Abstract: A machine for making bio logs includes a conduit with a feed opening along a top side and a chamber below the feed opening. A door over the feed opening is movable between open and closed positions by a first piston connected to the door. A plunger disposed within the conduit is movable between a retracted position and an extended position by a second piston connected to the plunger. A method of making bio logs includes retracting the first piston to move the door to the open position, retracting the second piston to move the piston to the retracted position, disposing a quantity of filling material into the chamber, extending the first piston to move the door to the closed position, and extending the second piston to move the plunger to the extended position.