Urban metabolism can be defined as the sum of the technical and socio-economic processes that occur in cities, resulting in growth, production of energy, and elimination of waste. This classification of urban environments encompasses quantifying outputs, inputs and storage of energy, nutrients, water, materials and wastes for an urban region. Although this article was written years ago, quantifying data varies temporally. I wanted to express my confusion about why the research varies. It was expressed that studies were made in the 1970s and interest dropped off in the 1980s. No further information was provided on the matter, so as the reader I am left with the question of why this happened. I am sure a further study could be conducted; my immediate thoughts were political conflicts or lack of funding as more research broke out in the 1990s.

When defining the urban metabolism factoring scale is of major concern. When factoring in such a matter, the author describes the review of two separate methodical approaches to the idea of urban metabolism. The two approaches being energy equivalence and the flow of resources. In particular, solar energy was the universal metric in the study as recognition of the variation in the quality of different forms of energy were made, while the mainstream of study being the flow of resources because it was more readily accessible and easily understandable when communicating with local government officials.

Research references across the globe were provided about urban metabolism. Some places including Hong Kong, London, Toronto, Phoenix, UK, Lisbon, Ireland, and BangKok. The author primarily focuses on a single application for urban metabolism, although still provides research on every application in which it was used. I felt that was an important thing to note as most articles would cut out the unnecessary information, but the reader can get ideas on other applications in this article. The author reviews the application in terms of all things encompassing sustainability. The terms include urban greenhouse gas accounting, urban design, sustainability reporting, and mathematical modeling for policy analysis. These are just the practical applications for urban planners.

There are four major urban activities: to reside and work, to clean, to transport and communicate, and to nourish and recover. There are four major components to urban metabolism: energy, food, water, and construction materials. These features can be taken into account when reconstructing cities. An example of this would be New Orleans after hurricane Katrina. This framework of thinking is being implemented within the industrial ecology community, which now focuses on urban and social metabolism. The author provides a list of several advantages of the application of urban metabolism framework. Some which include, accounts for inputs and outputs to the system, integrates social science and biophysical science/technology, and necessitates analysis of policy and technology outcomes with respect to sustainability goals.

This paper did a wonderful job at reviewing research on urban metabolism as a whole. The author referenced over 50 papers in total all pertaining to research on urban metabolism in different years. The author also starts off in the first couple paragraphs providing the reader with questions to ponder while learning about urban metabolisms research history. The author leads out with the idea that further work needs to be done and explains that an important future direction that needs to take place is more implementation to economic, social, and health indicators into the framework of the research. I could not agree more with that statement. When understanding the research that has been done these factors were lacking when understanding the urban metabolism as a whole.

Kennedy, C., et al. “The Study of Urban Metabolism and Its Applications to Urban Planning and Design.” Environmental Pollution, vol. 167, no. 8-9, Aug. 2012, p. 184–185, doi:https://doi.org/10.1016/j.envpol.2010.10.022.