Stuck in the Middle

Lynn Merrill

ON ONE SIDE OF THE RECYCLING EQUATION are the mills, which are demanding the highest quality materials possible. On the other side are the suppliers, residences and businesses that recycle paper and other materials. And in the middle of it all is the materials recovery facility (MRF), with the conveyors, screens and balers working together to produce various marketable grades of recyclables from an ever-increasing amount of material.

Limiting the contamination of recyclables has been a challenge in the past, and mills have increasingly drawn a line in the sand. They now are demanding that MRFs address contamination issues or face rejections of their loads. At the same time, with recycling programs maturing and new materials coming in the front door in record volumes, increasing throughput per hour while simultaneously reducing operating costs has become a significant challenge. The solution comes in the form of better equipment and more automated separation of materials than before.

RRT Design & Construction, Melville, N.Y., designs and constructs MRFs. Since 1989, RRT has completed more than 300 projects. “Retrofits right now represent more than 50 percent of our business today,” says Nat Egosi, president of the firm. “That's been a significant change that's been occurring for the last five to 10 years. MRFs that were built in the early 1990s are well into their 10th to 15th year of life. The equipment has either reached the end of its repair life, or there have been technology changes. There's a certain amount of obsolescence and the need to do all this retrofit work.”

The types of improvements are striking, Egosi adds. “Five or 10 years ago, it was all about cutting costs,” he says. “The direction today is more about improving quality, safety, automation and flexibility.”

That translates into capital investments to replace equipment with slower throughputs with equipment that can process more material in a shorter period of time. “There are a number of reasons for this,” Egosi says. “One is to get everything done in a single shift as opposed to two shifts, or to be able to accommodate the growth in material or change in composition of material. There's significantly more plastic containers and, on the fiber side, significantly more corrugated and other types of paper other than [newsprint].”

Because of mills' demands, MRF operators are working to improve the quality of the materials as much as possible. Egosi says operators are paying attention to screening and making sure that burden depths — the thickness of material on conveyor belts — are adequate to allow sorters and equipment to recover the best possible quality of materials.

MRFs also are showing an increased demand for optical sorting equipment for plastics. “Most people say that they are interested in optical sorting and as soon as you present to them the cost, they're buying,” Egosi says.

What Egosi has not seen is the physical expansion of the MRF buildings themselves. “What I see is people putting more stuff into the tin can,” he observes. “What I see in future years would be the need to expand the building infrastructure as opposed to the equipment infrastructure.”

Dirtier Materials

Driving the above trends are several factors, according to Egosi. He says that the material has gotten dirtier, and that mills have become more concerned and vocal about the degradation of the quality. Also, the composition of paper material has changed from being newsprint with some magazines to also including a significant amount of corrugated and other types of fiber materials, such as office paper that's been shredded at homes and is in bagged form.

Burden depth becomes critical in this mix as well. “There is a desire to better meter the material,” Egosi says. “This way the material is presented to the sorter in a way that they can better sort the material and also so that what they are sorting is a small fraction of all the fiber.”

As a result, MRF operators are now modernizing plants that previously had only a conveyor belt by installing various screens to automate the separation of corrugated fiber material and to screen out fines in order to produce a better quality material. The screens are built to separate a portion of the material so that the remaining burden depth is thinner, allowing the sorters to concentrate on that material.

To create different handling characteristics for the recyclables and to separate one material from another, the screens are designed to operate at different speeds or are built with various opening sizes or with discs of different shapes.

Optical sorting for plastics has advanced over the last decade, and combined with a significant increase in both the value of plastics as well as the volume found in the waste stream, the technology has become more attractive to MRF operators. “There's been improvement, and they're more efficient,” Egosi says. “They can recover a higher percentage of material.”

The explosion of single-serve, polyethylene terephthalate (PET) plastic bottles has driven the demand for optical sorting systems. “If you studied the composition of the material in the typical MRF operation 10 years ago and compare it to today, there would be 15 times more bottles to sort,” Egosi says. “Suddenly, these MRFs are finding that they have to have more sorters for plastic than they did 10 years ago.”

Steve Miller, president of Eugene, Ore.-based Bulk Handling Systems, which designs, manufactures and installs material handling equipment for the solid waste and recycling industries, describes his firm's typical schematic for a MRF today. “If you're looking at residential single stream, a standard set up of the screens would be to first separate out cardboard with an OCC [old corrugated container] separator,” he says. “We would then do some pre-screening to remove the glass content. The material then goes to a news sorter to take out the newspaper fraction, and the remaining material then would move to [a screen] that separates fiber from containers.” Containers are often sorted through a combination of optical sorting devices, magnets, eddy currents and manual sorting.

Miller agrees with Egosi that mills now have higher standards for their recyclables. “In terms of quality, if you're going to be a long-term player in the industry, [the mills] need quality materials,” Miller says. “To the extent that they can get high quality material delivered to them, that's the extent that they are able to economically produce products for their customers. If you're a newsprint mill, for example, and you're being delivered poor quality, that's going to show up in your residue cost, in chemical costs and in slower times on your machines. Eventually, you won't be competitive.”

The push to further automate MRF sorting processes will continue into the future, Miller says. “There are still some things that people are doing manually,” he says. “In single-stream systems, there's still a high percentage of residue in the stream. You have sorters that are pulling this material out. Continued automation down the line is needed to try and eliminate that labor cost — that's still the most important cost in the system.”

Lynn Merrill is a San Bernardino, Calif.-based contributing writer.