Material Separation Practices/Equipment

Posted by Carol Brzozowski On March 3, 2016 In MSW Management Weekly, Processing, Waste

Steven Viny, CEO of Envision Waste Services in Cleveland, OH, regards it as such: “We’re always going to need landfills. There’s a time and a place for a single-stream MRF [Material Recovery Facility]. There’s a time and a place for a waste-to-energy unit. There’s a time and a place for mixed waste processing.

“The industry has changed. The material we handle has changed. It’s lighter in weight, and that means organics are a bigger component. Of the material that remains, what’s the most cost effective way to deal with it and advance our industry to a point where we become a materials processing industry as opposed to a disposal industry? I think the dirty MRF is really the next frontier.”

Viny points out that there are a “bunch of moving parts right now that demand attention in the waste industry that is almost like a perfect storm.”

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The era of the thick Sunday newspaper has given way to electronic media, which has led to a significant diminishment of fiber in the US wastestream.

Thick-based plastic soda bottles have given way to plastic beverage containers so thin that “some people call them water bags,” says Viny. “The water is a structural element and once you’ve finished drinking water, you can easily crush the plastic in your hand.”

Technology has led to finding ways to make packaging stronger by design and require less weight, Viny point out. “If the nation isn’t drinking any more soda than they drank before, then the waste or the load of recyclables weighs less,” he adds. “The same is true with aluminum cans. When I first started in the recycling business two decades ago, it was 25 aluminum cans to the pound. Now it’s something like 39. Containers of all types have become stronger by design so they can use less raw product.”

That has caused a tremendous light weighting in the recycling stream and rubbish stream, notes Viny.

With the landfill business being a fixed-cost business with respect to site acquisition, cell development costs, environmental compliance, and human resources, “how do you make it up when you lose a significant portion of volume because of this light-weighting of trash?” asks Viny.

“We’ve seen landfills go from small local landfills to larger, more regional landfills. We’ve seen consolidation in the industry that helps to control costs,” he says. “With waste becoming light-weighted and volumes being reduced, it ultimately will lead to a price increase at the landfill if they want to maintain the same level of profitability that they maintained in the past.”

The same holds true in recycling, Viny contends. “There’s a cost to run the same recycling truck around the neighborhood,” he says. “Trucks cost more today than they did for a comparable unit a decade ago. Engines are lower emission. The price of steel has gone up. As fleets age and need to be replaced, the capital expense is a higher cost than it used to be.”

Wages have risen and benefit packages have increased, Viny says. With the light weighting of recyclables “that means the same truck driving the same route and picking up at the same number of homes has a lower payload,” he adds. “Recycling commodities fluctuate in value. Right now the value has gone down. The challenge is how do you continue to pick up recyclables when the collection cost is greater than it has been and the tonnage and value has gone down?”

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Another factor: China’s green fence. “If you had recyclables that nobody wanted, you sent them to China,” says Viny, adding the country’s green fence policy ended that practice.

“Now if you want to market recyclables, you have to make a responsible pack, and whether you export it or use it domestically, it has to meet ISRI [Institute of Scrap Recycling Industries] quality standards,” he adds.

Historically, single-stream MRFs have relied on star screens to separate fiber and plastic film from beverage stock. “The star screen sends fiber in one direction and beverage containers in another,” says Viny. “The fiber is processed with star screens to remove the larger items—the OCC—and then the smaller items like fiber and newspaper.”

Sorters lift contamination off the line by hand and that which remains is baled and sold as product. Anything the worker removes is contamination and discarded.

But if a worker doesn’t catch something, the contamination remains in the product. “Here’s no way to control contamination and assure a specification when you have workers pulling off contamination because you simply can’t see every inch of the belt,” says Viny. “To meet a specification, it’s simply not a viable way to do it any longer.”

Specifications cannot be met by a negative sort, but rather, the recycling industry has no choice now but to go to a positive sort, “where you literally jettison from the belt, sort and remove the items you seek, and if you miss something, the product ends up as a discard—but the product you do separate is of the quality you seek,” says Viny.

