Heat-transfer-aid particles entrained with 1) biomass particles, 2) reactant gas, or 3) both are fed into the radiant heat chemical reactor. The inner wall of a cavity and the tubes of the chemical reactor act as radiation distributors by either absorbing radiation and re-radiating it to the heat-transfer-aid particles or reflecting the incident radiation to the heat-transfer-aid particles. The radiation is absorbed by the heat-transfer-aid particles, and the heat is then transferred by conduction to the reacting gas at temperatures between 900° C. and 1600° C. The heat-transfer-aid particles mix with the reactant gas in the radiant heat chemical reactor to sustain the reaction temperature and heat transfer rate to stay within a pyrolysis regime. The heat-transfer-aid particles produce a sufficient heat surface-area to mass ratio of these particles when dispersed with the reactant gas to stay within the pyrolysis regime during the chemical reaction.