BLACKSBURG -- Soybean oil produced some of Duke Energy's electricity Thursday as the utility completed a first-of-its-kind test of biodiesel to fuel power plants.
Duke's Mill Creek combustion- turbine plant normally runs on natural gas and diesel fuel. But this week, one of its eight units sampled blends of diesel and biodiesel, which is made from vegetable oil.
Because it comes from plants, biodiesel could help Duke produce some of its power from renewable fuels. N.C. legislators are considering a bill to require that part of the state's electricity come from such domestically produced sources.
The new fuel could also help the company meet widely expected future limits on releases of carbon dioxide, the gas blamed for global warming. Plants remove carbon dioxide from the atmosphere, so biodiesel lowers net emissions by up to 75 percent.
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Biodiesel won't change Duke fundamentally. The fuel is relatively new to the market and the power plants that could use it supply only a small fraction of the company's electricity.
Duke says its tests at Mill Creek, on a unit that can produce 80 megawatts of power, were the largest U.S. trial of biodiesel on a plant of that type and size. The unit could supply about 80,000 homes if it ran constantly, but is typically used only at times of peak demand.
"I've been in biodiesel since 1990, and this is the biggest test ever," said Howard Findley of Peter Cremer N.A., the Cincinnati company that supplied the biodiesel. "It's a game changer."
Stephen Smith of the Southern Alliance for Clean Energy, a frequent Duke critic, said he was intrigued by the test.
"We applaud thinking out of the box, and Duke's doing that," he said. "I would give (CEO Jim) Rogers and his crew some kudos for being innovative."
Duke recently solicited offers from other renewable-energy suppliers, bringing in 70 responses.
At Mill Creek, the company tested 100 percent biodiesel and three biodiesel-diesel blends composed of 80 percent, 50 percent and 20 percent biodiesel. Early results were good, company officials said, but the data won't be fully analyzed for months.
Officials from General Electric, which made the plant's turbine generators, fuel providers and the industry-supported Electric Power Research Institute monitored this week's tests.
It's become obvious that the biodiesel tested this week won't harm GE's turbines, said General Electric's Colin Wilkes, sitting at computer screens that flash the turbine's emissions.
Duke operates two other large combustion-turbine plants in the Carolinas. Because turbines at the plants can produce energy from a cold start in less than half an hour, they're used only when power demand is highest, such as on hot afternoons and cold winter nights. Such plants generate about 1 percent of Duke's power.
For biodiesel to join the plants' fuel mix, it would have to show financial, operational and emissions benefits, said Mary Huller, Duke's project manager. Technical issues remain, especially with the high-biodiesel fuel blends Duke tested this week.
Biodiesel also needs broader acceptance by the marketplace, experts say. Only a fifth of the nation's biodiesel-making capacity was tapped last year. And unlike natural gas, the fuel can't yet be shipped by pipeline.
But the potential is alluring.
Biodiesel could give Duke another fuel option without changing hardware. The company might be able to use the turbine plants more if biodiesel lowered emissions, Huller said. Biodiesel-fueled plants could also act as backup power for future renewable energy, such as solar and wind power.
Leonard Angello of the Electric Power Research Institute doesn't expect biodiesel to replace petroleum. But he said that at least a dozen utilities are interested in using it as a backup to diesel and natural gas.
"They're all looking for alternatives and fuel flexibility," he said.