Sus­tain­able car­bon fibers based on algae

Pro­ject coordin­at­or Prof. Thomas Brück, head of the TUM Chair of Syn­thet­ic Bio­tech­no­logy, emphas­ises: ​“With the joint Green­Car­bon pro­ject, we have taken a major step towards sus­tain­able indus­tri­al car­bon fiber pro­duc­tion.” In addi­tion to TUM, the Fraunhofer Insti­tute for Inter­fa­cial Engin­eer­ing and Bio­tech­no­logy IGB, the com­pany SGL Car­bon, and the aerospace group Air­bus are also involved in the con­sor­ti­um, which is fun­ded by the Fed­er­al Min­istry of Research, Tech­no­logy, and Space (BMFTR). 

Nov­el pro­duc­tion pro­cess for car­bon fibers

Car­bon fibers are light­weight, yet extremely stable and res­ist­ant. In the form of car­bon fiber-rein­forced plastics, they are used in a wide vari­ety of applic­a­tions: in air­craft and vehicles, wind tur­bines, but also in sports equip­ment, such as bicycles, ten­nis rack­ets, and skis. These light­weight mater­i­als are made from acryloni­trile, a raw mater­i­al that has tra­di­tion­ally been obtained mainly from pet­ro­leum-based propylene.

Research­ers at the Wern­er Siemens Chair of Syn­thet­ic Bio­tech­no­logy at the TUM School of Nat­ur­al Sci­ences invest­ig­ated the extrac­tion of oils from pho­to­syn­thet­ic­ally act­ive microal­gae. ​“Through pho­to­syn­thes­is, microal­gae bind the green­house gas CO₂, among oth­er things in the form of algae oils,” explains Prof. Thomas Brück. Gly­cer­ine was then extrac­ted from these valu­able oils using chem­ic­al processes. 

Fraunhofer research­ers have suc­ceeded in devel­op­ing a pro­cess that can be used to cata­lyt­ic­ally con­vert bio­gen­ic gly­cer­ol into acryloni­trile, the key raw mater­i­al for car­bon fiber pro­duc­tion. This pro­cess has been developed on a labor­at­ory scale at the Straub­ing branch of Fraunhofer IGB to such an extent that it is now ready for the next scal­ing step, indus­tri­al applic­a­tion. ​“We have thus cre­ated the con­di­tions for the pro­duc­tion of sus­tain­able car­bon fibers that have the same high-per­form­ance prop­er­ties as con­ven­tion­ally man­u­fac­tured car­bon fibers,” says Dr. Arne Roth, depart­ment head at Fraunhofer IGB. 

The pro­duc­tion of sus­tain­able car­bon fibers was the respons­ib­il­ity of indus­tri­al part­ner SGL Car­bon, a glob­al lead­er spe­cial­ized in the devel­op­ment and man­u­fac­ture of car­bon-based solu­tions. The com­pany pro­duced 50k heavy-tow car­bon fibers, which con­sist of bundles of 50,000 indi­vidu­al fil­a­ments and are mech­an­ic­ally very stable, in accord­ance with recog­nized industry stand­ards. These were used to man­u­fac­ture car­bon fiber-rein­forced plastics, known as com­pos­ite laminates.

The European aerospace group Air­bus was also involved in the Green­Car­bon pro­ject as an asso­ci­ate part­ner. Air­bus uses car­bon fiber com­pos­ites as high-per­form­ance mater­i­als for man­u­fac­tur­ing com­pon­ents for air­crafts and heli­copters, and invest­ig­ates pro­cesses that enable more sus­tain­able pro­duc­tion of these mater­i­als from renew­able raw materials.

Air­bus there­fore con­duc­ted a tech­no­logy screen­ing and con­duc­ted a life-cycle assess­ment of the vari­ous tech­no­logy options, in par­tic­u­lar. Inspired by the good res­ults, Air­bus is work­ing on demon­strat­ing the tech­no­logy for fly­ing vehicles. For instance, the maid­en flight of a research heli­copter made from car­bon fibers from renew­able sources took place in 2024, prov­ing the suit­ab­il­ity of these tech­no­lo­gies for avi­ation applications.

Fur­ther research and devel­op­ment needed

Build­ing on the prom­ising res­ults of the Green­Car­bon pro­ject, the part­ners now want to optim­ize the tech­no­logy and bring it into wide­spread indus­tri­al use. Accord­ing to the research­ers, the new man­u­fac­tur­ing pro­cess can in prin­ciple also be used for the sus­tain­able pro­duc­tion of acryl­ic acid, a build­ing block for many poly­mers that are still pro­duced from fossil raw mater­i­als today.

“Our Green­Car­bon value chain thus offers new poten­tial for the raw mater­i­als trans­ition in the chem­ic­al industry, espe­cially in the pro­duc­tion of car­bon-based high-per­form­ance mater­i­als,” says Brück. The con­sor­ti­um hopes to receive renewed fund­ing for the fol­low-up pro­ject from the BMFTR.