Abstract: The present invention provides methods for producing a mixture of sugars from a solid biomass feedstock using a counter current extraction apparatus and a dilute acidic solution.

Abstract: An apparatus to separate components of a solid feedstock is described. The apparatus may include a threaded shaft that has a plurality of reaction zone segments along the length of the shaft that are separated from each other by dynamic plug segments. The threads of the shaft have a first thread pitch in the reaction zone segments, and a second thread pitch in the dynamic plug segments. The apparatus may also include a motor to rotate the shaft, and an outlet coupled to a second end of the shaft, where one or more solid components of the solid feedstock exit the apparatus through the outlet. The apparatus may additionally include a feeder to supply the solid feedstock to the threaded shaft, and a pump to provide a rinse fluid to the threaded shaft, where the rinse fluid flows in the opposite direction of the solid feedstock along the shaft.