The upcycling of waste biomass into valuable materials by resource-efficient chemical transformations is a prime objective for sustainable chemistry. This approach is demonstrated in a straightforward light-driven synthesis of polyols and polyurethane foams from the multi-ton waste products of cashew nut processing. The photo-oxygenation of cardanol from nutshell oil results in the formation of synthetically versatile hydroperoxides. The choice of the workup method (i. e., reduction, hydrogenation, epoxidation) enables access to a diverse range of alcohols with tunable alkene and OH functions. Condensation with isocyanates to give rigid polyurethane foams provides a resource-efficient waste-to-value chain that benefits from the availability of cardanol and installation of OH groups from aerial O2.