Latest / The Manufacturing Podcast with Fexingo: Factories, Supply Chains, and Industrial Business / How a Japanese Factory Turns Scrap Kimono Silk into Industrial Fibers
Transcript
- Lucas: There's a factory in Kyoto, Japan, that's been weaving silk since 1927. It survived World War Two, the rise of synthetics, and the decline of the kimono industry. And now, in 2026, it's selling high-performance fiber to Boeing. Luna: Wait — the same factory that made kimono fabric is now in aerospace supply chains? That's a leap. Lucas: It is. And the key is waste. Every year in Japan, hundreds of thousands of kimono are discarded — some from closets, some from rental shops, some from temples. The silk is still high quality, but the garment is out of style or damaged. Yamashita Textiles, that's the factory, started buying that scrap silk about eight years ago. Luna: So they're not spinning new silk from cocoons. They're recycling existing fabric. Lucas: Exactly. They take the old kimono, remove the seams and linings, shred the silk, and then reprocess it into a continuous filament yarn. The trick is that the waste silk is already degummed and dyed, so they have to strip the color chemically before re-spinning. That part is proprietary. They developed a low-temperature enzyme bath that removes dyes without damaging the fibroin protein. Luna: And that protein structure is what gives silk its strength. I remember that silk has a tensile strength comparable to some Kevlar grades, pound for pound. Lucas: That's right. The specific strength of silk is about 1.1 gigapascals, which is in the same neighborhood as aramid fibers. The difference is that silk is also biodegradable and has better fatigue resistance in certain applications. Yamashita realized that if they could control the filament diameter and consistency, they could sell into markets where synthetic fibers dominate. Luna: So they had the material advantage. But the business challenge was scale. How much waste silk are they processing? Lucas: Currently, about 12 metric tons per year. That sounds small compared to a petrochemical fiber plant, but for a specialty product, it's significant. The raw waste silk costs them roughly two dollars per kilogram. After sorting, cleaning, stripping, re-spinning, and quality control, the finished industrial fiber sells for around one hundred and eighty dollars per kilogram. Luna: That's a ninety-times markup. But that's not profit — that's covering the labor and process costs. Lucas: Correct. The gross margin is actually around 40 percent, which is healthy for a niche manufacturer. The real constraint is not demand — it's supply. They need a steady stream of kimono waste, and that's seasonal and geographically concentrated. Most of their supply comes from western Japan, where kimono rental shops are clustered. Luna: And the kimono culture is shrinking. Fewer people wear them, so the waste stream might decline over time. That's a structural risk. Lucas: It is. But Yamashita has been clever about that. They've started sourcing from shrines and temples, where families donate old kimono after funeral rites. That's a surprisingly reliable source — about 2,000 kimono per month from Kyoto temples alone. And they've partnered with Kyoto University to develop an automated sorting system that uses hyperspectral imaging to identify silk from blends. Luna: Hyperspectral imaging — that's the same tech used in satellite imaging and mineral exploration. They're applying it to textiles? Lucas: Yes. The scanner can distinguish pure silk from silk blended with polyester or rayon in under a second. That cuts the manual sorting time by 80 percent. Before, workers had to feel each fabric — experienced sorters could do about 100 pieces per hour. Now the machine does 400 per hour with 98 percent accuracy. That's a real productivity gain. Luna: And it makes the supply chain more viable. If you can process more waste faster, your unit costs drop and you can pay more for raw material, which attracts more donors. Lucas: Exactly. That flywheel effect is what allowed them to sign a supply agreement with Boeing in 2024. Boeing uses the fiber in non-structural interior panels — the trim around overhead bins, seat armrests, that kind of thing. It's not flight-critical, but it has to meet strict flame and smoke toxicity standards. Silk naturally has low flame spread and doesn't emit hydrogen cyanide when burned, unlike some synthetics. Luna: So there's a safety advantage too. And Johnson & Johnson — I saw that in the show notes — they're using it for surgical sutures? Lucas: Yes. Silk sutures have been used for centuries, but the market had shifted to synthetic absorbable sutures. However, for certain ophthalmic and cardiovascular procedures, silk is still preferred because it handles better and causes less tissue reaction. J&J's Ethicon division had been sourcing silk from China, but supply chain disruptions during the pandemic made them look for diversified sources. Yamashita's