Global demand for food and bio-based products grows at a fast pace, and have led to the vision that natural resource use and emissions associated with modern systems can and should be substantially reduced by shifting towards a circular food system. To move towards a circular and climate-neutral society, implies minimizing the input of finite resources, encourage the use of regenerative ones, prevent leakages of natural resources (e.g. carbon), and stimulate the reuse and recycling of resources in a way that adds highest value. Carbon sequestration in shells locks away carbon which is unique for animal protein production, and it is therefore often compared to primary producers such as seaweed (marine) or forest (terrestrial) production. Just taking account for shell material, and not tissue, shows that carbon capture is somewhat in the lower range but still in the same order of magnitude compared forestry. Translating to theoretical monetary values (CO2 equivalents) indicates that carbon sequestration in shells only resembles a fraction of annual market revenues. As shells are now considered to be a waste product, the development of biobased products might add another (commercial) value to shellfish production, which at the same time may substitute fossil sources, e.g. in cement applications, adding to climate ambitions.