Hydrothermal-mechanical treatment of lignocellulosic biomass for production of fermentation products

A simple process for converting lignocellulosic biomass into fermentation products is disclosed. Biomass may be subjected to a steam or hot-water soak to dissolve hemicelluloses. This step is followed by mechanical refining， such as in a hot-blow refiner， of the cellulose-rich (and lignin-rich) solids. The refined solids are then enzymatically hydrolyzed to generate sugars. Certain embodiments provide a process for producing ethanol， comprising: digesting a cellulosic biomass feedstock with steam or hot water to produce cellulose-rich solids， hemicellulose oligomers， and lignin; conveying the digested stream through a blow-line refiner; separating a vapor from the refined stream; introducing the refined stream to an enzymatic hydrolysis unit to produce sugars; fermenting the sugars to produce ethanol in dilute solution; and concentrating the dilute solution to produce an ethanol product. Enzymes and microorganisms may be introduced at various points in the process. The invention may be applied to any other fermentation product.