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Alternate raw materials explored at symposium

Posted on June 1, 1997

To use recording industry parlance, cereal straws and urban wood are rising on the charts with a bullet. Both were subjects of interest at WSU conference.

The subject of making particleboard and medium-density fiberboard from cereal straw furnish established a distinct presence at the 31st International Particleboard/Composite Materials Symposium April 8-10 in Pullman, Washington.

While the symposium program was not overbalanced with strawboard topics, the buzz around the symposium venue at Washington State University and nearby hospitality sites was intermittently directed toward the subject, and the registration list was sprinkled with execs and technical people from current and prospective producers and regional agro-economic development agencies.

Graham Heslop, managing director of Compak Systems Ltd., said Compak has had 10 years of commercial experience around the world supplying small-scale plants that will process a variety of agrofibers into industrial grade particleboard. They include wheat straw, sugar cane bagasse and residues from rice, barley, oats, rapeseed, flax, hemp, jute sisal, maize and linseed.

Compak’s plants have annual capacity of 12,000 m³ (6.8 million ftz, ¾-in. basis), compared with a typical conventional wood-based board plant’s capacity of 200,000 m³ (113 million ftz, %-in.). “The idea is to build numerous small plants throughout a producing area,” Heslop said.

Tubular in shape, agricultural raw materials must be split or flaked, he said. Because the waxy epidermal layer makes binding with conventional resins difficult, Compak’s system uses polyurethane MDI, an isocyanate resin applied at a rate of 3%. A self-releasing agent is incorporated into the resin and release chemicals are applied to press platens and mat surfaces. Ideal moisture content of straw is 12% to 14%. It is supplied as harvested, without artificial drying. The high MC and a slow press cycle are necessary to achieve core bond, Heslop explained.

Meanwhile, research is being undertaken to broaden the range of strawboard binders to include urea-formaldehyde and phenol-formaldehyde. Effy Markessini, managing director of Marlit Ltd., described a project being undertaken by a European consortium of seven industrial partners (board makers, equipment and resin suppliers) and three universities in six countries. Marlit, a resin producer based in Greece, is coordinating the project.

The morphological structure of straw is more complicated than wood, she explained. The surface layer is waxy and concentrations of ash and silica are higher. The consortium’s solution is a chemi-thermo-mechanical treatment which chops fibers in an attrition mill and defibrates the material at atmospheric pressure in a range of 40-100°C (104-212°F). The system produces high shear forces which completely disrupt the epidermic cells. The resulting fiber from wheat or rice straw makes good MDF, and the system can be tuned to produce a coarser particleboard furnish, Markessini said.

Treatment dramatically reduces swell and increases internal bond when used with UF, modified UF and phenolics, she continued. Improvement is also brought to PMDI board properties, but not so great as with UF, “because you start with a better board.”

The system can be adjusted to process furnish for four different types of board-100% MDF, 100% particleboard, partial replacement of wood furnish with straw to alleviate raw material shortages; and addition of straw fibers to particleboard to improve density profile and machinability. Markessini said tests at EW Valentin & Sohne KG in Mittenaar-Bicken, Germany, showed substitution of straw as high as 30%-40% can be made on a conventional woodbased particleboard line.

Straw MDF can be made 10%-20% cheaper than wood, based on a 300 m³/day (169.500 ftz/day, 4-in.) plant, she asserted, and capital investment is 5% to 10% cheaper.

Markessini said the process produces no effluents, and formaldehyde-free emissions meet the most stringent regulations. The process and some machinery are patented and will be commercialized soon. Urban wood use grows.

Another non-traditional source of board furnish is urban wood, which can range from recycled materials such as pallets and demolished buildings to clean scrap from construction projects.

Urban wood is a major component in the raw material supply for Willamette Industries’ MDF plant in Eugene, Ore., a rebuilt 1962-vintage particleboard plant that began production in its resurrected form early in 1996. David C. Smith, who was plant manager at the time, described the conversion and raw material supply process (see WOOD TECHNOLOGY, June 1996, pp. 30-32).

Successful mechanical conversion of urban wood is essential, pointed out Roland Jager, sales manager of Pallmann Maschinenfabrik GmbH. He described how the Italian company SIA Srl operates eight plants producing more than 3,000 m³ (1.7 million ftz, %-in.) per day of quality particleboard using urban wastewood as its only raw material resource.

This is wood that has been used previously but is in fresh condition with low contamination, Jager explained. Examples are beams, trusses, doors, windows, paneling, crates, pallets and fruit boxes.

Collected wood is presorted by species and degree of contamination. Among SIA suppliers, separate containers are used for each sort. Unusable wood is converted into fuel. Material is preshredded, usually by a high-speed hammer shredder that opens up the wood sufficiently to release heavy contaminants. The Italian producer uses a large, high-speed drum chipper for this purpose, sacrificing heavy knife wear for more control of geometry, Jager said.

