Abstract: Clogging and prolonged down times are avoided in a pelletizer for paste type materials such as sludge by providing an extruder hopper with at least one, preferably two, lower edge slide gates which can be opened to permit movement of a clogged screen zone out of alignment with the discharge opening of the hopper. The clogging material can be scraped off from the screen portion that is taken out of alignment with the hopper discharge opening. The cutting of the extruded sludge is accomplished by an oscillating lower screen section that slides back and forth below the upper screen section. The upper screen section is provided with two, preferably three zones, two of which are perforated and one of which is unperforated to form a closure for the hopper discharge opening. Screeding non-pelletizable material off the screen surface is accomplished either by a separate screeding device or by operating the slide gate or gates as screeds.