Fly ashes present several minerals that along with carbon dioxide (CO2) represent a promising nutrient source and an alternative to reduce environmental problems. Thus, the objective of this study was to investigate if CO2, thermoelectric fly ashes and reduction in nitrogen supply alters the production of macromolecules in Chlorella fusca LEB 111. For this purpose, 1.5 or 0.75 g L-1 of NaNO3, injection of 10% (v v-1) of CO2 as well as 0, 40 and 120 ppm of fly ashes were studied. The protein content was not impaired in cultivations with 0.75 g L-1 of NaNO3 since nitrogen was not fully consumed. Nevertheless, this cultivation strategy increased carbohydrate content by up to 25%, which could be fermented to produce bioethanol. Therefore, Chlorella fusca presented not only potential for CO2 biofixation and assimilation of nutrients from fly ashes but also for enhancement of carbohydrates accumulation when the nitrogen supply was reduced.