Sustainable carbon fibers for the energy transition

The Carbon Lab Factory Lausitz (CLFL) plays a key role in the structural transformation of the Lausitz region and is set to become a lighthouse project for the production of sustainable, cost-effective and competitive carbon fibers in Europe. This unique infrastructure is designed to map the entire value chain—from bio-based raw materials to technical textiles and high-performance components. The cross-state collaboration between Saxony and Brandenburg was initiated by the Fraunhofer Institute for Applied Polymer Research IAP in the Potsdam Science Park, the Institute for Lightweight Structure at Chemnitz University of Technology, and the Institute of Lightweight Design and Value-added Management at Brandenburg University of Technology Cottbus-Senftenberg.

The Fraunhofer IAP contributes its extensive expertise in developing spinning processes for the production of bio-based fibers, including the optimization of raw materials and carbonization technologies. Pilot-scale spinning systems for producing white precursor fibers and lab-scale carbonization units have been in successful operation at the Potsdam site for many years. As part of CLFL, Fraunhofer IAP is now building a pilot-scale carbonization plant (Black Line) and a pilot precursor fiber production line (White Line) in Brandenburg.

The BTU Cottbus-Senftenberg / Institute of Lightweight Design and Value-added Management is developing bio-based sizing systems tailored to the novel carbon fibers in order to fully exploit their reinforcement potential in later applications and to achieve the most ecological overall system possible. In addition, the institute is conducting research on environmentally friendly composites made from modified natural fibers combined with residual or bio-based matrices, offering a sustainable alternative to conventional material systems such as glass fiber reinforcements. To ensure future viability, the department is also actively involved in educating and training school students from the Lausitz region on these topics.

The development at Fraunhofer IAP and BTU Cottbus-Senftenberg is being funded by the Federal Office for Economic Affairs and Export Control (BAFA) with personnel funding totaling five million euros over four years through June 2027 (funding reference: 46SKD154A/B). Personnel funding is provided by the German Federal Ministry for Economic Affairs and Energy (BMWE) under the STARK program for strengthening transformation dynamics and revitalization in lignite mining areas and power plant regions.

The Chemnitz University of Technology  / Institute for Lightweight Structure is establishing a carbonization pilot plant (Black Line) in Boxberg/Saxony, which will serve as a satellite facility of the university. In order to map the entire industry-oriented production chain through to the final component, the novel carbon fibers will be further processed and researched on a pilot scale into two-dimensional technical textiles, thermoplastic tapes, and profiles. The project budget of over 62 million euros is being provided by the Saxon State Ministry for Infrastructure and the Saxon State Ministry for Regional Development.

The Carbon Lab Factory Lausitz represents a globally unique research and development environment that encompasses every step from material development to market-ready products:

Raw material

• development and synthesis of innovative materials for precursor fibers
• biogenic raw materials (e.g., cellulose)  
• pilot project (existing buildings / Schkopau)

Spinning fibers

• production of the precursor fiber
• development of spinning processes
• modification of fibers using catalysts and additives
• plant scale: (existing facility / Potsdam) 
• pilot scale: (NEW / Guben)

Carbon fibers

• development of thermomechanical processes (30 to 3,000 °C)
• surface activation and finishing of the fiber
• laboratory scale: (existing facility/ Potsdam)
• plant scale: (NEW / Guben)
• pilot scale: (NEW / Boxberg)

Components

• carbon fiber reinforced plastic (CFRP)
• fabrics and woven fabrics
• tapes und profile

The Carbon Lab Factory Lausitz is integrated into the research infrastructure in the Lausitz region, where, for example, the Lausitz Science Park serves as a future hub for joint initiatives with local innovation drivers.

The Lausitz Science Park is an emerging research and business park located in the vicinity of the Brandenburg University of Technology Cottbus–Senftenberg in Cottbus, Germany. Its goal is to closely connect research institutions, companies, and spin-offs in one location in order to strengthen innovation, technology transfer, and economic development in the Lusatia region.

The park focuses on several future-oriented fields: energy transition and decarbonization, health and life sciences, global change and transformation processes, as well as artificial intelligence and sensor technologies. In this environment, scientific institutions, transfer initiatives, and industrial partners collaborate. These include, among others, the Center for Hybrid Electric Systems Cottbus, the Energy Innovation Center, and the DLR Institute of Electrified Aircraft Propulsion, as well as industrial partners such as LEAG, BASF Schwarzheide, Deutsche Bahn, and Rolls-Royce.

The close spatial proximity of these actors enables early cooperation, joint development projects, and testing formats. In this way, the Lausitz Science Park acts as a central hub for networking and innovation within the innovation corridor between Lusatia and Berlin.

The site is being developed within the framework of Germany’s Structural Strengthening Act and is intended to attract new research institutions, start-ups, and small and medium-sized enterprises in the long term. This will create additional jobs and attractive working conditions for science, research, and technology-oriented companies. At the same time, the park contributes to retaining highly qualified professionals in the region and attracting new talent to Lusatia.

to the Lausitz Science Park

As a renewable raw material, cellulose offers significant environmental advantages over conventional fossil-based precursors such as polyacrylonitrile (PAN). In addition, its processing involves fewer toxic byproducts and less hazardous chemicals. The molecular base structure of cellulose is provided by nature itself – eliminating the need for the complex synthesis required for PAN.

