A California company is nearing completion of a manufacturing plant that soon will be turning out medium-density fiberboard (MDF) made from rice straw instead of wood fiber.

CalPlant 1 is building the $315 million facility on 276 acres of land in Willows, California, some 85 miles north of Sacramento, in an important rice-growing region. When complete, the company says, the plant will produce the equivalent of 140 million square feet of 3/4-inch MDF per year.

MDF, almost all of which is currently made with waste wood fiber, is widely used in cabinets, doors, and floor substrates. CalPlant 1 said its panels will have no added formaldehyde and will have the same performance characteristics as wood-based MDF.

According to the company, the process has several environmental benefits, including the use of 300,000 tons of rice straw per year—about 20% of the rice straw produced in the Sacramento Valley. All of the feedstock for production will come from rice growers no more than 25 miles from the plant.

After California banned the practice of burning waste rice straw in 1991, some farmers began flooding fields with water after harvest to accelerate the decay of the waste straw. The use of rice straw to manufacture MDF would give farmers another option for disposal.

Output from the plant will be enough to meet 30% of the California MDF market, according to a company news release.

In addition to medium-density board, CalPlant 1 will produce panels in a range of densities and in thicknesses up to 30 mm (1.18 inches). Plywood manufacturer Columbia Forest Products, an early investor in the project, will market the panels.

The plant is being constructed on land owned by the family of Jim Boyd, a rice farmer who originally approached Jerry Uhland, now the president of CalPlant, with the idea in the 1990s, Architect Magazine said in an article about the company. Boyd died in 2009 but his daughter Suzy is active in the company.

The panels will use pMDI as a binder, helping the MDF comply with federal regulations designed to limit formaldehyde emissions. CalPlant vice president Elizabeth Whalen told Architect the company hoped to move to a more naturally derived adhesive in the future, such as the soy-based resin used in some of Columbia’s panel products.

The panels are expected to be ready for sale in the first quarter of next year. They will be distributed through Columbia Forest Products and also sold directly to manufacturers that use a lot of MDF, such as millwork, cabinet, and flooring producers, Whelan said in an email to GBA. The MDF will be available across North America, she said, adding, “but logistically speaking, the freight costs, especially on thicker material, will be a factor for some buyers.”

A full-scale launch of the product—including a brand name—will take place in the first quarter of next year. The MDF will be “priced competitively” with wood-based panels now on the market.

The company’s focus is on California at the moment, Whelan added, but that could change in the future.

“Rice is grown in other regions of the U.S. and globally,” she said, “making rice straw as a raw material an abundant and annually renewable resource, so ultimately we’d like to expand this technology to other regions.”

Non-wood MDF is uncommon

MDF is typically made with waste sawdust and shavings derived from lumber production, says Jackson Morrill, president of the Composite Panel Association, a trade group. Efforts to use alternatives, such as wheat and rice straw, have proved largely unsuccessful in the past. Dow BioProducts, for example, abandoned efforts to make fiberboard panels with wheat straw and a polyurethane binder in 2005 because it cost too much to produce.

One non-wood MDF on the market is Wheatboard, which is made of wheat straw and a non-formaldehyde binder called MDI. It’s available through Chesapeake Plywood, a distributor in Baltimore, where a 4×8 sheet of 3/4-inch material costs $65.20 ($43.47 per unit when bought in a unit of 50 sheets).

Early attempts at making MDF with agricultural waste straw failed for a number of reasons, Morrill said, but the new plant in California is “progressing nicely” and represents a 20-plus-year effort by its founders to bring the idea to fruition.

A key selling point for the rice-straw MDF is the use of a resin that contains no formaldehyde, a chemical listed as a human carcinogen by the International Agency for Research on Cancer. Although most MDF is manufactured with urea-formaldehyde binders, Morrill said in a telephone call that those panels are still able to meet emissions limits established by the U.S. Environmental Protection Agency and the California Air Resources Board.

MDF made with no-added-formaldehyde resins is available, Morrill said, but it’s not common. Producers have stuck with urea-formaldehyde for a number of reasons, including cost and production issues that can crop up with resin substitutes.

Morrill called CalPlant a “win-win-win” because it will help to solve what had been a environmental headache for California rice growers. The manufacturing process also could represent an important tool for combating air pollution elsewhere. In India, for example, rice straw is consumed in huge fires that blacken the sky. Capturing the rice straw in a product with a potentially long life also would appear to offer some of the same carbon-capture advantages that wood products have. Morrill, however, said he didn’t know how carbon sequestration between the two materials compared.

Water use and methane issues 

CalPlant lists reduced water use as an environmental advantage of its manufacturing process—fewer fields would have to be flooded after harvest—but the state’s Department of Water Resources also sees some advantages to the practice.

Peter Bostrom, chief of the department’s water use and efficiency branch, said farmers typically flood fields with 3 to 4 inches of water after harvest. He said he didn’t have an estimate of exactly how much water is used annually for that purpose, but said a “significant number” of acres across the Sacramento Valley are flooded each year.

Is that an environmental problem? Not necessarily. The artificial flooding creates habitat for migrating birds, could help fish in the region’s rivers by providing places where insects can breed, and helps flush salts from the soil. Flooding takes place in fall and winter, which is not prime irrigation season, and the water can help recharge underground supplies.

“The actual water cost is probably minimal,” he said. “The Sacramento Valley has traditionally been a floodplain through history, so often these areas would have been flooded anyway in the winter. In some cases, the flooding of these fields can occur from winter rain alone.”

Bostrom, a former rice farmer himself, said rice straw can be used as bedding for animals and for soil retention at construction sites. It also can be chopped up and turned into the soil, although that practice can lead to rice stem disease if rice is planted in the same ground the following year and crops are not rotated. Flooding does not allow the disease spores to build up, so it’s been “relatively effective” in that way as an alternative to burning.

CalPlant will give farmers another option for disposing of the straw. “What’s being proposed fits into the state’s and the department’s perspective of trying to promote a variety of ways to improve water use and environmental concerns across the valley across multiple fronts,” he said. “You can’t flood the entire valley in the winter, so this provides another option for using rice straw.”

Rice cultivation also has an impact on methane emissions. According to the California Air Resources Board (CARB), the flooding that’s an integral part of rice cultivation makes rice paddies a source of methane through a process called methanogenesis. The more than 540,000 acres of rice paddies in the state account for 2% of statewide emissions, contributing an average of 797,000 metric tons of CO₂ equivalent per year between 2000 and 2017.

CARB didn’t break down the emissions that could be attributed specifically to post-harvest flooding, so it’s not clear how operations like CalPlant might change the emissions picture.

Methane emissions from rice fields are a problem, CARB spokesman Dave Clegern said, but “their contribution pales when compared to methane emissions from dairies and other livestock facilities.” Those operations account for more than half the annual methane emissions in the state.

Still, CARB has developed a carbon offset protocol for rice farmers, which describes the most effective means for reducing the release of methane.

-Scott Gibson is a contributing writer at Green Building Advisor and Fine Homebuilding magazine.