Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)The techno-economics of greenfield projects of a first-generation sugarcane biorefinery aimed to produce ethanol, sugar, power, and n-butanol was conducted taking into account different butanol fermentation technologies (regular microorganism and mutant strain with improved butanol yield) and market scenarios (chemicals and automotive fuel). The complete sugarcane biorefinery with the batch acetonebutanol-ethanol (ABE) fermentation process was simulated using Aspen Plus (R). The biorefinery was designed to process 2 million tonne sugarcane per year and utilize 25%, 50%, and 25% of the available sugarcane juice to produce sugar, ethanol, and butanol, respectively. The investment on a biorefinery with butanol production showed to be more attractive [14.8% IRR, P(IRR > 12%) = 0.99] than the conventional 50:50 (ethanol:sugar) annexed plant [13.3% IRR, P(IRR > 12%) = 0.80] only in the case butanol is produced by an improved microorganism and traded as a chemical. O 2012 Elsevier Ltd. All rights reserved.135316323Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [2007/00341-1, 08/57873-8]