Abstract
In mid-eighteenth-century England, sewage waste became a critical environmental and public health problem. One proposed solution was to recycle urban waste onto farm fields as fertilizer, and sanitarians undertook a series of studies to examine the feasibility and potential profit of this approach. In 1855, for instance, British agricultural chemist John Lawes followed the fertilizing components of sewage from plant growth through human consumption and excretion and back to plants. This approach necessitated a complex accounting of the waste and consumption of different demographic categories of the population. Lawes first determined the nutrient content of human food, measured the amount of carbon and nitrogen exhaled during respiration during human metabolism, and measured the volume and chemical composition of urine and feces produced by urban inhabitants. The amount and type of food consumed was determined for boys and girls by examining their diets in schools, asylums, prisons, and workhouses. Lawes collected data on the carbon and nitrogen consumed by sailors and soldiers, and men and women in prisons, workhouses, and infirmaries. He concluded that the nitrogen in London’s sewage was equivalent to one-third of the wheat consumed by the population of London each year. Similarly, J.L.W. Thudichum, in an 1864 paper, “On an improved mode of collecting Human Voidings,” proposed to collect and sell the fertilizing elements contained in the urine of London’s population. Accounting for everything from the percentage of an infant’s urine that never makes it to the sewers, to the declining concentration of nitrogen in the voidings of the elderly, to the amount of nitrogen that might be imported into London via the “fluid excretions” of visitors, he estimated that 237,250,000 gallons of urine would be produced each year in London, containing 14,218.1 tons of ammonia.
These sanitarians were conducting what Baccini and Brunner, in their book Metabolism of the Anthroposphere, would call a material flow analysis, an approach to examining urban environments that is formalized and expanded in this second edition of their book. The material flow analysis (MFA) is at the center of these authors’ approach to studying the environmental impact of cities. By tracing the flows of goods (i.e., food, cars, building materials), and their constituent substances (i.e., nitrogen, iron, copper) in and out of cities or regions, and their cycling within these systems, MFA can help identify sources of pollution, sites of waste, and opportunities for more efficient use of goods and materials. Material flow analysis intersects with the interest of planning primarily in the question of metabolic design, how to use policy to alter the fluxes of materials in cities and regions. Planning scholars will find this book in equal measure fascinating and frustrating, but definitely worth the trouble.
As the above example from nineteenth-century London demonstrates, this approach to urban analysis is not new. However, the quantitative modeling tools and available data, as well as the expanding interest in and concern for urban environmental problems, have made this approach more powerful, as Baccini and Brunner demonstrate in a series of case studies of urban and regional metabolism. Material flow analysis is but one of the recently developed methodologies for examining urban environments, but the authors usefully discuss the relation between MFA and other indicators, such as Statistical Entropy Analysis, Life Cycle Assessment, Ecological Footprint, and Sustainable Process Index. The book is dense with terminology, much of it likely to be unfamiliar to most readers. The authors define the anthroposphere as the “complex technical system of energy, material, and information flows” (p. 1). The anthroposphere is a global realm. Rather than taking a global perspective, however, this book primarily deals with what they term “urban systems,” defined as “open geogenic and anthropogenic networks that are connected with each other” in which cities, “places of high densities of people, physical goods . . . and information,” are the nodes in the network. These nodes are “connected by flows of people, goods, energy, and information” (p. 5). The term metabolism, by analogy to its biological definition as the transformation of materials during physiological processes in individual organisms, is used to describe the physical flows and stocks of energy and matter.
