The long-term stability of direct carbon fuel cells, based on solid oxide fuel cells with molten Sb and Sb-Bi anodes, was examined for operation with activated charcoal, rice starch, and bio-oil fuels at 973 K. With intermittent stirring of the fuel-metal anode interface, the anode performance was stable, and reasonable power densities (approximate to 250 mW/cm(2)) were achieved for periods up to 250 h. With Sc-stabilized zirconia, severe thinning of the electrolyte occurred in regions of high current flow. No electrolyte thinning was observed with yttria-stabilized zirconia as the electrolyte operating at the same current densities. (c) 2012 American Institute of Chemical Engineers AIChE J, 59: 3342-3348, 2013