The Montgomery County Council, confronting an issue that has been dodged for 15 years, opted yesterday to build a $170 million trash-to-energy incinerator in rural Dickerson, a move it admitted was substantially more expensive but politically less costly than building it in the heavily populated Shady Grove area.

In a dramatic straw vote after a day of often-emotional debate and a personal appeal from County Executive Sidney Kramer, the council voted 4 to 2 to locate the mass-burn facility in the remote western part of the county.

The action, which will be put to a formal vote July 7, means the county would transport all its garbage 18 miles by rail from the Shady Grove Transfer Station near Gaithersburg to Dickerson.

The expense associated with transporting the garbage has been estimated at $10 million annually or about $24 per household a year.

In a related vote yesterday, the council targeted a goal of recycling between 15 and 30 percent of all the county's trash, up from the current 7 percent.

That action, officials said, increases the likelihood that the council will dramatically increase its mandatory recyling program. The county currently requires newspaper recycling in the southern part of the county, but may expand the program and require residents to separate cans and bottles from the rest of their garbage.

The council, grappling for the last month with Montgomery's crisis of mounting garbage and shrinking landfill capacity, has had a list of technical and legal questions to decide. But yesterday there was only one issue: Dickerson or Shady Grove -- two communities that have vigorously fought the incinerator.

Kramer, who had reaffirmed the decision of his predecessor, Charles W. Gilchrist, to place the facility in Dickerson, canceled his appointments yesterday morning when it appeared that the seven-member council might be leaning toward Shady Grove.

In the council chamber -- filled to capacity and decorated with the banners and pamphlets of Dickerson residents and environmentalists opposed to the proposal -- Kramer recited the history of how he came to believe Dickerson is the best location. "To change direction now will affect the entire credibility of the government process . . . to no good end," Kramer said, adding "the proper decision is Dickerson."

Council member William E. Hanna Jr. provided some of the most moving moments of the day, explaining how he changed his position on the difficult issue. He said his first inclination was to go with Dickerson, as recommended by Kramer. However, he said, the more he read background papers on the issue, the more doubts he had because of obvious technical and economic benefits of the Shady Grove site.

Shady Grove, near the population centers of Gaithersburg and Rockville, is the site of the county's transfer station, where garbage is shifted from neighborhood collection trucks to 18-wheel rigs for transport to the Oaks Landfill in Laytonsville.

Hanna explained that the county bought the land with the intention of constructing an incinerator there and the transfer station was even built with a removable wall to accommodate the new facility. To locate the property in Dickerson requires purchase or lease of land from Potomac Electric Power Co.

The other major drawback to Dickerson is transporting trash from Shady Grove and then to haul the resulting ash back to Shady Grove for disposal in a landfill. "Is it better," Hanna asked, "to move your trash 50 feet or 18 miles?"

Hanna, who lives in Rockville, said he received phone calls until midnight from constituents who didn't want the mass burner for a neighbor. He said at the start of the council discussion he "honestly" didn't know how he would vote.

At the end of the discussion, as the council wound down from often acrimonious debate, Hanna looked out over the audience and sighed, "I know I'm going to hate myself in the morning . . . . {But} I cannot in good conscience vote for Dickerson."

His voice breaking, Hanna said, "I'm going to vote for Shady Grove." His speech was applauded by members of the Sugarloaf Citizens Association, who live near Dickerson and have vowed a lawsuit against the decision.

Council President Rose Crenca joined Hanna in favoring Shady Grove. She said she was troubled by the fact that CSX Corp. has a monopoly on rail service to Dickerson and she was concerned about cost as well as quality of service and possible interruption, caused by a strike or a derailment, such as last week's CSX accident at the Takoma Metro station.

Council members favoring Dickerson -- Bruce T. Adams, Michael L. Gudis, Michael L. Subin and Isiah Leggett -- expressed concern that to switch the direction taken by the county executive would further delay the project, now set for completion in 1993. The county's only operating landfill in Laytonsville will reach capacity in 18 months.

Supporters of the Dickerson site noted that about 200,000 people live near Shady Grove, compared with 10,000 in Dickerson. Kramer argued that such a facility is more compatible with a less densely populated area.

Critics contend such reasoning is purely politics because there are fewer voters to anger.

Dickerson residents reacted with disappointment and anger to the straw vote, which is not binding on the council. They said they will try to change some minds before the July 7 vote. One possible advantage could be the return of council member Neal Potter, who is recuperating from a heart attack and who favors Shady Grove.

"It's not over until the fat lady sings," Crenca said. But council staffers predicted that the straw vote won't change and that a move to make Dickerson the unanimous choice of the council will succeed.