OMAR FREILLA WAS BECOMING the activist equivalent of a rock star even before the Rockefeller Foundation handed him $100,000 and one of its inaugural Jane Jacobs medals this summer, even before Leonardo DiCaprio featured the eco-entrepreneur in his global-warming documentary, The 11th Hour. So it's refreshing that the first thing the 34-year-old sweetheart of the environmental blogosphere tells me when we meet is that he doesn't want this story to be about him.

"It's about ... them," he says, gesturing at a young man who works part-time silk-screening T-shirts, a grandmother on public assistance, a file clerk for a Manhattan law firm, and a part-time teacher's aide. To understand why these people have turned up to help start a recycled-building-materials cooperative—Freilla calls it "a worker-owned Home Depot for used stuff"—it's important to understand the place where it is blooming.

The South Bronx was noisy, smelly, and run-down when Freilla was a kid. Since then things have generally improved. But as New York City has wrestled with pollution, other boroughs have managed to shove not just the problem but also its often unpleasant solutions into the South Bronx, creating what one of Freilla's colleagues calls "one of the nastiest, filthiest, most polluted places in the whole U.S."

The once thriving area has for decades served as the nation's cautionary tale of urban failure. Congressional District 16, which includes most of the South Bronx, remains the country's poorest, according to the most recent U.S. census figures. Median estimated household income in the district was about $21,100 in 2006, compared with $46,500 for the rest of the city and $48,500 nationally. Unemployment stands at 14 percent, or higher in some neighborhoods, compared with 6 to 8 percent for the city as a whole. Childhood asthma rates here are among the nation's highest. Schools continue to fail and violence to pervade people's lives.

FREILLA GREW UP NEARBY IN THE LATE 1970s, when industries and the middle class were fleeing the South Bronx for the suburbs. Postwar highways had sliced through the business districts and plunged them into decay, and landlords were abandoning their buildings or torching them for the insurance money. When Freilla started school, drugs, declining municipal budgets, blackouts, and gangs had turned entire blocks of his hometown into urban deserts of razor wire, rubble, graffiti, and trash.

A combination of luck, high test scores, and a supportive Dominican family helped Freilla land a spot at the Bronx High School of Science, one of the city's premier secondary schools, and then a scholarship to Morehouse College in Atlanta. Freilla's mother had nurtured his interest in science, tuning the TV to nature shows and taking him to the American Museum of Natural History, and in college he studied biology and environmental science. Freilla dispatched his homework quickly and spent much of his time organizing protests against problems such as school cutbacks and police brutality. At Miami University in Oxford, Ohio, on a fellowship to study for a master's degree in environmental science, Freilla expanded on his ideas about the links between politics, economics, and the environment, researching Winton Hills, a chronically poor neighborhood of Cincinnati and the site of the city's last urban landfill.

Freilla returned to the South Bronx the day after graduation in 1998, determined to apply what he'd learned to his hometown. Though not as abandoned and chaotic as during his childhood, the area "had become a magnet for polluting industries like power plants and waste companies," he says.

As transportation coordinator for the New York City Environmental Justice Alliance, Freilla called upon the city and state to reduce traffic from trucks hauling waste and buses returning to parking barns, switch to cleaner vehicles, and close certain highways. In 2001, Freilla joined the staff of a group called Sustainable South Bronx and worked to encourage green practices in the neighborhood. But he says ecofriendly businesses won't automatically bring prosperity to the inner city. "If history is any guide, the profits generated by green businesses will largely enrich the predominantly white, middle-class and upper-middle-class [owners]," he says. "I began to think of incubating businesses here, run by people here, worker-owned.

"New York City produces approximately 50,000 tons of trash each day," Freilla continues. "Approximately a third of that moves through waste transfer stations in the South Bronx before being exported to distant landfills and incinerators, which also happen to be in low-income communities of color."

The solution? Four years ago he formed Green Worker Cooperatives, an umbrella organization set up to hatch locally owned, environmentally smart businesses.

DURING ONE OF MY VISITS, we gather in the renovated building that used to house the American Bank Note Company, a remnant of the days when the Bronx was a bustling manufacturing center. The co-op is prepping members to create and manage a store, ReBuilders Source, that will sell recycled building and construction waste: the doors and windows, counters and sinks, and appliances and hardware that usually end up in landfills.

