The present invention provides an apparatus and a method for conversion of cellulosic material, such as chopped
straw and
corn stover, and household waste, to
ethanol and other products. The cellulosic material is subjected to continuous hydrothermal pre-treatment without addition of chemicals, and a liquid and a
fiber fraction are produced. The
fiber fraction is subjected to enzymatic
liquefaction and saccharification. The method of the present invention comprises:performing the hydrothermal pre-treatment by subjecting the cellulosic material to at least one soaking operation, and conveying the cellulosic material through at least one pressurized reactor, and subjecting the cellulosic material to at least one pressing operation, creating a
fiber fraction and a
liquid fraction;selecting the temperature and
residence time for the hydrothermal pretreatment, so that the fibrous structure of the feedstock is maintained and at least 80% of the
lignin is maintained in the fiber fraction.