Lignin’s Big Leap

Still seeking commercial-scale opportunities, Lignol continues to collaborate with companies that are eager to buy high-purity lignin in bulk. Is this abundant byproduct of pulp and paper milling and biorefining poised for new and higher uses?
By Tom Bryan | March 10, 2014

Lignin has long been considered an abundant, low-value byproduct of pulp and paper milling, and somewhat of a burden to biorefining, but Lignol’s Mike Rushton remains confident that the substance is poised for new and higher uses. As research is conducted globally to find ways to mitigate the challenges of separating lignin from the most prized parts of biomass—cellulosic sugars—Rushton says industrial buyers are ready and waiting for big volumes of a super clean product no one is currently making.

“There aren’t any commercial producers of high-purity lignin, and we aren’t one either, yet,” Rushton admits. “We’re aspiring to be.”

So for now, the most common use for existing lignins remains decidedly low-tech—it’s often a boiler fuel for mills and biorefineries—but the promise of large volumes of new and better lignin products, along with a plethora of markets for them, is alive and well. In North Carolina, researchers have developed an inexpensive technique for removing lignin from plant material used to make ethanol. In Belgium, scientists are modifying the lignin in poplar trees, through biosynthesis, to more readily extract sugars. And in Finland, one company is developing ways to isolate lignin and produce myriad products from the ubiquitous organic substance.

Years ago, before the current swell of lignin research began, Lignol Energy Corp. and its wholly owned subsidiary Lignol Innovations Ltd. introduced the American biofuels industry to the enticing idea of high-purity lignin as a coproduct of cellulosic ethanol production. While ethanol is no longer LIL’s target, the Burnaby, British Columbia-based company remains committed to its vision of building an industrial-scale biorefinery: a plant that would consume wood and turn out large quantities of high-purity lignin and biobased chemicals.

Rushton calls the company’s process its “big differentiator” because it allows lignin to emerge as a pure product that’s distinct from lignins produced through conventional pulp and paper milling and even other biorefinering techniques. The characteristics of lignin are determined by how it is extracted from biomass, chemically. LIL uses an organic solvent rather than an inorganic one, Rushton says, and the company’s process operates in a mildly acidic pH range rather than running at high alkalinity. “The lignin we make is quite different from other lignins that are out there,” he says, explaining that most lignins produced from the kraft and sulfite pulping processes contain sulfur and inorganic materials—sodium, magnesium and calcium—that are baked into the product. “Our lignin contains virtually no sulfur and very low ash content.”

According to the International Lignin Institute, between 40 million and 50 million tons of lignin are produced globally each year, mostly as noncommercial waste. Rushton says there are, in fact, sulfur-free lignins on the market today that are exclusively made by pulp and paper mills using sulfite processes. While those products are relatively free of sulfur, they’re not absent of other inorganics. “Sulfur isn’t the only issue, nor the only obstacle,” Rushton says, explaining that the value of lignin is relative to its end-use compatibilities. “The name of the game with lignin is to find applications where the product will work with other chemicals in varied formulations. Typically using it as a substitute for petrochemicals is the main goal.”

In industrial terms, lignin is an aromatic compound made of benzene rings, varied molecular structures that typically have six carbon atoms surrounded by six hydrogen atoms. “Different types of plants contain different types of lignin,” Rushton says. “These structures vary a lot, and they’re ultimately responsible for how lignin behaves.”

The appearance and consistency of lignin are also quite variable and highly contingent on process. Kraft lignin is brown in color and has the consistency of powdered instant coffee. “Its particle size is typically around 20 microns, so it’s quite fine,” Rushton says, adding that the so-called organosolv lignin that results from LIL’s process is also a brown powder. Lignosulfonates—a product that comes out of sulfite pulping processes—is water soluble and the type of lignin sold in the largest volumes globally.

While the markets for future lignin products are nearly endless, using high-purity lignin as a petrochemical substitution in resin manufacturing is particularly promising. Phenolic resins, or phenol formaldehydes, which are produced from benzene and natural gas, are used in a wide range of products including coatings, adhesives and molding compounds. “It’s a product with a fairly high carbon footprint, so if you could substitute high volumes of phenol with lignin, you could produce a much greener product,” Rushton says. “But you have to be able to do it at a competitive price and without loss of performance. That’s the opportunity we’re working on.”

With a virtual sea of applications awaiting high-purity lignin in manufacturing, material science, agriculture and even human health industries, the market opportunity is huge. “It is certainly a billion-dollar business, and probably bigger than that,” Rushton says. “We see the market for our lignin being hundreds of thousands of tons per year in a short time. Once we have the material available, there are lots of places where we believe we’ll be able to sell it—where it will be a good substitute for petrochemicals at a competitive price.”

Still on path to commercial-scale production, LIL continues to share its lignin with collaborators. Starting in 2009, the company built up large lignin inventories through production campaigns at its Burnaby demonstration plant, which remains operational. “The next step is to build a large-scale plant, which we are hoping to do with partners,” Ruston says. “We have quite a few active project opportunities at the moment.”

If and when LIL’s large-scale plant gets built, it will likely consume 300 to 400 tons of woody biomass and produce about 20,000 tons of lignin per year. As many as 30 companies worldwide have tested LIL’s lignins, including Kingspan, a manufacturer of rigid foam insulation; Huntsman, a maker of polyurethanes; and AJ International, a producer of resins used in the foundry industry. “Almost universally, they’re waiting for us to be able to sell them the stuff,” Rushton says. “That’s the hurdle for us. To develop a commercial supply.”

Author: Tom Bryan
Editor In Chief, Ethanol Producer Magazine