This work investigated the production of Scenedesmus sp. in semi-continuous mode in three pilot-scale outdoor raceways (7.2 m(2)) using flue gas for CO2 supply and centrate from the anaerobic digestion of urban wastewater as the sole nutrient source. Experiments were performed at different culture depths, 5, 10 and 15 cm, while evaluating two centrate concentrations (30% and 45%) at dilution rates of 0.2 and 0.3 d(-1). Under optimal conditions of 30% centrate, 0.3 d(-1) dilution rate and a 15 cm culture depth, a maximum biomass productivity of 22.9 gm(-2) d(-1) was obtained. The optical properties of the cultures were studied and the results showed a photosynthetic efficiency of up to 2.0% and a quantum yield of 0.3 g biomass E-1. Nitrogen and phosphorus removal rates of 3 g Nm(-2) d(-1) and 0.6 g Pm-2 d(-1) were recorded, respectively. Lipid productivity of 2.3 gm(-2) d(-1) was determined possessing a suitable fatty acids profile for biofuel production.