PROCESSING AND MARKETS

WOOD RESIDUALS IN SMALL

FIND BIG USES PIECES

HE PORK industry alwsys brags that they use everythin;: but the squeal. Soon, the lumber industry may be starting to brag ;hat they are using everything but the leaves. While the industry isn’t there yet, it has come a long way from the days

when most of the residuals that came from its mills either were consumed in teepee burn- ers or dumped somewhere.

In 1993, more than 110 millioc dry tons of wood residue were generated by the pri- mary wood processing plants in the United States. Of that total, about 25 percent is bark, 25 percent is sawdust and 50 percent are trimmings, such as slabs and end cuts. It is estimated that about 95 percent of those residuals are put t o some use such as the production of fiber products (Le., paper, particleboard, etc.), fuel or some other wood-based product. What remains is about 1.5 million tons of bark and 4.7 million tons of trimmings and sawdust.

One thing that has led the wood industry to utilize-so much of its residue is that it’s a volume commodity. During the processing of logs into lumber, the U.S. Forest Service es- timates that only about 63 percent of a har- vested tree can be converted into a solid lumber product, like two-by-fours and di- mensional stock. That means one third of the harvest would be waste if some other use weren’t found. Obviously, those in the pri- mary wood processing industry have a real interest in finding ways to use as much of the logs as possible. The other stimulus is the dwindling supply of timber that can be made into plywood and other products. While folks in forestry talk about all of the trees planted each year, it takes a long, long time t o produce a tree trunk that can be turned into a two-by-twelve or a piece of hardwood worthy of making a piece of fur- niture. This has led the industry to develop products that use smaller pieces of wood or wood fiber, e.g. plywood, oriented strand board (OSB) and particleboard.

Given that so much residue from the pri- mary wood processing industry is used, one might conclude that interest in finding ad- ditional markets would be limited. Howev- er, nothing could be further from the truth.

BIOCYCLE

I With a history of finding economic uses for leftovers, the wood industry explores sustainable options for creating higher value products.

Jim Glenn

Years ago, companies saw the use - any use - of residues as a sound, economic business practice. Today, many companies are look- ing to go beyond low value products such as mulch, animal bedding and fuel, and market to higher value end users. Additionally, with SO much material from the primary indus- tries already accounted for, consumers of wood residue are in need of additional sup- ply from sources such as secondary mills (furniture manufacturers, etc.), as well as the C&D and MSW streams.

TO MARKET, TO MARKET Many markets for residuals from primary

mills and other sources of wood by-products have become well established over the years, as in the pulp and paper industry, which is by far the largest user of residual wood. Chips from primary mills, for in- stance, accounted for more than a quarter (33 million tons) of the pulpwood consumed by the pulp and paper industry in 1994.

Engineered wood -which includes parti- cleboard and medium density fiberboard (MDF) - as well as hardboard and insula- tion board, all are made using small frag- ments of wood as their principal building block. Because of this characteristic, engi- neered wood products are good candidates to use residuals. In fact, of the estimated 11 million tons of fiber consumed by these prod- ucts in the U.S. during 1993, about 90 per- cent was residue from mills.

Presently, there are about 50 particle- board mills and another 20 MDF plants in the United States. Combined, these plants have more than 6,500 million square feet of capacity (three-quarters-inch basis), 5,000 million square feet of which is particleboard capacity. There are plans t o add another 1,000 million square feet of capacity, rough- ly split between the two. Most of these mills are located in the southern, far west and Great Lakes states.

At a recent workshop sponsored by the New York State Energy Research and De- velopment Authority, “Adding Value t o Wood Residue,” Brent English, an industri- al specialist with the U S . Forest Service’s Forest Products Laboratory (FPL) - part of the U.S. Department of Agriculture - not-

DECEMBEK 1996 35

I - Given that so much residue from the primary wood processing industry is used, one might conclude that interest in finding additional markets would be limited. However, nothing could be further from the truth.

Fuel pellets made from wood residue are being marketed for home use in energy efficient pellet stoves.

ed that “it’s best if products ‘pull’ the wood.” That’s certainly what happened in the case of particleboard and MDF. While demand for them was stimulated by a decreased sup- ply of suitable solid wood products, in many instances economics has made wood residu- als the feedstock of choice.

