In the last few years, biomaterials have been a target of interest at scientific, technological research and industrial level. The increasing of the environmental concern and the excessive use of petrol resources have conducted to the development of new biocomposites which will achieve a great importance into the future. It’s a fact that, allied to weight reduction, the automotive industry can benefit from the inclusion of these materials in cars, not only because of the installed fear of decline and extinction of oil reserves, but also because of the strong legislation that forces an increasing incorporation of these materials in automobiles. This topic presents a big potential because it seeks to find solutions for a sustainable development with environmental concerns in order to be able to obtain biodegradable solutions for the interior door trims. This book presents a study for replace the petrol-base polymers used in interior trims for a biocomposite made of a Poly(Lactic Acid) and Polyhydroxyalkanoate (PLA/PHA) thermoplastic matrix reinforced with cellulosic fibers without change the common technological used process - Injection moulding.