The widespread use of synthetic plastics which are commonly obtained from fossil-fuels entails severe environmental issues, associated with the steady depletion of fossil-fuels and the enormous stream of non-degradable waste generated. As a consequence, current trends in the food packaging sector are fostering the development of more sustainable biopolymeric materials, i.e. derived from renewable resources. In this sense, several terrestrial sources have been used in the extraction of biopolymers such as starch or gluten from corn, rice or wheat. However, these sources compete with their primary food use and different options need to be evaluated. In this context, marine sources and specially seaweed waste biomass can be considered a promising alternative. This is the case of Posidonia oceanica, an endemic plant of Mediterranean Sea whose leaves constitute a residue which is detrimental for the quality of the beaches. Consequently, this waste biomass can give a propitious alternative to conventional plastics generating renewable and biodegradable biopolymers without interfering in any other purpose of its raw material.