Take the case of Allegheny Particleboard LP in Kane, Pennsylvania. Speaking at the Adding Value Workshop, Chris Works, the plant’s operations manager, explained that when the facility was built seven years ago, it was designed to consume pulpwood from hardwood species, which at the time had a relatively low value. About four years ago, it began to take woodchips and sawdust from regional sawmills and recently has started to add urban wood to the mix. Gravitation to- ward these feedstocks is fueled by economics, according to Works. Today, only about 35

36 BIOCYCLE

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way to insure that urban wood is acceptable to end users (such as particleboard and MDF manufacturers) is source separation. Clean, untreated wood from pallets and di- mensional lumber isn’t likely to contain po- tential contaminants, he says.

MORE MARKETS, HIGHER VALUE? Even though particleboard didn’t begin to

exhibit significant commercialization until the 1960s and MDF wasn’t introduced until then, today both are well established prod- ucts and, as described above, both are large sinks for wood residuals. There are, howev- er, other products that offer the promise of a higher value for the residue or the promise of markets for residues that don’t meet stringent specifications.

One of the most encouraging areas is us- ing wood in other types of composites. For instance, wood has been combined with ce- ment to produce materials broadly classed as cement-bonded wood composites for more than 60 years. These composites largely have been used to improve the acoustics and insulating properties of the cement, where strength isn’t a principal concern. Highway sound barriers are a prime example of this type of product.

Insul Holz-Beton International, a South Carolina-based firm, produces a variety of building products from cement-wood com- posites, including FaswalP wallforms, fram- ing blocks and a sound barrier. According to

Hans Walter, president of the company, the process uses a 10: 1 ratio of wood waste to ce- ment.

Wood residue is finding a home as a filler in numerous plastic products. One market is the plastic lumber sector, where at least a few manufacturers are utilizing up to 50 per- cent wood fiber to strengthen and improve the workability of the finished product.

Amore exciting development is the use of wood residue in more traditional plastic products. Several years ago, FPL identified the potential of using wood fiber as a rein- forcing filler in plastics. Advantages in- clude improving a product’s strength and dimensional stabil i ty, lower materials costs, reduced product weight and less pro- cessing time (because the wood allows the product t o cool faster in the mold). Howev- er, this work was met with a less than en- thusiastic response from the industry. It was a classic Catch-22: plastic com- pounders (firms that blend various fillers, additives and plastics) weren’t interested in producing an untried compound. Similarly, plastic product manufacturers, not fully aware of the advantages and without an ad- equate supply of wood-filled plastic, weren’t interested in using it.

To overcome this situation, the FPL em- barked on a demonstration project in 1994 t o develop compounding methods for intro- ducing wood fiber into plastics, inform plas- tics manufacturers about the product, and

I Timber shortages in the Northwest led Willamette Industries to utilize urban wood to help supply its particleboard mill in Eugene, Oregon.

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BIOCYCLE DECEMBER 1996 37

Photo courtesv of Strandex CorD.

Extruded wood-plastic demonstrate the use of wood-derived fillers composites with water in commercial applications, says English of resistant properties can be FPL. The product demonstrations ranged used for products such as from flower pots to automobile parts. In all, exterior decking’ siding and 18 manufacturers conducted tests on the window sills. wood-plastic blends. As described in the ac-

companying article (“Recycled Wood and Plastic Composites find Markets”), several compounders are producing wood derived fillers in various formulations.

While wood derived fillers may find a niche in the plastics industry, fillers account for less a than four million pound per year market. Even if wood residue captured a siz- able portion of that market, that still is only

. - Z H a modest dip in the sawdust bin. It is more likely that wood-plastic products aimed at replacing solid wood, as particleboard does, have greater potential to remove sizable piles of wood residuals. One such product highlighted at the Adding Value Workshop is StrandexO, a wood composite profile made from a blend of 70 percent wood or oth- er cellulose and 30 percent plastic resin. Be- cause of its water resistant properties, it is used to replace wood in products such as windows, doors and skylights.

BURNING WOOD, A NEW WAY Making life easier for homeowners has

spawned a new use for wood residuals. While many people like the idea of burning wood at home, the work involved is definitely a hin- drance. Over the past few years, fuel pellets made from wood residue have begun to be marketed for use in specially designed pellet stoves. The pellets offer convenience and burning efficiency when compared to cord- wood (leaving less than one percent ash).

The pellet market has grown substantial- ly over the last several years. During the 1993-94 heating season, pellet sales were es- timated to be 523,000 tons. By 1995-96, sales from the more than 60 pellet mills in North America had grown to 654,000 tons. According to the Pellet Fuels Institute, the retail price for wood pellets ranges from about $90 per ton in the midwest to $120 per ton in the northeast. rn

38 BIOCYCLE DECEMBER 1996