A method of drying and pyrolysing a carbon-containing feedstock in a reaction chamber that is thermally insulated and gas sealed, having one or more inlet ports in an upper portion thereof above a top of the carbon-containing feedstock, and one or more outlet ports in a lower portion thereof below the top of the carbon-containing feedstock, the one or more inlet ports being connected to an oxygen containing gas source to thereby facilitate the supply of oxygen containing gas to the reaction chamber, the one or more outlet ports enabling gases generated within the reaction chamber to escape the reaction chamber after percolating downwards through the carbon-containing feedstock, the method including the steps of: loading a batch of the carbon-containing feedstock into the reaction chamber through a resealable hatch; providing a controlled flow of oxygen containing gas to the reaction chamber from the oxygen containing gas source via the one or more inlet ports and operating an ignition source thereby to initiate combustion of a top portion of the feedstock to provide heat for drying and pyrolysing the remaining feedstock in the chamber; maintaining the combustion after the combustion has been initiated by controlling the flow of oxygen -containing gas, such that hot gaseous combustion products percolate downwards through the solid carbon-containing feedstock transferring heat to a bulk of the solid carbon-containing feedstock and raising a temperature thereof to a point where pyrolysis reactions commence and an increasing volume of pyrolysis product gases are released into the reaction chamber and those pyrolysis product gases which flow to the upper portion of the chamber undergo combustion with the oxygen-containing gas available directly in the vicinity of the inlet ports; thereafter reducing the flow rate of the oxygen-containing gas to establish a zone or region of volatiles combustion involving complete consumption of all incoming free oxygen in the upper region of the reaction chamber with no free oxygen available to contact the remaining solid carbon-containing feedstock, the volatiles combustion generating a net flow of hot combustion product gases downwards through the bulk of the pyrolysing carbon-containing feedstock 1 serving to heat the bulk and drive the drying process and pyrolysis reactions; regulating the flow of oxygen-containing gas entering the chamber inlet in response to temperature measurements within the reaction chamber, to achieve and maintain a minimum target temperature measured near a bottom of the reaction chamber within a range of 150°C to 600°C while not exceeding a maximum temperature measured at the upper region of the reaction chamber within a range of 500°C to 1000°C; and stopping the flow of oxygen -containing gas and allowing the system to cool, then unloading the pyrolysed batch of carbon-containing feedstock through the resealable hatch. loading a batch of the carbon-containing feedstock into the reaction chamber through a resealable hatch; providing a controlled flow of oxygen containing gas to the reaction chamber from the oxygen containing gas source via the one or more inlet ports and operating an ignition source thereby to initiate combustion of a top portion of the feedstock to provide heat for drying and pyrolysing the remaining feedstock in the chamber; maintaining the combustion after the combustion has been initiated by controlling the flow of oxygen -containing gas, such that hot gaseous combustion products percolate downwards through the solid carbon-containing feedstock transferring heat to a bulk of the solid carbon-containing feedstock and raising a temperature thereof to a point where pyrolysis reactions commence and an increasing volume of pyrolysis product gases are released into the reaction chamber and those pyrolysis product gases which flow to the upper portion of the chamber undergo combustion with the oxygen-containing gas available directly in the vicinity of the inlet ports; thereafter reducing the flow rate of the oxygen-containing gas to establish a zone or region of volatiles combustion involving complete consumption of all incoming free oxygen in the upper region of the reaction chamber with no free oxygen available to contact the remaining solid carbon-containing feedstock, the volatiles combustion generating a net flow of hot combustion product gases downwards through the bulk of the pyrolysing carbon-containing feedstock 1 serving to heat the bulk and drive the drying process and pyrolysis reactions; regulating the flow of oxygen-containing gas entering the chamber inlet in response to temperature measurements within the reaction chamber, to achieve and maintain a minimum target temperature measured near a bottom of the reaction chamber within a range of 150°C to 600°C while not exceeding a maximum temperature measured at the upper region of the reaction chamber within a range of 500°C to 1000°C; and stopping the flow of oxygen -containing gas and allowing the system to cool, then unloading the pyrolysed batch of carbon-containing feedstock through the resealable hatch.