CANCUN, Mexico - Clambering over garbage heaps, rummaging through trash cans, Supriya Bhadakwad didn't set out to save the planet when she was 13 years old, just her family. But two decades later, in the global arena of climate negotiations, the sari-clad Indian woman and other scavengers are making their voices heard, tilting with big corporate players in a tug-of-war over the world's dumpsites.

The Goliaths they're taking on are companies building incinerators worldwide to burn waste from landfills, material generations of "waste pickers" have survived on. Many of the projects are supported by private funds raised under the U.N. climate treaty.

Bhadakwad had come 11,000 miles to the annual U.N. climate conference in Cancun on behalf of 6,000 organized landfill recyclers in her native Pune, India, to demand access to the waste now trucked instead to a new incinerator. Without their dump, they're trying to survive by going door to door for trash in a community 12 miles away.

"We have a right to the waste that can be recycled," Bhadakwad told a reporter. "We want to continue making a living without interference from such big private companies."

Their environmentalist allies say some 15 million people worldwide depend on scavenging for a meager livelihood. And these advocates and poor recyclers have an environmental argument to make.

Incinerators not only produce toxic pollution, but "by burning waste they increase carbon dioxide emissions," the biggest global warming gas, said Mariel Vilella, a campaigner with the international group GAIA, the Global Alliance for Incinerator Alternatives.

By collecting and recycling plastic bags and bottles, glass, aluminum and other material, those 50 million scavengers "represent a huge opportunity to reduce greenhouse gas emissions," Vilella told reporters, since what's destroyed must be replaced by items newly manufactured and transported in a process using up natural resources and producing more greenhouse gases.

In a report issued here Friday, the U.N. Environment Program saluted the waste pickers, saying, "The role of the informal recycling sector should not be underestimated." A chart indicated the scavengers of New Delhi, for example, prevent several times more emissions than a large waste-to-energy plant in the Indian capital.

"For decades we've been part of the solution for solid waste management on this planet," said Exequiel Estay, head of a Chilean scavenger association. "We demand that our jobs become sustainable."

They're also demanding that organized waste pickers and civic groups around the world have access to a global fund within the U.N. climate treaty structure to support local recycling programs. Such a fund is one item under discussion at the Cancun conference.

Under the U.N.'s Clean Development Mechanism (CDM), international support already flows to some incinerator projects that burn waste to produce energy - instead of burning fossil fuels that produce even more carbon dioxide - and to projects that capture methane gas emitted by landfills.

Because they reduce greenhouse gas emissions, those projects are awarded CDM credits that can be sold on the booming global carbon market, to help coal-fired.

power plants elsewhere, for example, meet their emissions reduction quotas.

The GAIA group proposes alternative approaches: Don't burn anything, but deliver decomposing organic waste to facilities that will capture and use methane gas for electricity production, and leave solid waste to the landfills for waste-picker collection.

"In San Francisco, 77 percent of all solid waste is diverted in this way," said GAIA's Christie Keith.

Her organization and other supporters flew representatives of scavenger associations from eight nations to Cancun to, among other things, raise their concerns with the CDM board of directors at an open discussion Tuesday, when they urged the board to reconsider its approval of such incinerator and landfill projects.

On Wednesday, a dozen garbage recyclers from Latin America, India and South Africa unfurled banners on the steps of a conference meeting hall, with slogans reading "Respect for Waste Pickers" and "Zero Waste for Climate Justice."

"We Are Climate Fighters," they declared.

The appearance on the world stage of people from the dumps of poorer nations, seeking the subsidies of the rich, points up how global warming is changing not just the climate but is upending entire sectors of traditional economies, as more and more billions of dollars are mobilized in the new realm of carbon finance.

For Bhadakwad, making her way through the conference crowds in a brilliant saffron-and-violet sari, the air-conditioned U.N. stage was a long way from the refuse heaps of Pune, where she and her husband divided the jobs of collecting and separating recyclables to support their three sons.

"I started at age 13 because of the economic condition of my family," she said. "My father was an alcoholic, that's why."

Could she have imagined she was helping the planet?

"I wasn't aware of these issues," she said, smiling at the question. "I didn't know we were helping the climate. But now I've come to know about it, about all the consequences of waste management."