Pozzotive In The News

Raw building materials are highly carbon-intensive. The News joined a tour of a Connecticut facility that is helping Yale lower its carbon emissions by making a cement substitute out of recycled glass.

3.5 million glass bottles on the wall. 3.5 million glass bottles. Take one down, pass it around, and it might end up as cement in Yale’s Physical Sciences and Engineering Building under construction.

Yale’s ongoing construction on upper Science Hill will feature 600,000 gross square feet for the School of Engineering and Applied Science and more. In accordance with Yale’s promise to achieve net-zero carbon emissions on campus by 2035 and zero actual carbon emissions by 2050, the development will include a thermal utilities plant that will produce energy for the facilities.

But even if operations are sustained by on-site energy production, creating a building from raw materials is quite carbon-intensive. Instead, some of Yale’s building materials will use Pozzotive, an industrial filler made from recycled glass such as drink bottles — the equivalent of 3.5 million of them, to be precise, according to a slideshow used during a recent tour of the glass recycling facility.

At the tour last month, organized by several students at Yale’s School of the Environment, a group of Yale affiliates explored Urban Mining Industries’s facility in Beacon Falls, Connecticut, where recycled glass is processed and turned into a powdery building material known as pozzolan.

Concrete is an essential building material for modern-day structures. Standard concrete consists of aggregate like pebbles or gravel, sand, water and cement — the powdered binding agent, often confused with concrete, that gives concrete its integrity.

“This isn’t chemistry that we’re inventing,” Chris Cotulio, a material sustainability specialist at O&G Industries — a construction company that has worked with Urban Mining Industries — said during the tour. “The ancient Romans and Greeks used volcanic ash as a pozzolan in their structures over 2,000 years ago, and a lot of them are still standing because it makes more durable concrete. So this is just a modern twist, using a post-consumer recyclable as a vehicle for that silicon dioxide.”

Chris Cotulio leads the Yale group through the plant, pointing to machinery that cleans and filters glass particles.

During the tour, Cotulio and Urban Mining Industries CEO Louis Grasso Jr., who invented Pozzotive, walked Yale members through the process of creating the finished product.

The facility receives post-consumer glass from nearby material recovery facilities that collect refuse from ordinary recycling bins. Upon arrival, the material is put outside in foul-smelling mounds of muddy grit. Given the imperfect recycling systems, contamination from organic matter, plastics and metals isn’t uncommon.

The raw recycled glass is cleaned mechanically in a tumbler that Grasso called a “dryer” — which he said differs from most plants’ chemically intensive cleaning processes.

“Everything is really done correctly and transparently, so no chemicals or water goes through the dryer,” Grasso told the News. “The dryer tumbles the glass on itself, and it breaks off the paper labels, and it breaks off the dried organics as it goes through the tumbler or dryer.”

Grasso founded the company over two decades ago and has since taken on large projects like the more-than-$3 billion JPMorgan Chase high-rise in Manhattan, which used 52,000 cubic yards of pozzolan-substituted concrete to build floors, according to the Pozzotive website.

This project and more were covered in a tour led by Cotulio and Grasso. In the factory control room, Cotulio showed the visitors the systems and operations screen, where a schematic of the factory’s operations is constantly monitored for changes in operations and efficiency.

“What we’re seeing is an example of where the sustainable option is the better option,” Ayushi Khan ENV ’24, a postgraduate associate at the Yale Center for Industrial Ecology, said. “So this is a great, amazing example of why recycling can be so lucrative sometimes, and the better option sometimes. And this is easy to scale.”

Natural forces like motion, gravity and density are utilized by the plant to process this raw material. Harmful batteries are then removed by giant magnets. Powerful fans blow out the lightweight plastics while leaving the denser glass pieces behind.

Metal objects, such as batteries, can be dangerous if left in the filtered glass. After a high-powered magnet removed them, they were collected in large bins for transport to special waste facilities.

Mechanical grinding, akin to a geode tumbler, breaks down the glass pieces into the plant’s final product: pozzolan.

Pozzolan can be substituted for new cement at rates of 15 to 50 percent, according to Cotulio, though Grasso has experimented with blends containing up to 70 percent substitution. Due to the chemical composition of cement, a baseline proportion of cement is required to mix with water and make concrete, so full replacement with pozzolan is not possible.

The remainder of the cement is usually supplemented with fly ash, which is a coal-burning byproduct, or slag, a remnant of iron smelting. However, a partial replacement of traditional cement already significantly reduces carbon emissions, Cotulio said.

Recycling a ton of glass back into glass bottles saves roughly 166 kilograms of carbon dioxide, Cotulio said in his tour presentation. By comparison, recycling glass into concrete saves 980 kilograms — nearly a ton of carbon emissions.

According to Cotulio, benefits of Pozzotive’s cement include increased resistance to chloride — useful for when sidewalks are salted in the winter — and that it shrinks less due to temperature fluctuations compared to traditional concrete, which can lead to structural cracks.

“It was also pretty amazing that the product itself is cost parity with regular cement, which means it’s the same cost,” Alfonso Panis SOM ’26, who was also on the tour, said. “It’s really just the supply chain, at least to my mind, that’s the bottleneck, like the raw material sourcing.”

The Urban Mining Industries facility is located at 105 Breault Road in Beacon Falls.

Correction, March 23: An earlier version of this article misstated the name of the concrete alternative made from recycled glass. It is Pozzotive, not Pozzitive.