Long before President George W. Bush mentioned switchgrass in his State of the Union address, a group of Iowa farmers searching for economic opportunities and solutions for water quality and erosion problems turned to the native prairie grass. Today, with 10 years of research under their belts, the farmers are gearing up to produce switchgrass for commercial use.
The four counties in south central Iowa-Lucas, Wayne, Appanoose and Monroe-comprising the Chariton Valley RCD contain highly erodible soils on rolling terrain. The immediate problem in the early 1990s centered on Lake Rathbun, a man-made lake which had experienced several fish kills and was targeted by the U.S. EPA because it had high levels of Atrazine, a pesticide commonly used in corn production. The Chariton Valley group considered using grass to mitigate the environmental issues and while investigating which grass to pursue, they learned that the U.S. DOE had already identified switchgrass as a promising energy crop. In 1996, Chariton Valley RCD landed a DOE grant to launch a comprehensive study on switchgrass.
Switchgrass, a native, warm-season prairie grass, which can grow to 5 feet, is widely used on Conservation Reserve Program (CRP) acres along with other species of prairie grass. It has potential as an energy crop because it produces about 70 percent of the energy that an equal weight of western coal would produce. Yet, there's a huge difference between using light seeding rates of switchgrass as part of the grass mix planted on CRP acres and maximizing its production as a biomass crop. For the RCD board there also was the challenge to create new economic development opportunities. The Chariton Valley Biomass Project dove into the details, recruiting researchers from Iowa State University and the University of Iowa to conduct numerous studies that are now available on a Web site, www.iowaswitchgrass.com. Among the topics covered are:
• How to improve a thin stand of switchgrass on CRP acres
• How different varieties of switchgrass perform on different soils and terrains
• The impact of grass production and harvesting practices on wildlife, soil and water quality
• The soil carbon sequestration potential for switchgrass
• Preliminary variety comparisons and production costs
While the project covered a lot of ground, much of the field work was cut out of the budget when the funding began to dwindle, says Dora Guffey, coordinator of the Chariton Valley RCD. They still needed to work on varieties, and to find out whether a switchgrass monoculture could have disease and pest problems. "We have much to learn yet," she says. Also, educational materials and crop budgets aren't in place to help farmers evaluate the crop. "You have to realize that it's not like corn," Belden says. "There have been no economic drivers to create the infrastructure for farmers. The biomass industry [today] is probably where the seed corn industry was in the 1930s. The production systems date back to the era when we broke the prairie and just started using fertilizer. You can't handle square bales with an 8-inch [grain] auger. There's no elevator in place and no Chicago Board of Trade to put a value on it. An infrastructure has to be built."
Although the fieldwork was curtailed, the group was able to identify potential markets in the early years of the project. The farmers approached their power provider Alliant Energy Corp. to ask if the company would consider using switchgrass to cofire the 726 megawatt Ottumwa Generating Station. Alliant understood the importance of reducing its emissions and helping their farmer customers solve environmental problems and meet economic development goals, says Bill Morton, a project engineer with Alliant. "It's been an interesting multifaceted story."
Test Burns Generate Data
Alliant provided oversight for the project when the test burn phase started in 2000. Those burns provided crucial information to the power provider. Morton says they relied on a Danish engineering firm with several years experience cofiring wheat straw in Europe. As it turned out, introducing switchgrass was not a big investment or challenge, he says.
The test burn phase took many years to complete because of the time needed to accumulate enough switchgrass to conduct adequate tests, Belden says. For the first phase in 2000-'01, they needed 1,300 tons of grass, or 2,600 bales, to make sure the existing processing equipment could deliver the needed volume of ground switchgrass. "It couldn't," Belden says flatly. "It couldn't deliver the capacity needed to fuel the boilers, and there was too much dust in the building with the equipment designed by the engineers." That led the group of farmers to redesign the processing system in the middle of the burn.
In 2003-'04, they burned 800 tons of grass, intensively monitored emissions and collected numerous fly ash samples. Fly ash from the Ottumwa Generating Station is used to make concrete. "The Powder [River] Basin coal used in Iowa is free enough of other chemicals that it can be mixed with concrete," Belden explains. "It has significant value. We had to prove that adding switchgrass fly ash to the mix wouldn't alter the properties." Rather than change its ASTM standards for fly ash, the Iowa Department of Transportation, the major customer for the fly ash produced at the Ottumwa Generating Station, agreed to approve the product if it was proven not to alter the concrete properties. That approval came in June 2005.
The farmers then had to prepare for one last large test burn. "We had to accumulate a projected 25,000 tons for a long-term burn of 90 days or about 2,000 hours," Belden says. They didn't meet that goal, but the Danish boiler scientists involved in the project were certain a 1,600 hour burn would provide all the necessary information. A total of 31,000 bales of switchgrass at about 1,000 pounds each were burned for nearly three months.
