With only a small percentage of plastics recycled, determining the best way to recycle and reuse these materials may enable greater adoption of plastic recycling and reduce plastic waste pollution. Researchers at the National Renewable Energy Laboratory (NREL) of the US Department of Energy (DOE) studied the benefits and trade-offs of current and emerging technologies for recycling specific types of plastics to determine the most appropriate options.
The researchers presented a comparison of various technologies for closed-loop recycling, which allows plastics to be reused through mechanical or chemical processing, eliminating the need for raw materials derived from fossil fuels. They looked at technical metrics such as material quality and retention, as well as environmental metrics including energy use and greenhouse gas emissions.
“We know that cost is one of the primary factors – if not what it is the said Taylor Okert, lead author of “Technical, Economic, and Environmental Comparison of Closed Recycling Technologies for Ordinary Plastics,” which appeared in the journal ACS Sustainable Chemistry and Engineering. “But I think it’s very important to remember that there are other things that are just as important to our lives on this planet, and we need to consider these environmental influences as well.”
Its co-authors, all from NREL, are Avantika Singh, Jason DesVeaux, Tapajyoti Ghosh, Arpit Bhatt, Geetanjali Yadav, Shaik Afzal, Julien Walzberg, Katrina Knauer, Scott Nicholson, Gregg Beckham, and Alberta Carpenter.
The article describes the effectiveness of closed-loop recycling technologies in polyethylene terephthalate (PET) and three types of polyolefins: high-density polyethylene (HDPE), low-density polyethylene (LDPE) and polypropylene (PP). These plastics have many uses. For example, PET is used to make bottles, trays, and carpets. High-density polyethylene is found in milk jugs, bags, containers, and toys. LDPE is commonly used to manufacture squeezable bottles, caps, and bags. Meanwhile, PP is used to make yogurt tubs, hangers and straws.
Recycling rates for these polymers in the United States varied during 2019, from 2% for LDPE to 15% for PET bottles and containers.
“PET is like a common single-use water bottle,” said Uekert. “You can recycle that. But the other end probably won’t look like a bottle. It’ll look like a plastic tray to put food on or it might be made into a plastic fiber that can be used for clothing. It goes back to the same type of plastic, but not necessarily the exact same type of plastic product.” .
Two methods of closed-loop recycling are available for HDPE, LDPE, and PP plastic: mechanical, where the plastic is ground, melted, and made into something new; and solvent-based dissolving, which removes impurities so that the plastic is of a quality suitable for reuse. These same processes can be used on PET in addition to three chemical recycling techniques: enzymatic hydrolysis, glycolysis, and methanogenesis.
More than 400 million metric tons of plastic waste are generated globally each year. Current recycling strategies can capture a small fraction of these plastics, but there is a lack of consistent data on the capabilities and impacts of these processes. The NREL study quantitatively characterized the performance of plastics recycling technologies—including factors that would normally only be discussed qualitatively, such as pollution tolerance—and established a methodology to compare new recycling processes as they emerge.
“It’s not just that you can recycle plastic,” Okert said. “Appear Effective way Can you recycle this plastic? “
Although mechanical recycling outperforms all other technologies as well as virgin plastic production across economic and environmental measures, the process produces lower quality plastic. The researchers said that increasing the quality and quantity of recycled plastic through improved sorting and pretreatment could improve mechanical recyclability.
“To enable a truly circular system where we keep as much material as possible in the economy, that’s when we really need to improve [material] “Retention comes through things like better sorting and better returns for recycling operations,” said Uekert. “If you have a process that only has a 75% yield, you end up needing a little bit more electricity, a little bit more chemicals, to recycle one kilogram of plastic than if you had something like 90% or higher. That means that The overall environmental impacts, and the total cost, will go down the more you keep the materials.”
The researchers pointed out that recycling should be approached as an opportunity to decarbonise, using technologies that use electricity that can be generated from renewable sources.
The funding came from the U.S. Department of Energy’s Office of Bioenergy Technologies and Office of Advanced Materials and Manufacturing Technologies as part of the BOTTLE Consortium, a collaborative effort representing Bio-Optimized Technologies to keep thermoplastics out of landfills and the environment.
NREL is the US Department of Energy’s primary national laboratory for research and development in renewable energy and energy efficiency. NREL is operated for the Department of Energy by the Alliance for Sustainable Energy LLC.