As we struggle to get our collective arms around the concept of urban sustainability, various ways of understanding material and energy flows associated with cities have emerged in the literature. Of course, this is not new. Historians have noted that, one hundred years ago New York City was dealing with streets covered with horse manure and coal ash. In Europe, concerns about supplying materials to cities were discussed in the early 1900s, and continued (after a hiatus) into the late twentieth century from a new perspective of environmental impact, leading to the development of methods for economy-wide material flow analysis (MFA) and their application to cities (Barles 2010). This method, used in many current studies of urban metabolism, allows for tracking of material inputs, changes in stock, export of goods, and release of waste and pollution; indirect material requirements to support these flows can also be computed. While the MFA methodology also draws on energy analysis and is considered to be readily adaptable to include energy, in practice there is wide variation in the inclusion of embodied energy components.