ALBANY, N.Y. — Farmers, businesses and state officials are investing millions of dollars in ethanol and biofuel plants as renewable-energy sources, but a new study says the alternative fuels burn more energy than they produce.

Supporters of ethanol and other biofuels contend they burn cleaner than fossil fuels, reduce U.S. dependence on oil and give farmers another market to sell their produce.

But researchers at Cornell University and the University of California, Berkeley say it takes 29 percent more fossil energy to turn corn into ethanol than the amount of fuel the process produces. For switch grass, a warm-weather perennial grass found in the Great Plains and eastern North America, it takes 45 percent more energy and for wood, 57 percent.

It takes 27 percent more energy to turn soybeans into biodiesel fuel and more than double the energy produced is needed to do the same to sunflower plants, the study found.

"Ethanol production in the United States does not benefit the nation's energy security, its agriculture, the economy, or the environment," according to the study by Cornell's David Pimentel and Berkeley's Tad Patzek. They conclude the country would be better off investing in solar, wind and hydrogen energy.

The researchers included such factors as the energy used in producing the crop, costs that were not used in other studies that supported ethanol production, Pimentel said.

The study also omitted $3 billion in state- and federal-government subsidies that go toward ethanol production the United States each year, payments that mask the true costs, Pimentel said.

Ethanol is an additive blended with gasoline to reduce auto emissions and increase gasoline's octane levels. Its use has grown rapidly since 2004, when the federal government banned the use of the additive MTBE to enhance the cleaner burning of fuel. About 3.6 billion gallons of ethanol were produced last year in the United States, according to the Renewable Fuels Association, an ethanol trade group.

The ethanol industry claims that using 8 billion gallons of ethanol a year will allow refiners to use 2 billion fewer barrels of oil. The oil industry disputes that, saying the ethanol mandate would have negligible impact on oil imports.

Ethanol producers dispute the new study, saying the data are outdated and don't take into account profits that offset costs.