NOVELTY - Method (M1) for manufacturing ethanol from a particulate lignocellulosic biomass feedstock, involves subjecting a first amount of particulate lignocellulosic biomass feedstock to hydrolytic liquefaction under heated conditions to form a hot liquefied digest slurry, cooling hot liquified digest slurry by pumping the slurry through a first passage of a heat exchanger to transfer heat to a cooler liquid in a second passage of the heat exchanger, and fermenting xylose to ethanol after cooling.    USE - The method (M1) is useful for manufacturing ethanol. The method (M2) is useful for processing lignocellulosic biomass. The method (M3) is useful for recovering heat from pretreated lignocellulosic biomass (all claimed).    DETAILED DESCRIPTION - Method (M1) for manufacturing ethanol from a particulate lignocellulosic biomass feedstock, involves subjecting a first amount of particulate lignocellulosic biomass feedstock to hydrolytic liquefaction under heated conditions to form a hot liquefied digest slurry, cooling hot liquified digest slurry by pumping the slurry through a first passage of a heat exchanger to transfer heat to a cooler liquid in a second passage of the heat exchanger, and fermenting xylose to ethanol after cooling, where the slurry comprises (i) dissolved biomass components (10 wt.%) on a dry weight basis of the biomass feedstock, and xylose, and (ii) undissolved lignocellulosic biomass particulates comprising lignin and cellulose. INDEPENDENT CLAIMS are included for the following:    (1) method (M2) for processing lignocellulosic biomass, involves (a) incubating a mixture comprising a first amount of a solid, particulate lignocellulosic biomass and a first amount of a liquid processing medium containing at least one dicarboxylic acid under heated conditions effective to form a biomass digest composition exhibiting a lower yield stress than the mixture and in which at least 10 wt.% of the solid, particulate biomass is converted to dissolved biomass components in the liquid medium, and digest composition including undissolved lignocellulosic biomass particulates, passing a flowable liquid digest medium at least partially comprised of the dissolved biomass components and the undissolved lignocellulosic biomass particulate through a first passage of a heat exchanger when passing a second amount of a liquid processing medium containing at least one dicarboxylic acid through a second passage of the heat exchanger to transfer heat from the flowable liquid digest medium to the second amount of liquid processing medium to provide a preheated liquid processing medium, and combining the preheated liquid processing medium with a second amount of solid, particulate biomass, or (b) subjecting solid, particulate lignocellulosic biomass to acid-catalyzed liquefaction under heated conditions effective to form a biomass digest slurry in which at least 10 wt.% of the solid, particulate biomass has been converted to dissolved biomass components in the liquid medium, the digest composition also including undissolved lignocellulosic biomass particulates, and passing the biomass digest slurry through a first passage of a heat exchanger while passing a liquid medium through a second passage of the heat exchanger so as to transfer heat from the biomass digest slurry to the liquid medium; and    (2) method (M3) for recovering heat from pretreated lignocellulosic biomass, involves pumping a hot aqueous liquid digest slurry through a first passage of a heat exchanger at a linear velocity sufficiently high to cause the particulates to enhance the generation of turbulent flow, where the digest slurry is comprised at least 15 wt.% total biomass solids on a dry weight basis, and 10-45% of the total biomass solids are dissolved in the aqueous liquid, and recovering heat from the hot aqueous liquid digest slurry by transferring heat from the slurry to a fluid pumped through a second passage of the heat exchanger.