Abstract: An improved method for making compressed structural fiberboard by extruding agricultural fibrous matter into a compressed structural fiberboard. The improved method includes providing a preselected volume of agricultural fibrous matter and preconditioning the agricultural fibrous matter to have a predetermined moisture level. The agricultural fibrous matter is separated and cleaned, and steam is added until a predetermined level of moisture is reached within the agricultural fibrous matter. Borax is also added to the agricultural fibrous matter to prevent the formation of bacteria. The agricultural fibrous matter is conveyed throughout the process on conveyors having variable drives, wherein the level of the agricultural fibrous matter on the conveyors is sensed such that a signal is provided to adjust the speed of the conveyors in order to provide a predetermined level of agricultural fibrous matter. The agricultural fibrous matter is then extruded to form a compressed structural fiberboard.