BioCycle January 2005, Vol. 46, No. 1, p. 36
Biomass sources that come from manure, switchgrass, C&D debris as well as landfills supply renewable electricity.
Kristin Stewart Kujawa
“JUST as a wise investor maintains a diverse investment portfolio, a successful utility needs to make certain that it has a diverse portfolio of generation sources,” says Bill Johnson, manager of Agricultural Compliance for Alliant Energy, headquartered in Madison, Wisconsin. Alliant’s generation portfolio includes 434 megawatts of renewable energy – enough to power over 110,000 homes. “With projects utilizing landfill gas, switchgrass, anaerobic digesters, windpower and hydropower, Alliant Energy has developed opportunities for some of its agricultural customers to directly participate in the renewable energy industry, where the stars are coming a little closer to alignment.”
The service territory for Alliant covers parts of Iowa, Wisconsin, Minnesota and Illinois. “There’s enough biomass located in Iowa alone, if utilized efficiently, to affect a portion of the state’s energy needs,” continues Johnson. “While the supplemental income it provides may not keep a farm in business, energy sales are likely to be a welcome addition to any farming enterprise.”
GASIFICATION WITH LARGE IMPACT
The line “one man’s trash is another man’s treasure” could easily sum up the relationship between Alliant Energy and BFC Gas & Electric, one of the diversified companies located in Cedar Rapids, Iowa. BFC processes more than 150 tons of industrial, agricultural and construction waste every day and converts it into renewable energy.
Materials used include sawmill waste; construction and demolition wood; energy crops such as switchgrass, sweet sorghum and poplar trees; crop residues like corn stalks, corn cobs and seed cord; and nonrecyclable low-grade paper.
The materials are recycled into a biogas which is then used to produce steam to drive a turbine generator. One ton of fuel is used for every megawatt of electricity produced – enough electricity to power approximately 1,000 homes.
Environmental benefits of this process are significant. By utilizing materials that would otherwise be sent to a landfill, the biomass operation results in a 98 percent volume reduction. Only six tons of ash are produced for every 120 tons of material processed – a 95 percent reduction over traditional procedures. The ash residues are then recycled into a composting mixture.
SWITCHGRASS AS A FUEL ALTERNATIVE
Switchgrass was once a natural prairie grass that grew abundantly in the poor soils of southern Iowa’s rolling hills. The excellent burn qualities of switchgrass, coupled with the decrease in farm incomes, sparked an interest in growing the plant on marginal land as an alternative energy crop. The major benefit of burning switchgrass is lower carbon dioxide emissions.
The Chariton Valley Biomass Project in Chillicothe, Iowa, was developed to investigate and test switchgrass, and other grasses grown in southern Iowa, as a supplemental fuel source for coal-fired power plants. The project is a cooperative effort between Alliant Energy, Chariton Valley Resource Conservation and Development and the U.S. Department of Energy. The Alliant Energy Ottumwa Generating Station (OGS), a 675 megawatt (net) facility located in southern Iowa, has completed two test burns using five percent switchgrass in its fuel mix. The project’s initial test took place in December, 2000 and provided a good opportunity to validate the potential of switchgrass as a supplemental fuel source. The project team conducted a second interim test burn in December, 2003. Throughout the duration of the second test, 1,500 tons of locally grown switchgrass were cofired with coal at OGS to successfully produce significant amounts of electricity.
A long-term test burn of 25,000 tons of switchgrass has been planned for summer, 2005. If the final test burn is as successful as the first two, the project could use up to 200,000 tons of switchgrass and involve as many as 500 farmers annually. Future plans include cofiring biomass with coal to generate a sustained supply of 35 megawatts of biomass-derived electric power at the OGS. Additional benefits include having a reliable domestic fuel for energy production, enhancing the quality of the air and water and increasing the economic rewards from marginal cropland.
While this project has posed material handling challenges, it has the potential to provide a successful market for 50,000 acres of switchgrass grown on the highly erodible soil areas of southern Iowa. Alliant Energy is one of only two utility companies in the country known to be working with switchgrass.
Alliant is partnering with Midwest dairy farms to implement anaerobic digester systems that turn livestock waste into a clean, renewable source of electricity for the farm, reduce manure management costs and lower utility bills at the same time. Often the engines and generators produce two to three times more electricity than is needed by the farm, which allows Alliant Energy to purchase and redistribute the excess energy.
Environmental benefits of using manure to efficiently generate electricity include: Odor is reduced 90 to 95 percent, significantly reducing the fly population; Methane, which has roughly 22 times the global warming effect of carbon dioxide, is no longer released into the atmosphere; Solids from the manure are used for livestock bedding and as a soil conditioner; and Liquids are converted to fertilizer, which has approximately one-half the phosphorus content of manure.
Alliant Energy and its subsidiary RMT, Inc. (an engineering and environmental management consulting firm) joined forces with the Sauk County, Wisconsin landfill to capture methane gas to generate electricity. Launched in June, 2003, the Sauk County landfill houses the first landfill multiturbine installation in Wisconsin (there are eight 30-kilowatt Capstone microturbines on-site).
Additional Alliant Energy landfill gas projects include: A 20-year agreement to purchase electricity generated at the city of Janesville, Wisconsin landfill; Purchasing electricity produced at the Superior Glacier Ridge Landfill in Mayville, Wisconsin (this project produces two to four megawatts per hour of renewable energy); A partnership with National By-Products in Berlin, Wisconsin, on a new generating facility that increases the state’s supply of renewable energy by 2.4 megawatts per hour; and A local high school in Antioch, Illinois that uses landfill gas microturbine powered electricity.
More details on Alliant renewable energy programs are available by visiting www.alliantenergy.com. Kristin Stewart Kujawa is with Alliant Energy.