MATERIAL FLOW ANALYSIS Urban Mining A Contribution to Reindustrializing the City

Paul H. Brunner

Today’s most advanced societies are service- the term to describe exploitation of resources oriented economies. The main resources of such from landfills, others apply it to traditional re- societies are knowledge and information created cycling schemes of materials, such as con- by and embedded in people and institutions. struction debris, iron, plastics, or glass. The Classical resources, such as materials, energy, purpose of the present column is to introduce and land, are of less value for service-oriented a more comprehensive interpretation of urban societies. mining. I incorpo- Nevertheless, even rate two additional if one acknowledges the Megacities can produce sufficient aspects—creating a primary role of intel- amounts of secondary resources for goal-oriented knowl- lectual resources, mate- large-scale production of raw ma- edge base by preserving rial resources are still information from the backbone of all soci- terials by urban mining, and cities production through eties. We cannot pursue are always in need of energy. Thus, recovery, and locating our daily activities with- combining plants for metals recycling facilities out the provision of ce- within service-oriented ment, steel, aluminum, such as iron, aluminum, and cop- cities—to develop the cellulose, polyethylene, per in cities with utilization of waste concept into a new linear alky benzene sul- energy from such plants to fuel the strategy to increase the fonates, and many other sustainability of the materials. Given the city (heating and cooling, electricity) urban metabolism. high volatility of re- seems an attractive option for im- First, to facilitate source prices and the proving the sustainability of cities. effective urban mining, still heavy pollution we require comprehen- of primary production, sive information about recycling becomes mandatory. A new approach materials and substances. For the exploitation of toward recycling is “urban mining.” The term de- primary ores, intrinsic properties, such as element notes the systematic reuse of anthropogenic ma- concentration, abundance, availability, specia- terials from urban areas. It is based on the fact that tion, and partner minerals, determine whether a large stocks of materials are incorporated into particular substance can be economically mined. cities, in particular in buildings and infrastruc- The same applies to the recovery of substances ture but also in landfills. These stocks represent a from urban material flows and stocks. For exam- large resource potential that will eventually—at ple, for the effective recovery of aluminum, one the end of the product lifetime—become avail- must know whether it is present as solid metallic able for reuse. There is no general definition for aluminum (Al) in a car body or building part, urban mining yet: Whereas some researchers use as kaolin (Al2O3 · 2SiO2 · 2H2O) in newsprint, or as aluminum hydroxide Al(OH)3 in antacids. c 2011 by Yale University Depending on how it is used, it can be recovered DOI: 10.1111/j.1530-9290.2011.00345.x economically or will be “lost forever.” Thus, the Volume 15, Number 3 information necessary for decisions about urban www.wileyonlinelibrary.com/journal/jie Journal of Industrial Ecology 339 MATERIAL FLOW ANALYSIS mining comprises all relevant flows and stocks there were 18, and in 2015 there will likely be of a particular substance, from production to 22; UN 2006). utilization and disposal at the end of the life- To establish such a comprehensive “urban time. In particular, data about use during the mining” strategy, we have to better understand product lifetime are important (location, flows the system “city.” In particular, it is important and stocks, density, speciation, partner elements, to take into account the different phases of dissipative losses). This information—a cadaster urban development: Most cities grow, some are of secondary resources—forms the basis for de- in a (temporary) steady state, and a few are termination of priorities for recovery, for design shrinking. In growing cities, the import of solid of effective reclamation systems with advanced materials—essentially construction materials— logistic and recycling technologies, and for en- outweighs the export because of the long lag vironmentally sound final disposal of nonrecy- time between production and disposal (several clables. The new knowledge base is necessary to decades). Today, this is particularly the case for advance from the present state of recycling to a fast-growing Asian cities, where the input-output next “urban mining” state, where materials are re- ratio for solid materials is greater than 10:1. For covered in a more focused and effective way that such cities, recovery of materials from the ur- takes valuable as well as hazardous substances into ban metabolism cannot make significant contri- account along their path from origin to use phase butions to meeting demand. Thus, although re- and final sink. cycling, for example, of construction is of Second, urban mining not only attends to ma- importance for environmental protection, it does terials but represents a more comprehensive ap- not alleviate the need for primary resources. Con- proach that includes energy. The concept of ur- versely, some shrinking regions, such as cities in ban mining to date has not taken into account eastern Germany (Schiller et al. 2010) or in the the question of where recycling takes place. Lo- former Soviet Republics, are in a different situa- cating urban mining processes close to the sources tion: Their demand decreased due to population of secondary materials and thus within service- and economic losses, and thus material consump- oriented urban areas has significant advantages. tion today is lower than before. Due to a smaller Transportation of wastes and recyclables requires population, part of the aging material stock is not energy, and so does recycling and processing. needed anymore and becomes obsolete. Thus, the Hence, short transport distances and processes potential output exceeds the input. For such ar- with high energy efficiency are mandatory for sus- eas, urban mining strategies seem attractive (and tainable urban mining. Urban mining performs are, in fact, actively practiced: Missing power best, in view of these criteria, when recycling lines in some industrial urban areas are noticeable facilities are located within the city: Megacities examples). can produce sufficient amounts of secondary re- Some cities are close to a steady state: Im- sources for large-scale production of raw materi- port and export of materials are in balance. For als by urban mining, and cities are always in need these mature cities, the urban outputs represent of energy. Utilizing surplus energy from recycling more than a marginal contribution to the re- plants for metals such as iron, aluminum, and cop- source needs. For them, it is conceivable that per to fuel the city (heating and cooling, electric- a large fraction (more than 80%) of primary re- ity) seems an attractive option for improving the sources can be substituted by secondary resources. sustainability of cities. This relates only to large Due to the difference in composition and speci- urban areas populated by several million inhabi- ation, however, not all outputs can be recycled. tants, however, because economy of scale applies There will always be a certain need for primary to both recycling processes and primary resource resources as well as for “sinks,” such as inciner- extraction. It is noteworthy that the number of ators, treatment plants, and landfills for cities with more than 10 million inhabitants is nonrecyclable residues of the urban metabolism. abundant and growing (in 1950 there were two There are more benefits to such an urban min- such cities, in 1975 there were three, in 2000 ing strategy of bringing industrial processes back