Freilla got the idea when he learned that about 40 percent of New York City's trash comes from construction and demolition. "I thought it would be easy to do," Freilla says of his idea to replace transfer stations with a reuse store. "People wouldn't need a degree to work there."

And there will be jobs. Recycling, reuse, and manufacturing businesses that use recyclables generate 10 to 90 times more jobs than the disposal industry, according to the Institute for Local Self-Reliance.

To recruit members, the co-op opened a Green Worker Co-op Academy last fall, offering weekly sessions to teach locals about environmental issues and how cooperative businesses work. In one exercise, Freilla led a "toxic tour" of the South Bronx, an introduction he repeats for me on a summer afternoon.

In a tone that's realistic but undaunted, Freilla begins the lesson: A plant cheerily called the New York Organic Fertilizer Company processes up to 40 percent of New York's treated sewage sludge, drying it into pellets for farmers. Two blocks down, a wastewater-treatment plant sits along the East River. A medical-waste transfer station, Stericycle, has replaced a medical-waste incinerator. Seemingly everywhere are freeways, parking lots, and trucks pumping out fumes. At scores of transfer stations, haulers dump every imaginable kind of waste—household, construction, and automotive—until it can be shipped to landfills outside the city. In one lot mangled drywall and wood pile up; another forms the resting place for a two-story-high pile of car engines, and next to that rises a gigantic pile of shock absorbers.

A funny smell hangs over a new, flawlessly landscaped little park near the Bronx River: the unmistakable tang of the city's not-so-well-rinsed OJ bottles and milk jugs at the plastic-recycling transfer station next door. Several locals tell me it's nothing compared with the "eau de sludge" that on hot summer days remains overpowering even two miles away.

So far research conclusively ties only asthma to all this activity, but residents claim that the emissions cause additional health problems such as immune disorders and high infant mortality. Whether the Bronx needs more trash businesses is a source of endless dispute in the borough, and even Freilla's project has come under fire.

"Is this the best we can do in terms of jobs?" asks Marian Feinberg, environmental health coordinator at For a Better Bronx, who remains skeptical of Freilla's plans. She worries that a recycling business will only "increase the amount of waste and traffic in the South Bronx."

That criticism also sparked controversy over a 28-acre brownfield site where the city wants to build a jail. Late last year, Freilla, in partnership with Sustainable South Bronx and others, instead proposed an eco-industrial park that would include several recycling enterprises and employ about 300 people. But critics, including local U.S. representative José Serrano (D), have decried a plan they say will bring more trucks and debris to the area.

Freilla has pulled back from the eco-park dustup to focus on ReBuilders Source. He argues that the castoff materials are already in the neighborhood, so why not make something better out of them? "The city's major export is now trash," Freilla says. "ReBuilders Source will be an alternative to that." He hopes the store will be the first start-up of many, the beginning of a coalition that will transform the blighted South Bronx. "We want worker cooperatives on every corner," he says. "We're out to create a model for a democratic and green economy."

As we continue the tour, people shout hellos to Freilla. He's known on the street for his activism, but also for playing drums in the Dominican-Haitian folkloric band Pa'Lo Monte and for sharing the bounty from the thriving vegetable garden he tends with his wife. To each well-wisher, he waves back with the effortless charm of a politician. Occasionally, people rush up to give testimonials. "He's the man!" gushes a local PTA president. "I'll pay you for that," Freilla says.

BACK AT CO-OP HEADQUARTERS in the old bank note factory, Freilla turns to a large dry-erase board that hangs on an exposed brick wall. Using a marker, he outlines the constellation of power in the average board meeting: "Chairperson. Secretary. Treasurer. Facilitator." He turns to face the four founding co-op members. "So. Who wants to do what?" Freilla asks, eyebrows raised, soft voice excited, expectant.

The members shift in their chairs. They seem eager but also uneasy. Some have a hard time arranging childcare during meetings; others shoehorn in co-op commitments after a long workday and a three-hour subway commute. For a few moments, no one says anything. Freilla lets the silence become a prod for initiative. The roar of the Bruckner Expressway two blocks away, the school bus depot four floors below, and New York City's ever-present soundtrack of sirens and car alarms assert themselves. Then the awkwardness passes. People raise their hands and volunteer.

Heather Millar is a freelance writer based in Brooklyn, New York. Her last feature for Sierra was "Charlotte's Way" (July/August 2006).