Engineers Make Quality, Low-Cost Carbon Fiber from Coproducts of Paper, Energy Production

(Iowa State University) Xianglan Bai illustrates her development of biobased carbon fiber with two beakers in researchers’ hands. The first contains low-cost, low-value and plentiful softwood kraft lignin, the tough stuff that strengthens and waterproofs the cell walls of trees and plants. The natural binder is a coproduct of paper production.

The second contains a low-value, watery fraction of bio-oil, a liquid fuel produced by a thermochemical process called fast pyrolysis. The process uses heat to break down corn stalks, wood chips and other biomass to produce a bio-oil for heating that can be divided into fractions with various properties and performance characteristics. (The process also produces a solid biochar that can be used as fertilizer.)

“We’re taking lignin, considered a low-value byproduct of the paper and pulp industry, and aqueous bio-oil, also considered to be a low-value product, and putting them together to come up with a high-value product,” said Bai, an Iowa State University professor of mechanical engineering and an associate director of Iowa State’s Bioeconomy Institute.

‘Real-world solutions’

Carbon fiber is a strong and ultra-lightweight material used in aerospace, transportation, wind energy and infrastructure applications. You’ll also find it in sport and performance industries such as high-end bicycles and motorsports.

It is typically manufactured using petroleum-based materials. But the high costs of those precursors are raising the costs of carbon fiber and limiting its use to premium applications.

The U.S. National Science Foundation, as part of its Translation to Practice program, which aims to “turn scientific discoveries into real-world solutions,” is supporting further development of Bai’s biobased carbon fiber with a four-year, $2 million grant.

It’s the ‘thermo-mechanochemistry’

Bai and her research group have been researching the production of biobased carbon fiber since 2015, with much of the work focused on lignin as a potential source material.

This wasn’t a new idea. Japanese researchers started looking at lignin for carbon fiber back in the 1960s. But the performance of the resulting carbon fiber was inferior to petroleum-based versions.

Even after decades of trying, the biobased carbon fibers didn’t have the performance levels required for use in cars and other performance-critical industries.

With the support of several grants from the U.S. Department of Agriculture, Bai and her research team have developed several patented and patent-pending technologies “that enable the production of low-cost, lignin-based carbon fibers with exceptional performance properties,” Bai said.

One example is introducing “thermo-mechanochemistry” of lignin, a new material chemistry her group recently discovered. The process heats lignin and puts the spun fiber under increasing mechanical stress, fundamentally changing its chemical transformation and the evolution of its material structures. The result is much stronger carbon fiber while maintaining costs below $5 per pound.

Researchers measured a tensile strength, or stretching, up to 2.45 gigapascals in the biobased carbon fiber and a tensile modulus, or stiffness, up to 236 gigapascals. That easily meets U.S. Department of Energy carbon fiber recommendations for the auto industry of 1.72 for tensile strength and 172 for tensile modulus while keeping costs from $5 to $7 per pound.

Another example of innovation in Bai’s lab is using watery bio-oil to modify non-softening lignin into melt-spinnable precursors. The modified lignin reduced the stabilization time for spun fiber from tens of hours to two to four hours, reducing production bottlenecks and costs.

Commercial production

The new grant will allow Bai, her research group and industry collaborators to move from batch production in a lab to commercially relevant continuous production.

Additional leaders working on that transition include Tannon Daugaard, an engineer and faculty member for the Bioeconomy Institute and a co-founder of Rise Energy, an Ames-based startup; and Ryan Smith, deputy director of the Bioeconomy Institute, also a co-founder of Rise Energy, which is supplying bio-oil to the project.

Major collaborators include Harper International of New York state, Latis Materials of Maine and Rise Energy.

The result could boost the value of paper and bio-oil production while providing the country with a domestic source of high-performance, biobased carbon fiber.

“Commercializing this breakthrough technology could significantly reduce manufacturing costs,” the researchers wrote in a project summary, “while securing a reliable domestic supply of a critical structural material, thereby strengthening U.S. economic competitiveness.” READ MORE