Nano vs. macro cellulose: Impact on different levels

Mark Willliamson

A couple of very different paths are emerging as contenders in the Canadian industry's search for new, profitable uses of pulp fiber resources.

Diversification of Canada's forest industry fiber products is an important plank in FPAC's Vision2020, which targets an additional $20 billion per year in revenue from forest resources. Some of that extra revenue - or perhaps a significant amount - may come from new, innovative ways to use the fiber from Canadian pulp mills. A couple of very different paths are emerging as candidates for the industry's fiber revival. First, there's small-scale and highly purified nanocellulose – basically deconstructed fibers - that can be used in correspondingly small quantities. Then, there are the familiar macro-scale pulp fibers that some pulp producers are now using or testing in bulk quantities for non-traditional and innovative biocomposite applications. It's impossible to compare them on an even footing since they are aimed at end-use applications where the value metrics are quite different. Small quantities of nanocellulose can have a big physical impact in special applications whereas larger quantities of macro cellulose displace petro-chemicals and significantly reduce the environmental footprint of more common products. The impact of each is on a different level.

Baled long fiber pulp vs. nano crystalline cellulose powder. New applications of both may play a part in the industry's revival. Photo sources: Metso (left) and CelluForce (right)

NCC: Specialty chemical

Nanocellulose derived from wood pulp is grabbing a lot of headlines since it has captured our fascination with its promise of super-strong composites and its unique and diverse physical properties. Who would not appreciate the promising applications that include aerospace, automotive, electronics, military, food packaging, and pharmaceutical industries? The intriguing list of possibilities goes on and on.

In Canada, Domtar and FPInnovations are putting their efforts into commercializing nanocrystalline cellulose (NCC) through their CelluForce joint venture. The pre-commercial scale 1 tpd pilot plant linked to the Domtar, Windsor kraft pulp mill has been open for over one year now.

NCC is a highly refined specialty chemical and small quantities by weight fraction are expected to impart significant and unique changes in a material's physical properties. So far, no breakthrough commercial applications have been announced, but commercial trials with many collaborators continue. Presumably, an agreement with an end user would require a commitment to build a commercial scale plant.

Bulk uses of fiber

But what about the good old macro-scale cellulose commodity that kraft pulp mills have been producing in thousands of tons per day for decades? You know the type of fiber that you can actually see without a microscope. Does it have a value-added life outside the traditional papermaking applications? Most certainly it does, as indicated by recent developments which incorporate a considerable amount of wood pulp fiber in products that presently use less environmentally friendly or energy intensive raw materials. These applications include biocomposite car parts, electronic product cases, industrial storage containers, furniture, appliances and a host of products currently made from fiberglass reinforced plastics (FRP).

Specialty pulp fiber applications are not new; Tembec's Temiscaming and Tartas, France mills and a few others around the world have been doing this for years and there is a well developed and very specialized market. Moreover, the many years it takes to develop the technical know-how to refine and customize fibers for diverse end users is a considerable barrier to commodity pulp producers. However, the fledgling market for biocomposite materials is attracting large commodity paper pulp producers like Weyerhaeuser, UPM and Södra Cell who are now producing plastic/fiber biocomposites from pulp fibers produced in existing mills. Of course, there may be some closely guarded secrets and special process conditions required to produce fibers that combine effectively in a plastic matrix and provide the needed physical specifications. Also, there is a crucial expertise needed at the plastic processing and molding level. Nevertheless, the end products developed so far can use fibers in bulk quantities, maybe 40% or more. That's music to the ears of pulp producers.

Lighter and greener car parts

Weyerhaeuser was the first off the mark in automotive parts applications by announcing that it has partnered with Ford over the past three years to develop ways to use pulp fiber in lighter weight parts that can displace traditional fiberglass reinforced plastics. Also, it's a green solution that consumers are looking for. Armrests are one of the first prototypes that met Ford's specifications.

Weyerhaeuser has gone beyond the development with Ford by marketing their biocomposite product as a general purpose thermoplastic molding material. Check out the THRIVE® product on the Weyerhaeuser website. The brochure lists well-defined standard product specifications for ready to mold composite pellets ranging in fiber weight content from 20% to 40%. A special product for custom compounders contains 70% fiber.

