Vehicle transportation makes up for a large proportion of global greenhouse gas emissions and is a major contributor of the climate crisis. Even though bikes emit practically no greenhouse gases, the production phase still cause environmental damages. Especially the choice of materials dictates the sustainability of a bike. Thus, the aim of this project is to problematize the current material choices made in the bike industry and explore how sustainable materials can be applied in a product-oriented industry to find sustainable design solutions. The material used in the project is provided by PaperShell Industries that supply a cellulose based and circular material for B2B. In order to fulfil the aim of the project a bike saddle was designed. The theory of circular design was guiding the design process, and various methods was applied. Focus groups were combined with co-designing in an innovation process. The design process was divided into three parts: research, ideation, and realisation. In the first part, focus groups, benchmarking, research ergonomics and research through design were conducted. The second part included brainstorming, mind mapping/tree diagram and moodboard. In the final step sketches and CAD-models were made and an innovation process was applied. Following this design process, the author concluded that fully cellulose based materials are suitable for the bike industry because of the low climate impact. The material also has the right properties for a bike product. The project suggests that circular design can be realized by implementing sustainable materials such as cellulose based materials,