While computers at one time didn’t have the processing power to handle the sort of tasks that near-infrared requires at a scale that makes sense for the waste industry, they do now, he points out.

That means the industry can do a positive sort from unsorted MSW and ISRI spec material, says Viny. Obtaining ISRI-spec materials through a single-stream system also can be accomplished.

However, “if you can do it with raw trash, is it economically feasible to do the second pickup again?” he questions.

Some parts of the country, such as in the hot climate of Arizona, require two weekly pickups, he says. “In areas where state regulations require a pick up twice at a home—picking up rubbish one day a week and recyclables another day—that could continue to make sense, but in areas where you are only required to pick up once per week, the dirty MRF makes a lot of sense,” says Viny.

One challenge in single-stream recycling is the setout rate, Viny points out. “You rely on the individual to put 100% of the recyclables in the recycling bin, and it just doesn’t happen,” he says. “You never get the volume of the recyclables in a two-day pickup system that you would have in a dirty MRF.”

If an operation has a goal of 30–35% recycling, it could be accomplished with two pickups: one for garbage which becomes a discard, and one for recyclables, notes Viny. “With the advent of new equipment, you could do a positive sort of those recyclables and you make ISRI-spec material,” he adds. “That can happen, and single-stream MRFs can and will become more advanced, and the quality of the sort will be sufficient to meet industry specs. By the same token, if your goal is to get to 70% recycling or get beyond that 35% bubble, then really the only way to do it is by mass burn or the dirty MRF approach. If you eliminate one pickup, then the costs associated with going to 70% diversion are very compelling. You’re able to compete favorably in many cases with pure land disposable.”

As a single-stream MRF heavily relies on a disc screen, it can impede the ability to process waste, Viny contends. “The problem with a disc screen is that anything that can wrap around a spinning object is going to wrap around a spinning object. Now you’ve got a series of spinning shafts at a high rate and film plastic, videotape, twine, wire, and anything that can wrap around those shafts is going to wrap around the shafts,” he says. “A dirty MRF is a system that typically avoids something like a star screen and uses different technology to accomplish the same goals.”

Western Placer Waste Management Authority (WPWMA) in Roseville, CA, is a study in what happens when an operation puts an increasing focus on mixed waste processing. “It goes without saying that when you have a mixed waste MRF, you have a much higher quantity of material you’re going to be processing, because it’s essentially a mining operation,” says Eric Oddo, environmental engineering program manager.

“You’re mining that gold out of the rest of the wastestream. You’re going to have a larger facility, probably a greater level of equipment, and a greater level of staffing, and so it can generally be a higher cost upfront. What you end up seeing over time is you have a high degree of flexibility and control over that wastestream.”

The WPWMA Joint Powers Authority operation is comprised of local cities and Placer County, providing regional services in mixed waste sorting via its MRF and solid waste disposal through its landfill to 300,000 residents. The operation also handles green waste composting and C&D.

When WPWMA started in 1995 there had not been many examples of dirty MRFs from which to model its operations, so the authority created its own blueprint. “We had a rudimentary system in terms of screening and sorting, and over time using Machinex equipment, we’ve improved our ability to screen and sort materials,” says Oddo.

“In the end, we rely on sorters to make that decision of what is recyclable and what is not. I think that’s really where we’re sitting in the catbird seat—we have that flexibility of being able to dynamically and quickly adjust to market conditions and wastestream conditions, and pull out what is recyclable and marketable at any given time.”

Of late, the operation has seen a decline in the amount of newsprint in the wastestream, but still quite a bit of mixed paper.

“We’re seeing more of a change in the markets than in the wastestream itself,” points out Oddo. “In terms of how this operation runs, it’s very much dominated by market conditions that are both domestic and international.”

Also keeping an eye on trends are equipment manufacturers who have to answer the call for the technology needed to process the changing wastestreams.

