Asphalt mixtures rely heavily on petroleum-based bitumen. The extraction and refining of bitumen generate significant greenhouse gas emissions during production. They deplete non-renewable resources and maintain cost dependency on crude oil. To address these issues, bitumen is often modified or partially replaced with alternative additives, including bio-materials. These introduce new opportunities but also uncertainties regarding the structure, chemistry, and rheology of bituminous binders. BIOBIT, an international trilateral research project, comes to identify suitable bio-materials and evaluate their impact on the performance of bituminous binders and asphalt composites. The project will investigate whether bio-materials enhance or weaken overall binder performance, and what proportions can be added without compromising structural, chemical, or rheological integrity. Additives may lead to enhanced, optimum, or mediocre performance, making it essential to define thresholds or ranges that ensure durability and efficiency. The project will also investigate handling, mixing, and ageing behaviour of bio-modified bitumen, while addressing concerns about toxicity, environmental degradation, and recyclability. Via this sustainable approach, bio-derived materials can be incorporated into bitumen. The optimum goal is to achieve scalable, high-performing bio-based bitumen that contributes to a circular economy. This collaborative initiative between Warsaw University of Technology, the University of Antwerp, and TU Wien brings together diverse expertise to pioneer sustainable infrastructure solutions.