As much an opportunity as a threat, the trend toward circularity plays directly to the petrochemical industry’s core competency—turning waste into useful materials by chemical transformation.
That waste was originally the by-products of petroleum refining, but increasingly it will also be the industry’s own product: plastic, recovered after use. The development of chemical-recycling technologies will be key. Just as important, and perhaps more difficult, will be the logistical issue of collecting plastic waste and distributing it for processing.
“I think this is most assuredly the next phase of the petrochemical industry,” says Robin Waters, director/plastics analysis at IHS Markit. “The petrochemical industry grew a very efficient linear chain for taking energy and converting it into materials that support growing populations. The next phase is to repurpose what is produced in the linear chain and build a more efficient model.”
Waters and his team at IHS Markit are conducting a new study, Changing Course: Plastics, carbon, and the transition to circularity, to be released in August. “The petrochemical industry has the most prominent opportunity to exhibit what circularity is by doing what they do best, which is manipulating molecules in a commercial setting,” says Waters. “Just as they have taken crude oil and natural gas and done an excellent job providing consumers with usable materials, they really hold the key to repurposing those materials if we can collect them—and collecting them is probably the big issue.”
Broadly speaking, plastics can be recycled mechanically or chemically; which of the two is more environmentally sound is a complex economic calculation. In the first analysis, mechanical recycling is preferred because it consumes fewer resources to obtain a useful product, but it has important limitations. One is the problem of mixed plastics.
A simple solution is to recycle mixed plastics into large-volume demand sinks that are not sensitive to the quality of the resins. In the case of asphalt modification and concrete construction, incorporating plastic waste improves physical properties and reduces raw-material cost and significantly reduces the amount of energy consumed and greenhouse gases emitted during production. However, most of the plastics’ value is lost.
“Some of these bulk applications have a low value in use, so you’re not really getting the full value of recycling,” notes Anthony Palmer, vice president/chemical consulting at IHS Markit and coauthor of the report. “You’re spending a lot of money on infrastructure, and the end use that you’re putting this into is quite low-valued.”
Fully exploiting the greater inherent efficiency of mechanical recycling requires an integrated system of disposal, collection, and sorting capable of supplying “clean” streams of plastic waste sorted by resin. “Mechanical recycling requires a lot of cooperation,” says Waters. “It may involve some redesign of our packaging, to make packaging more common in terms of the materials that we use. And that certainly can be done. And then sorting at collection, where [people give] much more attention to how they throw their trash out and what containers they put them in. But this society can make mechanical recycling work to a very large degree, and that is the most sustainable approach to doing this.”
However, even clean streams are not truly uniform because plastics consist not only of resin but also the many additives used to adjust their performance. These additives cannot be removed mechanically, and being unidentified, they will affect the performance of the recycled resin in unpredictable ways.
“There has to be an alignment between the recycling infrastructure and the way you would use the recovered material,” says Palmer. “There’s a limit to what you can really do with mechanically recycled material before properties deteriorate. And there are some segments, such as food and medical, where you’re probably not going to get any significant mechanically recycled material into the stream.”
“That’s where chemical recycling can come into play,” says Waters. “By returning these materials back to the basic molecules, you don’t have the traceability issues of additives.”
A flurry of announcements in recent weeks suggests rapid progress for chemical recycling: Pyrowave, a developer of a microwave-based polystyrene (PS) recycling technology, closed a series B round of investment led by tire-maker Michelin; Ineos announced it would build a plant using technology developed by Plastic Energy to convert waste plastic into feedstock for its steam crackers; and Agilyx licensed its recycling technology to Lucite International for recycling polymethyl methacrylate in Europe, and to Toyo Styrene for recycling PS in Japan.
Even so, fundamental issues have barely been probed, Robins says. “One of the key questions that we’re still trying to answer is what a world-scale capacity looks like for any of these units. Many have not shown feasibility beyond the pilot stage. How many do we have to build, where are we going to put them, and what is the capital cost of making these units economically feasible? Nobody really knows that at this moment, so they don’t know how to scale the infrastructure.”
“You really can’t overestimate the importance of logistical concerns,” adds Palmer. “Do you want satellite operation or centralized operations? It’s a real challenge, particularly for chemical-recycle schemes. So people are looking at the technology development, but in order to get the economics, you’ve got to have scale, which compounds the issue of logistics and local collection of the plastic. So there are two problems that have to be solved, the technology and the logistics, and they have to be done hand-in-hand.”
Waters expects the petrochemical industry to transform itself by solving these issues. “There’s a whole industry to be conceived here, and it’s the petrochemical industry that understands how that might happen,” he says. “The chemical industry of the future is not going to be about just capacity loading, it’s going to be about meeting consumer needs in the most economical, energy-efficient, and emissions-responsible way.”
By: Clay Boswell
Source: Chemical Week
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