In Japan, cellulosic nanofibers look to leave the lab

Pancakes that stay fluffy even when packaged and shipped far away. Cars that weigh 15% less. Running shoes that are lighter and more rugged. These are a just few of the consumer goods on the market or under development in Japan in which wood-derived cellulosic nanofibers (CNFs) are a vital component. In a heavily forested country with a rich history of woodworking, CNFs have great appeal, but so far the material is mostly a curiosity.

CNFs’ potential has long been known. Soon after they were discovered in the 1970s, researchers saw that they offered many possibilities because of their low weight and a tensile strength several times that of steel. With sustainability now a concern for makers of consumer products, the fact that CNFs come from wood enhances their appeal.

Because they are hard to produce economically, however, CNFs have so far caught on commercially only in niche applications. According to Yano Research Institute, a Japanese market research firm, just 80 metric tons (t) of CNFs were produced globally in 2022. The institute says the first commercial product containing CNFs was launched 6 years ago. Soon after, the Japanese sports shoe firm Asics started adding CNFs to the midsoles of some shoes to strengthen them while reducing their weight. The company is said to have sold 10 million pairs of these high-performance shoes.

Yano predicts that as use of CNFs increases, production will grow to 3,000 t by 2030. Several companies and research groups in Japan are trying to boost CNFs’ market appeal and lower production costs. They draw optimism from the renewable origins of CNFs and the chance to derive a high-value product from Japan’s abundant forests.

The chemical producer Asahi Kasei is one major company that recognizes CNFs’ promise. “We are continuing to develop CNFs as a key material beneficial to carbon neutrality and the circular economy,” says Tomofumi Maekawa, manager of the Sustainable Polymers Laboratory at Asahi Kasei. “We have successfully combined the material with polyamide and polyacetal and embarked on assessment of sample products. Our goal is to offer commercial quantities of the products in 2025.”

CNFs are made by converting wood fiber into particles that are typically 5–20 nm wide and several micrometers long. Producers tout CNFs as having minimal environmental impact during production and disposal. Beyond being extremely light, CNFs are as elastic as aramid fiber and offer low thermal expansion and contraction like glass.

Nanosize cellulose has other interesting properties. When wood fibers are finely ground or broken into nanosize particles, their overall surface area grows dramatically. This provides unique gelling properties and high emulsifying power.

Scientists in Japan claim two notable breakthroughs in this area. One is the TEMPO oxidization process, which generates CNFs by employing the 2,2,6,​6-​tetramethyl-1-piperidinyloxy (TEMPO) radical as an oxidation catalyst and, as a follow-up step, treating CNFs with ultrasound. The research garnered three Japanese scientists the 2015 Marcus Wallenberg Prize, a Swedish award that has been called the Nobel Prize of the forest industry.

Nippon Paper Industries committed to CNF research around 2010. Building on the TEMPO process, company scientists swapped out sodium ions with silver and copper ions—a pivotal step in creating diapers with enhanced deodorizing power.

In a project coordinated by the Japanese government’s New Energy and Industrial Technology Development Organization, Sumitomo Rubber Industries and Mitsubishi Chemical added TEMPO-​​derived CNFs to auto tires in 2019. According to Fuminari Nonomura, deputy general manager of Nippon Paper’s R&D division, the result was a tire with greater rigidity and strength in the direction of the tire’s treads but more flexibility in the vertical direction—a combination that enhances both durability and ride comfort.

The other major breakthrough in CNFs is a more mechanical method of creating the fibers, dubbed the Kyoto Process. Using the technique, a consortium of Japanese paper makers, chemical companies, and auto part manufacturers developed a concept car about 5 years ago that weighs about 15% less and consumes 11% less fuel than conventional cars of comparable size.

Japanese firms seem determined to turn the country’s CNF research advances into a viable business. Taking advantage of the TEMPO oxidation process, Nippon Paper built a 500-metric-ton-per-year CNF plant in Ishinomaki, Japan. And Sumitomo Rubber created a CNF-containing tire, though it is no longer sold.

Indeed, companies have been challenged to apply CNFs to auto tires and other commercially viable products. “A major bottleneck is to convey CNFs dispersed in water,” Nonomura says. But Nippon Paper has established technology to supply CNFs in the form of powder, he adds. “We intend to soon put the new process into practical use in a bid to lower production costs.”

