A composite board is made from waste medium density fiber (MDF) board or waste particle board that includes solid urea formaldehyde. The waste board is chopped and milled into particles having a size between 20 mesh and 150 mesh, creating a waste flour. After removing moisture from the waste flour, the dried waste flour is mixed with a thermoplastic to bind and encapsulate the waste flour. Internal lubricants are added to improve the flow characteristics of the blended material, and external lubricants are added to present sticking of the mixture to an extruder or mold. Mineral fillers are added to improve the flexural modules of the composite board, and a plasticizer can be added to improve the physical properties or mechanical characteristics of the mixture. An ultraviolet absorber, a biocide, and a pigment can also be added. The blended material is extruded or molded into a desired shape. When cooled, the thermoplastic hardens to form a solid composite board.