This project addresses the need for sustainable materials in response to environmental degradation caused by human activity, particularly since the mid-20th century. Organic waste, such as Posidonia oceanica, significantly contributes to pollution and greenhouse gas emissions. The designer’s role in addressing these challenges is highlighted, focusing on repurposing Posidonia oceanica waste into new materials. The study investigates the transformation of organic waste into usable composites, examining the feasibility of creating sustainable materials with unique properties. The primary goal is to use Posidonia oceanica waste as reinforcement in composite materials. Specific objectives include experimenting with biocomposites using mycelium, bio-cooking processes with gelatin, agar-agar, and Posidonia. The project follows five stages: information gathering and analysis, experimentation, testing, results compilation, and final documentation. A material innovation methodology, alongside non-standardised tests, was employed to confirm the hypothesis that a composite material could be made from Posidonia oceanica waste, including data on its potential combinations with other materials.