Sorting recycling is a drag. So these UMass grads are teaching AI to do it.

The Somerville startup rStream is piloting its new waste-sorting technology at UMass Amherst

AMHERST — As students rush into the UMass Campus Center food court to grab a quick bite between classes, the hustle seems to stop only for a moment when they approach the trash.

One diner pauses, contemplating whether a condiment-smeared plastic container goes in the trash or recycling. The student eventually throws it into one of the bins, assured that — wherever it winds up — they won’t have to see that trash ever again.

But just across the Campus Center’s busy concourse, students toss trash instead into a a nondescript hulk of gray metal designed to make that dilemma irrelevant. The AuditPRO, something of a souped-up garbage receptacle, churns away — seeking to make a dent in the millions of tons of trash that wind up in landfills and oceans every year.

The AuditPRO, designed by a pair of UMass alumni, takes pictures of refuse as it moves along a conveyor belt. It then uses those thousands of images to train an artificial intelligence program to sort discarded materials more efficiently than humans would.

“Technology like this has the potential to play an integral role in not only waste reduction, but building more of those circular economy markets that begin with understanding what materials you have coming into the system in the first place,” said Kathy Wicks, director of sustainability at UMass Amherst Dining Services.

The addition of the machine, created by Somerville startup rStream Recycling and developed at Boston’s Greentown Labs, is part of a semester-long pilot at UMass. But the company’s efforts are already drawing attention at the federal level. The development of the AuditPRO was funded in part by the National Science Foundation, and this month rStream received a $1.25 million grant from the US Department of Energy to continue its work.

For now, the machine can’t actually sort trash itself. It’s enough of a challenge to train computers to differentiate specific kinds of recyclables from one another. Ian Goodine, co-founder of rStream and a UMass alum, jokingly describes AuditPRO in its current form as a “fancy photo booth for trash.”

But the technology is advancing quickly. Goodine and fellow co-founder Ethan Walko began developing the AI program just last year, and they believe it could be sorting trash mechanically sometime in 2024.

rStream is one of a handful of tech startups taking on a tricky economic problem that’s been plaguing the waste disposal industry.

For years, US municipalities could depend on a robust overseas market for minimally sorted recyclable waste. That meant consumers became accustomed to throwing bottles, cans, and papers into one big “single stream” bin with a general belief that the materials would get reused.

This image shows how rStream's system attempts to differentiate items.Lane Turner/Globe Staff

But in 2017, China, a major buyer of US recyclables, changed its policy to dramatically restrict contamination. While the change affected all types of reusable materials, it’s raised particularly urgent environmental concerns when it comes to plastic, which has never been especially easy to recycle.

According to the US Environmental Protection Agency, about 8.7 percent of plastic waste in America was recycled in 2018, and 27 million tons of plastic was dumped into landfills that same year. A separate analysis by the environmental advocacy group Beyond Plastics estimated that the share of plastic waste that is recycled may have fallen as low as 5 percent by 2021.

It was in the context of the shifting global recycling market that Goodine and Walko began working on what would become rStream. As undergrads in 2020, the two cooked up an idea for a senior design project focused on turning post-consumer plastic into filament for 3D printing.

But as they began to explore the life cycle of plastic, they decided to set their sights on a more fundamental problem: how to divert recyclable waste back into productive use.

Soon, Goodine and Walko found themselves in the basement of the UMass Campus Center in Tyvek suits, separating recyclables from non-recyclables by hand, and dumping the sludge onto tarps.

The physical drudgery of manual separation helped illustrate why the demand for post-consumer recyclables had become so low.

“At the end of the day, the hard part isn’t the reprocessing, it’s collecting enough useful materials at a high enough quality and purity for the whole system to be worthwhile,” Goodine said. “So we said, ‘Wait a second, sorting could be our opportunity to do something that helps people.’ And we have been sorting things ever since.”

If sorting by hand wasn’t economical in China, chances are it wouldn’t be economical in the United States. So the two engineering majors turned to the emerging field of AI, with a particular interest in the recent enhancements in image and pattern recognition.

After they earned their bachelor’s degrees in 2021, Goodine and Walko stayed on at UMass for a postgraduate program in mechanical engineering. During those studies, they took a class on AI in which they created an early demonstration of a software program that seemed to be able to tell the difference between types of waste.

With that early success in hand, they began to apply for funding.

rStream was officially founded in 2021, while the two were in graduate school at UMass. And this year, the company won a $275,000 National Science Foundation Small Business Innovation Research grant, which helped them develop the AuditPRO.

The money from the Energy Department will help the company with its next challenge.

Back at their facility in Somerville, the co-founders are developing a machine that would combine the AI “brain” they are testing with a completely automated system that decides if a material should be recycled or not, and then actually sorts it.

Inside the AuditPRO, a camera took photographs of a cardboard box passing underneath on a conveyor.Lane Turner/Globe Staff

Although this technology could make sorting waste easier, Kirstie Pecci, executive director of the environmental nonprofit Just Zero, cautioned that the economics of recycling are difficult to solve.

Even if waste is well sorted after it’s been thrown away, Pecci said, small pieces tend to intermingle: organic waste with paper, for instance, or glass with plastic. That reduces the market value of (and the financial incentive to recycle) post-consumer materials.

With plastic, Pecci added, there’s the added problem that there aren’t always good uses for recycled material. The most important thing people can do, she said, is to reduce the production of plastic waste.

“We need to stop using plastic. There is no ... safe, economical, or climate-friendly way to use plastic,” she said. “The only way to address the plastic problem is to create less plastic.”

But in places like a crowded university food court, people look for convenience.

Every year, UMass Amherst produces approximately 3,000 tons of waste that gets sent to landfills, and rStream believes products like AuditPRO can help push that number down.

“[The solution] all starts with the ability to sort, which is derived from the ability to make accurate detections,” Walko said. “This pilot that’s going on right now is allowing us to validate the accuracy of those algorithms and improve upon them just using machine-learning techniques.”

Now, the founders hope to conduct more pilot programs at different universities, so when students throw something away, they won’t have to think too hard about where it might wind up.

“The AuditPRO is really the perfect step to accelerate towards the next opportunity,” Goodine said. “It’s an indication that there’s a huge opportunity ahead for us.”

Patrons lined up for food inside the UMass Campus Center.Lane Turner/Globe Staff