Plastics and the Circular Economy
As society and world governments further embrace sustainability, increasing emphasis is being placed on the move from a linear to a circular economy.
For centuries, the global economy has been linear, taking, making, and discarding materials, often as single-use products. According to the World Bank, each year the world produces over 2 billion tonnes of municipal solid waste, much of which ends up in landfills. Wealthy countries, which represent about 16% of the world’s population, create 34%, or 683 million tonnes, of waste overall. Of the waste from these countries, 51% consists of materials that could be recycled but that have instead been discarded. And of that amount, plastics make up 44%.
The financial and environmental costs of a linear economy are considerable, particularly in the case of long-lasting plastics. Billions of dollars’ worth of viable plastics end up in landfills, where, thanks to their durability, they will persist for hundreds of years. Meanwhile, millions of tonnes of plastic drift into the world’s oceans every year.
READ MORE: Closing the Circle
A circular economy moves away from this path to a more sustainable route, aiming to eliminate waste and the consumption of finite resources. To achieve that goal, products must be made and then used for as long as possible. When the items no longer function, the materials must be recovered to create new goods from the original products. In other words, recycling and reuse
Starting the Circle
Plastic plays an important role in this economic model. By definition, a plastic is a material that contains one or more organic polymer substances of large molecular weight as an essential ingredient. Plastic is also solid in its finished state, and, at some stage in its manufacture or processing into finished articles, it can be shaped for purpose.
A versatile material, plastic can be recycled and go on to other uses as lumber and decking material, clothing, toys, lawn furniture, and an array of other items.
In order for plastic to get to that second or third incarnation, however, it must first be managed, identified, and recycled in a consistent, responsible manner. That is where ASTM International’s committee on plastics (D20) comes in. The committee is working with various stakeholders to improve the reuse of plastics and the plastics’ marketplace.
Currently, the committee oversees close to 500 standards in the form of test methods, specifications, recommended practices, nomenclature, and definitions. The standards cover plastics’ components, compounding ingredients, and raw materials, which may be fossil in origin (including petroleum, natural gas, or coal/carbon) or renewable (sugar cane or corn derivatives, among others). The standards also address finished plastic products such as sheets, rods, tubes, pipes, cellular materials, and molded or fabricated articles. And they support critical areas such as specimen preparation and methodologies for mechanical, thermal, optical, and analytical testing.
“D20 is really focusing on the standards that will be required to sustain the very lifeblood of the plastics industry and meet societal challenges, be it in the circular economy with recycling and understanding how these materials degrade and what that means to the environment,” says committee chair Mark Lavach.
In the past, plastics test methods and specifications dealt with products created from virgin materials and a consistent raw material stream. They were well characterized and predictable.
“When we start talking about the circular economy, we naturally go to recycling, and the nature of the stream changes,” says Lavach. “When you produce and try to sell a recycled material, unless its properties are adequately categorized, it sometimes makes it difficult for the buyer of this stream to use it. Equipment likes consistency. It doesn’t like variability. We have to create usable standards that enable consistency of supply that both the buyer and seller can agree to and utilize. To the degree possible, people buying the recycle stream want a consistent supply.”
Challenges and Considerations
Crafting standards for sustainable plastics is not without difficulties. According to Lavach, customers expect to receive a predictable material from which they can manufacture unvarying parts. It’s not an unreasonable expectation, and it requires additional considerations. John Stieha, chair of the subcommittee on thermoplastic materials (D20.15) and a consulting engineer, agrees.
“For decades, the process was set up to produce plastics from feedstocks out of the ground, from plant sources, and from all these locations that are really consistent and that minimize the influence of other factors,” says Stieha. “Once it’s in the hands of the consumer, though, you’ve exposed it to the world. The challenge is to make sure that we can recover these materials and convert them into new products that perform consistently and meet expectations.”
Plastic in the marine environment is a problem that standards will help solve.
Rick Fluet, chair of the subcommittee on film, sheeting, and molded products (D20.19) and laboratory quality specialist at NOVA Chemicals Corp., notes specific concerns for recycle processors.
“Reflecting on multi-material structures, do those materials have similar processing parameters? Are they compatible or will they segregate out during downstream recycle processing? How do recycle processors segregate and classify multi-material structures based on their composition? To meet desired performance requirements, many plastics products such as films incorporate varying — and in some cases drastically different — plastics materials. An example of such a product is a multi-layer blown film structure. The ability to recycle these types of products becomes very difficult as the materials incorporated into the structures are often incompatible, do not process the same, and are difficult to separate,” Fluet says.
As Fluet indicates, some plastics present obstacles to recycling. Even so, others seem to be suited to a circular economy. Thermoplastics in particular can be remelted, reshaped, and resolidified almost indefinitely. They can be recycled and converted into other parts such as polyester, nylon, and carpet fiber.
Although thermoplastics seem prime for reuse, Stieha notes that some types of thermoplastics tend to be recycled more easily than others. He cites soda bottles, which are made from polyethylene terephthalate (PET) as an example.
