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From forest to market.

From Forest to Market

How do lumber manufacturers ensure that their shipments of green lumber reach export markets in pristine condition? What production strategy must they follow to sort jack pine lumber from a mix of spruce-pine-fir lumber in order to sell it on specialty markets at a higher price? Why are waferboard manufacturers convinced that their product is the panel product of the future? Why do they believe that they can significantly expand their market share in both domestic and export markets?

Most Canadians, including the majority of chemists, would be surprised to learn that the key elements of the answers to these questions flow from the work of a handful of chemists. At Forintek Canada Corp., and in a small number of other laboratories, chemists have been prompt to find solutions to help the solid wood products industry solve production problems and seize market opportunities.

What are some of the opportunities for chemists in an industry which operates at such great distance from industrial and university laboratories? Why should chemists take a closer look at the solid wood products industry as a rich source of interesting research initiatives?

A brief overview of the industry will set the stage for a review of three areas of research in which significant findings are about to pay handsome dividends and which present yet more challenges for chemists.

The Solid Wood Products Industry

Canada is known as a forestry nation. Virtually every region in Canada depends to a significant degree on the forest products industry. It is a chief element of Canadian economic activity and the employment of one in every 10 Canadians is related directly or indirectly to forest products. The solid wood products sector which Forintek serves is composed of softwood lumber, hardwood lumber, and panel products manufacturers. Canada is the world's largest exporter of softwood lumber, with 50% of international trade and 15% of world production. Softwood lumber production totalled an estimated 54.2 million cubic metres (22.9 billion board feet) in 1986. The total value of shipments was $5.5 billion, with export shipments amounting to $4.9 billion. An important lumber manufacturing by-product, pulp chips, were valued at $1.4 billion in 1986. Other residual by-products such as sawdust and shavings are a $200 million source of raw material for other wood-based industries. The industry employs 56,000 people in lumber manufacturing and 35,000 in related harvesting and forest management activities. The hardwood lumber industry produced about 1.4 million cubic metres or 590 million board feet of lumber valued at $278 million in 1986, employing about 6,000 people. The panel products sectors (structural: softwood plywood and waferboard/orientated strandboard; non-structural: hardwood plywood, hardwood veneer, particle-board and medium density fibreboard, hardboard and insulation board) produced shipments valued at $1.39 billion and directly employed 13,500 people in 1986.

The solid wood products sector faces serious challenges. The quality of wood from old-growth forests is declining. The properties of wood from managed forests are different from those of wood from the old-growth forests. This will have an impact on the nature and end-use of wood products in the future. Other materials are making serious inroads into the traditional markets for wood; competition from other countries, as well as trade barriers, are threatening Canada's position in international markets. The need for research is great as the industry prepares to address these challenges and seize new market opportunities.

Three opportunities in which Forintek and its member companies have considerable interest are species separation for higher value products, control of sapstain, and stabilization of waferboard. Each one is attractive for research chemists.

Species Sorting for Higher-Value Products

Lumber is sold by grades determined by grading agencies. The higher the grade, the higher the price. Prior to 1970, several sets of grading rules were in effect throughout Canada. This created many marketing difficulties. To alleviate this problem the dozen or so species groups used in lumber manufacturing were combined into the four groups recognized today. The use of fewer species groups made the choice of lumber less confusing and was a good marketing strategy. It also made handling of logs easier because much of the raw material processed in Canadian mills comes from mixed stands. With mixed species groups it is not necessary to sort logs by species and therefore makes mills more productive in terms of lumber output.

Over the past decade, however, several political, demographic and environmental factors have combined to increase interest in species sorting on the production line. These include the 15% tax on softwood lumber exported to the US, projections of long-term weakening of residential housing markets, and depletion of high-quality, old-growth hardwood and softwood reserves through harvesting or environmental restrictions. As a result, specialty softwood lumber markets have become more attractive to Canadian producers. This situation presents marketing opportunities and the challenge of enabling lumber manufacturers to sort species on high speed production lines.

Given current forestry practices and the design of existing mills, the addition of automated equipment to sort logs and lumber by species would not be unreasonable. Development of fully automated equipment for sawmills to identify and separate wood species to meet the requirements of specialty or other markets, however, is a technologically challenging task. Any automated system would have to be able to identify up to about 40 logs or 70 to 120 pieces of lumber per minute to meet the production requirements of a modern sawmill.

