The invention is related to a method for processing biomass derived from plants or animals, comprising the steps of: a. pre treating said material with an aqueous solution of acid or base; b. subsequently passaging saturated or super heated steam through said material, wherein the water activity of the process is controlled by means of temperature and pressure of the super heated steam to be less than 1, preferably less than 0.8, more preferably in the range of 0.4-0.8. With such a process it is possible to disintegrate or make more accessible for subsequent treatments the lignocellulose from lignocellulose containing materials, like wood or other plant material, chitin from exoskeletons from Crustacea like crabs and shrimps, and proteins such as keratin from pig hair or chicken feather, for further derivation, like acylation, oxidation, etherification, carboxymethylation or esterification, or further enzymatic hydrolysis, and/or for production of chemicals, e.g. as sugars from carbohydrates for fermentation processes such as the production of (bio-) ethanolor as keratine hydrolysates for applications in paper or cosmetics.