A method to process lignocellulosic biomass into ethanol under conditions of high biomass loading is disclosed. Pretreatment of biomass was conducted at a high concentration of solids but with a relatively low concentration of ammonia relative to the dry weight of biomass. The pretreated biomass was washed to remove inhibitors and to minimize the carry-over of the inhibitors to the subsequent steps of saccharification and fermentation. The pretreated-washed biomass is ground at some point prior to saccharification. Enzymes are added to allow saccharification and biomass liquification. More solids are added in a fed-batch manner as saccharification proceeds to ultimately obtain fermentation of a high-biomass concentration and get a higher ethanol titer. The amount of solids added in the fed-batch is such that the process achieves optimum hydrolysis to sugars by the saccharification enzymes.
 This invention was made with the United States government support under contracts No. DE-FG36-04G014236 and DE-FG36-04G085007 awarded by the Department of Energy. The United States government has certain rights in this invention.