Lawmakers from both parties are increasingly focusing on alternative fuels to address climate change and energy independence, but there are signs that some in Congress are worried about the potential negative environmental effects of such technologies.

Biofuels, including ethanol, and coal-to-liquids technology, which converts coal into fuel, have gained interest and support as alternative-fuel options because of their potential to replace oil imports with domestically produced resources.

Ethanol, made mostly from corn in the United States, also is frequently cited as a solution for reducing greenhouse gas emissions. The upcoming farm bill is expected to be a vehicle to further expand use of ethanol.

But last month, Rep. Henry Waxman (D-Calif.), chairman of the House Oversight and Government Reform Committee, asked the National Academy of Sciences to investigate “the environmental and economic advantages and disadvantages of various specific biofuel and coal-to-liquid technologies.”

“While federal support of these programs could likely have a significant impact on the levels of production and consumption of these fuels, we must be careful to chart our policies on the best information available in order to avoid unintended consequences,” Waxman wrote Feb. 20 to the head of the academies. “Of particular concern is the need to address U.S. dependence on oil while not exacerbating the problem of global warming.”

And while ethanol is widely embraced as an achievable — and in many parts of the country, politically popular — technology for weaning the United States off foreign oil and for addressing climate change, there is disagreement about whether it actually reduces greenhouse gas emissions.

The Congressional Research Service in January cited evidence that ethanol use may not actually produce a net reduction in the use of fossil fuels when the amount of energy used to produce the fuel is considered.

The production of corn-based ethanol also has other environmental drawbacks, including water pollution from the large amounts of fertilizer used to grow it. Growing corn also requires vast quantities of water, a resource that is increasingly scarce in some drought-prone parts of the country.

In addition, low blends of ethanol in some areas of the country can contribute to ground-level ozone pollution.

Deron Lovaas, the vehicles campaign director for the Natural Resources Defense Council, acknowledged the environmental problems of corn-based ethanol but added that research into cellulosic ethanol, which can be made from virtually any plant, will mitigate those risks.

“Corn will always have a role,” Lovaas said, “but we need to move beyond corn.”

The CRS also noted the potential environmental benefits of cellulosic ethanol, including lower greenhouse gas and air pollutant emissions as well as providing more energy than corn-based ethanol. However, producing cellulosic ethanol in large quantities is cost-prohibitive.

The federal government is currently researching ways to reduce the production costs of cellulosic ethanol. Those research efforts are expected to receive a funding boost in the 110th Congress.

Environmentalists are even more concerned with growing Congressional support for coal-to-liquids technology, which produces carbon dioxide emissions along with other environmental hazards caused by coal mining. The NRDC’s Lovaas last year described switching from petroleum to coal to power transportation as “breaking a smoking habit only to take up crack cocaine.”

Despite environmentalists’ antipathy toward the technology, lawmakers from coal-producing states are promoting it. Democratic presidential contender Sen. Barack Obama (Ill.) has teamed up with Sen. Jim Bunning (R-Ky.) to introduce legislation to promote the coal-to-liquid technology.

And last week, House Majority Leader Steny Hoyer (D-Md.) introduced energy independence legislation backed by nearly 100 Democrats that allows the Defense Department — one of the largest fuel consumers in the country — to enter into long-term contracts to procure “unconventional fuels,” including liquid coal.

Rep. Earl Pomeroy (D-N.D.), a backer of the bill, defended the coal-to-liquid provisions during its March 1 introduction, saying that carbon sequestration technology will mitigate greenhouse gas concerns. “The notion that coal can’t be used is a dated notion,” he said.