Process for the production of fermentable sugars from biomass

A process for the production of fermentable sugars from cellulose-containing biomass, the process comprising the steps of:

• (a) treating the biomass with a dilute acid capable of dissolving hemicellulose wherein the time and temperature of the treatment and the acid strength are selected so as to obtain a liquid phase containing most of the biomass hemi-cellulose and a solid phase containing most of the biomass cellulose.
• (b) separating the cellulose-containing solid phase from the liquid base,
• (c) subjecting the resulting solid phase to rapid pyrolysis at atmospheric pressure and at a temperature in the range 400.degree. C.-600.degree. C. so as to obtain a crude product containing sugars and anhydrosugars, in a reactor where the residence time of pyrolytic vapors is less than about 2 seconds,
• (d) adjusting the water content of the crude product to form an aqueous phase containing fermentable carbohydrates and a water-insoluble phase, and
• (e) separating the aqueous phase from the water-insoluble phase.