Weyerhaeuser has partnered with Ford to use pulp fiber in lighter weight car parts that can displace traditional fiberglass reinforced plastics. Armrests, as shown above, are one of the first prototypes that met Ford's specifications. Source of graphic: Ford Motor Company

Also in the race, Canada's Magna Interiors and Exteriors is developing biocomposite processing techniques to displace FRP in its car parts manufacturing processes. In a recent Pulp and Paper International Magazine article Magna's William (Will) Harney, Executive Director of Research and Development, describes the incentives. "Our number one incentive is to support our customers' requirement for weight reduction in their vehicles (hence better mileage). The fiber-reinforced polymer matrix should be at least cost neutral to be attractive and offer the same or better functional properties."

How much weight can be saved and how much fiber can be used in the composite? Harney says that a 40% by weight fiber weight fraction polypropylene composite part would be at least 15% less dense than the same glass fiber-reinforced plastic part. Magna is working on ways to increase the maximum renewable content in a polymer composite which at the moment is above 50% by weight fraction.

Right now, pulp fiber from several sources in Canada is being screened at Magna's research partner Alberta Innovates Technology Futures (AITF). Harney elaborates on the program's goals: "Our goal is to look at different commercially available fiber inputs across the country. We want to understand the relative merits of each fiber type, each tree species and develop a robust solution." The term commercially available is a key element in their thinking. He adds, "The objective is not to make an expensive product that the market will not bear." That sort of thinking implies that pulp mills could produce a commodity pulp with little capital expenditure and maybe some process management expertise and fiber property control.

Wood fibers replace glass fibers

This industrial storage box is made from GreenCore's biocomposite that contains wood fiber.GreenCore Composites of Toronto is another player in the biocomposite field. The company's NCell ® process technology produces biocomposites that replace energy-intensive fiberglass reinforced plastics. The fiber/plastic composites have been successfully piloted in many applications, from automotive parts, to rigid containers, furniture, and industrial products with pilot sales in industrial and consumer markets. GreenCore's ability to replace up to 40% of synthetic polymer content with wood fibers provides weight savings of up to 20% compared to traditional glass fiber materials.

In addition, specialty pulp producer Tembec has developed a new biocomposite which uses a patented process that reconfigures cellulose fibers into a three-dimensional matrix. Combining this matrix with an eco-thermoset resin containing lignin creates a three-dimensional, lightweight structural biocomposite. Some applications include railway ties, lamp posts, bridge components and other construction and transportation uses.

In Europe, UPM is marketing its ForMi fiber reinforced plastic composite and Södra is promoting DuraPulp polylactic acid (PLA) and fiber blend. The fiber supply is from the companies' existing mills. After previously announcing some development in electronic device casings and audio speaker enclosures UPM has recently revealed an application for kitchen cabinet frames with a Finnish kitchen manufacturer.

A new fiber frontier

Dissolving pulp for viscose staple fiber is another outlet for forest fibers and there have been quite a few future kraft mill re-openings and dissolving pulp conversions announced lately. That's of course healthy for the Canadian industry. However, dissolving pulp is an established, longstanding worldwide market which is growing but showing signs of oversupply lately. In contrast, nanocellulose and innovative macro fiber bioproducts represent step changes to the cellulose application market- essentially a new fiber frontier.

All of these different cellulose applications are very new and the market development for nanocellulose and alternate applications for macro pulp fiber is really just beginning. For NCC to take off committed end users will have to be enlisted and decisions to invest in production facilities will have to be made. This could be an add-on to an existing pulp mill or a remotely located plant with baled or rolled pulp as feedstock. As reported in a recent IPW Magazine article, CelluForce foresees initial commercial plants of perhaps 50 tpd. Not large scale production, but the value of the product is high.

For bulk uses of baled pulp, existing pulp mill processes would be used, but there are a few questions. It remains to be seen (or at least revealed) if any significant capital expenditures will be required to produce an application specific pulp other than paper grade. It would be nice to think that a pulp mill could switch from a papermaking grade to a grade for plastic composites seamlessly with maybe a few tweaks in the fiber properties. But is it that easy? Naturally, current producers are not telling.

Pulp mills have been producing paper grade pulp for decades and they know their customer's needs like the back of their hand. Customer service is second nature. Not so with plastic processors or other end users. To ensure that a new fiber supply business flourishes pulp producers will have to form close bonds with end users or machinery suppliers who have the application knowledge.
Will a nanocellulose refinery supply the needs of many diverse and specialized end users and will biocomposite grade pulp be part of a traditional kraft mill's production schedule? Time will tell if these new uses for fiber are economically attractive and the way of the future.