Abstract: The invention is directed to a machine for compacting agricultural fibrous matter into a board, comprising a hopper for receiving the agricultural fibrous matter; an extruder comprising an extrusion passage downstream of the hopper; and a ram configured for moving in a reciprocal manner along the extrusion passage; wherein the extrusion passage further comprises a movable wall configured for moving between a feed position, opening the extrusion passage to the hopper, and an extrusion position, closing the extrusion passage.