The main technologies used in modern recycling plants, also known as materials recovery facilities (MRFs), are being successfully integrated into new mixed waste processing facilities (MWPFs). As such, they are increasing diversion from landfills and maximizing recovery of marketable materials, according to a report released by the American Chemistry Council’s Plastics Division.
While both types of facilities divert materials from landfills by increasing the recovery of marketable commodities, MRFs require recyclable materials to be removed from the waste before being processed, usually through curbside collection programs.
MWPFs, on the other hand, extract recyclables directly from municipal solid waste. This can increase recycling rates, according to some in the industry.
“Technologies for recycling and recovering post-use resources are constantly evolving as is the waste stream — which creates opportunities to consider new strategies and innovations,” Craig Cookson, ACC’s senior director of recycling and energy recovery, told Environmental Leader. “Our shared goal is to direct more valuable post-use plastics from the waste stream toward greater circularity.”
The report also says some MRFs have been converted to MWPFs, so additional municipal solid waste materials can be diverted from landfill through recovery as marketable materials, transformed into a feedstock for solid engineered fuels or used in waste-to-energy processes.
Authored by solid waste management consulting firm Gershman, Brickner & Bratton, Supplemental Report: The Evolution of Mixed Waste Processing Facilities—Technology and Equipment Guide examines 10 types of equipment including optical sorting systems; bag openers, which free materials from closed plastic trash bags; air separation systems and densifiers, which compact the material streams into a smaller, more transportable form. The report evaluates the quality of the finished product, the volumes that are captured versus lost, and the speed at which the processing equipment works.
For example, optical sorting systems, which use optical near-infrared light and sensors, have been used in MRFs since the early 2000s and more recently in MWPFs, the report says. This recycling technology uses a light source to illuminate unsorted materials, which reflect different wavelengths. Sensors determine if the material can be recycled based on those wavelengths, and then the materials are “ejected” into separate bins, or ejection housing, with an air nozzle.
One of the challenges associated with optical sorting systems, the report says, is that there is a materials size limit on what the unit can read and eject. For most municipal solid waste applications, this means plastic pieces must be at least 1 or 2 inches or the machine will miss it.
Meanwhile in Indianapolis…
The report comes just months after the city of Indianapolis and Covanta reached an agreement to suspend Covanta’s $45 Advanced Recycling Center, a mixed waste processing facility that was supposed to open this year.
Covanta had said the new facility would increase recycling by five times the current rate and recover up to 80 percent to 90 percent of resources such as recyclable paper, cardboard, plastics and metals, at no cost to the city or its residents.
“In contrast, a citywide curbside program would require tens of millions of dollars in new recycling bins, trucks, labor, fuel and maintenance, in addition to other expenses,” Covanta’s Scott Holkeboer told Recycling Today in an interview last year.
The project was suspended after drawing controversy for its single-bin approach, collecting recyclables and municipal solid waste in a single container to be sorted at the facility. It also locked the city into a $112 million commitment through 2028 and would force the city to pay a $4 million annual penalty if it implemented a recycling program, Waste Management World reports.
While Covanta’s financial lock-in may have been its ultimate undoing in its deal with Indianapolis, it also illustrates the concern that a single-bin approach, common with MWPFs, will contaminate the recycling stream. But as technology advances continue to improve MWPFs recovery capabilities, as illustrated by the ACC’s report, those concerns may not hold as much weight.
As Harvey Gershman, report author and president of Gershman, Brickner & Bratton writes in a Renewable Energy from Waste column, “MWPFs offer an opportunity for increased recyclables diversion, including organics, and production of a cleaner, higher-quality fuel residual product…If moving from source separation allows more materials to be recycled and converted to a fuel feedstock, resulting in even higher diversion from landfills, aren’t we better off?”
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