In the previous article, I outlined the growing global problem of plastic pollution. Global treaties and new technologies that address the manufacture, use, and reuse of plastics are needed to tackle this problem.
Some companies are already working on the problem.
Researchers have tried several different reuse approaches for addressing the growing global plastic waste stream. Plastics are almost exclusively made from petroleum, and they retain a lot of potential energy after they have been used. So, it may seem to make sense to simply burn them for power.
The main challenge with this approach is that combustion of plastics creates several undesirable pollutants, such as dioxins and furans. Waste plastics may also contain undesirable components. PVC, for example, is polyvinyl chloride, and the chlorine atoms can form corrosive hydrochloric acid when combusted.
Pyrolysis is a different approach that involves the thermal degradation of plastic waste in the absence of oxygen to produce a liquid oil. Although it suffers from similar problems, this decades-old approach seems to be the most common. But it creates many undesirable byproducts, and the resulting oil requires significant additional processing.
But one Canadian company believes they have found a novel solution to the problems that have plagued the pyrolysis approach. This approach opens the door to options never considered possible before.
Aduro Clean Technologies of Sarnia, Ontario, was founded in 2011 with a focus on upgrading bitumen, which is a semi-solid form of petroleum found in abundance in Canada. 70 years after the emergence of the Canadian bitumen industry, this small company identified that trace metals that are native to the bitumen, and are a nuisance in oil refining, play an important catalytic role in breaking down complex bitumen components, thus improving its properties and value.
Furthermore, the company discovered that certain bio-based materials could replace hydrogen gas required in hydrocracking reactions. Next, the company recognized that the same chemistry it applied to upgrade the bitumen and renewable oil could be applied to plastics, for their controlled conversion into liquid hydrocarbons under milder conditions than unselective, decades-old pyrolysis methods.
The Aduro approach involves addition of water, naturally-occurring metals, and bio-based material such as glycerol or cellulose. This deconstructs the long molecules (polymers) in waste plastics into smaller molecules. The approach is analogous to the hydrocracking process in a refinery but is conducted at much lower temperatures without the requirement to add hydrogen gas or use exotic, expensive catalysts.
In a fortuitous twist, the company’s analysis of the waste plastic problem revealed that the source of hydrogen equivalents is also available in waste plastic. In other words, upcycling waste plastics is self-sustaining. When hydrogen equivalents are needed, some waste plastic of the appropriate type, or even foam from the millions of mattresses discarded every year, can be added into the mix. This opens the door to stand-alone, cost-efficient waste plastic processing operation that could serve best the local community the waste is associated with.
Aduro refers to its process as Hydrochemolytic™ Technology (HCT). When applied to plastics, it is Hydrochemolytic™ Plastics Upcycling (HPU).
And in recent lab runs, HPU produced 99% pure, diesel-like paraffin oil from polyethylene with a yield above 90%. Though the product could be used as fuel, Aduro CEO Ofer Vicus told me the real prize within reach, thanks to HPU, is efficient chemical recycling of polyethylene (PE) for use in production of more polyethylene in a fully circular mode
The company anticipates successful results on other members of the plastic family such as polypropylene (PP) and even polystyrene (PS). The company intends to start with PE-upcycling to prove the simplicity of its process by building a 10 metric-ton-per-day precommercial unit in 2022 followed by other pilots that will deal with higher mixture of the plastic families.
“Society raised the bar high for plastic recycling,” Vicus told me, “And HPU aims to meet it!”