Analyses of chemical recycling, some of them critical, previously have focused on whether or not plants have been able to reach scale or, in some cases, whether they can handle mixed plastic feedstock as well as some initial advocates of the technology claimed.
An article published in late June on the investigative journalism website ProPublica.org adds one more element of criticism in asserting that at least one process categorized as chemical recycling, also termed advanced recycling by some of its backers, do not convert much of their inbound feedstock back into plastic.
The report by ProPublica reporter Lisa Song cites several sources and portrays an attempt to gather data from numerous companies and organizations in part to determine what happens to a discarded piece of plastic when it enters either a mechanical recycling process or a chemical recycling process.
Song’s conclusion: While anywhere from 55 percent to 85 percent of discarded plastic directed to a material recovery facility (MRF) and next-stage mechanical recycling step becomes plastic again, pyrolysis-based chemical recycling processes convert just 15 to 20 percent of inbound material back into plastic.
The consensus of sources interviewed by Song was that via pyrolysis, from 80 to 85 of plastic scrap heading to a pyrolysis facility instead becomes diesel fuel, hydrogen, methane and other chemicals.
That result may be unsurprising to professionals within the recycling and polymers industries, but Song says the low-double-digit result may not be well received by people who construe the chasing arrows symbol on plastic objects as meaning the item can be turned back into plastic.
She also looked into dilution practices undertaken by users of mechanically recycled and chemically recycled materials, again finding the pyrolysis process came up short.
Users of postconsumer recycled-content resins (PCR) in some applications may need to blend that material with virgin resins, with the PCR comprising from 25 to 50 percent of the total product.
While a naphtha product that can be used in new plastic formulas is created via pyrolysis, Song writes that much of “the naphtha created using recycled plastic is contaminated” with chemical additives mixed in “to make products bend or keep them from degrading in the sun.”
Polymer makers who wish to use this naphtha can “overpower” those contaminants by diluting them with virgin naphtha made from crude oil, according to Song. She writes, though, that unlike the 25-to-50 percent blend common in mechanical recycling, “at least 90 percent of the naphtha used in pyrolysis is fossil fuel naphtha [and] nothing that comes out of pyrolysis physically contains more than 10 percent recycled material.”
Citing Steve Jenkins of energy and commodities industry consulting firm Wood Mackenzie as her source, Song concludes that three years in the future, “At best, the world could replace 0.2 percent of new plastic churned out in a year with products made through pyrolysis.”
Courtesy : recyclingtoday.com
