Carbon fiber seems relatively good for the environment—it makes cars and planes so much lighter that they get way better gas mileage, right? True, but this simple analysis forgives the fact that cured carbon-fiber structures are extremely energy-intensive to produce. That's why BMW sourced the carbon fiber for its i3 and i8 cars from Moses Lake, Washington, where hydroelectric energy drastically lowers the footprint of its carbon.
Now researchers at the Technical University of Munich have discovered a process that turns that notion on its head—CO2-negative carbon fiber. That's right, producing polyacrylonitrile feedstock from algae and curing it using parabolic-reflected solar energy produces fibers that match the properties of hydrocarbon-derived fibers while leaving the atmosphere with less CO2 in it than if the carbon fiber had never been produced.
TUM's algae bind CO2 in sugars and algae oil, then a special oil-forming yeast makes yeast oils from the algal sugars and cell walls. Enzymes attack these algal and yeast oils to form fatty acids and glycerin. The glycerin goes on to become carbon fiber while the fatty acids can be used as lubricant additives.
The AlgaeTec research facility on the university's Ludwig Bölkow Campus in suburban Munich was partially funded by Airbus as part of its algae-powered flight project, which aimed to derive bio-kerosene from algae. Algae-derived jet fuel may never prove economically viable, but the TUM researchers say that large-scale production of CO2-negative carbon fiber has the potential to offset all carbon produced by the aviation sector.
How large-scale? "The size of Algeria," says Synthetic Biotech chairman Thomas Brück. That sounds absurd, but the algae involved thrive on saltwater, sunshine, and CO2, and the Sahara has access to plenty of the first two. The CO2 would be the trickier ingredient to source in our Algeria-sized farm because TUM's process relies on a direct, rich stream of CO2 exhaust from a steel production plant. (A fossil-fueled electricity plant's exhaust stream would also work.)
It's unclear how many steel and/or energy plants would need to be constructed in the Sahara for this to play out, but we're car people, not airplane people, so let's content ourselves with smaller-scale operations sized to supply automotive carbon fiber co-located with existing plants in areas sunny enough to support both the algae growth and the curing operations. (And if we end up displacing some agriculture, at least TUM claims the algae's economic yield is up to 10 times greater than with wheat or corn and has no fertilizer runoff.)
Vehicle structures aren't the only automotive-related use for this CO2-negative carbon. TUM also proposes replacing steel or stressed, reinforced concrete in highway bridge beams with a bold new technology that sandwiches granite or other gneiss stone (formed under high temperature and pressure) between two sheets of carbon fiber. Known as CarbonFiberStone (CFS), I-beams made of this sandwich material are said to have the strength of a similar steel beam with the weight of an aluminum beam and vastly lower carbon footprints than that of aluminum, steel, or concrete.
Need more? How about strapping on a set of skis made of CFS? Swiss company Zai AG's Spada skis are made using Swiss Alpine Calanca gneiss and ordinary carbon fiber. They are lighter than aluminum, highly flexible, and boast superior vibration-damping properties to traditional skis. Priced at about $6,850 to start, they're among the priciest skis extant, but Mother Earth will thank you.
Speaking of price, the TUM team is not yet ready to compare the cost of algal carbon fiber with that of current products, though the team is confident the process can be made price competitive.
What about end of life? TUM testing suggests that once locked away in carbon fiber, the CO2 stays out of the atmosphere. But to be certain, Brück's team suggests burying used-up, shredded carbon fiber in coal seams. Imagine what our descendants will make of it when they mine it millennia hence.