Urban Metabolism

Urban metabolism broadly refers to the sum of material resource transformation and processes in cities, often measured through flows within an urban system. As a boundary metaphor, research paradigm, and methodological tool, urban metabolism has been employed in a variety of fields in diverse ways. Industrial ecology contains the most mainstream and largest body of work so far. It approaches urban metabolism from a systems-based perspective and accounting of flows, stocks, inputs, and outputs, with the goal of planning and optimizing material throughput for urban sustainability. A subfield within industrial ecology called the Vienna school incorporates ecological economic principles through the concept of socioeconomic metabolism to link socioeconomic transitions with material throughput shifts within and beyond the urban context. Mass-balance accounting using material and substance flow analysis continues to be the most common quantification methodology for urban metabolism case studies of cities and urban regions around the world. However, other emerging tools such as the emergy synthesis, life cycle analysis, ecological footprint, network analysis, and increasingly complex modeling have been developed, refined, and expanded over the past few decades. The field of urban ecology presents a similar systems-based perspective on urban resource transformation but finds the industrial ecology’s input-output framing and metabolism’s organicist metaphor less appropriate within a cities-as-complex-ecosystems framework. Finally, critical social sciences draw from the Marxist theory of metabolism to frame socionatural circulation, exchange, and transformations associated with capitalist production. In cities, urban political ecologists mobilize urban metabolism as a metaphor to capture the hybrid socionatural, uneven, and power-laden processes of the urban production of nature. Despite urban metabolism’s heterogeneous definitions and diverging intellectual histories, recent works have attempted to build on the strengths of each of these fields while transcending individual limitations. Conceptual and methodological integration of urban metabolism approaches is necessary to enable an interdisciplinary outlook on urban sustainability challenges.