This chapter deals with the modelling and analysis of a proposed industrial symbiotic system in Karlstad (Sweden), involving algal cultivation, a combined heat and power (CHP) plant and a wastewater treatment plant (WWTP). It has been organized into two parts – the first one focusing on the modelling, and the second one, on the application of the model and an energetic and environmental analysis performed using the model developed in the first part. The focus is on the actual symbiotic relationship, the associated flows of materials and energy, and the environmental performance of the symbiotic system, located in Karlstad. In the proposed symbiosis, exhaust gases from the CHP are used as a source of carbon dioxide for the photosynthetic algae (which in the process double up as carbon sinks) as well as a source of heat for drying the harvested algal biomass.  Recovered waste heat is used to maintain an appropriate temperature in the cultivation pond and the nutritional needs (nitrogen and phosphorus) of the algae are fulfilled by circulating digestate water from an anaerobic digester at the WWTP. Two possible scenarios for bio-energy recovery (from the algae) were studied - anaerobic digestion (Scenario A) and direct combustion in the CHP (Scenario B).  The outcome is encouraging and shows that algae can be cultivated at the location of the CHP plant in Karlstad, over a longer period of time, vis-à-vis a stand-alone system, and thereby the average daily output can be augmented from 14 to 18 g/m2. From an environmental point of view, Scenario B fares better than Scenario A. The integrated system has a net energy ratio (NER) of 2.6 for Scenario A; and 5.3 for Scenario B The model and the analysis based on it clearly show that there are excellent opportunities for cultivating algae for use as biofuel locally in Karlstad, which can be harnessed by resorting to industrial symbiosis. A full-scale, detailed life-cycle environmental analysis focusing on a range of environmental impact categories can be carried out in the future.