The use of a binary mixture of solar molten salts (60 wt% NaNO3 and 40 wt% KNO3) as a heat transfer medium for the production of a solar fuel by the thermochemical conversion of biomass is investigated in the present paper. Thermochemical conversion can be a route for converting the surplus solar irradiation via the direct contact of nitrate molten salts and biomass into storable chemical fuel. Traditional fixed-bed pyrolysis and molten salts pyrolysis have been carried out under an inert atmosphere at a temperature of 500 degrees C. The composition of the permanent gases and the bio-oil produced has been analyzed along with the temperature profiles inside the reactor. Two distinctive pathways have been observed: an endothermic process in the case of traditional fixed-bed pyrolysis and an exothermic process in the case of molten salt pyrolysis. An attempt has been made to identify possible causes for such differences. The financial support of the Spanish Ministry of Economy and Competitiveness from project ENE2014-54942-R is gratefully acknowledged by the authors.