A tubular solid oxide fuel cell stack was modeled, and its operation on biomass syngas was investigated. The objective of this work was to develop a computer simulation model of a biomass gasification-solid oxide fuel cell system capable of predicting performance under various operating conditions and using diverse fuels. The stack was modeled using Aspen Plus and considers ohmic, activation, and concentration losses. It was validated against published data for operation on natural gas. Operating parameters such as fuel and air utilization factor (U-f and U-a, respectively), current density j, and steam to carbon ratio (STCR) were varied and had significant influence. The model was run on wood and miscanthus syngas. The results indicated that there must be a trade-off between voltage, efficiency, and power with respect to j and that the stack should be operated at a low STCR and a high U-f. Also, the stack should be operated at a U-a of similar to 20%. Operation on biomass syngas was compared to natural gas operation and, as expected, performance degraded. Better stack performance was observed for wood syngas compared to miscanthus syngas. High efficiencies were predicted making these systems very promising. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3407524] All rights reserved.