Disclosed herein is the use of terrestrial plant materials (e.g., leaves and bark) that contain biopolymer materials to produce hydrocarbon-rich crude oils that can be refined further into hydrocarbon-based biofuels, via the hydrous pyrolysis method, which involves heating to subcritical temperatures and pressures in an aqueous medium. One can also isolate the aliphatic biopolymers and utilize them as feedstocks for production of the hydrocarbon-rich crude via hydrous pyrolysis.