NOVELTY - A system (10) to evacuate biomass from chamber (12) having at least two walls each corresponding to associated wall plane comprises grating (28), knife (24), at least two parallel knife guides and two elongated and flexible traction elements. The grating extends between two of wall planes and forming bottom of chamber. The knife has elongated main blade portion extending between two of wall planes. The traction element is pullable collaboratively to move knife along the knife path. A portion of biomass in chamber is evacuated through grating when knife is pulled along knife path.    USE - System to evacuate biomass from chamber having at least two walls each corresponding to associated wall plane.    ADVANTAGE - The system removes shovelable materials in elongated chamber from below.    DETAILED DESCRIPTION - System (10) to evacuate biomass from chamber (12) having at least two walls each corresponding to associated wall plane comprises grating (28), knife (24), at least two parallel knife guides and two elongated and flexible traction elements. The grating extends between two of wall planes and forming bottom of chamber. The knife has elongated main blade portion extending between two of wall planes. The elongated main blade portion has elongated cross-section oriented parallel to grating and two opposite downwardly sloping faces each leading to corresponding opposite cutting edge. The knife has at least two guiding units. Each guiding unit is positioned on corresponding side of elongated main blade portion. The at least two parallel knife guides receive corresponding guiding unit of the knife and collaborates in guiding knife along knife path (26) oriented parallel to both grating and wall when knife is moved along knife path. Each of the traction elements is connected to corresponding side of main blade portion. The traction element is pullable collaboratively to move knife along the knife path. A portion of biomass in chamber is evacuated through grating when knife is pulled along knife path.    DESCRIPTION OF DRAWING(S) - The drawing is a side elevation view illustrating an elongated chamber and system to evacuate materials.    System (10)    Chamber (12)    Knife (24)    Knife path (26)    Grating (28)