Michael Drolet, solution sales manager at Steinert US, notes three trends relating to the wastestream that are the driving factors for what material separation practices and equipment are needed to address them.

First is single stream. Drolet doesn’t see a growing trend toward its adaptation. “Where it is already in place—primarily on the East Coast where the larger programs are—I don’t think this will fade out soon, because the population is already used to it,” he says. “They do it right, and for the large waste processor, it adds some kind of value: a cleaner product and maximum product recovery.”

Second is the implementation of the dirty MRF, toward which Drolet has noted a trend in the last five years. “That’s become regional,” he says. “Everywhere a community is trying to plan waste diversion where there is no single-stream program or a weak single-stream program, they might be tempted to go towards a dirty MRF for numerous reasons,” he says.

Communities may easily derive larger diversion rates in places that offer transformation diversion credits, such as California.

The third line, which Drolet notes is also picking up steam, is refuse-derived fuel or waste-to-energy programs where there is mass burning or the creation of fuel out of waste. “This model is getting more interesting economically speaking because it wasn’t in the past, but with the energy prices going up, it is getting more and more viable,” he says, pointing out that this is a regional consideration as well.

In a dirty MRF, “you’re still pulling out a fairly good amount of money out of the tipping fees, while the single stream gives you much more recovery,” says Drolet. “With single stream, you’re ending up with much more plastic at the end of the month than a dirty MRF because the material is cleaner, the material is easier to catch, and the residual is much lower. Because it’s source-sorted, landfill costs are cheaper. You’re getting more commodity value because the material is cleaner; you have access to more quantity of material.”

Rutger Zweers, sales director for STADLER America, says the direction in which the wastestream is heading “strongly depends on the location of the project, current infrastructure in place in regards to hauling and curbside separation of recyclables, as well as city or state guidelines to increase recovery rates from landfills.

“Ultimately, a need or requirement to divert more materials from the landfill will be a key driver to process more wastestreams,” adds Zweers. “The location of the project, composition of the waste, and its available markets will provide foundations for these projects to become feasible.”

The allowance and use of an engineered fuel, as commonly done throughout Europe, would allow non- or low-value recyclable materials to find another use such as at cement plants or alternative waste conversion technologies to either make a liquid fuel or heat or power generation, Zweers says.

Gary Brooks, director of recycling solutions for the Environmental Solutions Group, says one major challenge in a dirty MRF is the expense of all of the specialized pieces of equipment required to perform the process correctly. “The other major challenge is the contamination of the recyclables,” he adds. “It can be difficult to sell the commodities sorted in a mixed waste facility because of this reason.”

On the other hand “one upside to a mixed waste recycling facility is having access to 100% of the recyclable materials and the elimination of the ability for recyclables to go into the wrong bin. Also, with mixed waste recycling there is lower collection/capital spend on fleet because fewer trucks are needed.”

At CP Group, “we believe there is a place in the industry for both single-stream and mixed waste processing,” says Terry Schneider, CEO of CP Group, adding that “while single stream continues to thrive, we have seen an increase in interest in mixed waste processing.”

From a retrofit perspective, there are a few reasons why single-stream operators may want to upgrade their system to process mixed waste, he explains. “Since mixed waste MRFs process more tonnage overall, it can potentially run at a lower cost per ton than single stream, pushing the diversion cap higher. Hauling costs may also be lower.”

Operators of single-stream systems interested in moving toward dirty MRFs can replace old 2D/3D separators with more modern separators and screens such as the CPScreen, which is designed to be easy to maintain and doesn’t wrap, says Schneider. Operators also can add optical sorting equipment or transitions and conveyors to minimize spillage.

Chris Hawn, North American sales manager for Machinex Industries, says in attending industry trade shows, he’s noticed “a lot of market reaction to commodity pricing, which has everybody scrambling to find better ways and better mousetraps to do things so that margins start to grow back to where they should be and people can make money in recycling.”

Contact Details

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