The use of concentrated solar energy for gasification of biomass is an efficient means for production of hydrogen rich synthesis gas. Utilizing molten alkali-carbonate salts as a reaction and heat transfer medium offers enhanced heat transfer, faster kinetics, and stability for solar transients. The effect of the molten salts on gasification of switchgrass is examined in terms of the reaction rates and product composition. Experiments were carried out in an electrically heated molten salt reactor. Switchgrass was gasified with steam at 1200 K in an inert gas and with salt. Reactivity indexes were calculated from measured gas production rates. Product composition was established via mass spectrometry. In salt, the total useful syngas production increased by 30% while reducing net carbon dioxide production. Reactivity increased 81%. Secondary products, in the form of condensable tar and unreacted char, were reduced by 77%.