How algae can turn CO2 emissions into sustainable carbon fibres

Not only do we need to reduce carbon dioxide emissions to limit global warming, we also need ideas to remove existing CO2 from the atmosphere. This is more obvious and feasible than you might think - if you see the greenhouse gas as a resource.

The research team led by Thomas Brück sees it this way. The professor heads the Werner Siemens Chair for Synthetic Biotechnology at the Technical University of Munich and is the director of the Algae Technology Centre there. In cooperation with researchers from RWTH Aachen and the startup CleanCarbonTechnologies GmbH, as well as a large OEM from southern Germany, a process was developed in the BMBF-funded GreenCarbon project that uses CO2 to produce carbon fibers. The key to this is algae, which convert carbon dioxide into algae oil, from which the fibers are then produced.

Innovative methods for producing carbon fibres from algae

To date, carbon fiber production has been a very energy and cost-intensive petrochemical process, but there is another way. Researchers at the Algae Technology Centre at the Technical University of Munich are extracting glycerin and free fatty acids from the microalgae called Microchloropsis salina using a multi-stage enzyme-based hydrolysis process. The glycerin is converted into acrylonitrile in an innovative chemocatalytic process, which is then polymerized into polyacrylonitrile (PAN) - the basic material of all carbon fibers - using an established process (Dralon process). In a subsequent process, PAN is then pyrolyzed to form the actual carbon fiber in the absence of oxygen. To do this, the fibers are burned at 1,000 degrees Celsius in the absence of air. Sounds like a lot of energy consumption? Not if, like the researchers do, you use sunlight or laser beams focused on parabolic mirrors. This, like newly developed catalysts, is one of the process’s patented innovations.

“Carbon fibers produced in this way are chemically and therefore qualitatively completely equivalent to conventional fibers,” emphasises Brück. He and his team have already produced 350kg of algae-based carbon fibers in this way.

Sustainable biofuels: The surprising byproduct of algae-based carbon

Brück has been working on producing fuels from algae for more than a decade. The glycerine produced in this process is of interest to the pharmaceutical and cosmetics industries, but the large quantities involved mean that this is not a serious sales market. Hence the idea of producing carbon fibers from the by-product. Conversely, this means that biodiesel and biokerosene are produced as a ‘by-product’ of sustainable carbon fiber production. And in large quantities: ten kilograms of fuel can be produced from every kilogram of glycerine obtained from the algae.

The starting material is saltwater algae, which, when exposed to nutrient stress, can store up to 70 percent of its mass as oil. The green stuff grows quickly - but also needs a lot of space if industrially relevant quantities of material are to be extracted from it. “That is the challenge,” says Brück, “You need 100 hectares of land to extract 9,000 tons of carbon fibers.” Mineral oil companies are the wrong people to contact to create the necessary conditions; agricultural companies are needed.

Eco-friendly fibres: Why this process Is truly organic

According to Brück, there is enough land for cultivation in Africa, Australia, Southeast Asia, and also in Greece. The saltwater algae thrive in sunny regions that are not too hot,” he says. In contrast to rapeseed oil, whose glycerin could in principle also be used for the process, the algae are content with fallow land that is hardly suitable for agriculture, for example in the hinterland of marine waters. There is therefore no competition with food production.

Apart from that, algae oil production is significantly more profitable than rapeseed oil. Brück explains: “While one hectare of rapeseed monoculture produces an oil yield of around 1.5 tons per year, one can produce around 19 tons of algae oil per year on the same area using algae cultivation.” The only hurdle is scaling: “You would have to invest in the cultivation of algae on a large scale.” So far, only areas of ten hectares have been cultivated - a factor of ten is needed.

CO2-negative carbon fibres: A game-changer for sustainability

The effects on the ecological balance would be outstanding. “Our carbon fibers are CO2-negative,” emphasises the researcher. “We have proven this. Our calculations are cited in the IPCC World Climate Report.”

The process represents an active reduction in the main greenhouse gas CO2. Since the algae oil-based glycerin originally comes from atmospheric CO2, the carbon fiber serves as a permanent and value-added CO2 store. “The industrial use of this fiber therefore potentially enables additional revenue through CO2 certificates,” explains Brück. At the end of the life cycle in a vehicle, the fibers can be recycled and fed into another material cycle. If this is not possible, old parts could be stored in empty coal seams, for example. In any case, carbon dioxide equivalents would be permanently removed from the atmosphere. The topic of CO2 storage can be thought of as being so useful.

This article originally appeared on AMS’ sister site, Autombobil Produktion