NOVELTY - A solar thermal reactor comprising outer protection shell (7) and inner reaction shell (3) having inlet and outlet is provided. The shell (7) is partially transparent or has opening (8) to atmosphere for transmission of solar energy. A gas stream comprising entrained biomass particles is flown from the inlet to the outlet of the reaction shell and particles are heated in the reactor through solar thermal heating to 950degrees C in portion by exposing the reactor to source of concentrated light. The particles react to form products comprising hydrogen and carbon monoxide.    USE - Method for partially reacting biomass particles to form reaction products comprising hydrogen, carbon monoxide, carbon dioxide (claimed), higher molecular weight hydrocarbon such as methane and ethane, and hydrocarbon containing oxygen-containing functional group such as alcohols, used as diesel fuel, jet fuel, transportation fuel, heating fuel and fuel for stationery electric power generation. The hydrogen produced is used as combustion fuel, desulfurization agent for gasoline and for chemical synthesis.    ADVANTAGE - The reaction of the biomass particles is performed without the addition of a catalyst.    DETAILED DESCRIPTION - A solar thermal reactor comprising an outer protection shell (7) and inner reaction shell (3) having an inlet and outlet is provided. The shell (7) is partially transparent or has an opening (8) to the atmosphere for transmission of solar energy. A gas stream comprising entrained biomass particles is flown from the inlet to the outlet of the reaction shell and particles are heated in the reactor through solar thermal heating to 950degrees C in portion by exposing the reactor to a source of concentrated light. The particles react to form products comprising hydrogen and carbon monoxide. The volume average equivalent spherical particle diameter of the biomass particles is 10 micron-10 mm. The biomass particles contain less than 15% of ash content and more than 50% of non-ash content. INDEPENDENT CLAIMS are included for the following:    (1) reduction of metal oxide particles chosen from zinc oxide, tin oxide and iron oxide (Fe3O4); and    (2) solar thermal reactor system for heating particles entrained within a gas.    DESCRIPTION OF DRAWING(S) - The drawing shows the horizontal cross-sectional view of a solar reactor having single non-porous inner reaction shell and outer protection shell.    Inner reaction shell (3)    Outer protection shell (7)    Opening (8)    Concentrated solar thermal radiation (91)