“Unfortunately, there are a lot of these bottles, but there tends to be a consistent feedstock because they tend to be better sorted. Consumers generally know to recycle them. It’s a valuable plastic that ends up in things like automobile parts. Part of your car is probably made out of pop bottles,” Stieha says.
According to a 2018 U.S. Environmental Protection Agency report, PET bottles and jars were recycled at a rate of 29.1% in the United States. Overall, in 2018, the U.S. recycled plastics at a rate of 8.7%. Worldwide, the plastic recycling rate for that year was approximately 20%.
Post-Consumer Recycled Plastics
Historically, there has been a dearth of standards for post-consumer recycled plastics (PCR) and PCR suppliers, which has had a negative effect on recycling efforts. To address this deficiency, the subcommittee on recycled plastics (D20.95) is drafting three new PCR specifications.
The new specification for recycled polyethylene materials (WK74657) identifies recycled polyethylene (PE) materials in accordance with a cell classification system. The proposed standard indicates material origin, physical properties, total recycled content, quality metrics, and regulatory guidance when known. The standard will be used to classify recycled materials comprised of multiple materials and those containing additives to promote specific physical properties or compatibility.
Jeffrey Biesenberger, chair of D20.95, describes the purpose of the standard. “The goal with the proposed standard is not to have binary decisions with a lot of vocabulary. We want to reduce things to a chart so that you can characterize any polyethylene that’s in that space and represent whether you know or don’t know its performance or properties.”
FOR YOU: Standards for Biodegradable Plastics
“We’d like to give recyclers the choice to alloy their recycled material with other materials to make it perform better, like an impact modifier, and create a different performing material, one that its performance can be characterized,” Biesenberger continues. “A classification system that lets you pick out or omit properties that are or aren’t important to you, such as tensile strength or the level of polypropylene contamination in polyethylene, satisfies the need to characterize from a product-design standpoint and to declare what the post-industrial or post-consumer content levels are in the materials bought and sold.”
The other two specifications will cover polypropylene (PP) and PET. “These three standards will be very different because their supply chains are very different. Some recyclers only do one. Some may do more than one. It’s a supply chain issue from start to finish, and other than performance, the biggest hurdle will be having a product that’s FDA [U.S. Food and Drug Administration] compliant for direct food contact,” says Debra Wilson, material science director for Berry Global and vice chair of 20.95. Wilson is leading the PP effort. She adds that these standards will address actual performance needs and appropriate testing criteria, whereas the resin codes are simply resin identification codes that do not add much value in defining performance of a specific recycle stream.
“We’re going to utilize the standards that D20 has already developed, as applicable, but our work may involve developing new test standards as well, to be able to test these materials differently than you would a prime resin for quality and performance purposes,” she says.
Ultimately, Wilson says, the subcommittee’s goal is to develop meaningful standards that will help the plastics industry in the use of PCR.
Microplastics in the Marine Environment
According to Lavach, the work of D20.95 and the subcommittee on environmentally degradable plastics and biobased products (D20.96) is complementary. “There’s substantial overlap in terms of generating the techniques that will be used to help the recycling industry look at degraded plastics and how to evaluate the quality of the raw material supply of recycled materials,” he says.
Currently, D20.96 is developing a new specification for biodegradable products in the marine aqueous environment (WK75797). This work item will replace the withdrawn specification for non-floating biodegradable plastics in the marine environment (D7081). The proposed standard covers all plastics, including microplastics, which the U.S. National Oceanic and Atmospheric Administration (NOAA) defines as plastic particles less than 5 millimeters in length (the size of a sesame seed). Microplastics can arise from the degradation of larger pieces of plastic, from microbeads, and other sources.
“This standard will not address all situations for water biodegradability. It will add to what we know now,” says Kelvin Okamoto, Ph.D. He is the chair of D20.96 and president of Green Bottom Line. “One of the biggest issues we have is that almost all of current testing is done at 30 degrees Celsius. Most waters in the world are at 20, 10, or 0 degrees Celsius. The work to determine the correlation between those lower temperatures and 30 degrees Celsius has not really begun, and that testing could take time to complete.”
Okamoto adds that people must understand that they have to put standards in place with what they know now. “It may not be the absolute standard down the road, but through the ASTM process, the standard will be constantly updated as more information is made available,” he says.
The subcommittee is looking for organizations willing to help fund a 10-year project involving costs for a lab, researchers, and equipment. Plus, WK75797 only pertains to salt water. As a result, the subcommittee will need to test for fresh water and brackish water, each at different water temperatures and at different simulated depths with the associated filtered sunlight to see if microplastics degrade differently in
The work of these subcommittees and the D20 committee in general is expected to have a positive impact on plastics’ sustainability, and Lavach says the committee is poised to lead a worldwide effort.
“D20 is positioning itself at the forefront of this effort, working with organizations like the American Chemistry Council, the McArthur Foundation, and global and grassroots efforts, all of them saying, ‘We’ve got to do a better job,’“ Lavach says. “You’ll see the plastics industry respond and make sure the products in the industry conform to and help with societal norms and needs. Through the standardization process, D20 will guide these efforts, especially over the next 10 to 20 years.” ■
Kathy Hunt is a U.S. East Coast-based journalist and author.