A method of producing a biodegradable foamed product with qualities of uniformity of mechanical and physical properties throughout the product including: a finished foam thickness of up to 1 metre; a finished foam surface suitable for packaging applications; the method including the steps of: (a) preparing a bio-degradable raw material ready for foaming by an extrusion process; (b) placing the material into a mould to form a work piece; (c) placing at least one workpiece into a microwave cavity, wherein the microwave cavity includes: (i) a selection of one or more magnetrons focused on cavity with a total power density of up to 10W/cm 3; (ii) a selection of one or more magnetrons by pre-determination of working volume, final product shape and mould shape; (d) microwaving at least one said work piece to form a bio-degradable foamed product; wherein said mould comprises a susceptor comprising a microwave interactive material, characterized in that the microwave interactive material is dispersed throughout the mould of step (b); such as to enable the internal surface of the mould to be heated uniformly by microwave radiation wherein the susceptor reaches steady state operating conditions, where the maximum surface temperature is from 80°C to 140°C such a temperature being greater than a melt temperature of said material being foamed in said mould and high enough to prevent vapour condensation on the surface of the foamed article. a finished foam thickness of up to 1 metre; a finished foam surface suitable for packaging applications; the method including the steps of: (a) preparing a bio-degradable raw material ready for foaming by an extrusion process; (b) placing the material into a mould to form a work piece; (c) placing at least one workpiece into a microwave cavity, wherein the microwave cavity includes: (i) a selection of one or more magnetrons focused on cavity with a total power density of up to 10W/cm 3; (ii) a selection of one or more magnetrons by pre-determination of working volume, final product shape and mould shape; (d) microwaving at least one said work piece to form a bio-degradable foamed product; wherein said mould comprises a susceptor comprising a microwave interactive material, characterized in that the microwave interactive material is dispersed throughout the mould of step (b); such as to enable the internal surface of the mould to be heated uniformly by microwave radiation wherein the susceptor reaches steady state operating conditions, where the maximum surface temperature is from 80°C to 140°C such a temperature being greater than a melt temperature of said material being foamed in said mould and high enough to prevent vapour condensation on the surface of the foamed article. (a) preparing a bio-degradable raw material ready for foaming by an extrusion process; (b) placing the material into a mould to form a work piece; (c) placing at least one workpiece into a microwave cavity, wherein the microwave cavity includes: (i) a selection of one or more magnetrons focused on cavity with a total power density of up to 10W/cm 3; (ii) a selection of one or more magnetrons by pre-determination of working volume, final product shape and mould shape; (i) a selection of one or more magnetrons focused on cavity with a total power density of up to 10W/cm 3; (ii) a selection of one or more magnetrons by pre-determination of working volume, final product shape and mould shape; (d) microwaving at least one said work piece to form a bio-degradable foamed product; wherein said mould comprises a susceptor comprising a microwave interactive material, characterized in that the microwave interactive material is dispersed throughout the mould of step (b); such as to enable the internal surface of the mould to be heated uniformly by microwave radiation wherein the susceptor reaches steady state operating conditions, where the maximum surface temperature is from 80°C to 140°C such a temperature being greater than a melt temperature of said material being foamed in said mould and high enough to prevent vapour condensation on the surface of the foamed article.