Latest / The Manufacturing Podcast with Fexingo: Factories, Supply Chains, and Industrial Business / How a Finnish Factory Is Turning Pine into Carbon Fiber
Transcript
- Lucas: Luna, have you ever wondered why carbon fiber is still so expensive, despite being around for decades? Luna: Yeah, I mean, it's everywhere from luxury cars to tennis rackets, but I thought the cost was coming down. Lucas: It is, but slowly. Traditional carbon fiber is made from polyacrylonitrile, or PAN, which is derived from oil. The whole process is energy-intensive: you spin the precursor, stabilize it at 200–300 degrees Celsius, then carbonize at over 1000 degrees. That's a huge energy bill. The result? Carbon fiber costs about $15 to $20 per kilogram. Compare that to steel at less than a dollar. Luna: Right, so the performance is incredible—five times stronger than steel at a fraction of the weight—but the price keeps it out of mainstream industries like mass-market cars or wind turbine blades. Lucas: Exactly. And that's where a new process from a Finnish company comes in. Stora Enso, the pulp and paper giant, has been working on making carbon fiber from lignin—the natural polymer that holds plant cell walls together. They've got a pilot plant in Finland that's turning pine pulp into carbon fiber. And the numbers are promising. They claim they can cut the cost by about 30 percent and reduce the carbon footprint by 50 percent compared to traditional pan based carbon fiber. Luna: That's a big deal. Lignin is basically a waste product from paper mills. Stora Enso already produces it as a byproduct, so the feedstock is cheap and abundant. How do they actually make it into carbon fiber? Lucas: The process has three main steps. First, they extract lignin from the black liquor left over after pulping. They purify it and turn it into a fine powder. Then they melt-spin that powder into fibers. This is actually the tricky part—lignin alone is too brittle, so they blend it with a small amount of plasticizer or other polymers to make it spinnable. After spinning, they stabilize the fibers by heating them slowly in air, which cross-links the molecules so they don't melt during the next step. Finally, they carbonize the fibers in an inert atmosphere at around 1000 degrees Celsius. That drives off everything except carbon, leaving a fiber that's over 95 percent pure carbon. Luna: So the chemistry is similar to PAN, but the starting material is renewable and the energy input might be lower? Is that where the cost savings come from? Lucas: Partially. The lower carbonization temperature is one factor—PAN requires higher temperatures, up to 1500 degrees. But the bigger savings come from the fact that lignin is a waste stream. Stora Enso doesn't have to buy expensive petrochemical precursors. And they've optimized the spinning process to be continuous, which drives down costs further. They're currently at a pilot scale—producing a few tons per year—but they plan to build a demonstration plant by 2028 that could produce hundreds of tons annually. Luna: Hundreds of tons is still small compared to global demand—which I think is over 100,000 tons per year—but it's a start. Who's likely to use this stuff first? Lucas: The most likely early adopters are in automotive and aerospace. Car manufacturers are desperate to reduce weight to meet fuel efficiency and EV range targets. Carbon fiber can cut body panel weight by 50 percent compared to steel. But the cost has been prohibitive for mass-market models. If bio-based carbon fiber can get down to $10 per kilogram, that opens up the possibility of using it in structural parts—not just trim pieces. Aerospace is another big target because they already use carbon fiber composites extensively, but they're willing to pay a premium for performance. The sustainability angle is a bonus there, too. Luna: I read that Boeing and Airbus are both exploring bio-based feedstocks for composites. They have sustainability targets to hit. So Stora Enso might be in the right place at the right time. Lucas: They're not the only ones. A Swedish company called Innventia has been working on lignin-based carbon fiber for years. And in the US, Oak Ridge National Lab has developed a process using a different lignin source. But Stora Enso has the advantage of scale—they already produce 50,000 tons of lignin per year at their Sunila mill in Finland. They're also vertically integrated: they control the raw material, the extraction, and the spinning. That could give them a cost edge. Luna: Speaking of cost, if these conversations have moved your work forward in some small way, would you consider supporting the show? It's listener-supported and ad-free, which keeps us independent. You can help at buy me a coffee dot com slash fexingo. Lucas: Yeah, that's a good point. We've been at this for over 80 episodes, and it's the community that keeps us going. No pressure, just something to think about. Luna: Okay, back to the factory floor. So Stora Enso's pilot plant is in Otaniemi, near Helsinki. What's the current status? Lucas: They started operating