opinion : How plastics is turned into synthetic crude again

“When it comes to plastics, I am a fan of Reduce, Reuse, Recycle”, says Michaela Fraubaum. She is convinced that chemical recycling like the ReOil process is the ideal addition to well-established mechanical recycling methods. “There are fantastic products from mechanically recycled plastics, for recycling PET drinks bottles, for example, there are efficient methods to produce high-quality PET bottles again from the used ones”. And yet PET bottles account for only 20% of packaging waste. So, what about the rest?

“Our ReOil method also allows us to treat mixes containing different types of used plastic as we go so far back in the chemical process that everything is possible”, says the process engineer. “We are not tied to the source product and we produce a very pure raw material once again, namely synthetic crude”.

This is especially useful for products requiring a high purity level and for high-tech plastics. Michaela Fraubaum: “Think packaging for the food industry or medical products, which have to meet strict safety standards for good reason. It’s no problem to manufacture these products from chemically recycled plastic”.

How does the process work and what type of plastics can be used? Michaela Fraubaum explains: “In the plant we process mixed plastics like polyolefins or polystyrene, so wrappers or cups. We recycle plastic cups, for examples, that are left over as waste on Austrian Airlines flights”. Whether the packaging is suitable as feedstock for the ReOil plant can be seen by its recycling code: Numbers 02 (polyethylene – high density), 04 (polyethylene – low density), 05 (polypropylene) and 06 (polystyrene) can be recycled with the ReOil process.

The used plastics are presorted and delivered already shredded to the refinery, where we take the small pieces of plastic - known as flakes - and feed them into the process cycle. An extruder is used for this, melting the plastic at the same time. The first phase of the process is called the Solving phase.

“Plastic is a poor heat conductor, in effect it almost insulates itself”, says Michaela Fraubaum. “So it’s not that easy to heat large quantities. This is one of the greatest challenges of chemical recycling: How do I get the thermal energy in? Melted plastic is also very viscous, almost like honey, making it exceedingly difficult to transport through pipes”.

How to solve this problem? A solvent. We use an intermediate product gained from another process in our refinery. This means it’s already on site and we don’t need to procure it separately. This solvent blends into the plastic and thins the crude enough for it to pass through the pipes”.

“The second phase is the so-called Cracking stage. Here thermal energy breaks the plastic’s long hydrocarbon chains into shorter ones. What you need to know is that while crude and plastic are actually composed of the same chemical elements, the chains of molecules vary in length and have different structures”, explains the process engineer. “In the refinery we have lots of experience with cracking processes, as many refinery processes rely on cracking. From a chemical perspective, plastic is an ideal cracking medium as it contains so many hydrogen atoms. We are talking here about the so-called H/C ratio, i.e. how much hydrogen is contained relative to carbon. This is very good for plastic, that’s why relatively little residual material is left over and a high product yield is achieved. Basically, we have been able to apply our previous knowhow to develop the process and operate it”.

What happens next with the short chains? “In the third step, called Flashing, any substance that has a sufficiently short chain is separated off to be processed in the refinery and used again as a basis for high-quality plastics”. Any substance whose chains are still too long goes through the ReOil cycle once more.

Various intermediate steps involve separating additives such as coloring or stabilizers or fillers that had been added during the production and processing of the plastic. Purging these additives yields a synthetic crude that can be used to make plastic again, that has the same quality as “virgin plastic”, i.e. new plastic.

The ReOil process puts used plastics that could otherwise not be recycled – or at least not into plastic products of the same quality – back into the production cycle. “This makes us the perfect complement to mechanical recycling while also facilitating a genuine circular economy for plastics, just like with wastepaper for example. In fact, it’s even better as, unlike paper recycling, the ReOil plastic suffers no drop in quality. An old potato-chip wrapper really can become a new yoghurt pot, an IV bag or even a car bumper – all high-quality plastic products”.

But the advantages of this method don’t end here, as Michaela Fraubaum knows: “The synthetic crude yielded by this process is structured in a different way – in refinery-speak we say it is ‘lighter’ than fossil crude – and can then be fed directly into a later refinery process. Compared to processing fossil crude, we thereby skip some treatment steps like distillation, in turn saving energy”. Around 20 percent versus processing fossil-based crude. What’s more, with synthetic crude you don’t have to explore for it and produce it. When this is accounted for, CO2 savings of around 40 percent are achieved versus fossil crude.

Since the first attempts at ReOil in an in-house laboratory, quite a lot has been achieved in terms of research and development. “We managed to develop the process in the ‘Technikum’, like a small ‘test refinery’ within the refinery and that’s where we tested the idea with the solvent”, the engineer describes. Then, in 2018, a ReOil pilot plant started to operate and it was already fully integrated into the refinery’s normal process. “Taking the ReOil process out of the lab and into real-time operations, i.e. integrating it in the normal refining process, switching to continuous operation, and then scaling up accordingly was again a considerable amount of work. This required quite a bit of creative engineering and applied chemistry”, explains Michaela Fraubaum. But it has all been worth it: The plant has operated continuously for three years now, since when it has turned more than 500 metric tons of used plastic into synthetic crude – not bad for a pilot plant. And this is just the start. After all, the clear goal for the coming years is to scale up the process to several hundred times its original size.