Evolving policy frameworks and social pressure for more sustainable circular products stipulate new requirements for the product development process. Thus, the Design for X (DfX) processes are adapted for these requirements and applied to a case study that aims to transition a conventional bicycle helmet to a fully circular product that adheres to the Cradle to Cradle principle with a biological cycle. The DfX processes and the resulting considerations are utilized to investigate and overcome the challenges posed by the application of biological materials, such as mycelium, to a massproduced B2C product. Thereby the concept for a suitable composite comprising of several organic materials is conceived and tested. A new manufacturing process capable of massproducing helmets with said composite is developed with the DfX processes to make the concept economically viable. Initial drop-tests of helmet prototypes prove that the redesigned helmets have similar protective damping features to conventional helmets, and thus are functionally viable. The successful development of the bicycle helmet case provides evidence that the adaptation of the holistic DfX approach is feasible for overcoming the challenge of product development processes with increasingly complex new requirements.