Roadside trash is piling up here and thousands who make a living picking through other people's garbage are staring at a bleak future after Mexico's largest open waste dump was shut down.

Authorities have been scrambling to find a permanent replacement for Bordo Poniente on the outskirts of Mexico City -- the main landfill site for nine million of the urban area's 20 million inhabitants.

And the closure has dealt a harsh blow to about 4,500 people, known as "pepenadores," who sift through the waste searching for any scraps that can be recycled and sold for money.

"The waste is our living. Bordo Poniente is our whole life. We work here to be able to buy a house or a car, for everything, but especially to send our children to school," Pablo Tellez, one leader of one of the group of trash recyclers, told AFP.

Tellez directs some 1,500 people who fan out over the vast site which contains almost 80 million metric tons of waste over 1,100 acres (450 hectares).

Opened more than 30 years ago, Bordo Poniente used to take in up to 12,000 tons of trash a day, and mountains of garbage still tower some 17 meters (yards) high around the site.

Each scavenger has their specialty -- from metals to paper or plastic bottles.

Gloria, a 54-year-old single mother who declined to give her surname, has worked at the site for 40 years. Three of her seven sons work alongside her.

As she trawls the foul-smelling trash, alongside stray dogs and mosquitoes, Gloria's violet sweater turns black in minutes. Like the other workers, she wears no mask nor gloves for protection.

"It's difficult work, especially as a woman, but unfortunately I have no other choice because I didn't have the chance to study," she said.

Workers have no fixed salary, but are paid for what they collect by intermediaries who sell the waste on.

-- Every-increasing waste --

"I work 12 hours per day and I can earn up to 800 pesos per week (around 60 dollars), depending on the type of material I find," Gloria said.

City officials shut down the dump a month ago under pressure from federal authorities wanting to reclaim land they say risks polluting the city's water system.

City officials say the closure will reduce greenhouse gas emissions significantly and have announced a plan to set up a bio-gas plant at the site.

But they have yet to produce a long-term solution for dealing with the ever-increasing waste.

"They didn't have a 'Plan A' and they don't have a 'Plan B' either," said sociologist Hector Castillo from the UNAM university, who has studied Mexico's waste industry for several decades.

"They need large pieces of land that they don't have in the city."

For now, authorities have made deals with smaller private dumps in the neighboring state. Since they are further away, collection has been disrupted and makeshift dumps have appeared in parks and on streets.

Despite some ambitious plans, new waste disposal systems are a challenge to apply in a metropolitan area where more than half of some 50,000 waste industry employees work informally.

"It's very complicated," Castillo said.

The pepenadores and their sometimes mafia-like bosses are battling to remain part of the lucrative industry as it slowly evolves.

For now, rubbish trucks illegally continue to dump waste at Bordo Poniente, providing temporary relief for the scavengers who swarm over each new arrival.

"Mexico is a very large city. Household waste won't stop from one day to the next," Tellez said. "All that we ask of the government is ... that they let us work."