The solar thermochemical steam-based gasification of carbonaceous materials is investigated using concentrated solar energy as the source of the high-temperature process heat. Vis-a-vis conventional autothermal gasification, the solar-driven process delivers a higher syngas output of higher quality and lower CO2 intensity because no portion of the feedstock is combusted and its energy content is solar upgraded. The operation of a solar gasification pilot plant for a 150 kW(th) solar-radiative power input was experimentally demonstrated using a packed-bed solar reactor operated in batch mode. The experimentation was carried out in a solar tower. Six different carbonaceous waste feedstocks have been successfully processed: industrial sludge, fluff, tire chips, dried sewage sludge, low-rank coal, and sugar cane bagasse. The calorific value of the produced syngas was upgraded by a factor of up to 1.3. The solar-to-fuel energy-conversion efficiency, defined as the ratio of the heating value of the fuel produced to the solar and feedstock energy inputs, varied between 22 and 35%.