Plastic. It’s not hard to see how anyone who is appalled at the despoliation of the environment could think that the world would be better without it. Nearly 10 per cent of the world’s oil is used in making it. It has enabled the proliferation of cheap goods — cramming closets, landfills and otherwise-unspoiled places where it could remain for decades, if not centuries.
Yet, because it’s so much lighter than the steel and glass it has replaced in vehicles and elsewhere, plastic has massively reduced fossil fuel emissions. And in the midst of a global pandemic, the need to securely protect food and personal items with impermeable packaging is essential.
Like it or not, plastic is going to be with us for a while. Can we learn to get along?
Conventional recycling, in which waste plastic is collected, sorted, cleaned, shredded, and then melted down and pelletised to be reused, has the potential to ameliorate the problem — except that it isn’t working. Less than 10 per cent of all the plastic trash ever produced has been recycled. There are a lot of reasons for this, but most of them come down to the question of value. That’s because every time plastic is recycled in this manner, it loses value.
But there is good news on this front: chemical recycling. Sometimes known as advanced recycling, it’s a process that decomposes plastics to basic components called monomers, or even further into simpler compounds, removing impurities, then reassembling these ingredients into virgin plastic that is indistinguishable from new. With chemical recycling, items that previously were being downcycled can now be turned into constituent materials that can be recycled indefinitely with no loss in clarity, quality or performance.
A number of companies, large and small, are already doing this in different markets with different types of plastics.
Nylon: Carpet-go-round
Nylon is used in a variety of applications, from tires, to rope, to durable car parts, to textiles and carpeting. It was the first plastic to be chemically recycled for two reasons. First, one common form of nylon, nylon 6, is made from a single monomer, called caprolactam, which makes the breakdown of polymers into constituent parts somewhat simpler. Second, nylon is a relatively expensive plastic, which makes the value proposition attractive.
The Italian company Aquafil developed a chemical recycling process for nylon 6 after several other companies had failed, according to CEO Giulio Bonazzi. Strongly motivated to develop an ecologically friendly way to produce nylon, Bonazzi started back in 2011 with the development of a process that converts waste nylon to virgin Econyl nylon through chemical depolymerization. The process uses a series of steps to break nylon into a resin that is indistinguishable from oil-based resin.
Aquafil’s journey continued in 2013 with a collaboration with Healthy Seas recovering nylon fishing nets from the ocean to be recycled. In 2018, the company opened a carpet recycling facility in Phoenix, retrieving waste carpets collected under California’s stewardship law. The carpets are processed into pellets that are shipped to Slovenia for final purification. Bonazzi says that even with the shipping cost, the process is generally cost-competitive with virgin nylon.
Aquafil has built a second carpet recycling facility in Woodland, California, and Bonazzi says it plans to build a processing plant in the US Considering that perhaps 5 billion pounds (2 billion kilograms) of carpeting go into landfills each year, this an opportunity to capture value that would otherwise literally go to waste. Interface and Tarkett are among the carpet makers using Econyl yarn.
Polyester: Supply chain challenges
California-based Circular Polymers also recycles waste carpeting. The company extracts PET (a form of polyester) fibers, densifies them, then sends them to material producer Eastman in Tennessee. Eastman puts the fibers through its carbon renewal technology (CRT) process, which extracts the essential components from which new materials can be made. Eastman CEO Mark Costa says this arrangement, which began in November 2019, will divert millions of pounds of carpeting in its first year alone.
According to Tim Dell, vice president of innovation at Eastman, CRT can work with a wide variety of plastics except PVC. It uses steam at high temperature and pressure to break the plastics down into syngas, “a mixture of carbon monoxide and hydrogen, the reactive building blocks of virtually all plastic packaging materials,” Dell says. These building blocks can then be reassembled into new plastics and fibers.
“One of the biggest challenges we have is getting access to sufficient quantities of waste plastic feedstock.” – Tim Dell
Eastman has modified its process for producing cellulosic acetate, a type of plastic used to make eyeglass frames, buttons, cigarette filters and similar items, to allow it to accept chemically recycled material blended with virgin feedstock. Dell says they plan to feed 50 million pounds (20 million kilograms) of waste plastic into the process this year.
The process theoretically could be run entirely on waste plastic. However, says Dell, there currently isn’t enough of the stuff available to feed into the system. “One of the biggest challenges we have is getting access to sufficient quantities of waste plastic feedstock,” he says. “Basically, we have to build a new supply chain.”
“We’ve converted this waste plastic from zero end-of-life value and are doing something that creates value,” Dell says. “We have to do that to make the economics work.” Right now, waste plastic is economically disadvantaged with respect to fossil fuels, despite the fact that’s essentially free, because the supply chains are not robust, making it cheaper and easier to simply buy from the oil companies.
“Over time as those supply chains are developed, those costs will come down,” Dell says.
Eastman recently signed an agreement with eyewear supplier Mazzucchelli to accept previously unrecyclable pre-consumer waste to process into new acetate. And it expects a second advanced recycling process, which it calls polyester renewal technology (PRT), to come online in 2022. This process is specifically aimed at polyester-based plastics, such as PET, from which many types of plastic bottles are made. A lot of PET is being recycled, but much of it has been colored or contaminated, so it cannot meet performance standards. PRT breaks the polyester into its two base monomers: dimethyl terephthalate and ethylene glycol, and then turns them back into polyester building blocks, much as Aquafil does with nylon.
