NOVELTY - Production of a pretreated feedstock (A) comprises: providing (A); wetting (A) in an aqueous stream to produce a wet (A) (I); pressing (I) through one or series of roll presses to remove a portion of water and soluble substances and to shear (I) to produce a pressed (A); slurrying the pressed (A) to produce a slurried (A); and carrying out dilute acid pretreatment of the slurried (A) to produce pretreated (A).    USE - The process is useful to produce pretreated feedstock that is hydrolyzed by cellulase enzymes to produce glucose, which is fermented to ethanol (claimed).    ADVANTAGE - The process is a continuous process with continuous feeding of (A) and continuous withdrawal of the pretreated (A) (claimed). The process is economically and commercially viable; reduces the alkalinity of the feedstock, which decreases the acid requirements and degradation of sugar products; requires much less power input and cost than a dry grinding process; reduces the particle size of feedstock without requiring excessive power or capital equipment; and produces feedstock that is pumpable with a minimal amount of aqueous solution. The process is effective on a wide variety of feedstocks that are available in large quantity at low cost and contain high levels of carbohydrates, which correspond to a high potential ethanol yield.    DETAILED DESCRIPTION - Production of a pretreated feedstock (A) comprises: providing (A) (grasses, cereal straws and/or stover), where (A) (80%) has a particle length of 2-40 cm; wetting (A) in an aqueous stream at 0.25-10 times the maximum water holding capacity of (A) to produce a wet (A) (I); pressing (I) through one or series of roll presses (comprising rolls with circumferential v-shaped grooves) to remove a portion of water and soluble substances and to shear (I) to produce a pressed (A) (having a particle size such that, when pressed (A) (having a consistency of 35% dry solids after passing through a nip point in the one or more roll press in the series) is slurried to produce a slurried (A), which is capable pumping at a dry solids (8-20%)); slurrying the pressed feedstock particles to produce a slurried feedstock (having a dry solids (8-20%)), which is pumped into a pretreatment reactor; and carrying out dilute acid pretreatment of the slurried feedstock at 160-280degreesC to produce pretreated (A).