Since only a small percentage of plastic is recycled, identifying the best ways to recycle and reuse these materials may increase the adoption of plastic recycling and reduce plastic waste pollution. Researchers at the U.S. Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL) examined the advantages and trade-offs of current and emerging technologies for recycling certain types of plastics to determine the most appropriate options.
The researchers compared various closed-loop recycling technologies that allow plastics to be reused through mechanical or chemical processing, thereby eliminating the need for fossil fuel-derived virgin materials. They considered technical indicators such as material quality and retention, as well as environmental indicators such as energy use and greenhouse gas emissions.
“We know that cost is one of the main factors – if not This major – recycling drivers for companies looking to invest in this,” said Taylor Uekert, lead author of the book, “A technical, economic and environmental comparison of closed-loop recycling technologies for common plastics,” published in the journal ACS Sustainable Chemistry and Engineering“But I think it’s really important to remember that there are other things that are just as important to our lives on this planet, and we need to think about those environmental impacts as well.”
Her co-authors, all from NREL, include 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 outlines how closed-loop recycling technologies can efficiently process 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. HDPE is found in milk jugs, bags, containers and toys. LDPE is commonly used to make squeezable bottles, caps and bags. Meanwhile, PP is used to make yogurt tubs, coat hangers and straws.
In 2019, recycling rates for these polymers varied across the US, from 2% for LDPE to 15% for PET bottles and containers.
“PET is like a normal single-use water bottle,” Uekert said. “You can recycle it. But it will most likely not turn into a bottle from the other end. It will become a plastic tray for food, or it may be converted into plastic fibers that can be used in clothes. It will go back to the same type of plastics, but not necessarily the exact same type of plastic product.”
There are two closed-loop recycling methods for HDPE, LDPE and PP plastics: mechanical, which grinds up the plastic, melts it down and makes it into something new; and solvent-based dissolution, which removes impurities and gives the plastic a quality suitable for reuse. These same processes can also be used for PET, in addition to three chemical recycling techniques: enzymatic hydrolysis, glycolysis and methanolysis.
The world generates more than 400 million metric tons of plastic waste every year. Current recycling strategies can capture a fraction of these plastics, but consistent data on the capabilities and impacts of these processes are lacking. The NREL study quantitatively characterizes the performance of plastic recycling technologies—including factors that are usually only discussed qualitatively, such as pollution tolerance—and establishes a method to compare new recycling processes.
“It’s not just that you can recycle plastic,” Uckert said. “how is this Effectively Can you recycle that plastic? “
Although mechanical recycling outperforms all other technologies as well as virgin plastic production in terms of economic and environmental indicators, the process produces plastic of lower quality. Improving the quality and quantity of recycled plastic through better sorting and pretreatment could improve the feasibility of mechanical recycling, the researchers said.
“To be truly circular and allow us to keep as many materials as possible in the economy, that’s what we really need to improve our [material] Retention through better sorting and higher yields of the recycling process,” Uekert said. “If your process is only 75% yielding, you’re going to end up needing slightly more electricity, slightly more chemicals to recycle a kilo Plastic has 90% or more yield than you. That means your overall environmental impact, your overall cost, will decrease as you increase material retention. “
Recycling should be seen as a decarbonization opportunity, the researchers note, with the technology using electricity that can be generated from renewable sources.
Funding came from the U.S. Department of Energy’s Bioenergy Technologies Office and Office of Advanced Materials and Manufacturing Technologies as part of the BOTTLE Consortium, a collaborative effort representing biooptimized technologies to keep thermoplastics out of landfills and the environment.
NREL is the U.S. Department of Energy’s primary national laboratory for renewable energy and energy efficiency research and development. NREL is operated for DOE by the Alliance for Sustainable Energy LLC.