Biomass conversion to fuels and chemicals requires new approaches to evolve efficient and economically viable processes. Hydrogenations of biomass-related substrates can convert highly-oxygenated biomass components to feedstocks which more closely resemble petrochemicals. The high hydrogen pressures needed for such reactions adversely affect the process economics, but the use of supercritical solvents could overcome this barrier by enhancing the mutual solubilities of reactants as well as the transport of materials and energy in the reaction system. We have used a fixed bed reactor to evaluate supported transition metal catalysts and supercritical solvent media for intensified hydrogenations of biomass constituents at mild process conditions. We have used a building block approach, beginning with small-molecule biomass derivatives, to understand better the reaction mechanisms involved in biomass hydrogenations. Such an understanding is essential for developing novel methods to produce and upgrade biomass-derived feedstocks for fuels and chemicals production.