NOVELTY - Producing (M1) a product alcohol involves: providing a feedstock slurry comprising fermentable carbon source, undissolved solids, and oil; separating a portion of the undissolved solids and oil from the feedstock slurry where an aqueous solution comprising fermentable carbon source, a wet cake comprising solids and an oil stream are formed; and adding the aqueous solution to a fermentation broth comprising microorganisms.    USE - For producing a product alcohol selected from ethanol, propanol, butanol, pentanol, hexanol, and fused alcohols (claimed) in industrial and scientific applications such as fuels, reagents, and solvents; for separating feed stream components for improved biomass processing productivity; for removing oil from a fermentor feed stream in the production of fermentative alcohols, where butanol is used as an important industrial chemical with a variety of applications including use as a fuel additive, as a feedstock chemical in the plastics industry, and as a food-grade extractant in the food and flavor industry.    ADVANTAGE - The process and system remove undissolved solids and/or oil from feedstock slurry and improve the processing productivity and cost effectiveness. The improved productivity include increased efficiency of product alcohol production and/or increased extraction activity relative to processes and systems that do not remove undissolved solids and/or oil prior to fermentation. The process and system lead to increased extraction activity and/or efficiency in product alcohol production as a result of the removal of the undissolved solids, where the increased extraction efficiency includes stabilization of the partition coefficient, enhanced phase separation, enhanced mass transfer coefficient, operation at a lower titer, increased process stream recyclability, increased fermentation volume efficiency, increased feedstock load feeding, increased product alcohol titer tolerance of the microorganism, water recycling, reduction in energy, increased recycling of extractant, and recycling of the microorganism.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) separating (M2) feed stream components for improved biomass processing productivity involving: a) providing a feedstock slurry comprising fermentable carbon source and undissolved solids; b) separating at least a portion of the undissolved solids from the feedstock slurry where an aqueous solution comprising fermentable carbon source and a wet cake comprising solids are generated; c) contacting the wet cake with a liquid to form a wet cake mixture; and d) separating at least a portion of undissolved solids from the wet cake mixture where a second aqueous solution comprising fermentable carbon source and a second wet cake comprising solids are generated;    (2) separating (M3) feed stream involving: providing a feedstock slurry comprising fermentable carbon source, undissolved solids, and oil; separating at least a portion of the oil and undissolved solids from the feedstock slurry where an aqueous solution comprising fermentable carbon source, an oil stream; and a wet cake comprising solids are generated; and c) contacting the wet cake with a liquid to form a wet cake mixture; and d) separating at least a portion of undissolved solids and oil from the wet cake mixture where a second aqueous solution comprising fermentable carbon source, a second oil stream; and a second wet cake comprising solids are generated;    (3) a system comprising at least one liquefaction unit configured to liquefy a feedstock to create a feedstock slurry, where the liquefaction unit comprises: an inlet for receiving the feedstock; and an outlet for discharging a feedstock slurry, where the feedstock slurry comprises fermentable carbon source, oil, and undissolved solids; and at least one separation unit configured to remove the oil and undissolved solids from the feedstock slurry to create an aqueous solution comprising the fermentable carbon source, an oil stream, and a wet cake comprising the portion of the undissolved solids, the centrifuge comprises: an inlet for receiving the feedstock slurry; a first outlet for discharging the aqueous solution; a second outlet for discharging the wet cake; and a third outlet for discharging the oil.