The Tennessee Valley Authority could be generating more "alternative" energy for less cost, if only the public wasn't so enamored with wind and solar power.

Methane gas, formed as human and animal waste or garbage decays, produces more power dollar for dollar. It's half as expensive as wind power and a tenth the cost of solar power, according to TVA figures.

But, coming from a stinky mess, it lacks appeal to the rate-paying public. TVA depends on ratepayers' choosing to pay extra to help fund alternative energy sources.

"From a marketing viewpoint, it's hard to promote," said Jim Keiffer, TVA senior vice president of marketing. "You're asking people to pay a premium for green power."

That's why TVA's program, Green Power Switch, available through distributors including Nashville Electric Service, requires that at least half the energy it creates come from the favorites: solar and wind.

They are the face of the program.

From October 2006 to this month, about 1 percent came from solar panels, 33 percent from burning methane and 66 percent from wind turbines.

About 74.8 million kilowatt-hours were generated, which is about how much electricity 4,730 average homes would have used during that time.

The agency's Web site doesn't mention how much energy comes from methane. The seldom-photographed operation is not exactly scenic: The gas is pumped in pipes from sludge-laden lagoons at a Memphis wastewater facility to an otherwise coal-burning TVA plant.

Costly solar panels have been sprinkled around the Tennessee Valley - most at high visibility locations, including schools and the Adventure Science Center in Nashville. Brochures also emphasize windmills standing on a ridge in East Tennessee.

"We had to get it out there that green power was available and that it worked," Keiffer said.

Most customers skip it

Convincing is still needed. Just 12,500 of the more than 3.7 million households using TVA-produced electricity have signed up to pay more for the agency to be greener.

The program remains part of the TVA's marketing branch based in Nashville, unlike coal, nuclear and hydroelectric generation, which are housed in the agency's power division.

Ellie Throop of Mt. Juliet said she understands how many consumers might find using the sun and wind to run appliances and lights "prettier and easier to stomach."

She herself has no objections to methane, but she's concerned about what she doesn't know about the program. She had been paying $12 extra on her electric bill to support clean energy but dropped out of the Green Power Switch program earlier this year.

She felt she got more "warm fuzzy pictures and green imagery" than facts.

"I was trying to understand how directly the extra amount of money I'm spending is actually contributing to the environment," she said. "Why couldn't I just designate where what I'm currently spending goes? Why should I have to pay more?

"That's when, as a consumer, you start to feel tricked. You wonder if this is a legitimate expense."

Federal law calls for the agency to create electricity at the lowest feasible cost, officials say, leaving them to ask customers to pay more to develop green power sources. More than 600 utilities and cooperatives nationwide offer a green pricing option.

Throop said she might re-enroll as she learns more.

A boom in interest is coming from colleges and universities - including Middle Tennessee State University, where students lobbied to increase their fees for cleaner energy and conservation. Five dollars a semester per student is going to Green Power Switch, covering about 10 percent of the Murfreesboro school's electrical use.

TVA put in $13 million

Students are generally gung-ho about all aspects of green power and, while adults can be turned off to it, some of the youngest take great delight in the idea of making electricity from methane gas.

"When I told a group of first-graders that we make power out of stinky diapers, they just loved it," said Holly Jordan, TVA marketing manager for residential products.

The Green Power Switch program cranked up in 2000, and since then TVA has put just under $13 million - $1 million of it was from a grant - into capital investments on the three alternative energy sources.

About $3 million has been pumped into solar panels for 0.03 megawatts of power, $4 million has gone for three windmills for 2 megawatts, and about $6 million for 8 megawatts from methane, according to TVA's marketing division.

TVA is also buying power from a private company that put up 15 windmills in East Tennessee near the first three.

The contract with that company prohibits the agency for proprietary reasons from disclosing just how much the various green sources are costing per kilowatt hour, Keiffer said.

General costs were provided. Typically in this country, solar costs 40 to 60 cents per kilowatt hour, wind 8 to 12 cents and methane 4 to 6 cents, according to information from his department.

For a few years, the program brought in more money from ratepayers than the cost of such power that was produced. An internal inspector general's report found a 42 percent deficit in 2003.

Officials said the program, which weathered a few missteps, had taken time to set up. That situation is reversed today.

Emphasis makes sense

One of TVA's staunchest critics, the Southern Alliance for Clean Energy, doesn't fault the agency for where it has put its money in this case.

Gil Melear-Hough, director of renewable programs for the nonprofit, said more energy should come from methane, but what ratepayers want matters.

"In focus groups and surveys, you ask people what they're willing to pay extra for and they say they're willing to pay more for wind and solar - premium green power," he said. "There was good logic behind what TVA has done."

Melear-Hough, a member of the Green Power Switch Steering Committee, said he hears from some ratepayers who suspect the extra money doesn't go for alternative fuel sources.

There's no doubt that it does, he said. An annual independent audit by the Center for Resource Solutions in California confirms that.

"We are strong supporters of the Green Power Switch program," Melear-Hough said. "There's nobody in the Southeast generating more green power than TVA. We just don't think it's enough."

His group wants TVA to focus on helping consumers save energy and make more use of all the cleaner, renewable fuel resources that don't have waste-disposal problems.

The green power program so far produces less than 1 percent of the energy that TVA creates.