Why is Recycling of Postconsumer Plastics so Challenging?

Abstract

The ubiquitous use of plastics has been driven by their combination of low cost and properties, but these attributes directly challenge waste management schemes for plastic recycling. Some postconsumer recycling programs are now nearly 50 years old, but a significant fraction of plastics still finds landfills or other dumping strategies at their end of life. With the growing concern regarding plastic waste, especially ocean plastics, there is a need for innovation and alternative strategies for the economic translation of plastic waste to valued product(s) that will promote their efficient circular utilization. This review first describes the technical and economic hurdles associated with the recycling of postconsumer plastics, but then it focuses on providing an overview of emergent strategies to recover plastic waste through new polymer design, new recycling processes, and chemical transformations to value-added products. Specific challenges discussed include plastic waste sorting and separations, product variability including additives, and the high efficiency/low cost in which the existing petrochemical industry can produce virgin polymers, in particular polyolefins. Although a wide variety of technical strategies have been demonstrated for recycling of plastics through both mechanical and chemical means, the commercial success of these different strategies is generally limited by either performance, including large variance in key metrics, or economics where the products can match the performance of virgin materials but the recycling process is expensive. Successful capture of postconsumer plastic waste through recycling likely will depend on economic incentives and government regulations.

Selective C(sp3)-C(sp3) reduction and metathesis of ketones

“…Degradative cyclization of poly(phenyl vinyl ketone). Development of e cient, atom-economical methods for transformation of plastics into valuable-added chemicals is important to stimulate their recycling and reduce the relevant wastes 4,5 . However, deconstruction of C(sp 3 )−C(sp 3 ) backbone of polyole ns remains a signi cant challenge and usually suffers from drastic reaction conditions, poor selectivity, low valueadded products, and low e ciency.…”

“…However, deconstruction of C(sp 3 )−C(sp 3 ) backbone of polyole ns remains a signi cant challenge and usually suffers from drastic reaction conditions, poor selectivity, low valueadded products, and low e ciency. In contrast to polyesters 38 and polyamides 39 , catalytic degradative cyclization of polyole ns remains almost unexplored 4,20,35 . Encouraged by the above results, we deliberately focused our investigation on the previously unexplored cyclizative degradation of poly(vinyl ketone) that are an important class of smart and packing materials.…”

“…The deconstruction of organic molecules is becoming increasingly important in view of synthetic promise, economical bene t, and environmental impact [1][2][3][4][5][6] . Among a variety of approaches, catalytic C−C bond hydrogenolysis is unarguably one of the most desirable, straightforward and versatile pathways.…”

Challenges and Opportunities for Recycled Polyethylene Fishing Nets: Towards a Circular Economy

“…This recyclate has a low Mw, a property that greatly influences the environmental stress cracking resistance of PE materials. Moreover, the presence of inorganic impurities, previously detected, together with a certain level of degradation caused during the recycling process [45,46] also determines the lower ESCR performance of the rFN. On the other hand, raw resins PE3, PE4 and PE5 have overall higher ESCR values due to its high Mw, which helps to increase the tie molecular density [47][48][49].…”

Assessment of Performance and Challenges in Use of Commercial Automated Sorting Technology for Plastic Waste

“…Current technologies used to sort plastic waste are based on Near Infrared (NIR), Xray Fluorescence (XRF), and VIS (color analysis by camera or spectro-colorimeter) [23][24][25]. Some other technologies, such as mid-infrared (MIR), shape recognition, hyperspectral imaging, electrostatic separators, and barcode scanners, show potential for sorting plastic recyclables but are yet to be used in large scale plastic sorting [26][27][28][29].…”