This study examines the economic viability of a production process of microalgae to generateelectricity, considered as a joint activity with ethanol in order to meet rising demand provided energy caused by thecountryâs economic growth. The production of this alternative energy source in conjunction with an ethanolplant maximizes the gains of both, and bring benefits to the environment, with the microalgae capturing the carbondioxide emitted by the ethanol plant. Through production and cost estimates, an investment analysis of theproject to generate energy from microalgae is done according to the criteria of net present value, internalrate of return and the ratio of benefit to cost. The result obtained by applying the three criteria is to confirmthe economic viability of the production process of microalgae to generate bio-electricity in Brazil.