Power Pairings

Power plants use high-pressure, high-temperature steam to spin the turbines that generate electricity, yet two-thirds of the total energy combusted in the process is wasted. Ethanol plants use steam energy to power evaporators, distillers and dryers. To take advantage of those synergies, some have found it beneficial to collocate ethanol plants and power plants.
By Susanne Retka Schill | June 05, 2007
Corn and coal country don't overlap much, which is probably one reason why there aren't many ethanol facilities collocated with public utility plants. Some well-capitalized, large ethanol plants do have combined heat and power but it's surprising that the promise of low-cost steam hasn't attracted more ethanol plants to power plants. Interestingly, one five-year-old collocation and another more recent one were initiated by power companiesnot ethanol producers looking for low-cost steam.

Jeff Endrizzi, manager of the Big Stone Power Plant in Big Stone City, S.D., says the company was looking for an industry to utilize its excess boiler capacity. "Our boiler capacity and turbine capacity are slightly mismatched," he explains. At 2 percent to 3 percent, it was a small amount for the 450 megawatt power plant, but sufficient steam for another industry. When the effort to develop an ethanol plant in the area started in the late 1990s, Otter Tail Power Co., manager and co-owner of Big Stone Power, approached the farmers and ethanol plant developers. "There was a natural hesitancy," Endrizzi recalls. "The designers of ethanol plants know how to successfully build systems. Changing power sources causes concern, not knowing how much work it would take or how successful it would be."

Blaine Gomer, general manager of Poet Biorefinery-Big Stone, says the usage of steam from the power plant a half-mile away has worked well for the ethanol producer. The plant was expanded this spring bringing the nameplate capacity up from 40 MMgy to 75 MMgy. An initial concern in using steam from the power plant was the substantial upfront capital investment of several million dollars for the steam line and re-boiler. That has been offset by several benefits, the first of which was cutting the plant's natural gas use by 50 percent and total energy cost by about 25 percent compared with similar plants, Gomer says. The ethanol plant gets all of its energy for the evaporators and distillers from the power plant steam, but continues to use natural gas to power the dryers. "Another huge benefit is that all the water that we bring in is reused and recycled," Gomer says. "The water we use here comes from the power plant's retention ponds, which comes from a nearby lake. We are reducing our domestic water usage by 85 percent."

The 450 megawatt power plant, managed by Otter Tail and owned by Otter Tail, Northwest Energy and Montana-Dakota Utilities Co., produces 3.6 million pounds of steam per hour (measured as mass) from western coal. After doing some generating work, 100,000 pounds of steam per hour is piped to the ethanol plant in 10-inch overhead steam pipes. Endrizzi says the insulated pipes lose very little heat, even in cold weather. "There's not a noticeable change between winter and summer," he says. Condensate from the ethanol plant is returned to the power plant in a closed-loop system.

Blue Flint Collocation
A 1,500-foot steam line connects Blue Flint Ethanol to its power source, the 1,116 megawatt Coal Creek Station. The 25-year-old power plant was sited alongside the Falkirk Mine near Underwood, N.D., in order to maximize the efficiency of its lignite coal power source. The 50 MMgy Blue Flint plant began producing ethanol from corn this spring. Great River Energy, the Minnesota generation and transmission cooperative that owns Coal Creek Station, approached Headwaters Inc., a coal services companynew to liquid fuelsto partner with them in the project.

Although building an ethanol plant on the extreme western edge of corn country in central North Dakota doesn't seem feasible, the developers are confident they will have ample corn supplies. "We feel pretty comfortable about our corn sourcing," says John Baird, vice president for Headwaters Inc., the majority owner of Blue Flint along with Great River Energy. "We have a local draw area, plus contracts with producers up and down the rail line that services the site."

Low-cost energy was the big draw for the project, however, other benefits emerged as they got into the project, Baird says. The infrastructure surrounding the power station provided a big savings for the ethanol plant, from small things like security, telephone and power lines being in place, to larger infrastructure items like rail access, roads and water.

