Amanika Sahu,
Monash University

Imagine the gentle morning chorus of birds and the tranquil beauty of green scenery greeting you as you breathe in the fresh air. Yet, for the residents of Bandhwari, this is a distant dream.

Their reality is the Bandhwari landfill in India, where the only birds in sight are crows scavenging through mounds of waste. This stark contrast poses a question: how did we arrive at such a crisis? The answer may be as close as the discarded chip packet at your feet.

Mechanical vs chemical recycling

Humans produce about 300 million tons of plastic each year – equivalent to the weight of roughly 60,000 Melbourne Cricket Grounds filled to capacity with fans.¹ Yet only 9% of this is recycled.¹

Currently, mechanical recycling stands as the most prevalent recycling method. This approach has led to the creation of innovative and sustainable plastic products such as eco-bricks, plastic roads, and 3D-printed furniture.² However, it falls short in addressing hard-to-recycle plastics.

Incineration – a seemingly straightforward solution – converts waste to energy…but at a cost. Burning plastic releases a range of chemicals into the environment, including known pollutants dioxins and furans, and also leaves behind microplastics in the ash, creating further environmental pollution.³

“The same properties that make plastics so useful—their durability and resistance to degradation—also make them nearly impossible for nature to completely break down.”⁴

Instead, we must turn to chemical recycling: breaking down plastics to their molecular components – hydrogen and carbon – which are also the building blocks of fuels. This method can process a broader range of plastics, including mixed or contaminated ones, through techniques like depolymerization, pyrolysis, and gasification.⁵

Carbon building blocks

Carbon is an element found in all known life, and is the main component of plastics. Recycling carbon keeps it locked in a product, and prevents it from becoming harmful carbon-based greenhouse gases like carbon dioxide (CO2) or methane (CH4).

Soft plastics that have traditionally been hard to recycle and destined for landfill (e.g., chocolate wrappers) can be converted into oil. This oil can then be refined and turned back into food-grade packaging as part of a more circular economy.⁶ The carbon from plastics could also replace fossil fuel-based carbon for various chemical uses, like making medicines, or to replace fossil fuels as an alternative fuel for diesel engines.^7,8

Advancing technologies that allow us to recycle plastics in these ways not only tackles the problems of plastic pollution and waste management, but also address the global energy crisis by producing greener and cleaner fuel.

In Australia, a number of companies are progressing with recycling plastic into usable fuels. Licella has designed a Catalytic Hydrothermal Reactor (Cat-HTR) system, while Melbourne’s APR Plastics is using Biofabrik WASTX pyrolysis tech to turn kerbside plastic waste into valuable crude oil.^6,9 Advanced Recycling Victoria plans to establish a plastic recovery plant in Altona, and Viva Energy is investing in Geelong refinery infrastructure for waste-to-fuel processing.^10,11

At Monash University, Professor Sankar Bhattacharya has created a prototype plant that repurposes plastic and waste tires into diesel fuel.¹² The process involves pyrolysis, heating of shredded plastics to produce oil and gas vapours that can be separated for different purposes: heavy oil for wax, and light oil for power generation directly or to be further converted into gasoline or diesel. This initiative is timely, as China’s termination of waste imports has prompted Australia to find domestic recycling solutions.

The process, while energy-intensive, is designed to be self-sustaining by recycling the gases it produces. Professor Bhattacharya is working with local councils to scale this technology, aiming to reduce landfill waste and fossil fuel reliance.¹²

Factors to consider

Although effective, chemical recycling presents environmental and health challenges, including the release of various pollutants during the process. The problem of plastic pollution isn’t going to be solved through exacerbating another problem in the form of greenhouse gases.

The oil obtained from plastic waste is more volatile than standard diesel, increasing the risk of spontaneous ignition. The inconsistency of feedstock and the varied breakdown of polymers during pyrolysis add complexity.

Additionally, the current process requires extremely high temperatures, making it expensive and inefficient.¹³ More research is underway to address the environmental impacts, commercial feasibility, and handling of contaminated and mixed waste.

Research ongoing

Innovative techniques are being developed to transform plastic into fuel more effectively, without high temperatures or plastic residues. For instance, Washington State University researchers discovered a method using a ruthenium metal and carbon catalyst combination that can convert 90% of plastic waste into fuel within an hour at a lower temperature of 220°C, making it more efficient and cost-effective than current chemical recycling standards.¹⁴

A team from the University of Delaware employs hydrocracking, a chemical process that breaks down the carbon bonds in plastic, using a catalyst composed of zeolites and mixed metal oxides. This method uses 50% less energy than comparable technologies, operates at normal kitchen oven temperatures, and does not release carbon dioxide into the atmosphere.¹⁵

The Pacific Northwest National Laboratory developed a new method combining cracking with alkylation catalysts to produce gasoline-like fuel without unwanted by-products.¹⁶ This process is conducted at low temperatures and with high yield, reducing the cost of recycling plastics.

