Cellulose nanocrystals

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A Novel Class of Renewable and Sustainable Nanomaterials.

In recent years, the conversion of renewable lignocellulosic biomass and natural biopolymers into chemicals, liquid fuels and feed supplements has gained considerable attention. This is mainly due to the ever-increasing prices of petroleum and the high-energy intensity in production of chemicals and synthetic polymers. With appropriate conversion and extraction technologies as well as modification and characterization, biopolymers like CNC can be integrated into bio-based products.  Their use in novel materials and various applications favours the future use of cellulose and cellulose-based biomass components with substantial environmental and economic benefits.

Alberta Innovates Technology Futures (Tech Futures) plays a strategic role in bridging Alberta’s industries by transforming wood and crop waste into chemicals with commercial applications. The goal is to reduce the world’s reliance on oil, decrease our environmental footprint, and also grow the province’s economy. Dedicated research scientists at Tech Futures are experimenting with residue from crops and wood products to find new environmentally sustainable products made with Cellulose Nanocrystals (CNC). This could help revitalize Canada’s agriculture and forestry industries and pave the way toward providing novel bio-based greener materials for use in the energy sector and many other industries in Alberta.

Last fall, Alberta’s one-of-a-kind Cellulose Nanocrystals (CNC) pilot plant was commissioned at Alberta Innovates-Technology Futures’ (Tech Futures) Mill Woods facility. With capacity to produce up to 100 kilograms of CNC per week, the plant is helping advance new CNC-based products that have the potential to further diversify and increase the global competitiveness of Alberta’s economy.

The $5.5 million CAD pilot plant was created through a collaboration of the governments of Canada and Alberta with funding from Western Economic Diversification Canada (WEDC), Alberta Enterprise and Advanced Education (EAE), and financial contributions and ‘in kind support’ from Alberta-Pacific Forest Industries Inc. (Al-Pac). The plant is part of Tech Futures’ mandate to provide technical services and funding support to facilitate the commercialization of technologies, to develop new knowledge-based industry clusters and to help encourage an entrepreneurial culture in Alberta.

Two objectives motivated this significant investment. First, produce CNC from various forestry and agricultural feedstock in an effort to improve consistency, yield, cost efficiency, and chemical recovery. Second, develop an Alberta-based and industry-focused applications development program for CNC.

Figure 1. Schematic diagram of partial molecular structure of cellulose chain with numbering for carbon atoms and n= number of cellobiose repeating unit.

From cellulose to cellulose nanocrystals

Cellulose is the most important and naturally abundant organic biopolymer in the biosphere. It is the structural basis of plant cells produced from highly developed trees to primitive organisms such as seaweeds, flagellates and bacteria. Cellulose is the main constituent of wood (40-45%), cotton fibre (90%) and dried hemp (45%). It is comprised of carbon, hydrogen, and oxygen bioengineered as a linear homopolysaccharide chain with cellobiose as the repeating building blocks. Each block is composed of two adjacent anhydro-glucose rings connected via a β-1,4 glycosidic linkages as illustrated in Figure 2.

The number of glucose units in cellulose varies from 7,000 – 10,000. The cellulose molecules are linked laterally by hydrogen bonds into linear bundles. The extremely large number of hydrogen bonds results in a strong lateral association of the linear cellulose molecules. The strong association and almost perfect alignment of the cellulose molecules gives rise to crystallinity. The degree of crystallinity has a great influence on hardness, density, transparency and diffusion. X-ray measurements have shown that the crystalline regions are interrupted every 600 Å with non-crystalline or amorphous regions. In the amorphous region, the molecules are arranged in an irregular and non-periodic manner.  Therefore, the cellulose molecules can be considered as highly oriented (crystalline) for a distance about 600 Å, then pass through an area of poor orientation (amorphous) and re-enter a crystalline region. The pattern repeats throughout the length of the cellulose molecule.

Cellulose is odourless, flavourless, hydrophilic and is insoluble in most solvents, including strong alkali. It is biodegradable and can be broken down chemically, in addition to other techniques, into its monomeric building blocks for production of biofuels. By treating cellulose with concentrated acids known as acid hydrolysis, the amorphous regions can be broken up, thereby producing nano-sized cellulose-based crystals called nanocrystalline cellulose (NCC) or cellulose nanocrystals (CNC). CNC are elongated, rigid and rod-like or whisker-shaped particles with a rectangular cross-section. CNC can be prepared from any cellulose source materials including wood pulp, recycled paper and paperboard, cotton fibres, hemp, flax, bamboo, sugarcane bagasse and other agro-biomass.

Figure 2. CNC produced at Tech Futures’ pilot plant; cloudy suspension (1 wt%), gel-like (10 wt%), flake-like crystals, and very fine powder.

Growing market for CNC

Increased interest in CNC has led countries such as Israel, Germany, France, Sweden, Finland, Switzerland, Norway, and Japan to build several pilot or demonstration plants of different capacities. However, the most well-known CNC research and development centres, along with their various industrial partners and development clusters, are located in the U.S. and Canada. Celluforce, Inc. is the only demonstration-scale pilot plant currently operating in Canada. This facility, which was built as a joint venture between FPInnovations and Domtar, can produce up to one tonne/day of CNC. The other Canadian CNC units are pilot plants located at FPInnovations and Tech Futures with production capacities of 10 and up to 100 kg/week, respectively.