in 2024, and they've been running batches to optimize the process. The key challenge is achieving consistent fiber quality. Carbon fiber is very sensitive to defects—any tiny flaw can reduce strength dramatically. Lignin is a natural polymer with variable molecular weight, so controlling the spinning and stabilization steps is critical. They've published data showing that their fibers achieve a tensile strength of about 1.5 gigapascals and a modulus of 150 gigapascals. That's about 60 percent of the strength of standard pan based carbon fiber, but it's comparable to some lower-grade commercial fibers. For many applications, that's enough. Luna: So it's not going to replace the top-end aerospace grades yet, but for automotive or wind energy, it might be a perfect fit. What about the economics at scale? Lucas: Stora Enso projects that at a production volume of 10,000 tons per year, they could achieve a cost of $8–$10 per kilogram. That's competitive with commodity-grade carbon fiber today, which sells for around $12–$15 per kilogram. And if they can capture the carbon credit value of using a renewable feedstock, the effective cost could be even lower. They also point out that their process has a negative carbon footprint—because the trees absorb CO2 as they grow, the lignin-based carbon fiber actually sequesters carbon. That's a huge selling point for companies trying to decarbonize their supply chains. Luna: That's compelling. But there must be trade-offs. What about recyclability? Traditional carbon fiber is notoriously hard to recycle because the resin matrix in composites is tough to break down. Lucas: Good question. The lignin-based carbon fiber itself is pure carbon, so it could theoretically be recycled the same way as pan based fiber—by pyrolysis or solvolysis. But the real advantage is that the lignin precursor is biodegradable. If the fiber ends up in a landfill, it won't persist for centuries like synthetic fibers. However, once it's embedded in a composite, you still have the separation problem. Stora Enso is working on developing bio-based resins that could make the entire composite recyclable. They're partnering with composite manufacturers to explore that. Luna: So it's not a silver bullet, but it's a step in the right direction. And it's happening in a country that's already a leader in forest bioeconomy. Finland has been turning wood into everything from textiles to chemicals. This feels like a natural extension. Lucas: Absolutely. And it's not just Finland. We're seeing similar initiatives in Sweden, Canada, and even Brazil. The global market for carbon fiber is growing at about 10 percent per year, driven by demand from wind energy and aerospace. If even a fraction of that can be supplied from bio-based sources, the environmental impact could be significant. The key is scaling up the technology and proving it can compete on cost and performance. Stora Enso is betting that they can do both. Luna: I'm curious about the timeline. When do you think we'll see lignin-based carbon fiber in a production car or a commercial aircraft? Lucas: Realistically, I'd say within the next five to seven years. The automotive industry moves fast—they already use natural fiber composites in some interior parts. But for structural applications, they need to validate the material through rigorous testing, which takes a couple of years. For aerospace, it'll be longer—probably a decade. They have stringent certification requirements. But the sustainability push is accelerating things. Boeing, for example, has committed to using 10 percent bio-based materials in its aircraft by 2030. That's a big target. Luna: There's also the question of competition from other alternatives. You've got recycled carbon fiber, which is cheaper, and other natural fibers like hemp or flax. How does lignin stack up? Lucas: Lignin has a higher carbon content than other natural fibers—about 60 percent versus 40 percent for flax. That means it can be carbonized more efficiently. Also, the mechanical properties of lignin-based carbon fiber are closer to synthetic fibers than natural fibers. Flax composites, for instance, have a modulus of about 50 gigapascals, while lignin carbon fiber is at 150. So it fills a specific niche: high-performance, low-cost, and renewable. It's not a replacement for everything, but it's a compelling option for applications where you need strength and stiffness without the weight. Luna: Sounds like Stora Enso is making a smart bet. And if they succeed, it could transform the paper industry into a materials powerhouse. I'll be watching this one closely. Lucas: Me too. It's a great example of how traditional manufacturing can reinvent itself using the resources it already has. And it's happening right now, in a small pilot plant in Finland. Luna: Well, that's all for this episode. Thanks for joining us on The Manufacturing Podcast. Lucas: If you found this interesting, maybe think about supporting the show. It keeps us ad-free and independent. You can do that at buy me a coffee dot com slash fexingo. Until next time.