These pioneering methods represent promising strides towards more efficient and eco-friendly ways to recycle plastic waste into fuel. However, many of these technologies are still in the development and scaling stages.

A revolution to make the plastic industry circular

The journey from “landfill to oilfield” is not just a scientific endeavour but a societal imperative. By further investigating the plastic-to-fuel revolution, we could address the dual challenges of plastic pollution and energy scarcity – as long as we also mitigate any unwanted by-products.

References:

13. UN Environment Programme. (2022, February 16). World leaders set sights on plastic pollution. UNEP. www.unep.org/news-and-stories/story/world-leaders-set-sights-plastic-pollution
14. Waste Managed. (2024, February 7). Innovations in plastic recycling 2024 | waste managed. Waste Management Services | Recycling | WasteManaged. www.wastemanaged.co.uk/our-news/recycling/innovations-plastic-recycling/
15. Yang, Z., et al. (2021). Is incineration the terminator of plastics and microplastics? Journal of Hazardous Materials, 401(123429), 123429. doi.org/10.1016/j.jhazmat.2020.123429
16. Maxwell, R. (2024, May 6). Recycling idea gave Indigenous communities plastic hope. National Indigenous Times. nit.com.au/06-05-2024/11214/recycling-idea-gave-indigenous-communities-plastic-hope
17. Cheng, L., Chen, X., Gu, J., Kobayashi, N., Yuan, H., & Chen, Y. (2024). Chemical recycling of waste plastics: current challenges and perspectives. Fundamental Research. doi.org/10.1016/j.fmre.2023.12.023
18. Korycki, L. (2022, May 6). Plastics into oil at APR plastics. Waste Management Review. wastemanagementreview.com.au/plastics-into-oil-at-apr-plastics/
19. Vollmer, I., et al. (2020). Beyond mechanical recycling: Giving new life to plastic waste. Angewandte Chemie International Edition, 59(36), 15402–15423. doi.org/10.1002/anie.201915651
20. Padmanabhan, S., et al. (2022). Energy recovery of waste plastics into diesel fuel with ethanol and ethoxy ethyl acetate additives on circular economy strategy. Scientific Reports, 12(1), 5330. doi.org/10.1038/s41598-022-09148-2
21. Australian Renewable Energy Agency (2013, February 28). Licella Awarded Federal Government Advanced Biofuels Investment Readiness (Abir) Grant [Press release]. www.licella.com/wp-content/uploads/2017/06/licella-28-feb.pd
22. Advanced Recycling Victoria Pty Ltd (APP016941). (2022, September 21). Engage Victoria. engage.vic.gov.au/advanced-recycling-victoria
23. Prime Mover Magazine. (2024, April 15). Viva energy team up with cleanaway to address hard- to-recycle plastic waste. Prime Mover Magazine. primemovermag.com.au/viva-energy-team-up-with-cleanaway-to-address-hard-to-recycle-plastic-waste
24. Bhattacharya, S. (2019, August 23). Making waste plastic fantastic. Monash Lens. lens.monash.edu/@sankar-bhattacharya/2019/08/23/1351620/turning-plastic-into-fuel
25. Jia, C., et al. (2021). Deconstruction of high-density polyethylene into liquid hydrocarbon fuels and lubricants by hydrogenolysis over Ru catalyst. Chem Catalysis, 1(2), 437–455. doi.org/10.1016/j.checat.2021.04.002.
26. Jia, C., et al. (2021). Deconstruction of high-density polyethylene into liquid hydrocarbon fuels and lubricants by hydrogenolysis over Ru catalyst. Chem Catalysis, 1(2), 437–455. doi.org/10.1016/j.checat.2021.04.002.
27. Liu, S., et al. (2021). Plastic waste to fuels by hydrocracking at mild conditions. Science Advances, 7(17), eabf8283. doi.org/10.1126/sciadv.abf8283
28. Zhang, W., et al. (2023). Low-temperature upcycling of polyolefins into liquid alkanes via tandem cracking-alkylation. Science, 379(6634), 807–811. doi.org/10.1126/science.ade7485