A device for conveying inhomogenous solid matter, particularly biomass, includes an endless screw. The endless screw is located in a sleeve fitted with a counter screw, which allows better transportation, and the possible creation of a plug of compressed material at predetermined points on the screw, which isolates the device from the outside. The device can be coupled with at least one other endless screw, which can be put under a pressure greater than the device. The screw erodes the plug and transports the matter so obtained, for example to a pressurized reactor. With the device, a pressure difference between for example a raw material storage tank and a reactor does not lead to excessive cost in terms of pressurizing gas.