Waste plastic to fuel conversion

In this article for Intellectual Property Magazine, Partner Chris Hamer and Associate Matthew Morton explore the bright future of plastic recycling technologies and the IP trends set to accelerate a greener environment.

Plastics are an increasingly important material, used across the world in sectors such as packaging, building and construction, the automotive sector and in electronics. The European Commission estimates that global production of plastics had increased to 322m tonnes by 2015, and expects that number to double in the next two decades.

The chemical stability of most plastic materials is one of the many properties that makes these materials so attractive, particularly in sectors such as packaging, where plastic is an ideal material for sealing and preserving foods or medicines for example.

Plastic packaging accounts for around 40% of plastic waste generated and it is difficult to imagine this is going to change in the future, as abandoning plastic in packaging would have serious consequences for the storage and supply of perishable resources worldwide.

The stability of plastic that has contributed to its success is now, however, becoming one of its principle weaknesses. The disposal of large amounts of waste plastic into natural environments, where its stability in many cases allows it to persist for hundreds of years, can lead to increasing build up of plastic waste in these environments. This issue is increasingly one of public concern, although it is likely that any solution to the problem will need to come from economic incentives driving industry towards recycling.

Plastics have been recycled since the 1970s, and such recycling has historically focused on the processing and reuse of plastics in much the same form as the plastic products they were recycled from. However, in some cases such recycled plastics can have inferior properties in comparison to new, so-called ‘virgin plastics’, and as a result, particularly when producing new plastic is relatively cheap, the economic incentives for recycling are not always obvious. Nonetheless, if plastic waste can be repurposed to fill a demand for other chemical products rather than trying to compete with virgin plastic, then this can offer an opportunity to change what is often simply treated as a waste stream into a valuable resource. Higher costs for plastic disposal could up the economic incentives for trying to generate profit from waste plastic in the near future.

Repurposed plastics

One way that certain plastics can be usefully recycled is by pyrolysis, by which plastics are heated to high temperatures in the absence of oxygen, thereby breaking the plastic down into simpler hydrocarbon products without combustion. These hydrocarbon pyrolysis products can then be used to replace, or blended with, hydrocarbon materials obtained by refining petroleum feedstocks. Hydrocarbon pyrolysis products can be used to blend with transportation fuels or can find use in lubricant base oils.

Lubricant base oils are typically combined with additives to tailor their properties to produce lubricating compositions such as motor oils or lubricants for use in industrial processes such as metalworking. Lubricant base oils are graded into different groups according to American Petroleum Institute standards, based on their composition and purity. Higher classification oils are traditionally obtained by carrying out treatments of mineral oil stocks, including hydrotreating to remove non-carbon impurities (Group I), further hydrocracking to reduce the size of hydrocarbon molecules in the oil and further improve purity (Group II) and hydroisomerisation to alter the structure of the hydrocarbon molecules to improve oil properties such as pour point and viscosity (Group III). While the ‘higher’ groups of oil can give improved performance, the steps to upgrade base mineral oils incur additional energy costs and increase capex to provide specialised treatment units. Synthetic oils are also produced to give tailored high-quality lubricant oils without using mineral oil feedstocks.

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While the slow transition to electric powered vehicles, which do not require the same motor oils as internal combustion powered vehicles, could reduce lubricant demand, given the expense and lack of practical infrastructure for electric vehicles, it seems unlikely that demand for automotive lubricants will significantly decline in the short term. Electric cars nonetheless do need greases for lubricating their high-torque moving parts, which could potentially be supplemented by plastic-derived products. In addition, lubricants also find use in areas outside of the automotive sector and it has been suggested that despite movement towards electric cars, the opportunities for growth in the lubricants sector remain.

Polyolefin polymers such as polyethylene and polypropylene are made from very long chains of saturated hydrocarbons that in terms of molecular structure and overall composition are very similar to mineral oils, and by breaking down the hydrocarbon chains of the plastic into smaller parts, oils and waxes having similar properties to refined mineral oils can be obtained. Processed pyrolysis products can have very low sulfur, nitrogen and aromatics content compared to mineral oil sources, and so offer the potential for providing cleaner fuels. Oils and waxes obtained from plastics can also be used to provide feedstocks that can be refined and blended with existing products to produce high quality base oils. Other plastics that contain aromatic hydrocarbon rings, such as polyethylene terephthalate (PET) and polystyrene can also be decomposed to give liquid products containing aromatic hydrocarbons that have the potential for use in chemical industries. Polyvinyl chloride (PVC) poses some additional challenges when treated by pyrolysis due to formation of hydrochloric acid from the chlorine in the polymer, which can lead to corrosion of equipment.

Of course, a constant issue with all recycling technologies has been the feed material available, which tends to be unsorted and comprises a mix of different plastics. However, Professor Martin Atkins, chief executive of Green Lizard Technologies, who is involved in a planned 200,000 tonne waste plastic recycling plant in the US and a 50,000 tonne plant in the UK, states that recent technological developments have helped to address this particular issue.

Patent landscape

Growing interest in processes for repurposing plastic waste into higher value materials, such as oils and waxes for lubricants, can be monitored by observing patent filing trends in the area. Figure 1 shows numbers of international PCT applications found in a basic search for patent applications mentioning pyrolysis of plastics. While the number of applications appears to have remained relatively constant in recent years, it has roughly doubled over the past decade, increasing fourfold in the last 20 years.

Figure 1: Number of PCT applications and granted European applications by publication year that mention pyrolysis of plastics

Waste plastic to fuel conversion figure 1

One different way to look at the sector through patent trends is to look at how many patents are being granted each year. Taking a patent application from filing through to grant requires commitment on top of the cost of an initial filing, and so the number of patents going through to grant could better reflect the level of active commercial interest in the area. Figure 1, which also shows granted European patents, illustrates a sharp increase in the number of patents being granted the last few years. While it is not possible to say for certain what the reason for this is, it suggests an increasing desire for granted and enforceable patent protection in what seems to be a growing market.

Looking at the top filing entities in the field, many patent filings relating to plastic pyrolysis have historically come from large corporations such as Toshiba and Chevron, as well as BASF, who have recently announced a scheme to convert waste plastics into chemical feedstocks (Figure 2). In addition to large corporations, in recent times much of the activity in the plastic recycling field has come from relatively newer companies such as Trifol Resources, Recycling technologies and
Greenmantra Technologies.

Figure 2: Number of PCT patent filings by applicant (Search Output provided by Coller IP)

Waste plastic to fuel conversion figure 2

The trends in patent filings and the increased public interest in dealing with plastic waste in a more ‘green’ way point to a bright future for plastic recycling technologies.

For applicants filing patent applications at the UK Intellectual Property Office, it is also worth bearing in mind that technologies in this area will likely qualify for accelerated processing of patent applications via the free Green Channel programme.

This article was first published in the June 2019 edition of Intellectual Property Magazine.

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