Nanotechnology is a rapidly evolving technology, as science, engineering and technology have merged to bring nanoscale materials that much closer to reality. Since 2000, there has been increasing interest from different corporations, governments, research organizations, universities and the public to use CNC in various applications.

A versatile range of application

Cellulose nanocrystals are considered to be a novel eco-friendly bio-based nanomaterial with many desirable properties for utilization in various industrial and commercials applications. CNC has a high aspect ratio (length to width ratio) with typical lateral dimensions of 100-200 nanometers (nm) and longitudinal dimension of 5-20 nm. Their dimensions vary depending on the native cellulose source, extraction methods and recovery processes such as hydrolysis time and temperature. CNC has high tensile strength and can be compared to Kevlar fibre in stiffness, making it an excellent material for reinforcement of natural or synthetic matrix polymers. Recently, CNC was used as the filler phase in bio-based polymer matrices to produce bio-based nanocomposite with superior thermal and mechanical properties.

CNC has unique rheological properties. Dispersions of CNC at low concentrations provide high viscosity making it a great ingredient as a non-caloric stabilizer for food industry. In addition, CNC are highly shear thinning – a property which is particularly important in different coating applications as well as an ideal value-added bio-material with potential for utilization in stimulation, fracturing and completion fluids.

CNC has low density and exhibits other benefits such as optical properties that can be altered or controlled. CNC in composite films is considered to be gas impermeable and has been suggested to act as a barrier material for perishable foods and materials which are sensitive to air and oxidation. Recently, Tech Futures was awarded U.S. patent number 8,105,430. The patent describes the use of CNC as an additive for anti-icing fluids. The general technology could be used for other applications where water-based viscosity control is required. For the oil and gas sector, CNC can be utilized for improving drilling fluid, fracturing fluid and enhanced oil recovery. Demonstrating its ongoing potential, CNC is currently being exploited beyond the patent claims and a continuation patent may be filed.

The application of CNC has been considered for a number of major industrial sectors as the driving force to facilitate commercialization of CNC in large scale. These sectors involve packaging, aerospace, automotive, coating and consumer goods such as electronics and appliances. In addition, other sectors such as oil and gas, paper and paperboard, food, hygiene, absorbent products, medical, cosmetic and pharmaceutical industries stand to benefit from CNC. The utilization of CNC with its unique physical and chemical properties during formulation, manufacturing, and operation will directly impact and improve the quality and the performance of the final bio-based products.

The chemical and physical properties of CNC from several feedstock and production lines at the Tech Futures pilot plant are fully characterized to reveal their complete profiles for their quality and specific applications development. The ultrastructure, morphology, chemical composition, and purity are constantly tested by using state-of-the-art instrumentation located at Tech Futures, as well as the National Institute for Nanotechnology (NINT) and University of Alberta. Professor Yaman Boluk, a pioneer in the CNC field, is collaborating with Tech Futures on process development and optimization, surface modifications, and implementing the final CNC products during field testing in various industrial sectors. Meanwhile, efforts to develop experimental data and standardization terms, including lifecycle analysis to better understand the impact of CNC on human health and the environment, are underway.

CNC with its unique physical and chemical properties during formulation, manufacturing, and operation will directly impact and improve the quality and the performance of the final bio-based products.

The chemical and physical properties of CNC from several feedstock and production lines at the Tech Futures pilot plant are fully characterized to reveal their complete profiles for their quality and specific applications development. The ultrastructure, morphology, chemical composition, and purity are constantly tested by using state-of-the-art instrumentation located at Tech Futures, as well as the National Institute for Nanotechnology (NINT) and University of Alberta. Professor Yaman Boluk, a pioneer in the CNC field, is collaborating with Tech Futures on process development and optimization, surface modifications, and implementing the final CNC products during field testing in various industrial sectors. Meanwhile, efforts to develop experimental data and standardization terms, including life cycle analysis to better understand the impact of CNC on human health and the environment, are underway.

Alberta is uniquely positioned to build the CNC value chain because of its distinguished nanotechnology research institutes, well-known forestry companies, and proximity to the energy sector. The major advantage for the development of CNC and CNC-based products in Alberta is the innovation capabilities of research centered at NINT and the University of Alberta, coupled with their Tech Futures research network partners. Collectively, they have joined forces to help transform the forest industry by providing a new value proposition to enhance manufacturing, processing, and design technologies. Consequently, this will derive the production and implementation of smart bio-based materials which engineered intrinsically and functionalized with specific properties for advanced applications. 

Behzad Ahvazi, Ph.D.

He completed his Bachelor of Science in Honours program at the Department of Chemistry and Biochemistry and graduated with distinction at Concordia University in Montréal, Québec. His Ph.D. program was completed in 1998 at McGill Pulp and Paper Research Centre in the area of macromolecules with solid background in Lignocellulosic, organic wood chemistry as well as pulping and paper technology. After completing his post-doctoral fellowship, he joint FPInnovations formally known as PAPRICAN as a research scientist (R&D) focusing on a number of confidential chemical pulping and bleaching projects. In 2006, he worked at Tembec as a senior research scientist and as a Leader in Alcohol and Lignin (R&D). In April 2009, he held a position as a Research Officer in both National Bioproducts (NBP1 & NBP2) and Industrial Biomaterials Flagship programs at National Research Council Canada (NRC). During his tenure, he had directed and performed innovative R&D activities within both programs on extraction, modification, and characterization of biomass as well as polymer synthesis and formulation for industrial applications. Currently, he is working at Tech Futures as Program Lead for Biomass Processing and Conversion-BioResources sector.

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