A combustion kiln system, comprising: a pre-heating chamber which pre-heats supplied waste product; a combustion chamber which receives the pre-heated waste product from the pre-heating chamber and in which the pre-heated waste product is incinerated; wherein the pre-heating chamber comprises a cavity through which the supplied waste product is displaced and includes a plurality of air inlets which feed heated air into the cavity of the pre-heating chamber and a plurality of vents through which a gas stream is vented, wherein the pre-heating chamber is adapted to heat the supplied waste product to remove moisture from the supplied waste product prior to transfer to the combustion chamber and maintain a temperature within at least an upstream region of the cavity of the pre-heating chamber at less than 600 °C, such that the moisture is removed from the supplied waste product without any substantial release of chlorides from the supplied waste product; wherein the combustion chamber comprises a cavity, a transfer mechanism which provides a grate at a floor of the combustion chamber and transfers the pre-heated waste product through a combustion zone, and a plurality of air supplies (81a-d) which supply air to the cavity of the combustion chamber; a first heat exchanger which is fluidly connected to the combustion chamber and utilizes heat of a heated gas stream from the combustion chamber; characterised in that the combustion kiln system further comprises a second heat exchanger which is fluidly connected to the pre-heating chamber and utilizes heat of the gas stream from the pre-heating chamber, wherein an outlet of the second heat exchanger is fluidly connected to an inlet of the first heat exchanger, whereby the second heat exchanger pre-heats a fluid medium and the first heat exchanger receives the pre-heated heated fluid medium from the second heat exchanger and further heats the pre-heated fluid medium to provide a superheated fluid medium. a pre-heating chamber which pre-heats supplied waste product; a combustion chamber which receives the pre-heated waste product from the pre-heating chamber and in which the pre-heated waste product is incinerated; wherein the pre-heating chamber comprises a cavity through which the supplied waste product is displaced and includes a plurality of air inlets which feed heated air into the cavity of the pre-heating chamber and a plurality of vents through which a gas stream is vented, wherein the pre-heating chamber is adapted to heat the supplied waste product to remove moisture from the supplied waste product prior to transfer to the combustion chamber and maintain a temperature within at least an upstream region of the cavity of the pre-heating chamber at less than 600 °C, such that the moisture is removed from the supplied waste product without any substantial release of chlorides from the supplied waste product; wherein the combustion chamber comprises a cavity, a transfer mechanism which provides a grate at a floor of the combustion chamber and transfers the pre-heated waste product through a combustion zone, and a plurality of air supplies (81a-d) which supply air to the cavity of the combustion chamber; a first heat exchanger which is fluidly connected to the combustion chamber and utilizes heat of a heated gas stream from the combustion chamber; characterised in that the combustion kiln system further comprises a second heat exchanger which is fluidly connected to the pre-heating chamber and utilizes heat of the gas stream from the pre-heating chamber, wherein an outlet of the second heat exchanger is fluidly connected to an inlet of the first heat exchanger, whereby the second heat exchanger pre-heats a fluid medium and the first heat exchanger receives the pre-heated heated fluid medium from the second heat exchanger and further heats the pre-heated fluid medium to provide a superheated fluid medium.