A method for the production of a biodegradable foamed product 7 from a base material and a blowing agent 1. The base materials are mixed with a blowing agent and any other required additives 1. The mixture 3, after extrusion 2, is placed in a microwave transparent mold 6 and processed in a microwave via distinct steps. The first step preheats the extrudate to a temperature just below the flash point 6. The second step 7 rapidly heats the extrudate beyond the flash point causing the extrudate to foam in the mold 7. By utilizing this method it is possible to produce shaped articles with uniform properties and with packaging properties such as compressibility, resilience and shock absorption.