While there is a ways to go in increasing a steady demand for recycled resins, some of the chemical recycling technologies will likely be refined over the next several years and there are several operational plastics recycling plants in the U.S. producing and selling material that can be manufactured into virgin-quality “upcycled” products.
By Bruce Clark, PE and Thea Dirani
We are seeing the beginnings of a plastic recycling revolution in Europe, Australia and the U.S. Participants liken it to the beginnings of the solar and wind energy sectors where after the basic technology was proven it took awhile for the cost of production to come down to where it was competitive in many regions with conventional energy sources.
Driven by technological breakthroughs, regulatory, economic and environmental factors, start-ups around the world, with some partnering with big petroleum and chemical companies, are competing to see whose recycling technology can perhaps become the dominant one. Dozens of new plants are planned. This article will discuss the following:
• An overview of existing and up-and-coming plastics technologies and how they fit into the overall scheme of things.
• Could plastic recycling plants be placed at existing plants that produce large volumes of waste plastic or at commercial MRFs and is this the best solution (pros/cons)?
• Considering the last critical component to make a “circular economy” of plastics, can the economic incentive for plastic chemical recycling be attractive when compared to disposal in a landfill or a waste-to-energy plant and production of new plastics using virgin resin?
The plastics recycling industry is striving to break the “linear economy” that most plastics fall into, where because of economics and other reasons, they are used once and discarded into waste-to-energy plants, landfills and, in some countries, open dumps. The “circular economy” is the goal envisioned where plastics will be recycled, which creates value, can reduce plastic pollution and greenhouse gas emissions, and the waste of a valuable resource. Figure 1 is an idealized picture of the main parts of a circular economy for plastics.
Plastic Recycling Technologies
Plastic recycling technologies can be divided into two major categories; mechanical and chemical. Chemical recycling can be further differentiated into the following categories and definitions:1
1. Pyrolysis—The thermal breakdown of material without oxygen, resulting in the production of gaseous hydrocarbons that can be made into a range of hydrocarbon products including wax and oil and used as a chemical feedstock. The gas is often burnt to provide energy to the process, whereas the oil and wax can be sold.
2. Gasification—The partial combustion of material to produce carbon monoxide (CO) and hydrogen (H2), which is a mixture known as syngas. This gas can be burnt for energy or used in the production of new hydrocarbons.
3. Depolymerization—The use of chemicals to break down a polymer into its monomers or intermediate units.
4. Purification—Polymers are dissolved in a selected solvent so the polymer can be separated from any contamination before being precipitated back out and reused as a polymer.
Dissolution does not affect the chemical composition of the polymer. Figure 2 shows the relationship of chemical recycling technologies to the plastics supply chain. The goal of chemical recycling is to convert the plastic back to a form and chemical composition so that it can be reused to make new products over and over without sacrificing its original physical characteristics. The industry calls this pathway “upcycling”. Chemical additives (i.e., plasticizers, stabilizers, etc.), color, residues, odor, all must be removed in the conversion process so that essentially a virgin-like resin, oil or pellet is produced.
In mechanical recycling the waste is washed, melted and pelletized and can be used to make some lower value plastics. This pathway is known as “downcycling”. Mechanical recycling is limited to several reuse cycles, before the plastic wears out. According to The Waste and Resources Action Programme (WRAP), a UK recycling advocate, a pyrolysis process that produces oil that is burnt for fuel is not chemical recycling, however, depolymerization and dissolution produce high yields of polymer can be achieved. Changing the pyrolysis oil back into a polymer would be considered recycling.2
All types of plastics, including the hard to recycle mixed plastics, are being targeted. The product of the recycling technologies is not limited to making new bottles. Other products include feedstock for biofuels, oils, industrial wax and other chemical feedstocks. Table 1 summarizes the most common plastic feedstock and which chemical recycling technologies are targeting them.
Table 2, is a partial summary of some of the companies and their chemical recycling technologies in use today and those being developed that are in a non-commercial, pilot stage or laboratory scale. The landscape of players in this market changes frequently as new players emerge so the list is not complete by any means.
Petrochemical plants using gasification or pyrolysis have been around for 70 years or more and many were developed by Texaco and Linde, primarily for energy production from coal, natural gas, heavy oil or petcoke. Dedicated chemical plants that used waste plastic as a feedstock came along in the late 1980s and 1990s and were operated as research or pilot scale units by BP Chemicals, BASF, Solvay and Linde. Some of these plants essentially converted the plastic into energy feedstocks. The Linde process did produce monomers for production of virgin plastic materials. Many may not be currently operating. These plants are not listed in Table 2.