Cellulose also offers remarkable flexibility: depending on the spinning technique and process parameters, various fiber – and later carbon fiber – structures can be tailored, such as orientation, crystallinity, diameter, cross-sectional shape, surface area, and porosity.

Additives such as lignin – also derived from wood – can be directly integrated into the spinning solution, substantially increasing the carbon yield during conversion into carbon fibers.

During the activation step prior to carbonization, cellulose fibers behave like a sponge: when passed through aqueous baths, they efficiently absorb embedded catalysts or functional agents. These catalysts then become active during carbonization. This targeted tunability is currently unique and gives cellulose a technological edge as a raw material for sustainable carbon fiber production.

Since cellulose is non-meltable, it can be thermally converted in a stable manner – an essential prerequisite for its use as a carbon fiber precursor.

The catalysts embedded in the cellulose fiber activate during carbonization. They accelerate the conversion process, lower the required process temperature by up to 1,000 °C, and shorten furnace residence times. This saves both energy and costs.

The yield is also significantly improved: whereas conventional methods retain only about 15 percent of the initial mass as carbon fiber, the use of catalysts and additives increases this yield to around 45 percent by weight.

In addition, tailored fiber structures and properties can be adjusted during carbonization – for instance, by varying the temperature profile or through mechanical stretching.

These adjustments result in optimized material characteristics. The resulting bio-based carbon fibers achieve the performance level of petroleum-based high-modulus carbon fibers made from PAN or exhibit similar electrical and thermal conductivity as pitch-based fibers. This makes them particularly attractive for demanding applications in the energy and lightweight engineering sectors.

At Fraunhofer IAP, we produce bio-based carbon fibers from renewable raw materials such as cellulose, which serves as the starting material for our precursor fibers. Carbonization refers to the thermal conversion process in which the organic precursor fibers are transformed into carbon-rich fibers at high temperatures in the absence of oxygen.

For example, we flexibly spin cellulose into continuous fibers using industrially established processes such as viscose or Lyocell spinning. By adding substances such as lignin—also derived from wood—or catalysts, we significantly increase the carbon yield during the subsequent carbonization.

The structure of the precursor fibers—such as porosity, molecular orientation, crystallinity, and cross-sectional shape—is precisely controlled through the spinning process and the process parameters. This allows us to produce round, oval, or multilobal fibers. During the subsequent carbonization, we adjust the electrical and mechanical properties as well as the final fiber diameter by carefully controlling temperature, residence time, and mechanical stretching.

In this way, very fine fibers with diameters well below four micrometers can be produced. These are particularly suitable for energy-related material applications that require a high specific surface area, such as porous carrier structures for redox-flow batteries or gas diffusion layers in fuel cells.

Our carbon fibers are especially well-suited for use in electrochemical energy storage systems such as redox flow batteries. In these systems, they could be applied as planar, porous fiber structures—so-called carbon felts. The three-dimensional fiber network offers high specific surface area, is electrically conductive, chemically inert, and permeable to electrolytes—making it ideal as a permeable electrode.

The properties of our carbon fibers meet key requirements: they exhibit high carbon content, excellent electrical and thermal conductivity, tunable surface area and porosity, and very low levels of contamination. This makes them a sustainable and high-performance alternative to fossil-based materials and supports the development of long-lasting, efficient battery systems.

Our carbon fibers can significantly enhance fuel cell performance—especially as carrier materials in the gas diffusion layer (GDL). The GDL typically consists of a carbon paper and a microporous layer (MPL). Our target application is the carbon paper, which is produced via a wet-laying process similar to paper manufacturing using randomly arranged and bonded carbon fibers. The structure ensures uniform gas distribution while efficiently conducting electricity and heat. It is also permeable to liquids, ensuring stable water management within the fuel cell.

To fulfill this role, the carbon fibers must meet stringent requirements: chemical inertness, ultra-low contamination (ppm range), and high electrical and thermal conductivity. A high specific surface area—achieved via specialized cross-sections (e.g., lobular shapes) or ultra-fine diameters—is also advantageous. Our carbon fibers meet these criteria exceptionally well, offering a sustainable and high-performance alternative to conventional fuel cell materials.

Our carbon fibers hold strong potential for defense applications, particularly in lightweight structural solutions and functional components. Thanks to their high mechanical strength and low weight, they are ideal for components in vehicles, projectiles, or protection systems—where weight reduction and load-bearing capacity are critical.

They also offer excellent electrical and thermal conductivity, making them suitable for electromagnetic shielding, thermally stressed systems, or sensor-integrated composite materials. Tailored fiber structures—e.g., through adjusted porosity, specific surface area, or surface functionalization—enable further possibilities for functionally integrated solutions.