Some describe early experimentation with robotics in the construction and demolition (C&D) recycling space as erratic. However, operators are taking a second look at how optical sorters and other automated solutions can improve the recycling process, especially when it comes to materials such as wood, according to a 2024 MRF Operations Forum session titled C&D Recycling: Brute strength or finesse?
Led by moderator Terri Ward, executive director and CEO of the Construction & Demolition Recycling Association, Chicago, panelists discussed how the C&D operators are applying technology to automate and improve recovery.
The panel included William Cooper, director of business development for Brooklyn, New York-based Cooper Recycling; David DeVito, vice president of operations for ReSource Waste Services, Albany, New York; and Abel Pereira, general manager of GreenWaste, San Jose, California.
Six years ago, Pereira and his team introduced robotics to GreenWaste’s advanced C&D line to handle quality control, pulling everything but wood off the one line.
“They worked pretty well—then they started not working so well,” Pereira said.
GreenWaste initially employed five robots but ended up removing four. Now the company is revisiting optical sorting technology and robotics, Pereira said, which includes possibly using optical sorting in a quality control role to clean up wood and separate clean dimensional lumber.
“There’s been quite a bit of advancement in the last six years,” he said of optical sorters in C&D applications. “We’re looking forward to implementing that technology in our plant and hopefully [making] it a 24-hour plant like we always intended to. … We’ve always tried different technologies and [have] no regrets. We’re never going to get anywhere if we don’t try new concepts, new ideas.”
Early adopters
During conversations about whether C&D facilities embrace technology, Ward said she’s encountered a perception that facilities only use screens and manual sorters or that they simply grind everything up to create alternative daily cover. In reality, Ward clarified, C&D recycling has numerous crossovers with single-stream recycling, including technologies.
C&D recyclers often have to be innovators because it’s difficult to find off-the-shelf equipment that will work in the plants, Ward said. C&D debris can be difficult to process, and any equipment introduced to those recycling plants has to be reinforced, built tougher and heavier duty for C&D applications.
“We’re all challenged with end market capacity, and we’re all here trying to do a little bit better and come up with another way to remove things out of a waste stream,” DeVito said.
C&D recycling facilities constantly are looking for ways to recycle as much as possible and maximize profits while also tinkering with systems and trying different ways to improve efficiencies, Cooper said.
Finding the right balance between human labor amid staffing challenges and automation using robotics and artificial intelligence (AI) has been tricky for operators. Every process change has an equal and opposite reaction, which makes for a constant learning process, Cooper added.
For instance, he said Cooper Recycling uses optical sorters to separate wood from nonwood. Still, the technology is not as proficient as humans in sorting clean, dimensional lumber from medium-density fiberboard and engineered woods.
“You still have to have human beings doing some form of quality control,” Cooper said. “Everybody says, ‘Oh, … you buy this equipment, and it doesn’t call out sick.’ Well, yeah, it does. It calls out sick all the time, and you have to fix it.
“There are other forces driving the moves to technologies and technological adoption, but it’s all progressing in the right direction—[just] maybe not as fast as we all had thought.”
All three operators said they are seeking technology that can identify and eject high-quality wood from the stream and opticals that can spot batteries, which carry a high potential risk for starting fires.
Plant optimization
Pereira said GreenWaste operates four C&D transfer stations and five processing plants for C&D debris, each with separate lines based on the type of feedstock.
The company’s advanced C&D line is designed to process construction materials 24 hours per day, while another demolition-focused line is located at a closed landfill.
“That was the intent of having the robots on there,” Pereira said of the C&D line. “We start the process with presort with excavators pulling out the big chunks of concrete, big chunks of metal.”
After presorting with an excavator, GreenWaste feeds material through a shredder and then sends it to a ballistic separator to screen out the 5-inch minus and separate the 3D material. Material is further separated using disc screens and other various screens and, eventually, a trommel.
“At night you would just feed the plant automatically, which was the intent,” Pereira said. “But currently we’re running the plant … with the manual sorters. At the moment, we’re still looking into other opportunities with robotics and optical sorting.”
In New York, Cooper Recycling’s system processes and recovers ferrous and nonferrous metals, various grades of wood, stone, rock and brick and a small percentage of paper and plastics. The system preconditions the material through primary reducers or preshredders, Cooper said.
ReSource Waste has four processing facilities, and the company uses different technology at every plant, DeVito said.
“It all depends on what [we’re] going after at that plant. Are we trying to make more end-market wood to get into the [medium-density fiber]board? Are we trying to make more cover there?” he said. “We’ve designed each plant to do something a little bit different, so we direct materials to each one of our locations that makes sense.”
A typical process flow would include feeding material from a conveyor into a trommel, DeVito said, while other plants might use different types of finger screeners or eddy currents to recover nonferrous metals. Some of the plants have one shredder, while others incorporate two.
In one plant, ReSource uses a sink float tank where the heavies sink to one conveyor and the wood and plastics float up to another conveyor to be further processed. To pick through everything prior to processing, DeVito said the company primarily uses skid steers, loaders and excavators.
“I call it micro picking because we’re literally trying to pick out … cardboard out of the front end of the process,” he said. “The more we can pick out up front, the cleaner that all those products are.”
End-market challenges
Another challenge C&D recyclers face, Ward said, is pressure to hit high recovery rates of 85 percent or more, driven by sustainability and LEED (Leadership in Energy and Environmental Design) certification requirements, balanced with local pressures and end market issues.
At Resource in New England, DeVito has taken an innovative approach to developing unique end markets. One product Resource has worked on is a manufactured aggregate, which takes crushed asphalt, brick and concrete and mixes it with clean shingles, fine shingles and dirt fines to create a product that can be used for road base.
To avoid wet waste, which can’t be accepted into a landfill, DeVito created a solidification pit so the company can accept low-level contaminated wet dredgings from river and ocean cleanups and combine that with absorbent fine wood products to create a landfill cover product.
In the Northeast, DeVito said, companies are required to have a beneficial use license to be able to move products from landfills to get credits for recycling or reuse. ReSource has secured that license and is also one of only two companies in the state to get certification for waste-derived products that can be distributed and used in New Hampshire.
“So we try to get creative and legitimize what we try to do for end markets, even if it’s just a cover,” DeVito said.
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