Technology Aspects
With most new technologies, there is a point in time where the pre-commercial testing must end, and the technology and the balance of the plant processes and equipment assembled are scaled up to the commercial level. There is a limit to the prior testing, driven by the success or failure of these developmental efforts, the balance of off-the-shelf components versus those that must be designed from scratch, and financial pressures.
Our experience is that the pre-commercial testing, even though it may be carried out over years to refine the processes, is not an iron-clad assurance that the commercial plant will operate flawlessly, at least initially, on a continuous basis. Many pilots do not include all of the plant front-end or back-end equipment, either because it is not available in a small scale or those parts are considered less likely to have problems. This does not necessarily mean the complete plant will fail, but that some potentially significant extra costs and downtime may occur that require fixing before the plant can operate on a continuous basis at its rated capacity.
These problems can come from feedstock irregularities and insufficient preparation for the process, design complexities that result in greater emissions, higher energy usage, and unanticipated volume of waste by-products and odor, unexpected mechanical failures, and variable product quality.
Locating Recycling Plants
Where should a plastics recycling plant be located in relation to the source of waste feedstock? Should it be near a conventional MRF, near a plastics manufacturing plant where it can directly receive the plant’s discards and potentially have a ready off-take customer for the recycled plastic, somewhere equi-distant from all MRFs serving a region to try and reduce transportation cost? Some of the factors to consider include:
• Are plastics all coming from local sources or are some coming from far away regions?
• Does a facility generating waste plastic want to incorporate only their material into a recycling plant?
• Can the process accept the type of plastics(s) collected?
• Regarding the location of available real estate, does it have the zoning to allow processing facilities; is the land the right size?
• What about citizen’s concerns about possible odors and explosion hazards?
• Can the plant be permitted through the regulators for this use, and is the land price within the budget?
Most chemical recycling technologies require an initial processing stage where the target recyclables are separated from unwanted material (contamination), then washed, size reduced, dried and sometimes pelletized. The first activity—separation—is all important because this determines the feedstock volume. Better separation equates to higher volume and lower cost to produce the recycled product. Traditional waste management companies operating MRFs with advanced separation equipment, such as optical sorters equipped with artificial intelligence (AI), X-ray and ballistic separators/air-classifiers, can attain a high level of separation with very low levels of contamination. Following separation, the final steps have occurred in the front-end of the recycling plant, before the material is ready for the chemical conversion steps.
So, should a MRF and chemical recycling plant go together under one roof, to reduce transportation and handling costs, should they be in separate locations, or even on the same site, but in separate buildings? Again, there could be many factors to consider in order to answer this question. How much area is needed for a plastics recycling plant? That can be assessed knowing if the plastics are pre-processed offsite or require pre-processing at the plant. Is a plot available to accommodate both facilities? Will the same company operate both facilities? Are there specific safety concerns with certain plastics recycling technologies that would suggest they be separated?
A pyrolysis plant processing 60 tons of plastic per day (22,000 TPY) requires an area of about 24,000 square feet (sf). To generate 60 TPD of plastics, a mid-size MRF must process somewhere around 400 to 500 TPD of waste (not including food and yard waste) and its footprint is around 45,000 sf, not including administrative, parking etc. So, taken together the total area of around 70,000+ sf for pre-processing is likely not a problem on a greenfield site. However, many existing MRFs have little extra acreage to spare and might not be able to have a plant constructed adjacent to them or even nearby.
Economic Aspects
A significant factor in the business of chemical plastics recycling is the economic aspect—the cost of production. Economics is a critical lynchpin to make a “circular economy” of plastics. The current economics depends heavily on the cost of the feedstock—either virgin resin, produced from crude oil, or resin produced from chemical recycling. The other big economic consideration are the markets for the recycled oil. Financial returns are better as the product moves from fuels and industrial waxes, to naptha and, ultimately, polymers.
A fundamental question is: can production of plastics derived from chemical recycling be cost competitive with plastics produced from virgin plastic? A highly simplified economic analysis can shed light on how one looks at an answer. For example, in 2013 to 2014, the price of crude oil averaged $106 to $96 per barrel (average of $100 per barrel). The cost of producing plastic bottles, from virgin resin, averaged around $756 per ton. In 2021, the average cost of crude is $61 per barrel. So, the production cost would drop, perhaps to below $500 per ton.
