This paper reports the feasibility analysis of co-fired combined cycles (biomass-derived gas + natural gas) based on the gasification of sugarcane residues (bagasse and trash). Performance results are based on simulation of co-fired combined cycles. Feasibility analysis is based on estimates of the capital costs and O&M costs for such cycles, taking into account current and middle term costs of BIG-CC technology (both considering scaling and learning effects). A deep reduction of the investments regarding the gasification island and auxiliaries is a key point to make BIG-CC competitive in the electricity market, and the required learning can be reached with co-fired BIG-CC systems. Besides alleviation of technical problems related to gas turbine operation with biomass-derived gas, co-fired BIG-CC units can operate with relative flexibility regarding the fuel mix. The construction of 10-15 short- to medium-size gasification islands would be enough to induce important cost reductions due to learning effects. As long as the investment on the gasification island is reduced, and depending on the price ratio of natural gas and biomass, pure BIG-CC plants could achieve a reasonable level of feasibility regarding other options of electricity production. In the short run there is no advantage for co-fired combined cycles regarding the costs of reduction of carbon dioxide emissions, but in the middle run both co-fired and pure BIG-CC power plants can be a better option than capture and storage Of CO2. (C) 2007 Elsevier Ltd. All rights reserved.