Several years ago, the search for a chemical solution to this problem began. Chemists at the Forest Products Laboratories of Canada (now Forintek) developed chemical colour tests to differentiate western Canadian conifers. These tests were based on long-term studies of the phenolic extractives of western conifers. For example: Douglas-fir can be differentiated from western hemlock, true firs, spruces and western red cedar. This is achieved using a test based upon red colour formation by reducing the Douglas-fir heartwood extractive dihydroquercetin with zinc dust and concentrated hydrochloric acid. Similarly, pine wood can be distinguished from spruce wood. This test is based diazotized benzidine derivatives with pinocembrin, pinobanksin, pinosylvin and pinosylvin monomethyl ether, phenolic constituents in the pine heartwood. Species sorting by using chemical colour tests does present several problems: the need for several systems to separate all the species in a group, reaction speed, corrosiveness, health hazards, pot life, and specificity.

Since the early 1980s, chemists at Forintek have evaluated a number of modern analytical techniques as they tried to solve the species separation problem. Four key criteria have been chosen to determine the suitability of a technology for continual operation in the harsh sawmill environment. These are: speed, sensitivity, equipment reliability and ruggedness. Among the methods considered were invasive techniques such as pyrolysis gas chromatography, gas chromatography - mass spectrometry, and non-invasive techniques such as Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy, ultraviolet (UV) spectroscopy and UV-flourescence spectroscopy. In early 1987, Forintek identified ion mobility spectroscopy (IMS) as a possible sensing device for an automated species separation system.

IMS is a technique useful for detecting trace vapours. It has been commercially developed for battlefield detection of chemical warfare agents, and is under development for drug and explosives detection. It was thought that just as some woods can be differentiated by their smell when freshly cut, IMS may be able to detect chemical taxonomic markers volatilized from wood species. Research undertaken with the Unsteady Aerodynamics Laboratory at the National Research Council, Ottawa, demonstrated that IMS could be used to identify certain wood species. Forintek established an Industrial Steering Committee who set performance requirements for an automated sorting system, and requirements to be demonstrated for the continuation of the project. Forintek subsequently initiated a collaborative project with the Unsteady Aerodynamics Laboratory and contracted Barringer Research Ltd. to perform a mill trial and other work. The most important conclusion from these studies was that IMS works for species identification and can be used in the harsh environment of a sawmill. In a limited number of cases the chemical components responsible for peaks in the IMS plasmagram were identified and found to relate to those used in the original rationales in the development of dyes for species identification. At present, Forintek is putting together a consortium of industrial members to participate in the development of a prototype sorting system for evaluation in a sawmill.

Control of Sapstain for Greater Market

Acceptance

Much of the lumber shipped to export markets is unseasoned and needs to be treated with anti-sapstain chemicals to prevent the growth of sapstain fungi and mould, which give lumber an ugly appearance. This reduces the value of the lumber and results in financial loss for exporters. The degrade results from the high moisture content and nutrient status of freshly felled lumber. Post harvest control of organisms can be affected by rapidly reducing the moisture content of the lumber by, for example, kiln drying. Unfortunately, this is not economically feasible for much of the industry and is not suitable for large-dimension lumber. Lumber manufacturers, therefore, have had to use a chemical treatment to protect the lumber during the susceptible period. For 40 to 50 years, up to 1988, lumber manufacturers used water-soluble chlorophenates (usually sodium pentachlorophenol or sodium tetrachlorophenol) to protect lumber from sapstain. As a result of increased environmental concerns with respect to chlorophenols the Canadian industry is now using alternatives. Forintek is helping the industry in this area. It is involved in the search for alternative chemicals and formulations, and improved application methods.

Chemists in Forintek's western laboratory developed and run an Antisapstain Quality Assurance Programme (ASQAP) for industry members. In the ASQAP, samples of wood sent by industry are analyzed for the surface retention of chemical. This acts as a check of the mills' lumber protection processes. Originally, analytical methods were developed for measuring the retention of chlorophenates present on treated wood surfaces. For example, a retention of 50 [mu]g/c[m.sup.2] of lumber provides protection for up to one year during transit and storage. The program now covers the alternative registered chemical 2-(thiocyanomethylthio) benzo-thiazole (TCMTB) present in several formulations. In response to requests by Forintek members, the chemists are refining analysis methods for copper-8-quinolinolate (Cu-8) present in other commercial formulations, developing analysis methods for borate-based formulations now being used and also for chemicals for which registration is anticipated.

Present techniques used in wood protection rely on chemical compounds that are broad spectrum metabolic toxins. As environmental concerns grow and increased regulation and control in chemical use and practices are expected, Forintek is giving increased attention to another alternative, less toxic method for wood protection, biocontrol. Biocontrol techniques have been used for control of pests in agriculture but have received limited attention for inhibition of wood inhabiting fungi. Over the last five years Forintek has been studying the use of micro-organisms, principally fungi, as biocontrol agents for sapstain and mould. Potential control organisms were selected and screened for their antagonistic abilities against sapstaining fungi. Strains that are of interest in many cases produce antibiotics, but few of these strains have received attention with respect to their secondary metabolities. The identification of these substances, apart from aiding the understanding of the action of these agents, will assist in determining the suitability of the organisms for further study. Many fungi produce mycotoxins, compounds with known adverse affects on human or animal health. For example, one potential biocontrol strain, Byssochlamys nivea, was demonstrated to produce the mycotoxin patulin not only in liquid culture but on the surface of jack pine sapwood. The involvement of chemists is needed in the development of methods to screen the metabolities produced by an organism not only in liquid culture, but preferably determine their presence in trace amounts on wood substrates, which presents a complex matrix for analysis.