Nippon Paper has also commercialized a production technology for carboxymethylated CNFs. In 2019, it built a 30-metric-ton-per-year plant in Gotsu, Japan, that serves the food industry with powdered CNFs, which are similar to the common thickening agent carboxymethylcellulose.

Carboxymethylated CNFs excel in water retentivity and preventing drying, Nonomura says. In December 2018, the confectioner Tagonotsuki started adding CNFs to its dorayaki, a traditional treat consisting of two small pancakes and a sweet red bean filling. The fluffy, moist confection has a shelf life longer than that of comparable products, Nippon Paper says.

The food industry is finding more and more uses for CNFs, Nonomura says. Nippon Paper hopes to export the product as a food thickener that doesn’t need an added preservative. CNFs can be baked to make fluffy items that don’t deflate even after being packaged, he adds.

The Japanese government is also involved in developing CNFs. The Ministry of Economy, Trade and Industry sees them as carbon-neutral products that can be derived from forest resources abundant in Japan. What’s more, the commercially promising TEMPO process is from Japan.

Industry welcomes the government’s help with commercialization. “It is essential to improve the toughness of CNF from a technical point of view and reduce costs,” says Kazuo Kitagawa, a founding member of the industry group Nanocellulose Japan and a research fellow of the Kyoto Municipal Institute of Industrial Technology and Culture.

“The business environment for CNFs will change further when CNF technology is honed under the support of the government,” Kitagawa says. “It is no longer a fantasy that this material will be made with a Japanese process and used extensively in the global market.”

Although wood is the original raw material, Asahi Kasei is trying to develop a version of CNFs made from cotton linters. The company has been producing CNFs in Nobeoka, Japan, since 2017 and combines the product with synthetic polymers at its facility in Sodegaura.

Composites of CNFs and polyamide or polyacetal are promoted as having excellent sliding properties. “They can be applied well to gears and the like owing to a characteristic that they are never worn away, nor do they wear away counterparts,” Maekawa says. “When gears are coupled, they slide on each other without lubricants.”

As the world focuses increasingly on sustainability, CNF boosters envision the material helping improve the recyclability of plastics and other synthetic materials, notably polymer-fiber composites.

Asahi Kasei is considering replacing the fiber in glass fiber–reinforced plastic (GFRP) with CNFs. “When GFRP is recycled, fibers contained therein are broken down, and GFRP’s physical properties are degraded every time it is recycled,” Maekawa says. “On the other hand, CNF-reinforced plastics have a high level of recyclability, and their physical properties are degraded less when recycled.”

Asahi Kasei sees synergies between CNFs and the firm’s other operations. “We have a long history in the cellulose business using cotton linters as feedstock,” Maekawa notes. “We have know-how on feedstock handling and have already commercialized synthetic resins and rubber, both to be combined with CNF.”

CNFs are still an emerging business. Ryoichi Tanabe of Material ConneXion Tokyo, a materials advisory firm, sees potential for the material, given its natural origins and low carbon footprint. The use in Asics shoes was clearly a good fit, Tanabe says, and he’d like to see more such applications. In a best-case scenario, he says, high-tech applications come first, then the auto industry joins as a large-volume user and costs start to fall, creating what he calls “a positive spiral.”

For now, though, cost is very much an issue. Nonomura at Nippon Paper says samples of CNFs once sold for as much as 100,000 yen (around $750) per kilogram. The firm’s current goal is to get prices down to tens of thousands of yen. If prices can be squeezed to a few thousand yen, he says, the market will grow dramatically.

In Japan, CNF enthusiasts compare the nascent product to carbon fiber, a business in which firms such as Toray Industries endured decades of losses before turning the material from a niche product for golf shafts and tennis rackets into a major component of modern airliners. Toray is now the largest carbon fiber maker in the world.

In a 2018 paper on CNFs, Ryunosuke Funahashi of Mitsubishi Research Institute wrote that Japanese companies often persevere when others walk away. “The important thing,” he wrote, “is not to give up until the breakthrough point is passed.”

Katsumori Matsuoka is a freelance writer based in Japan.