Once the burn tests were completed the group had to find out how the switchgrass would be fed into the Ottumwa Generating Station process. The 726-megawatt Ottumwa Generating Station uses pulverized coal in a tangential boiler. The powdered coal is blown from eight corners of the boiler into seven rows of burners in each corner, firing to the middle and creating two fireballs. Adding switchgrass to the system was done by installing two inserts to blow ground switchgrass into the burner. The Danish engineers helped to determine the optimum particle size and the best place to introduce the material for the most complete burn. "We had to go into the wind box of the boiler and hook up the switchgrass tubes so they pitch and yaw with the burners and follow the fireball," Morton explains. "The only time the [coal and the switchgrass] mingle is at the fireball." In 2000, when the inserts were installed they cost about $30,000 each, plus installation costs.
Once the equipment was installed, it had to be determined whether the switchgrass would corrode metal boiler parts. "It's very expensive to clean a boiler or replace tubes," Morton explains. "From our studies with the three test burns and the data gleaned by the Danish, we know we can burn up to 10 percent by volume and not experience any real problems." Emissions were equally important. "We had to know exactly what those emissions are, and that had to be approved by the governing body-in our case the Iowa DNR (Department of Natural Resources)-so our permits weren't impacted," Morton says. That required multiple tests on stack emissions, particulate testing, gas testing, etc., providing the data that resulted in the U.S. EPA and Iowa DNR approving switchgrass for cofiring at the Alliant plant.
Table 1 shows the changes in emissions resulting from substituting 100,000 tons of switchgrass for a British thermal unit-equivalent amount of coal, which would be a 2.5 percent cofiring ratio at the Ottumwa Generating Station. Emissions data for nitrous oxide (NOx), sulfur dioxide (SOx) and particulate matter (PM10) were gathered from the second test burn. Emission impacts for volatile organic compounds (VOC), hydrogen chloride (HCl) and carbon dioxide (CO2) are generated from standard EPA emission factors. Negative values show a beneficial decrease in emissions.
The test burn at 2.5 percent switchgrass cofired with coal showed carbon dioxide emissions would be reduced by 250,000 tons per year. "Any reduction in emissions is significant," Morton says. "It's significant when it's as measurable as it was with a relatively small percentage of [switchgrass] going through." The changes for other emission components are shown in Table 1.
Pinning Down Costs
With the emissions data gathered, the fly ash coproduct questions answered and metallurgical impact known, Alliant is ready to start cofiring. "To go commercial, we're two to three years out yet," Belden says. "We have to build a significant supply to crank up a processing system. When we start we have to be large enough so we can feed the boilers 24/7 all year around."
To support the research phase, farmer cooperators had seeded between 5,000 to 6,000 acres to switchgrass, although only about 3,200 acres were harvested in any one year. The grass was planted on marginal land with environmental and wildlife sensitivity so not all of the acres were harvested each year. To go commercial, Prairie Lands will have to expand the acreage 10-fold or more to supply the 200,000 tons of switchgrass that Alliant would need.
Belden is waiting for the final project reports due in September to complete the processing group's feasibility study and business plan. "We'd love to pay the producers $55 to $65 a ton at our doorstep," he says. That payment to the farmer, plus the estimated cost of $20 per ton to process it puts switchgrass at a price disadvantage for Alliant when compared with western coal, which costs less than $20 per ton delivered. To help close the gap between the two, Belden says Alliant has agreed in the preliminary supply agreement to pass along part of the environmental benefits from switchgrass to Prairie Lands. "If we reduce nitrous oxide, we get paid for it, if we reduce sulfur, we get paid for that, and if they start taxing mercury emissions we get paid for that." Similarly, Prairie Lands will get credit for any biomass power they sell to consumers wanting to support the project; and if new tax credits become available that Alliant can use, a portion will be passed along to Prairie Lands.
"Whether this will fly or not will be based on the government incentives in place the first 10 years," Belden says, which he points out is no different than the oil industry, which was heavily subsidized in the early years. "The revenue stream will come 80 [percent] to 85 percent from tax credits and incentives," he says. That may include tax credits to Alliant or to producers, payments for CRP or a cost-sharing program for grass seed.
Because they are in Iowa, the promoters of switchgrass for power can't escape the impact of corn-based ethanol. Belden says their project will have to compete with $4 corn, providing competitive returns to farmers so they aren't tempted to plant their CRP acres to row crops. In the future, ethanol could become the primary market for switchgrass. "We're going to figure out how to make ethanol out of grass," he says. "We have to gear up the agricultural side to be able to deliver."
In the meantime, the Chariton Valley Biomass Project continues to develop switchgrass markets. Guffey says some members of their group are looking at machinery to pelletize switchgrass to fuel stoves. Once that project is in production they believe they can use the same machinery to pulverize switchgrass so it can be combined with plastic resin. However, more research is needed on the qualities of switchgrass in plastic. Another project, which is close to commercialization, is compressing switchgrass fibers to make construction boards. Yet another group is proposing an ethanol plant using switchgrass for power and heat, Belden says. Now that they've completed the research and development stage, the folks in Iowa have only just begun the quest to commercialize switchgrass.
Susanne Retka Schill is a Biomass Magazine staff writer. Reach her at email@example.com or (701) 746-8385.