A well-stocked pantry should include a little wheat straw. Café Yumm! in Eugene, Oregon, keeps a supply in its cabinets and features sunflower hulls at the tables as well. If the idea of eating these sounds unappetizing, don’t worry because these grain byproducts aren’t intended for baked goods. Wheat straw and sunflower hulls are just two of the latest materials to be used instead of traditional hardwoods to fabricate cabinets and furniture. Particleboard, oriented-strand board (OSB), medium-density fiberboard (MDF), and other composites formerly made from wood are now manufactured from agricultural wastes. These new composites make durable doors, walls, floors, roofs—even decorative tables.
Café Yumm! owner Mark Beauchamp has built three restaurants with a focus on recycled and environmentally friendly materials that include crop byproducts. The granite-looking dining tables are cut from Environ Biocomposite’s Dakota Burl, made from sunflower hulls. And the custom “wood” cabinetry backing is wheat-straw board, often called wheat sheet. The dining tables with their unusual speckled surfaces are a big hit, according to Beauchamp. “Customers are fascinated with it,” he says. “You can see them trying to figure out what it is.” He selected the material both for its eco-friendly and aesthetic characteristics. “Not only did it appeal to us because of its biocomposition, but also because of its organic warmth,” he adds.
Amber waves of grain
Agriculturally based materials are an answer to the urgent need for wood substitutes. While tables and shelving are terrific applications, residential construction might present the greatest potential use. New homes gobble up lumber at an alarming rate. It takes an entire acre of clear-cut forest—which needs thirty years or more to grow back—to provide lumber to build an 1,800-square-foot home, according to the U.S. Department of Housing and Urban Development (HUD). That’s a lot of wood when you consider that 1.5 million single-family homes were built or started last year in the United States.
By contrast, HUD estimates it takes only eighteen acres of wheat—a harvest easily replenished in a single year—to build an 1,800-square-foot house from straw-based boards and panels—and the straw supplies are enormous. About 60 million acres of wheat are grown in the United States annually, and more than 140 million tons of straw residue are a crop byproduct from wheat, rice, rye, corn, and grass seed each year in North America, say Washington State University researchers. Bountiful, renewable crop waste, while not the definitive solution, could become a sustainable replacement for wood.
What’s in composites?
Wheat straw is by far the most common ingredient in the new composite board mixes and often comprises 100 percent of the base fiber. Other materials include rice straw, sunflower shells, and rye grass, but the possibilities are endless. Research is under way to use cornhusks and stalks, hemp, bluegrass stubble, barley or oat straw, soybean plants, switchgrass, and bagasse (the sugarcane pulp left after the juice is extracted). Recycled paper or plastic, which are already fabricated into “lumber,” could also be blended with organic crop wastes in the near future.
To make straw board, the crop residues are cleaned and refined into similar-size particles. The fibers are then directionally sorted to create a uniform texture. Excess moisture is removed, and an adhesive is added to bind the fibers together. Pressure and heat are applied to form a long, uniform mat, which is then cut into boards or panels of varying lengths and shapes.
The biggest variable is the type of adhesive or resin used to bind the particles. While most companies boast emission-free, formaldehyde-free binders (sometimes made from soy), others prefer the strength of traditional petrochemical compounds, which may contain volatile organic compounds (VOCs) and outgas toxins. Dow BioProducts’ Woodstalk, Eco-Products’ WheatSheet, Environ Biofiber, and PrimeBoard products all are VOC- and formaldehyde-free, greatly improving indoor air quality at the manufacturing plant and the worksite.
Using crop-waste board
Materials such as OSB and MDF, commonly used for flooring, doors, and framing, are the latest trend in products made from crop residues. The high compression of the crop fibers gives structural components extra load-bearing capacity, along with insulation value and fire and water resistance. Termites and similar pests are deterred by the addition of the mineral borate.
Another application of straw board technology is structural insulated panels (SIPs), which typically consist of outer sheaths of wood composite and an inner core of insulation. New technology replaces both components with dense straw board.
Like their wood equivalents, nonstructural MDF and particleboard made from wheat sheet can be painted, sawed, and finished into handsome office and home furnishings. Composites, because they lack knots and grain and are uniformly dense, are perfectly suited for moldings and architectural details that can be tricky to carve from wood. Straw equivalents are usually lighter in weight than their wood counterparts, yet they hold screws and fasteners better, resist water, and don’t contain harmful formaldehyde. Standard particleboard, inexpensive and popular for shelving and cabinets, is by far the most common use for crop-waste board.
It appears that wheatboard is just as durable—and in some cases outperforms—its less green counterparts. Wheatboard met or exceeded North American Particleboard Standards when tested on a range of specifications, according to Neil Kelly Cabinets of Portland, Oregon. Wheatboard is stiffer than particleboard, resists breaking equally or better than particleboard, and performs well in terms of internal bonding and its ability to hold screws and resist splitting.
A few disadvantages
Unfortunately, a handful of agricultural-board manufacturers have gone out of business in the last few years, in part because of high start-up costs combined with low product demand. Paul Acker of Eco-Products, a green retailer in Boulder, Colorado, attributes some company fallout to inadequate consumer awareness of wheat sheet. “It’s not nearly as well publicized as it could be,” he observes. The average homeowner or carpenter probably hasn’t heard of wheat sheet, and only a few products are currently available at national home improvement retailers. So, until consumer demand increases, board made from crop waste can be pricey and hard to find unless it’s ordered through Internet companies.
There are also some notable drawbacks to using wheat. Removing post-harvest straws usually left in the field to decompose may rob the soil of valuable organic matter or subject it to erosion, warns James Shroyer, extension specialist in crop production at Kansas State University. “When farmers sell their straw, they’re actually mining their soils because of the nutrients being removed with the straw.”
However, in some circumstances, dependent on climate and type of grasses grown, straw disposal is desirable. Too much stubble left lying may create fungal or bacterial troubles for the next crop. It can be expensive for farmers to till under, and that process itself may cause further wind erosion. Burning straw is strictly controlled or illegal in many areas because of air-quality standards. In these regions, agricultural waste collection may prove to be practical and profitable without causing further environmental disruption.
Cabinetmaker Paul Yeager is optimistic about the future for materials such as wheat-straw particleboard. He chooses agricultural-waste composites frequently for their sustainability and appearance. Yeager was the green designer for the Midwest Environmental Advocates office in Madison, Wisconsin, where he used Dakota Burl for the front counter and conference table. “It’s such a decorative product,” he says, reflecting on the natural-colored flecks. He also salvaged wheat-straw lumber from the Dakota Burl packing crates and made them into cabinets. Yeager shrugs off the slightly higher price of the materials. “It’s like buying organic milk,” he says. “Yes, you pay a little more for it, but the high quality of the sunflower-hull material and the environmental benefits make it worth the cost.”
The potential is huge. The Maryland Grain Producers Association states that straw SIPs and boards could replace up to 90 percent of the framing lumber usually needed for residential or commercial construction. PrimeBoard predicts that only 25 percent of the wheat straw generated annually in the United States could fill 100 percent of the need for particleboard. Perhaps the field is ripe for harvest.
structural insulated panels (SIPs)
shelving, fiberboard, floor underlayment
wheat sheet fiberboard
Dakota Burl composite, wheat particleboard, Microstrand wheat panels
Industrial-grade wheat particleboard