By Omar Espinoza and Maria Fernanda Laguarda-Mallo
The U.S. forest products industry has been facing many struggles during the last two decades. A combination of growing competition from imports, the rise of electronic media, competition from substitute materials, environmental concerns, and the recent economy downturn, have caused thousands of mill closures and more than a million job losses between 2005 and 2009 alone . We now import the majority of our furniture . Plastic, steel, and hybrid materials have taken significant market share in products that previously were made almost exclusively of wood, such as siding, windows, and decking. Although the construction industry, a major driver for the demand of forest products, is slowly but steadily recovering, there have been structural changes that are not going to reverse, such as the increasing use of electronic communications.
However, some economic and social developments offer a promising future for the forest products industry. Millions of people are coming out of poverty and joining the middle classes in developing nations, such as China, India, and Brazil, and their growing purchasing power represents a great opportunity to make products that these populations need. Also, an increasing realization of the environmental attributes of wood is prompting governments and private enterprises to invest resources in research and development of new materials and products derived from this wonderful material; resulting in new and exciting applications. Similarly, the desire for energy independence and concerns for climate change are driving the development of renewable energy. Wood biomass is a carbon-neutral energy source which can provide thermal energy for district heating or with thermochemical or biochemical processes be converted into biofuels. In this paper, some examples of major innovations in wood-derived products and applications are presented. Engineered Wood Products
Engineered Wood Products
Wood is the most environmentally-friendly building material. Building products made from wood not only act as carbon storage, but also have lower environmental impacts during their manufacturing and disposal, at the end of their life cycle. This makes wood-based building products an excellent alternative to traditional materials.
One novel and promising product, developed in the early 1990s is Cross-Laminated Timber (CLT). CLT is a laminated panel made with solid wood boards (Figure 1) that are glued together alternating the direction of their fibers, similar to a plywood layout, which make CLT panels rigid, stable and strong . In addition to their light weight extraordinary mechanical properties, CLT offers other benefits such as excellent thermal and acoustic insulation, great fire performance, and a dramatically reduced installation time and costs, since most of the panels are manufactured and precut in a manufacturing plant with computer-numerical control machinery. For more on CLT, please read our article at this link.
Biobased adhesives are being developed to bond together wood composites. These adhesives are environmentally friendly since they do not produce harmful emissions, and facilitate recycling of wood structures. Structural materials are strengthened with wood fibers, for example novel cellulosic membranes are an alternative to petroleum-based resins. New cellulose-based insulation materials (Figure 3) have been developed, with a better environmental performance and better response to thermal and acoustic requirements than traditional materials .
Wood plastic composites (WPCs) combine plastic and cellulose fibers (Figure 4). Such products allow using recycled plastic bags and wood residues. Some WPCs are especially developed that can be used in extreme environments were solid wood, because of its natural characteristics, does not perform well, such as maritime, automotive and aerospace applications .
Beyond the construction industry, other sectors have also benefited from innovation in wood products. Such is the case of the textile industry. At the moment, some companies are commercializing cellulose fibers that, added to textiles like rayon (itself made from cellulose fiber, Figure 5), confers high strength to the final material. A research group in Canada is conducting research on cellulose filaments and gels. Such materials can improve the properties of a wide array of existing products, including paper, packaging materials, bioplastics, paints, varnishes, textiles, and cosmetics.
The ability to manipulate materials at a nano-scale (1–100 nanometers, one nanometer is a billionth of a meter) is completely changing the course of material science and engineering. This type of technology has a great potential, enabling the configuration of specific characteristics of a material at a molecular level, in order to address particular needs.
Novel applications for wood-based nanomaterials, such as carbon nanotubes (Figure 6) and cellulose nanofibers (Figure 7) have been developed . Nanotubes and nanofibers are used in the textile industry to make waterproof and tear-resistant fabrics. Added to concrete, they can increase its tensile strength and halt the propagation of cracks. Other uses include air filters and solar cells. These materials can be used to enhance the strength and durability of products. Over the last three years the Forest Products Laboratory has been evaluating a new wood-based nanomaterial that is composed of nanocrystals and nanofibers. This material is being developed to produce clear reinforced glass .
Due to their natural composition, trees are excellent sources of bioenergy . Over the last decades, state and federal governments have been developing policies to promote biomass-based energy, to increase energy independence and improve the environment. For example, the White House has recently issued an executive order to accelerate investment in industrial energy efficiency; setting the goal of deploying 40 gigawatts of new industrial combined heat and power (the simultaneous generation of thermal and electric energy from the same energy source) .
The USDA estimated that 14 billion tons of material is available in U.S. forests that could be used for these applications. The removal of this material (overcrowded trees, woody debris (Figure 8), diseased and fire-affected trees) would help reduce the risk of fire and improve overall forest health .
In a process known as biorefining, transportation biofuels can be also obtained from forest biomass (Figure 9) . Although obtaining chemicals from wood is not something new (lye, potash, rosin, turpentine, etc. were a major export during the colony), the technology to produce biofuels from forest biomass at a scale that can replace a significant part of the petroleum-based fuels is relatively new.
Some wood species have been genetically engineered to produce a more efficient feedstock for biorefining processes. The hybrid poplar or genetically modified aspen (Figure 10) has been developed to be a fast-grown species, low in lignin and high in hemicellulose, which are optimal characteristics of an efficient and sustainable biorefining feedstock .
Wood Modification Treatments
Wood modification can be defined as the thermal or chemical processes conducted to reduce the biological availability of wood to wood degraders as well as improve dimensional stability, durability and mechanical properties . In this section we discuss a few promising alternatives.
Thermal treatments are based on the fact that wood properties change when heated. By heating wood to 180-260 °C in an oxygen-deprived environment, this procedure can decrease the hygroscopicity of wood and improve its dimensional stability and decay resistance. Some less-desirable outcomes are an increase brittleness and loss of strength, which limits the application of wood thus treated to certain applications. Heat-treated wood is very popular in Europe.
- Wood acetylation is a chemical modification of wood, in which the hydroxyl groups in wood are replaced by acetyl groups. In acetylation, wood is heated and then impregnated with acetic anhydride. By permanently swelling wood, its dimensional stability is improved; and by removing the hydroxyl groups, biological attack is also reduced. Research has shown that acetylated wood performs exceptionally under harsh conditions, such as marinas and exterior decking.
- Furfurylation treatment is another of wood chemical modification technique, based on the use of furfuryl resins and heat. Chemicals are injected into the timber by impregnation. After impregnation, the wood is subjected to a curing process in which a new rigid polymer network is formed in the timber . This treatment has a positive effect on the durability, stiffness and hardness of the wood. Furfurylated wood is commonly used in Europe in the production of windows, buildings cladding, noise barriers, exterior decking, and patio furniture
The replacement of fossil-based carbon with renewable carbon from biomass led to the development of biorefinery facilities . A forest biorefinery is a facility that integrates biomass conversion processes and equipment to produce biofuels, biopower, and bioproducts from biomass, by efficiently using the entire potential of wood.
The processes of biorefining are identical to the ones used in petroleum refineries. Biorefineries allow making a more efficient use of the woody raw material, for many more applications. Innovation is still needed in developing more efficient enzymatic and catalytic chemicals .
This article enumerates some innovative wood products. However, many other products are being developed around the world and will soon be available to the public. Not every product is successful once it is introduced into the marketplace. According to the UNCE/FAO’s Forest Annual Market Review (2012), in order for a product to be successful, developers need to take into account: (a) cost and technology availability; (b) willingness of the market to adopt the product and (c) promotion strategies. The successful development of these new technologies to come anticipates a promising future for the forest industry.
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