Our cities have been paid more and more attention in addressing the global challenges of resource depletion and climate change, as they are consuming more energy and generating more waste. In the pursuit of solutions, algal biotechnology shows potential to be implemented as a decentralized urban energy system due to its high biomass productivity and its utilization of urban waste streams. A typical algae cultivation system requires water, carbon, sunlight and nutrients (primarily nitrogen and phosphorous), which are already contained in the urban waste stream and could be utilized after appropriate treatment [1].