Juan Pineda, 38, is a quality specialist, or “picker,” at the less-than-four-year-old Sunset Park recycling plant that processes some 15,000 tons of the city’s metal, plastic, and glass each month.

Hi-tech machines help sort the city’s waste into salvageable subsets — plastic with plastic, paper with paper. And human “pickers” like Pineda do the rest, scanning conveyer belts of incoming material to take out what doesn’t belong.

The smooth flow of recycling from your well-meaning curbside bag of bottles and newspapers to a city Department of Sanitation truck to facilities that collect and process and eject the recycling depend on that last human link, and those links aren’t employed by the city. At the Sims Municipal Recycling facility in Sunset Park, which has a long-term contract with the city, Pineda and other employees say they are being mistreated and are looking to unionize with the Teamsters.

The company has resisted the union push by 70 employees at the material recovery facility in Brooklyn, forcing city officials to prepare for the possibilities for that recycling if there were a strike.

In a telephone interview in Spanish, Pineda said his approximately $19-an-hour job is good, though it comes with quirks and difficulties.

Standing at the conveyor belts for long shifts, in a facility whose temperature he said could be too hot and too cold depending on the weather, pickers are liable to find strange things: money (which has to be brought to supervisors); dead animals (a cat, for example); syringes; and even firearms (so damaged by the machines, Pineda said, that it was hard to know whether they are real or fake).

Pineda and other workers claim, however, that their employer plays favoritism in advancement.

As employees of a city-contracted company, employees aren’t protected by the same health care, benefits or scheduling agreements that DSNY workers get. Workers say they weren’t given vacation on Martin Luther King Jr. Day and they lack a pension.

Sims did not return requests for comment. During the term of their current contract with the city, the company hasn’t experienced any disruptions of service due to labor disputes. But the situation has escalated to the point of a City Council hearing Tuesday morning.

The employees have the support of Sunset Park’s Council Member Carlos Menchaca, who said in a statement, “I will stand by our SIMS workers in Sunset Park every day until they win. Join us as we bring justice to the only facility processing waste in NYC without a union.”

The situation pits a combustible mix of progressive causes for the City Council and Mayor Bill de Blasio, who will also have to contend with the fact that the city’s main sanitation workers are organized by a Teamsters local, too.

Creation of the state-of-the-art facility was a commitment to city recycling and sustainability — placed on the water’s edge so that barges as opposed to trucks could carry the raw material to the plant, displacing some quarter-million vehicle miles annually, according to the company. The facility’s construction included recycled glass and crushed rock from the Second Avenue subway, all of which elevated portions of the site enough to remain dry during Superstorm Sandy.

DSNY spokeswoman Belinda Mager said in a statement, “Regardless of whether Sims’ workers at the Brooklyn facility unionize or not, we expect Sims to provide its contracted recycling services to the City over the long-term and to continue to be a reliable and cooperative partner in our citywide recycling efforts.”

In fiscal year 2016 alone, the city delivered 267,517 tons of metal, glass, and plastic as well as 149,544 tons of mixed paper to Sims, which operates multiple facilities.

“We want to grow with the company,” said Jordy Lopez, 22, another picker who is also involved in the union push in Brooklyn.

“Nobody wants a strike,” he said, “but our voices should be listened to.”