The bulk of the book concerns itself with how to perform and interpret MFA studies in a variety of urban systems. Chapter 3 introduces MFA and substance flow analysis (SFA), a subset of MFA that examines the flow of the constituent elements of the goods examined in an MFA. For instance SFA would analyze the flow of the substance nitrogen that is a component of the good, food, a subject for MFA. Chapter 3 introduces the study of the urban metabolism with an example almost identical to the nineteenth-century studies of Lawes and Thudichum, a material flow analysis of food in the urban system. The authors go through the construction of the MFA for food in some detail, but this analysis highlights some of the shortcomings of this book. The authors outline the steps required to create an MFA, but some steps are either missing or glossed over. For instance, the authors explain how to move from collecting the data necessary for constructing an MFA to the construction of the analytical model of stocks and flows. Yet the values for flows and stocks of food in the model they present differ from the numbers in the table from which they obtain their data. Why? Did they round? Did they choose numbers to make inputs and outputs balance? In the table, one value lies between 600 and 4800. They chose 800. Why? What is the justification? If readers are to take this as a guide to how to perform material flow analyses, these steps need to be spelled out. More useful for answering these kinds of questions about the actual construction of models of metabolic systems might be Practical Handbook of Material Flow Analysis (Brunner and Rechberger 2003), cowritten by one of the authors of this book.
Chapter 4 provides a case study of the construction and interpretation of regional metabolism, and applies MFA and metabolic analysis to a hypothetical but realistic region, based on the developed economies of the West, called METALAND, and creates MFAs for several of the most important urban processes. Chapter 5 examines three case studies in detail to illustrate ways in which an analysis of MFA can suggest the most efficient ways of directing policy toward improving the design of metabolic systems to reduce environmental impact. The authors present case studies in which they study phosphorus, copper, and solid waste. An MFA for phosphorus, for example, shows that phosphorus imports as fertilizer are used very inefficiently, and that stocks of phosphorus are accumulating rapidly in soils and landfills. Addressing agricultural use of phosphorus should be the priority for public policy. An MFA for copper shows that over the last century and a half, the flux of copper from mineral ores into the anthroposphere has been on the order of 2.4 million tons per year. Of this copper, about half ends up in landfills each year while the other half is added to the stock of long-term usage, that is, as buildings, vehicles, plumbing, and electrical networks. The copper stored in long-term usage and landfills is now on the same order of magnitude as the proven reserves of copper in mineral ores, suggesting that copper could be more efficiently “mined” from anthropogenic sources, reducing the environmental impacts of hard rock mining.
The book is at its weakest where the authors seek to theorize urban systems beyond the scope of MFA. Much of chapters 1, 2, and 4, for instance, present generalizations about the process of urbanization that the authors assume to be universal across space, time, and culture. As planners and urban historians, we know that urbanization has happened in response to varying economic and social pressures, at different times in different societies. The authors also seek to model “cultural evolution” using their metabolic approach, and present long analyses of the cultural evolution of, for instance, “skins,” as metaphors for clothing and housing. The authors categorize human activity into four main “activities,” to nourish, to clean, to reside and work, and to transport and communicate. It is hard to see, however, how this categorization advances our understanding of urban systems, or how it provides advantages for metabolic modeling. They make dubious claims that in modern cities, because of advances in information technology, “to reside” is now inseparable from “to work,” but it is not clear why it is any more inseparable from “to transport,” or “to nourish.” The forays into social theory are unfortunate, because the broad generalizations about cultural evolution are essentially irrelevant to the analytical framework of metabolism and MFA, and serve only to detract from the authors’ analysis.
This book would also have been improved if it were substantially shorter. MFA is introduced several times, and many of the examples from earlier chapters are repeated, with similar information appearing in several chapters. Further, extensive editing would have improved the book as well. At one point, the authors present what they term the four fundamental activities in any urban system. On the next page, they say there are five fundamental activities. At times they call these variously “processes,” “activities,” and “notions.” They make a point of carefully distinguishing “the term paper,” from “the name paper” but it is not clear what this distinction is. All of these might be overlooked except that their theoretical and conceptual framework relies on careful definition and use of just these terms, like activities and processes.
Nevertheless, this is a very interesting book and shows the benefits of using a material flow approach to analyzing and designing sustainable urban and regional environments.