Pyrolysis as a complementary technology in the circular tire economy

Willich, Germany – End-of-Life tires (ELTs) contain valuable raw materials. One of these is carbon black (CB), an industrially produced material that plays a crucial role in determining tire properties. In his doctoral dissertation, “Production and Environmental Assessment of High-Quality Carbonaceous Materials from End-of-Life Tire Pyrolysis,” Dr.-Ing. Sebastian Bogdahn investigated how recovered carbon black (rCB) can be produced from ELTs through pyrolysis and assessed the environmental impacts of the process. Bogdahn presented a condensed version of his dissertation defense presentation at a meeting of the AZuR Chemical Recycling Project Group in Dillingen/Saar on October 1, 2026.

Bogdahn’s dissertation addresses a fundamental question: How can End-of-Life tires be recovered and recycled to maximize their value? He identifies ELT pyrolysis as a complementary technology that can help close recycling gaps within the circular economy while providing an alternative to fossil-based carbon black (CB).

During pyrolysis, rubber granules obtained from processed ELTs undergo thermal decomposition in the absence of oxygen. The process produces three primary output streams: solid recovered carbon black (rCB), tyre pyrolysis oil (TPO), and pyrolysis gas.

Until now, technologies such as ELT pyrolysis have generally been evaluated separately from technical and environmental perspectives. Furthermore, life cycle assessments (LCAs) frequently rely on secondary data or published literature, and standardized assessment methodologies are often lacking. As a result, the findings are difficult to compare.

Bogdahn addresses these limitations by integrating a technology-specific process model with a detailed life cycle assessment model. This integrated approach enables a scientifically robust environmental assessment of ELT pyrolysis and the resulting secondary raw materials using reliable primary data.

A central technological component of the dissertation is the development of a process model that mathematically describes the material conversion occurring during pyrolysis. The model combines reaction kinetics, reactor behavior, and mass and energy balances.

Starting with laboratory-scale experiments, Bogdahn scaled up the model and subsequently validated it using a pilot-scale rotary kiln at the Institute of TH Köln (Cologne University of Applied Sciences). Comprehensive laboratory analyses of feedstocks and products supported both model development and validation.

The validated model makes it possible to identify optimal operating conditions and adjust the equipment accordingly. For the system investigated, a temperature of 650°C (1,202°F) and a residence time of approximately one hour proved optimal.

Under these conditions, the process achieved complete material conversion while producing high-quality rCB. The resulting product distribution was approximately 40% rCB, 37% TPO, and 23% pyrolysis gas by weight. These results provide the technology-specific primary data used in the life cycle assessment. Although the findings apply to the particular system investigated, the methodological approach can also be transferred to other pyrolysis technologies.

The full dissertation by Dr.-Ing. Sebastian Bogdahn is freely available at: https://doi.org/10.25819/ubsi/10977