TECHNOLOGY FOCUS - BIOLOGY - The input material is a biomass material.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - The biomass pre-treatment system further comprises a top opening, comprised in the chamber wall, adapted to receiving biomass material; a bottom opening, comprised in a side section of a compartment wall, adapted to removing processed biomass material; a slidable top lid that is adapted to seal the top opening when the top lid is in a top closed position; an openable bottom lid, where the bottom lid is adapted to seal the bottom opening when the bottom lid is in a bottom closed position; a top sealing unit such as a top gasket along an upper periphery of the top lid and/or along an upper inner periphery of the top opening; and/or a bottom sealing unit such as a bottom gasket along a compartment facing periphery of the bottom lid and/ or along a bottom lid facing periphery of the bottom opening. The system further comprises a top clearance between the top sealing unit of the top lid and the upper inner periphery of the top opening; a guideplate, preferably integrated with the chamber wall, for placing a withdrawn top lid or the top lid that is to be placed in the top closed position; a top sealing unit comprising a sliding sealing mechanism, comprising a slidable top lid supported on at least one slidable support unit; a slidable base in connection with the at least one slidbale support unit and adapted to slide over a support unit; and an actuating unit adapted for sliding the slidable base such that the slidable top lid is moved from an open position to a closed postion from beneath the top opening. The system further comprises a top sealing unit along an upper periphery of the lid and/or along inner periphery of the opening; a motor connected with the shaft, where the motor is adapted to rotating the cylindrical shaft; a relative height adjuster for varying relative height between the first end and the second end; stirring units, each stirring unit comprises a rotatable shaft having space curved stirring elements extending from the shaft, the stirring elements are adapted to mix a biomass material received in the chamber and to propel the received biomass material along a length of the chamber in a pre-determined direction. The system further comprises a pitch varying unit for varying the distance between the stirring elements; and/or a distance varying unit for changing the distances between adjacent shafts. The system further comprises a curve changing unit for changing facing-direction of the concave side of the stirring elements. The stirring elements include smooth space curved stirring elements. The stirring elements are selected from helical elements, fan elements, and spiral elements.