Cities are human creations requiring large amounts of materials and energy. Constant consumption of resources exerts pressure on the environment not only due to its exploitation, but also because once processed, the resources produce waste, emissions or effluents. Cities are responsible for more than three quarters of the emissions of greenhouse gases. It is anticipated that the urban population will increase by up to 80% by the mid-21st century, which will make the current energy model unsustainable, as it is based on the intensive use of fossil resources. A change in urban planning is required to meet the energy requirements of cities. Several studies mention that renewable energy must be used in cities, but they do not identify the resources and technologies that can be used to promote circular urban metabolism. A review of the literature establishes that there are eleven renewable technologies with different degrees of maturity that could reduce the import of energy resources, which would contribute to changing the metabolic linear model into a circular model. However, the applicability of the different possibilities is conditional upon the availability of resources, costs, policies and community acceptance.

This work evaluates the biogas production potential of the Ceibales landfill for feeding a power plant in the southern region of Ecuador. Biogas production is estimated through mathematical models that consider energy generation and technologies available to supply electricity plants. Characteristic landfill data are accounted for to analyze and develop these mathematical models. Once the generation capability of each source is identified, a decision can be made on the most suitable electricity generation technology. A local model (Ecuadorian model) is applied to calculate the potential of biogas and is compared with other models commonly used for evaluating this type of project. This type of renewable energy is attractive because it produces electricity from waste; however, it is not an attractive option unless its application is encouraged, as hydro has been encouraged through the investment of taxpayer resources. Technologies require a boost to become profitable, and even more so if they compete with traditional technologies.

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Previous research has identified 11 technologies that use resources that are available in or come from cities. It has been established that using these technologies, the flows from energy carriers required by cities could be reduced. These carriers can be electricity or fuels. Of the identified technologies, eight can produce electricity: biomass, biodigestor biogas, landfill biogas, waste incineration, tidal, small wind, small hydroelectric and photovoltaic technologies. The use of these technologies depends on the existence of resources and technical, economic and social or environmental factors. This research proposes the use of multiple-criteria techniques to select the most appropriate options for promoting renewable energy in cities. This approach was applied to the medium-sized city of Cuenca in Ecuador. Ecuador is a developing country, is an oil producer and has important water resources. The authors concluded that studies of the potential for implementing hydroelectric and solar photovoltaic energy and energy from landfill gas should be extended. The results coincide with the existing resources, implemented projects and the expectations of local professionals.