NOVELTY - Producing energy-dense biomass from cellulosic biomass, involves: providing feedstock comprising cellulosic biomass; extracting the feedstock with steam and/or hot water to produce an extract liquor containing each of hemicellulosic oligomers, lignin, and cellulose-rich solids; separating at least a portion of the cellulose-rich solids from the extract liquor to produce dewatered cellulose-rich solids; hydrolyzing the dewatered cellulose-rich solids, thus removing a portion of cellulose contained in it to produce intermediate solids and hydrolysate; and drying the intermediate solids.    USE - For producing energy-dense biomass used for producing biomass pellets from cellulosic biomass, in particular from agricultural residue; for recovering fermentable hemicellulosic sugars for producing a fermentation product (all claimed). The agricultural residues include corn stover, corn fiber, wheat straw, sugarcane bagasse, rice straw, oat straw, barley straw, miscanthus, and/or energy cane.    ADVANTAGE - The biomass pellets produced by the process have an energy content of 8500-12000 Btu/lb, preferably at least 10000 Btu/lb, on a dry basis. The present process prepares energy-dense biomass for combustion, while also recovers fermentable sugars from the starting biomass. The process prepares energy-dense biomass having improved combustion, with or without first pelletizing the biomass. The energy-dense biomass produced is capable of being fired alone or in combination with another solid fuel. The process also has good potential to recover various co-products, such as fermentable sugars, fertilizers, and lignin. The energy-dense biomass can be pelletized into biomass pellets, which have a similar energy density as torrefied pellets from wood. The hemicellulosic oligomers can be further hydrolyzed to produce additional fermentable sugars. The fermentable sugars can be fermented to ethanol or another product.    DETAILED DESCRIPTION - Process for producing energy-dense biomass from cellulosic biomass, involves: a) providing a feedstock comprising cellulosic biomass; b) extracting the feedstock with steam and/or hot water under effective extraction conditions to produce an extract liquor containing each of hemicellulosic oligomers, lignin, and cellulose-rich solids; c) separating at least a portion of the cellulose-rich solids from the extract liquor to produce dewatered cellulose-rich solids; d) hydrolyzing the dewatered cellulose-rich solids, thus removing a portion of cellulose contained in it to produce intermediate solids and a hydrolysate; and e) drying the intermediate solids to produce energy-dense biomass. An INDEPENDENT CLAIM is included for a process for producing biomass pellets from cellulosic biomass, involving: the steps (a)-(e); and f) pelletizing the energy-dense biomass to form the biomass pellets.    DESCRIPTION OF DRAWING(S) - The figure shows a simplified block-flow diagram depicting the process, where energy-dense biomass is produced optionally with fermentable sugars derived from mild hydrolysis of cellulose-rich solids.