Continued research in this area will provide an improved understanding of the chemistry and biochemistry of fungi and their interactions with control agents and the polymeric constituents of wood and could lead to the development of alternative `natural' chemical treatments. Such chemicals if developed are likely to be required in smaller quantities than those presently used and be less toxic to non-staining organisms since their mode of action would be specific to the metabolic processes of the staining species.

Waferboard: Product of the Future

Waferboard is a sheet material made from wood wafers typically 37-75 mm along the grain and 0.5-1 mm thick and of random width. Typically, it is manufactured as follows. Wafers are cut from roundwood bolts, mostly poplar. The dried wafers are tumbled in a blender with a finely powdered phenol-formaldehyde resin in order to distribute the resin particles over the surfaces of the wafers. The wafers are then formed into a low density mat, and finally the mat is hot-pressed at high temperatures and pressures of about 210 [degree] C and 2.7 MPa (400 psi) to form a waterproof bond between the wafers. In the press the mats are consolidated to a relative density of 0.65 considerably higher than the 0.4 relative density of popular from which waferboard is made. In recent years considerable advances have been made in the development of phenol-formaldehyde resins for waferboard, allowing lower resin contents and shorter press times to be used.

Dimensional instability has hindered the increased use of high densified wood-based composites in areas where high humidity or water exposure is expected to be encountered. Fortunately, it has been proven that dimensionally stable wood composites can be produced by using steamtreated furnish or by steam-pressing (ie. injecting steam into the mat or board during hot pressing).

In the former process, the wafers are first steam-treated and then pressed conventionally without steam-injection. Steam pretreatment was shown by chemical compositional analysis to cause some chemical changes in the wood, especially in the hemicelluloses. Because of the potential importance of the steam-pressing process to the industry, chemists and wood scientists at Forintek have compared steam-pressed wafers and boards with conventionally-pressed materials using classical wood chemistry methods.

No evidence was found for chemical compositional changes that could be responsible for the dimensional stabilization obtained by steam-pressing. Solvent extraction data showed insignificant differences between the amounts of extractable material for steam-pressed wafers and conventionally-pressed wafers and original wafers. The degrees of polymerization of the celluloses of the steam-pressed and conventionally-pressed wafers determined by cellulose nitrate viscosity measurements were virtually identical and indicated little if any reduction in D.P. from that in the original wood. By ball milling, a technique used in the isolation of wood components, no evidence could be found for the additional release of lignin-carbohydrate complexes as a result of steam-pressing. Hygroscopicity determinations indicated that steam-pressed wafers absorb less moisture than conventionally-pressed wafers at any given humidity. Internal stresses caused by absorption of water will therefore be decreased and produce a more stable waferboard. Through microscopic examinations differences were found in both the frequency of cellular deformations and the shape of density profiles between conventionally and steam-pressed waferboards. These differences are thought to be due to differences in heat transport in the wafer mats in the pressing processes.

An understanding of steam-pressing may not only allow the production of improved waferboard products and other innovative panel products, but also lead to other developments. For example wood chemists have been engaged for many years in the search for better and cheaper adhesives for use in the panel products sector. The adoption of steam-pressing may make the use of alternative adhesive systems, for example, lignin-based adhesives a reality.

It is clear that chemical research is making valuable contributions to the solid wood products industry. Addressing the industry's future challenges, however, will require the focused efforts of interdisciplinary teams on a wide range of technical problems. Chemists will be called upon to play key roles in the industry's efforts to conserve its share of domestic and export markets and to develop new products which meet the expectations of customers and regulatory agencies.

Acknowledgement

The author would like to thank J.A. Dangerfield and M. Poliquin for their support and helpful discussions during the preparation of this article.

PHOTO : A cant being positioned for breakdown into lumber. This headrig will cut about 20 boards per minute.

PHOTO : When manually grading lumber, a grader will sort about 100 pieces per minute.

PHOTO : Modern houses under construction using waferboard.
COPYRIGHT 1990 Chemical Institute of Canada
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1990 Gale, Cengage Learning. All rights reserved.

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Title Annotation:chemistry in solid wood products industry
Author:Sutcliffe, Roger
Publication:Canadian Chemical News
Date:Jul 1, 1990
Words:2718
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