Polyethylene: Bottles and bags
So what about polyethylene (PE), the cheapest plastic around, the one those pesky plastic bags, among other things, are made of? PE comprises roughly one-third of all plastic produced. And attempts to reduce its use are being thwarted today by Covid-19 concerns.
Some PE bags are collected at grocery stores and mechanically recycled into simulated wood decking. But there are other options coming to the fore. A startup in Menlo Park, California, called BioCellection has come up with a chemical recycling process for polyethylene that takes a different approach.
“Polyethylene is cheap, but it contains a lot of valuable carbon,” says BioCellection CEO and co-founder Miranda Wang. “The question is, how do you break that carbon out of its structure and turn it into something that people want?”
BioCellection focuses on how to extract the most value from the waste materials. Wang described the two-step process that breaks PE down into intermediates known as dicarboxylic acids, then builds those back up into more valuable products such as polyurethanes and materials for 3D printing. Some of these can be sold for more than 100 times what the plastic itself is worth.
The company has an agreement with the city of San Jose, California, to receive plastic waste from the city’s recycling stream. So, while these plastic bags are not being recycled into new plastic bags, they are being used to make something far more valuable that, according to Wang, will displace production processes that are more damaging to the environment.
Enough scale to make the sale
The key to chemical recycling’s success will lie in the value preserved in the material, but that will only attract interest if chemical recycling can be done at low cost.
It’s clearly easier to move barrels of oil or send it through pipelines than to move mountains of plastic waste. That’s a hurdle that recyclers must overcome. Capital expenditures are also high. But costs will fall with scale and infrastructure will improve — if the price is right. It’s a classic chicken and egg problem. But the fact that so many companies are pursuing it strongly suggests that scale will be achieved.
According to Chemical and Engineering News, dozens of companies are developing chemical recycling technologies, some with very ambitious targets.
For example, UK-based Plastic Energy heats waste plastic in the absence of oxygen to generate oil from which either new plastic or oil can be made. The company is building a plant that will chemically recycle up to 30,000 metric tons (33,000 tons) of plastic per year and is planning several additional plants in Asia.
Loop Industries of Quebec recycles PET with a depolymerisation process similar to Eastman’s PRT and has partnered with the Thai company Indorama Ventures to build a 44,000-tonne-per-year (40,000-metric-tonne-per-year) plant in Spartanburg, South Carolina. Loop is supplying Coca-Cola, Danone and PepsiCo with recycled PET for their bottles. And California-based Brightmark is building a pyrolysis plant in Indiana that is expected to convert 100,000 tonnes (90,000 metric tonnes) of plastic waste per year into diesel, naphtha and wax.
While these numbers are still small relative to the 300 million tonnes (270 million metric tonnes) of plastic produced each year, the stage is now set for significant growth.Major players are also getting into the act, too. Dow is partnering with Fuenix Ecogy Group with a goal of incorporating 100,000 metric tonnes (90,000 tonnes) of waste plastic into its production by 2025. And IBM is developing a catalyst-driven process for decomposing PET called VolCat that readily removes contaminants as it breaks the plastic into its constituent molecules.
While these numbers are still small relative to the 300 million tonnes (270 million metric tonnes) of plastic produced each year, the stage is now set for significant growth.
PureCycle Technologies is a subsidiary of Procter & Gamble that is chemically recycling polypropylene, with plans to process 60,000 tonnes (54,000 metric tonnes) per year. Chemical giant BASF is also moving into chemical plastic recycling, pursuing a pyrolysis approach.
Oil companies, concerned about reduced gasoline sales as the world shifts toward electric vehicles, are looking to plastic as way to replace some of the lost revenue. They will be competing, with their virgin feedstock, against recyclers in the plastics market. Shell, however, is hedging its bets, investing in its own pyrolysis recycling process. While that won’t help the company unload its stranded assets, it will at least bring in some new revenue.
What about carbon emissions?
Because it involves more steps, chemical recycling can use more energy than mechanical recycling. Therefore, if the energy comes from fossil fuels, it would appear that chemical recycling could be worse from a greenhouse gas (GHG) perspective.
However, when you consider the entire life cycle of the materials, chemical recycling can be superior because mechanically recycled plastics degrade with each cycle and so eventually must be replaced by virgin material, which largely comes from fossil fuels. Chemically recycled plastics, on the other hand, can be reused indefinitely.
In addition, the production processes tend to emit less carbon than production of plastics from petrochemicals. Eastman says its CRT produces intermediates with 20–50 per cent lower GHG emissions than the conventional petrochemical process. Likewise, it expects its PRT process to produce 20–30 per cent fewer GHG emissions. According to think tank CE Delft, as the plastics are broken down into more and more basic components, the greenhouse gas benefits decrease.
A study conducted by Argonne National Lab and reported in Chemical and Engineering News found that diesel fuel made from plastic waste produces up to 14 per cent fewer GHG emissions than diesel made from crude oil. Furthermore, a Dutch study by CE Delft found that “chemical recycling can make a substantial contribution” to efforts to reduce greenhouse gas emissions.
The key to chemical recycling’s success lies in the fact that, unlike mechanical recycling, it adds value to the waste rather than downgrading it. It’s a bit like the legendary alchemists who turned lead into gold. Most recycling in the past, says Wang, has been costly with little in the way of financial pay-off, and has had to be dragged uphill, with lots of government support and mixed success. Chemical recycling is likely to find a far more receptive audience that could help it quickly reach scale and to make the connections between supply and demand — both of which already exist in abundance.
This story was written by RP Siegel and published with permission from Ensia.com
