Pathways of Residual Straw for New Bio-Products Entailing Carbon Capture, Utilization & Storage Opportunities: Exploratory Case Study of Three Future Danish Pathways

Residual straw, a byproduct of cereal production, represents an underutilized biomass resource with significant potential to contribute to sustainable development and climate goals. This paper addresses the challenge of optimizing straw utilization in Denmark, focusing on its applications in renewable energy, materials production, and carbon storage. Guided by the principles of the circular bioeconomy (CBE), cascading upcycling, and carbon capture, utilization and storage (CCUS), the study investigates three case studies emphasizing: bio-refinery applications, biogas plant integration and prefabricated building materials. The theoretical framework emphasizes resource cascading to maximize the utility of straw across multiple applications. The methodology combines an exploratory case study approach with literature review and comparative analysis to evaluate the resource usage and environmental benefits of each pathway. The Bio-Refinery case demonstrates the potential to produce high-value products, such as prebiotics, ethanol and lignin, but highlights challenges related to scalability and high investment costs. The Biogas Plants case shows the highest cascading value today, efficiently integrating straw into renewable energy production, recycling nutrients through digestate and utilizing captured CO? for bio-product manufacturing. The Prefabricated Wall’s case offers long-term carbon storage but entails only one cascading step, while production is located outside Denmark, which limits its current contribution to the CBE. The findings indicate that biogas plants provide the most immediately feasible pathway due to their broad cascading profile and existing infrastructure, while the long-term potential of straw-based building materials requires the establishment of local production. A balanced strategy that integrates CCUS with cascading upcycling and CBE principles is essential for maximizing the environmental and economic benefits of straw utilization.