changes and a growing service sector, no significant improvements in overall material productivity have been observed.     

Cape Town’s Metabolism: Insights from a Material Flow Analysis

This work aims to contribute to the number of urban metabolism case studies using a standardized methodology. An economy‐wide material flow analysis (EW‐MFA) was conducted on the Metropolitan Municipality of Cape Town (South Africa) for the year 2013, using the Eurostat framework. The study provides insights into the city's metabolism through various indicators including direct material input (DMI), domestic material consumption (DMC), and direct material output (DMO), among others. In order to report on the uncertainty of the data, a set of data quality indicators originating from the life cycle assessment literature was used. The results show that domestic extraction involves significant quantities of non‐metallic minerals, and that imports consist primarily of biomass and fossil fuels. The role of the city as a regional hub is also made clear from this study and illustrated by large quantities of food and other materials flowing through the city on their way to or from international markets. The results are compared with indicators from other cities and with previous metabolism work done on Cape Town. To fully grasp the impacts of the city's metabolism, more work needs to be done. It will be necessary to understand the upstream impact of local consumption, and consumption patterns should be differentiated on a more nuanced level (taking into account large differences between household income levels as well as separating the metabolism of industry and commerce from residential consumption).     

Urban Metabolism and the Energy Stored in Cities

Using the city of Toronto as a case study, this article examines impacts of energy stocks and flexible demand in the urban metabolism on the resilience of the city, including discussion of directions for further study of the resiliency of the urban metabolism. An important element developed is the nominal residence time of the energy stocks. This value defines how long an energy stock lasts under typical patterns of energy use. The findings suggest that the residence times of many sources of energy overcome vulnerability when energy supply shocks last on the order of hours or a few days, but that the measure is limited to assessing only certain types of commonly used energy sources in aggregate terms. Discussion is included on the uncertainty of this measure and on the metabolic and resiliency implications of new technologies intended to reduce energy use and improve sustainability of cities and the use of the urban metabolism as a means of comparison. The methodology employed highlights how waste energy could be used to increase the resiliency of the city's water supply, but also how the study of the urban metabolism would benefit from a more disaggregate form in the study of sustainable and resilient cities.     

Food Consumption and Nutrient Flows: Nitrogen in Sweden Since the 1870s

Changes in food consumption and related processes have a significant impact on the flow of nitrogen in the environment. This study identifies both flows within the system and emissions to the hydrosphere and atmosphere. A case study of an average inhabitant of the city of Linköping, Sweden, covers the years 1870, 1900, 1950, and 2000 and includes changes in food consumption and processing, agricultural production, and organic waste handling practices. Emissions to the hydrosphere from organic waste handling increased from 0.57 kilograms of nitrogen per capita per year (kg N/cap per year) to 3.1 kg N/cap per year, whereas the total flow of nitrogen to waste deposits grew from a negligible amount to 1.7 kg N/cap per year. The largest flow of nitrogen during the entire period came from fodder. The input of chemical fertilizer rose gradually to a high level of 15 kg N/cap per year in the year 2000. The total load per capita disposed of to the environment decreased during these 130 years by about 30%.     

Global Phosphorus Flows in the Industrial Economy From a Production Perspective

Human activity has quadrupled the mobilization of phosphorus (P), a nonrenewable resource that is not fully recycled biologically or industrially. P is accumulated in both water and solid waste due to fertilizer application and industrial, agricultural, and animal P consumption. This paper characterizes the industrial flows, which, although smaller than the agricultural and animal flows, are an important phosphorus source contributing to the pollution of surface waters. We present the quantification of the network of flows as constrained by mass balances of the global annual metabolism of phosphorus, based on global consumption for 2004, all of which eventually ends up as waste and in the soil and water systems. We find that on a yearly basis, 18.9 million metric tons (MMT) of P is produced, of which close to 75% goes to fertilizer and the rest to industrial and others uses. Phosphoric acid is the precursor for many of the intermediate and end uses of phosphate compounds described in this study and accounts for almost 80% of all P consumed. Eventually, all of the P goes to waste: 18.5 MMT ends up in the soil as solid waste, and 1.32 MMT is emissions to air and water. Besides quantifying P flows through our economy, we also consider some possible measures that could be taken to increase the degree of recovery and optimization of this resource and others that are closely related, such as the recovery of sulfur from gypsum and wastewater (sludge), and fluorine from wet phosphoric acid production.     

Methodology and Indicators of Economy‐wide Material Flow Accounting

This contribution presents the state of the art of economy‐wide material flow accounting. Starting from a brief recollection of the intellectual and policy history of this approach, we outline system definition, key methodological assumptions, and derived indicators. The next section makes an effort to establish data reliability and uncertainty for a number of existing multinational (European and global) material flow accounting (MFA) data compilations and discusses sources of inconsistencies and variations for some indicators and trends. The results show that the methodology has reached a certain maturity: Coefficients of variation between databases lie in the range of 10% to 20%, and correlations between databases across countries amount to an average R² of 0.95. After discussing some of the research frontiers for further methodological development, we conclude that the material flow accounting framework and the data generated have reached a maturity that warrants material flow indicators to complement traditional economic and demographic information in providing a sound basis for discussing national and international policies for sustainable resource use.     

Investigating Reasons for Differences in the Results of Environmental,Physical, and Hybrid Input‐Output Models

It is vital to find reasons for differences in the results of environmental input‐output (EIO), physical input‐output (PIO), and hybrid input‐output (HIO) models for industrial and environmental policy analysis. Using EIO, PIO, and HIO models, China's industrial metabolism is calculated. Four reasons were found to account for differences in the results of analysis using EIO, PIO, and HIO models: the manner in which they deal with residential consumption, service sectors, and waste recycling, and the assumption of unique sector prices. The HIO model, which treats residential consumption as sectors of the intermediate delivery matrix, is preferred to the EIO and PIO models for analyzing industrial and environmental policies. Moreover, waste recycling in five sectors—agriculture; the manufacture of paper, printing, and articles for culture, education, and sports activities; the manufacture of nonmetallic mineral products; smelting and pressing of metals; and construction—should be comprehensively considered when using the HIO model to study problems related to these five sectors. Improvements in the EIO, PIO, and HIO models and future work are also discussed.