The invention relates to an apparatus and method for pyrolyzing a feedstock in an open container. The apparatus comprises a downer reactor with an entry located at the top end of the downer for feeding and an exit located at the bottom end of the downer for removing the container from the downer, the downer being divided into at least three vertically arranged zones by at least two locking systems on either side of a middle pyrolysis zone, wherein the at least two locking systems are configured to simultaneously close for sealing the pyrolysis zone, wherein the at least two locking systems are further configured to let through the container in an open position, the apparatus comprising heating means, cooling means and pressurizing means configured to adjust the temperature and pressure of at least the pyrolysis zone independently from the other zones
