Landscape and Urban Planning

Today, the sustainability of cities is a critical consideration in the development of modern societies. One important dimension of this concept is the influence of occupation intensity on resource consumption and its associated waste generation. Emergy analysis constitutes an appropriate methodology for evaluating the sustainability of cities, given that it integrates the different types of flows interacting in urban regions in a common basis of comparison, the solar emergy joule (seJ). In this study, emergy analysis was used to evaluate the environmental sustainability of the Island of Montreal, Canada, in 2005 and to compare its situation with that of other nine urban centers. Results indicate that the total emergy used in 2005 stood at 1.153×1023seJ, with renewable resources representing 3.2%, and a waste-to-emergy ratio of 0.09. In comparing the cities, it was observed that the empower density, an emergy measure for the intensity of activities, fell markedly when each inhabitant had about 300m2 or more of available land. Results for the Island of Montreal point to the need to improve the city's environmental performance. Particularly, the high empower density indicates that projects involving the re-development of recovered areas provide a significant opportunity for attaining this objective.

The integrated study of energy and urban systems has recently become a critical component of sustainability research and policy. Increasing urbanization of human societies combined with intense energy demands of modern economies have driven a recognition that sustainable practices require a systems approach to both the study and application of sustainability principles. Urban metabolism has emerged as a leading methodology for quantifying energy consumption and use patterns in urban environments. Though typically applied as a method of accounting for total energy and materials inputs and outputs into cities, its interdisciplinary history and methods allow urban metabolism to be expanded in ways that will allow more comprehensive and integrated assessment of the patterns and processes of urban energy systems. In this article, we review the concept of urban metabolism—including its two typical approaches: mass balance and “emergy” methods—and offer a means to expand urban metabolism into a platform that incorporates socioeconomic analysis, policy analysis, and additional quantitative methodologies (such as life cycle assessment). This expanded urban metabolism framework is more comprehensive analytically and builds upon the documented capacity of traditional urban metabolism to account for total energy and materials flows of cities to provide an integrated platform for analysis of both energy patterns and the causal processes that govern energy in contemporary cities.