The conveyor chugged along, full of material. Workers on either side, wearing hard hats and two gloves on each hand, quickly removed anything that looked out of place. Another conveyor resembling an escalator carried the remains up to an optical sorter, which identified more chaff to be removed, then a shaker table, and yet another conveyor past more picky workers and so on, in a clanky, smelly Rube Goldberg-style operation that separated valuable material from contaminants. On a mezzanine overlooking the spectacle, a few busloads of second graders, a wine columnist and his daughter looked on, transfixed.

This wasn’t a winery at harvest time, but the Montgomery County recycling center in Derwood, Md. I invited myself for a field trip to learn more about my carbon footprint as a wine drinker. Specifically, I wanted to know what happens to all those empty bottles I toss in my little blue bin every week.

They end up here, as shards of glass vibrating along the belt (thus the double gloves on each hand for the sorters). Ultimately, they end up in piles, sorted by color, commingled with fragments of beer, whiskey, soda and water bottles, before being sold to a glass manufacturer for reuse.

I learned not just about wine bottles during my visit, but also about how our trash is sorted and recycled, and a little about how careless we are with what we throw away.

Vineyard workers at a harvest sorting table remove “MOG,” or “matter other than grapes.” At the recycling center, they sort plastic from metal and glass, and remove “contaminants,” or anything not recyclable. I saw one worker tip over a box of cigars, still individually wrapped in cellophane, and quickly toss each into a large bin marked “TRASH.” Someone probably thought, “Is this recyclable? Well, someone else will sort it out.”

According to the Environmental Protection Agency, Americans generated about 254 million tons of trash in 2013 and recycled or composted just over a third of it. Per capita, that meant we recycled 1.51 pounds of 4.4 pounds of waste each of us generates every day.

The EPA didn’t say how much of that was wine bottles, but various studies have attributed as much as 60 percent of the wine industry’s carbon footprint to bottles. Most of that is the production and transport of empty and full bottles. But glass is endlessly recyclable, right? It shouldn’t be a problem.

Not exactly. Many counties and cities don’t recycle glass, even if they have recycling programs. Arlington County, in Virginia, recently suspended collection of glass, after its contractor decided it was not a financially viable product.

The recycling industry as a whole is “in disruption,” says Adam Ortiz, director of Montgomery County’s Department of Environmental Protection. “Recycling became a viable marketing channel for managing solid waste in the 1990s, but the systems haven’t evolved much since then,” he told me during my visit. China used to take a lot of our recyclables, but has scaled back dramatically because of contamination.

Montgomery County has domestic buyers for its recyclables, says Willie Wainer, head of solid waste management. But the county’s recycling remains viable because of its “dual stream” system, which requires residents to separate paper from containers (plastic, metal and glass). The county sold its paper to various mills for about $500 a ton at its peak, somewhat less now, but the paper is much higher quality when not commingled with other trash, a great advantage for the county.

“In a single-stream system, the paper gets dirty,” Ortiz says.

Glass is not worth as much as paper. The recycling center separates glass into three categories: clear; “gramber,” or green and amber (colored glass); and mixed, various glass contaminated by other matter. A ton of clear glass earns the county about $30, while a ton of gramber is worth $15. The mixed glass, a whopping 75 percent of the total, is worthless. The county pays a processor in Pittsburgh to collect it and turn it into something usable.

“We don’t want to discourage people from recycling glass,” Wainer said. “Everything gets recycled.” But rinse your bottles to keep them clean and more valuable.

Boxed wines? Jim Delaney, senior operations manager at the recycling center, pantomimed a gesture that reminded me of an umpire calling a batter out on strikes, complete with leg kick.

“Yank the liner out and put it in the trash,” he said. “The box goes in the paper bin.” Leave them together and both go into the landfill.

How about corks? Those are “contaminants,” Ortiz said. We should take our corks to stores such as Whole Foods Market and Mom’s Organic Market, which collect them for recycling into various products.

Aluminum screw caps? Not sorted out of mixed glass by the county, Ortiz said. He checked with the Pittsburgh processor, and told me after my tour that screw caps are recyclable. We should leave them off the bottle but toss them into the container bin, to avoid contaminating the glass further, he advised. The aluminum capsule remaining on the bottle is still a problem.

And cans? The county sells aluminum for $1,175 a ton, almost 40 times as much as the price for clear glass, and 80 times as much for colored glass, which most wine bottles use.

“I tell all my beer-drinking friends to buy cans instead of bottles,” Ortiz says.

Canned wines are trendy, but still a tiny fraction of the market. A few wineries are putting better wines in boxes. Kegs — reusable or recyclable — are a niche market for restaurants.

Wineries don’t give us many eco-friendly choices in wine packaging, and they won’t until we demand it. Meanwhile, we’ll do what we can.

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