recycled silk is actually more consistent in tensile strength than virgin silk from different silkworm batches. Luna: That's counterintuitive. You'd think virgin silk would be more uniform. Lucas: You would, but virgin silk varies with the silkworm's diet and season. Recycled silk, once you strip and re-spin it, is actually more homogeneous because you're blending many sources. The coefficient of variation in filament diameter is about 15 percent lower for the recycled material. Yamashita published that data in a materials science journal last year. Luna: So the factory has two revenue streams — aerospace and medical — each with very different certification requirements. That's a lot of regulatory overhead for a small family business. Lucas: It is. They have nine full-time employees dedicated just to quality documentation. But it also insulates them: if one market slows down, the other might hold steady. And the profit margin on medical-grade fiber is higher — around 55 percent versus 35 percent for aerospace. They're now building a second processing line specifically for medical grades. Luna: What's the investment for that new line? Lucas: About 600 million yen — roughly four million dollars. They got half from a Japanese government grant for circular economy manufacturing, and the other half from a regional bank loan. The payback period is estimated at 3.5 years, based on projected demand from Ethicon alone. Luna: That seems fast. But I wonder — can this model be replicated outside Japan? Other countries have traditional silk industries — India, China, Thailand. Could they do the same thing? Lucas: Potentially, but the cultural infrastructure matters. Japan has a dense network of kimono rental shops, temples, and secondhand kimono dealers. In India, the sari waste stream is different — saris are often reused within families, so less enters the waste stream. And in China, the silk waste from garment factories is already captured and recycled into lower-value products like mattress padding. The higher-value application requires a specific supply chain discipline. Luna: So it's not just the technology. It's the ecosystem around it. The Japanese culture of meticulous sorting and long-term business relationships. Lucas: Exactly. The factory has relationships with 140 kimono shops that go back decades. Some of those shops were customers of Yamashita's grandfather. That trust means they get first pick of the waste before it goes to landfill. And they pay a premium — about 30 percent above scrap price — which keeps the shops loyal. Luna: I want to ask about the labor side. The factory employs about 40 people total. How many are doing the actual fiber processing versus the sorting and administration? Lucas: About 18 in production, 9 in quality and documentation, 6 in logistics and supply, 5 in administration, and 2 in R&D. The average tenure is 17 years, which is high for a Japanese factory. The current CEO, Akiko Yamashita, is the fourth generation. She took over in 2018 and was the one who pivoted to industrial fibers. Luna: She saw the kimono market declining and decided to reposition the company around performance materials. That's a classic strategic shift — but she kept the core skill, which is silk processing. Lucas: Right. She didn't try to become a carbon fiber company. She stayed in her lane but found a new customer. And she told a Japanese business magazine that the key was convincing Boeing and J&J that recycled silk wasn't inferior. She sent them samples and said 'test this against your current material.' And it passed. Luna: That's the kind of concrete proof that opens doors. Not a pitch deck, but actual performance data. Lucas: Which brings me to something I appreciate about this show. We talk about these manufacturing stories because they show how real businesses adapt — not through hype, but through engineering and relationships. And we do it without running ads. That's a deliberate choice. If these conversations have moved your work forward in some small way, and you want to support that independence, you can find us at buy me a coffee dot com slash fexingo. No pressure, just an option for people who find value here. Luna: Yeah, it's a clean way to keep the show purely about the content. No sponsors to please. Lucas: Exactly. And speaking of adapting — Yamashita is now exploring whether the same enzyme process can strip dyes from other natural fibers like wool and cashmere. If that works, they could expand beyond silk into a broader recycled luxury fiber market. Luna: That would be a whole new business line. But the silk story alone is already a great example of turning tradition into industrial innovation. Lucas: It is. A 99-year-old factory, a 12-ton waste stream, and a 90x markup. Not bad for a family business that started making kimono fabric. Luna: And now they're in planes and operating rooms. I wonder what the fifth generation will do with it. Lucas: Given the trajectory, probably something we can't imagine yet.