In contrast, a pyrolysis plant in 2021 producing 15,000 tons per year (TPY) can produce resin at a cost of around $800 per ton in the U.S. If the plant produced 55,000 (TPY), the cost drops to $500 per ton.3 This does not include profit. So, observers indicate the smaller plants may not be profitable when the cost of crude oil drops below $100 per barrel. Larger chemical recycling plants under construction, with upwards of 100,000 TPY capacity, could drop the cost to below $450 per ton. So, the larger plants seem to have a better chance at an attractive economic return.
In the U.S. another fundamental question that arises is: can the economic incentive to chemically recycle plastics be attractive on a widespread basis when compared to disposal in a landfill or a waste-to-energy plant? The answer to that may be two parts, maybe yes, but not currently. Some of the other factors that affect the disposal versus chemical recycling issue are listed in Table 3.
On a national basis, there is a way to go in increasing a steady demand for recycled resins. Some of the chemical recycling technology seem to be commercial-ready and will likely be
refined over the next several years to reduce adverse environmental affects and conserve energy. Some technologies will not work out for economic and or technical reasons. However, there are several operational plastics recycling plants in the U.S. producing and selling material that can be manufactured into virgin-quality “upcycled” products. So, those isolated success stories will likely continue to happen.
Legislation
In the U.S., the waste recycling industry has grown based on each state, region and/or local municipality taking on its own rulemaking. At least six states have passed legislation promoting chemical recycling including Texas, Florida, Iowa, Tennessee, Wisconsin and Georgia. However, sweeping national scope regulations to stimulate plastics recycling are absent. Could we see national scope rulemaking in the U.S.? Maybe, if all the parties with a stake in the plastics recycling business see things the same way and see such laws as benefiting, or at least not hurting, their particular business. For example, the case of the petrochemical companies addressing a potential drop in demand for virgin resins with production of
recycled resins.
Another key seems to be locking-in end users of the recycled plastic resin and having a sufficient volume “spoken for” that would justify building a plant and operating it profitably. This is happening in the U.S. and even more so in the United Kingdom as they are aggressively passing regulations that require new products have a high percentage of content that comes from recycled plastics.
In response to regulatory pressure to reduce plastic waste and the availability of plastic resins derived from chemical recycling, some large industrial manufacturing companies in the European Union have announced commitments to use in some cases, up to 100 percent recycled material in their plastic products. Post-consumer plastic waste is the bigger, but more elusive, waste stream to manage and try to re-direct as a feedstock to some of these plants.
A potential short-term threat to this growing industry looms. Section 902 of the pending Clean Future Act that is being pushed through the House and Senate, places a “temporary pause period” (i.e., essentially a three-year moratorium) on new permitting for plastics manufacturing, including facilities that repolymerize plastics into chemical feedstocks. Some of the technologies that we mention in this article repolymerize plastic waste, so if passed, this could have a chilling affect on this segment of the industry. New rules that limit emission of greenhouse gases and other air pollutants from these facilities are to be finalized at the end of the “temporary pause period”.
In another odd twist, at the same time, the Department of Energy plans to provide $14.5 million in funding through the Plastics Innovation Challenge for projects supporting the development of advanced plastics recycling technologies and new plastics that are recyclable-by-design. So until the dust is settled on Section 902, “caution” is probably the watchword for investing in and commercializing some of these new chemical recycling technologies. | WA
Bruce Clark, PE is a waste and energy consultant with Ardurra (Tampa, FL). He has conducted technical and economic assessments of waste recycling and thermal, bio-chemical and
biological waste to energy technologies for the past 15 years. He can be reached at (813) 326-3498 or [email protected].
Thea Dirani is a chemical engineer with Ardurra. Her experience includes modeling a full-scale plant for conversion of methanol to DME a new vehicle fuel. She can be reached at
[email protected].
Notes
Chemical Recycling 101 – The Future of Chemical Recycling, British Plastic Federation and Recycling Technologies, undated.
Non-Mechanical Recycling of Plastics. Waste & Resources Action Programme (WRAP) UK, Oliver Goldberg, Sam Haig, Richard McKinlay, October 2019.
Plastic has a problem; is chemical recycling the solution? Alexander H. Tulio, October 6, 2019.
References
Non-Mechanical Recycling of Plastics, Waste & Resources Action Programme (WRAP) UK, Oliver Goldberg, Sam Haig, Richard McKinlay, October 2019.
Accelerating Plastic Recovery in the United States, McKinsey & Company, Manual Prieto, Andrew Ryba, Theo Jan Simons and Jeremy Wallach, December 20, 1019.
How Plastic Waste Recycling Could Transform the Chemical Industry, McKinsey & Company, Mirjam Mayer, Theo Jan Simon, Christof Witte, December 20, 2018.