A method for thermal decomposition of carbon-rich substances. Pyrolysis is used to transform substances into a synthetic gas. Bulk material including carbon enriched substances flows vertically in succession through an upper column, a moving bed reactor having an upper hollow chamber in the top thereof, a lower hollow chamber and a lower column, wherein the bulk material from the moving bed reactor is removed through the lower column. Pyrolysis is performed in the moving bed reactor and the synthetic gas is collected in the upper hollow chamber. The width and height of the upper and lower columns and the nature of the bulk material have an internal pressure loss which seals off the movable bed reactor and enables a continuous or batch-wise flow of bulk material. The pressure difference between the lower hollow chamber and the upper hollow chamber is at least 50 mbar. The pressure difference is stabilized by the bulk material inside the moving bed reactor.