Polymeric foams are used in many fields because they have a low density and they present insulation properties. Depending on the cell morphology of the foam, the applications are multiple. A closed-cell morphology foam is generally use for the packaging, construction or heat insulation whereas an open-cell morphology foam is preferably used for shock absorption, sound attenuation and tissue engineering. Combining extrusion with supercritical CO2 is an effective way to obtain foams with different morphologies. Indeed, depending on the operating conditions (T, P) and the CO2 solubility in the polymer, its injection into the barrel of an extruder will modify the rheological properties of the polymer melt. In addition, CO2 will act as a blowing agent upon depressurisation when flowing through the die. In our laboratory, this technology has shown great potential for the production of highly porous materials with different morphologies. In this study, we chose to work with a biobased and biodegradable polymer: the poly-(lactic acid). It is a thermoplastic biopolyester obtained by polymerisation of lactic acid, a molecule obtained by fermentation of renewable resource like corn starch that can substitute traditional petroleum based plastics. To promote foam with heterogeneous nucleation, starch was used as nucleation agent, giving a final product entirely made of a blend of biopolymers. The influence of several operating parameters on the foam properties has been studied: starch content, temperature and CO2 mass fraction. Foams with an expansion ratio greater than 20, that is a porosity over 95 %, have been obtained. Two different behaviours were observed for this high porosity: high open cell content with small cell size or low open-cell content with large cell size. The die temperature and the nucleating agent content have been identified as the most important parameters to tune the open cell content.