From an ethanol plant design perspective, the process design is identical to other plants, says Greg Loest, director of technology integration for ICM Inc., the designer of the Blue Flint plant. "The steam sent over the fence from Coal Creek Station is utilized in the entire ethanol production process from front to back," he says. Of the steam going to the ethanol process, 10 percent goes into the cook process, 30 percent into the evaporators and 15 percent into distillation. "In our design, the evaporation drives distillation," he adds. At Blue Flint, steam tube dryers for drying distillers grains account for about 45 percent of the steam energy used. The steam tube dryers are costly, two to three times more expensive than conventional natural gas dryers, but the system allows greater flexibility for future coproducts and better color and protein content of the distillers grains, Loest says.

In general, steam costs are nearly half that of natural gas costs, he says. Natural gas typically costs $7.50 to $8 per million British thermal units (Btus). A large power plant produces steam for $3 to $4 per million Btus. Even with the increased capital costs for building the steam lines and steam tube dryers, the savings in energy costs make the system economical compared with conventional ethanol plants.

More Plants Planned
With Blue Flint Ethanol in operation, Great River Energy is developing its second project in the Spiritwood (N.D.) Energy Park. "The Spiritwood Station is more of a conscious decision to build and site a power plant alongside two agri-processing facilities that need steam. They (project developers) approached us and asked if we'd be interested," says Mark Fagan, manager of business development for Great River Energy.

The power plant will provide steam to an existing barley malting plant owned by Cargill Malt, and to a planned 100 MMgy ethanol plant being developed by the Newman Group. Harold Newman, lead investor in the Newman Group, owns the 34-year-old AlChem Ltd. LLLC, a small 10 MMgy ethanol plant in Grafton, N.D. With the increasing cost of steam pipes, they are working to create a tight footprint for the three collocated plants, Fagan says.

Great River Energy expects to break ground on the $276 million plant this summer, once the permitting process is complete. The plant will use a circulating fluidized bed boiler, fueled by coal railed in from the Coal Creek Station. Fagan says the choice of boilers will make it easier to adapt to biomass-based fuel in the future. "It's going to be a highly efficient operation compared to a conventional power plant," he says. While a typical coal-fired plant converts 25 percent to 35 percent of the coal's energy into power, the added steam use boosts overall efficiency to 62 percent. The added efficiency means a smaller plant can generate electricity for a cost that is competitive with a large conventional plant.

Great River Energy is also working with economic developers in southeastern North Dakota to develop a third plant, which is still in the planning stage. "We want to take it to the next level and incorporate biodiesel as a steam user and do more integration with sharing of common equipment between the ethanol and biodiesel plants," Fagan says. In addition, Great River Energy is designing the power plant to use coal and biomass fuels from the outset.

Coal-fired power plants aren't the only steam generators being considered for collocating ethanol plants. In Idaho, Alternate Energy Holdings Inc. is completing public hearings and preparing the paperwork to file for local approval to build a nuclear power plant in Bruneau along the Snake River in southwest Idaho. CEO Don Gillespie says the public hearings have gone well. The project has received strong support from farmers looking for cheaper power for irrigation. Besides increasing the supply of electrical power in the region, Gillespie is proposing an ethanol plant be collocated to use waste steam. Like coal-fired plants, only one-third of the 4,500 megawatts of thermal energy to be produced by the proposed nuclear reactor will be utilized in generating electricity. A collocated ethanol plant would have ample steam power, with the size being determined by the potential feedstocks. The distillers grains coproduct can be used by neighboring cattle feedlots and dairy operations. Alternate Energy is also proposing the Idaho Energy Complex include a methane digester using manure from nearby livestock operations.

Once local approval is attained, the process moves to the federal Nuclear Regulatory Commission. While the plant design being proposed for Idaho has been proven abroad, the federal regulatory process will take nearly three years, Gillespie says. If approved, the plant will take another four years to build with the earliest operational date in 2015.

In the eastern United States, Green Renewable Energy, Ethanol and Nutrition Holding LLC (GREEN) is proposing to build a 100 MMgy ethanol plant that will be collocated next to a waste coal-fired electrical generation facility owned by Westwood Power Services. GREEN Holdings has received permits to build a biofuels terminal at the location of the proposed ethanol plant near Tremont, Pa.

With natural gas prices likely to remain high, such collocation projects will be closely watched as more developers are able to balance the high up-front capital investment with the potential energy savings.

Susanne Retka Schill is an Ethanol Producer Magazine staff writer. Reach her at sretkaschill@bbibiofuels.com or (701) 746-8385.