Nowadays, plastic foam materials exhibit massive environmental problem because petroleum based foams are difficult and expensive to recycle. This induces huge opportunities for biodegradable or renewable polymers and a lot of effort has been made to improve the development of biodegradable foams. The purpose of this work is to develop renewable biodegradable cushion foams with comparable mechanical characteristics with the commercial petroleum plastic foams such as the ones made of polyethylene, polystyrene, polyether... These foams were made with natural starch, and formed with a “Clextral BC21” co-rotating twin-screw extruder machine, equipped with a rectangular die. The originality of this work is that the foams are tailored as rectangular plates that could be thermoformed, and not as rounded chips that are already available in the market. Different process parameters were tested and several physical techniques were exercised on the resulted starch based foams to identify their cellular structure characteristics, their mechanical properties and their biodegradability (cushion curve tests, dynamic mechanical analysis “DMA”, bulk density, expansion ratio, foam microstructures and biochemical oxygen demand analysis “BOD”). The first results showed a comparable physical properties between our starch based foams and the commercial packaging plastic foams based on polystyrene and polyethylene. Then we studied the influence of the formula (the ratio between plasticizer and starch, the amount of natural fibers, the type of additives for expansion…), the process parameters on the quality of the expansion, the thickness of the cell membranes and the compression behavior.