340 Journal of Industrial Ecology MATERIAL FLOW ANALYSIS into the city than just energy saving and a shorter tional research is needed to pinpoint the main transport distance. (1) Having potentially pollut- potentials for recovery: Up to now, researchers ing recycling facilities inside the city boundaries have not known whether the major resource po- can prompt the rigorous application of best avail- tential is in the urban stock, in the landfills of mu- able technologies (BAT): Several million inhab- nicipal solid waste (MSW) and other wastes, or itants are watching the process on a daily basis, in the and residues from mining. Finally, which thus increases the likelihood that environ- economic modeling is needed to clarify which mental standards are strictly observed. A shining potentials of secondary resources promise an eco- example is the Spittelau nomic benefit and which pose marginal or even incinerator, close to the center of Vienna, de- negative assets. signed by Friedensreich Hundertwasser; real-time emissions are presented online on a large public References display close to the incinerator. (2) There is a better balance of intangible benefits between the Graedel, T. E. and J. Cao. 2010. Metal spectra as in- city and its hinterland: Today, the hinterland dicators of development. PNAS 107(49): 20905– gets the wastes and pollution from the primary 20910. production as well as by recycling, and the city Schiller, G., C. Deilmann, J. Reichenbach, K. Gruhler, gets the “clean” utility of the resources. (3) The P. Rohm,¨ J. Bumann, and M. Gunther.¨ 2010. Er- public has a chance to become aware of the large mittlung von Ressourcenschonungspotentialen bei der Verwertung von Bauabfallen¨ und Erarbeitung von material flows that are associated with modern Empfehlungen zu deren Nutzung. [Determining re- life. (4) Finally, the city will become less reliant source conservation potentials in the recovery of on imported resources by taking advantage of its and formulating recommen- own secondary resource base. dations on their use.] UBA Report No. UBA-FB To facilitate an urban mining strategy, we 001401. Dessau-Roßlau, Germany: Umweltbun- need to develop a new knowledge base. A general desamt. question relates to the information requirements: UN (United Nations). 2006. World urbanization Which information is needed for setting the right prospects, the 2005 revision: Executive summary, priorities, for planning and implementing appro- fact sheets, data tables. New York: United Nations priate measures, and for ensuring the overall cost- Department of Economic and Social Affairs. effectiveness of urban mining? Information re- quirements will extend across many materials and About the Author substances and will cover long time periods (e.g., several decades for materials in the urban stock Paul H. Brunner is professor of waste man- of buildings and infrastructure). Thus, to prevent agement at the Vienna University of Technology high costs and little utility, it is of utmost impor- in Vienna, Austria. tance to elaborate clear goals and strategies for the new knowledge base. Address correspondence to: Data about flows and stocks of materials and Paul H. Brunner substances will play a major role in urban mining. Vienna University of Technology There is already a large and increasing informa- Institute for Water Quality, Resources and tion base about the global, national, and some- times even regional use of metals (Graedel and Karlsplatz 13/226 Cao 2010). When broken down on the city level A-1040 Vienna, Austria and when augmented with information about the [email protected] possibility to recover these resources, such data www.iwa.tuwien.ac.at/iwa226_english/home. will be of high value for urban mining. Addi- html

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