An impact mill is used for coarse size reduction, releasing small contaminants such as nails and bolts. This process splits particles along the grain, opening them up. Final preparation after drying is accomplished by standard highspeed hammermills which complete size reduction along the grain and eliminate solid pieces, Jager said.

While the process will not produce thin and flat particles typical of ring flakers, Jager said the end product is widely used to make institutional furniture and trade show booths, proving that a quality board can be produced at a competitive cost.

Describing his company’s system for air separation of urban wood particles, Alfred H. Schenkmann, general manager of Schenkmann & Piel Engineering, said the “Hurriclon” system processes dry material with half the pressure drop of standard cyclones. Overs are removed to be remilled, fines are extracted for combustion, and the balance is divided into surface and core particles. Schenkmann & Piel’s Airgrader system also removes “soft” contaminants that remain after mechanical processing, he said.

Resin-free biomass system under trial Expanding on the subject of new raw material sources for panelboard, a paper written by Kenneth Scott, president of Convertech Group Ltd., described what is claimed to be the first continuous system to process biomass into a variety of useful products. The paper was presented by panel moderator William E Lehmann in the absence of Scott, who was in New Zealand for pilot testing of the system.

Biomass material reduced to hammermill size is washed in hot water, under pressure, to remove mineral products. This occurs in 100-ft vertical tube chambers at temperatures up to 220°C (432°F) Material then passes through steam suspension to undergo hydrolysis, and is dried.

Energy costs are low, Scott pointed out, because a primary thermal fluid heater, fueled with dry solids from the system, continuously recycles heat through the process stages.

Convertech has targeted chemical extraction and conversion (for alcohols, fuels, plastics), heat and power generation (bionatural gas) and agricultural products. The end use with which the symposium audience was most concerned, however, was panelboard.

Furfural recovered from hemicellulose during the biomass treatment can be used as a binder for fiber raw material-blended, formed into mats and pressed with conventional techniques, Scott wrote, with continuous pressing most desirable. The board produced will be relatively high in density-MDF or high-density fiberboard. It will be brown in color but should provide a stable base for paint and overlays.

The pilot plant is designed to produce 80,000 tons of biomass material annually. Plans are underway to double the plant’s size, according to Scott.

Furfural is a toxic material but can be handled safely in the Convertech process, Lehmann said during a question period. Processing should detoxify the material, he said. Furfural, a liquid aldehyde, also is used by the plastics industry.

Adding value: a necessary step

Another recurring theme during the symposium involved adding value to panelboard across the product range and enhancing marketing efforts as a necessity to keep up with plant capacity increases.

(Photograph Omitted)
Captioned as: MDF IS MADE FROM URBAN WOOD in a former particleboard plant rebuilt by Willamette Industries. Former plant manager Dave Smith described the conversion.

Richard L. Margosian, president of the Composite Panel Assn., outlined four keys to market growth for particleboard and MDF producers:

  1. Focus and refocus on key audiences-architects, specifiers, retailers and consumers.
  2. Expand and optimize markets. Mouldings have grown to 15% of the MDF market. Laminated flooring, at less than 1%, “has a tremendous future.”
  3. Communicate a consistent, effective message concerning physical and environmental attributes of the product.
  4. Improve “industry’s buy-in” through third-party certification of physical standards, advertising and participation in associations. While most particleboard and MDF is sold with a supplier’s certificate of conformity to standards, focus groups are asking for third-party certification, Margosian said.

The Composite Panel Assn. became a reality in March, 1997 as a consolidation of the National Particleboard Assn. and Canadian Particleboard Assn., Margosian explained. It represents 31 US and Canadian companies whose 70 particleboard and MDF mills represent 85% of the capacity in North America. With offices remaining in Gaithersburg, Maryland, and Montreal, Quebec, the association will represent its current constituency of wood-based particleboard and MDF manufacturers, and will seek to expand into similar products made of alternative fibers and resins, he said.

Similar challenges face makers of oriented strand board. John D. Lowood, president of the Structural Board Assn., expressed doubt that the new-home market, which has absorbed OSB capacity increases to date, can grow enough to absorb current huge OSB capacity additions.

New applications and markets are needed, enhancing the standard product by adding value. However, Lowood cautioned, development of value-added niche products may not work for every manufacturer. “It requires patience and may need deep pockets.” And, he asserted, success won’t come unless “technical capabilities are in place, process control is implemented, production costing is practical and marketing replaces selling.”

The symposium was co-chaired by Robert J. Tichy, research engineer, and Michael P. Wolcott, associate professor at the WSU Wood Materials & Engineering Laboratory. Attendance was in the neighborhood of 460. Next year’s symposium will be held March 31-April 2.

Copyright © 1997, Wood Technology. All rights reserved.