Biomass and a metal oxide, e.g., calcium oxide (CaO), are heated at ≥ 1400oC for short times using a thermal plasma or other suitable means. The reaction products are then rapidly quenched to ≤ 800oC. Reactions of the calcium oxide redirect the process chemistry to: (a) provide products valuable in their own right and as precursors to fuels, chemicals, chemical feedstocks, industrial gases, fertilizer, and pharmaceuticals; and (b) significantly reduce yields of unwanted substances such as tars and solid carbon. For example, using CaO, significant amounts of biomass carbon are converted to calcium carbide (CaC2). By reaction with water, calcium carbide can in turn be converted to acetylene (C2H2) by a well-established chemical process. Acetylene is a high heating value fuel, a feedstock to a wide range of chemicals, and an industrial gas. Reaction of CaC2 with nitrogen gas (N2) produces calcium cyanamide (CaCN2) which can in turn be converted to cyanamide (H2NCN) which is used in the production of pharmaceuticals and other organic compounds. Moreover, reaction of cyanamide with water or steam produces urea (CO(NH2)2) a fertilizer. This biomass conversion process also produces mixtures of CO and H2 (synthesis gas; syn gas) useful as a fuel and further convertible to chemicals and to various other fuels as well as industrial gases, including hydrogen (H2). Synthesis gas is now of interest as a substitute for coal-derived coke in blast furnaces to reduce the fossil-carbon footprint of the steel industry. When the biomass feedstock consists of concentrated waste pulping liquors, the process also recycles pulping chemicals such as Na2CO3 and NaOH. Heat recovered from the high temperature (biomass-treatment) reactor can be used to pre-heat and remove moisture from the biomass feedstock, e.g. to concentrate waste pulping liquors.