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What is hydrothermal liquefaction?

hydrothermal liquefaction

Dr Len Humphreys, Chief Executive Officer of Licella Holdings, tells Waste Management Review about the next generation of advanced recycling – hydrothermal liquefaction.

The topic of how we use and manage plastic exploded at the beginning of 2018, when China told the world it would no longer accept its plastic waste. 

The aftershocks were felt by waste contractors, councils and then the public; some councils even paused recycling collection.

Fast forward to 2022 and the rapid and systems-wide transformation needed to enable a local circular economy for plastic has not happened. The sad reality is that 87 per cent of plastic is still not recycled in Australia, according to the Plastic Waste Advanced Recycling Feasibility Study: Geelong-Altona Industrial Corridor 2021.

To achieve the Australian government’s ambitious National Waste Management Target of 80 per cent average resource recovery rate, plastics will require an additional 2.5 million tonnes of recycling capacity – that is a 13-fold increase on what is in place.

Advanced recycling is one piece of the puzzle to help achieve this. Also referred to as ‘chemical recycling,’ advanced recycling takes plastic back to its chemical building blocks; oil that can be used back into the local plastic supply chain. 

Critically, advanced recycling helps close the loop on the 87 per cent of plastic that still is not recycled in Australia each year. Unlike mechanical recycling, where plastic needs to be sorted by type, advanced recycling can process mixed plastics, including multilayer packaging.

Advanced recycling takes plastic back to the oil it came from, which enables the production of food-grade recycled plastic. It complements mechanical recycling by offering a solution for difficult to recycle plastic that currently goes to landfill or incineration. 

hydrothermal liquefactionA new approach

While older advanced recycling approaches, such as pyrolysis, are purely thermally based, a lower-carbon approach has emerged – one that uses water. 

Hydrothermal liquefaction (or HTL) is the next generation of advanced recycling. Moreover, the most commercially advanced HTL technology in the world is Australian – Licella’s Cat-HTR (Catalytic Hydrothermal Reactor) platform.

HTL was developed in a carbon constrained world. It uses hot, pressurised water to recycle more carbon from plastic than pyrolysis, while using less energy to achieve this. 

In addition, HTL moves hydrogen from the water into the product oil, making it easier to upgrade in a conventional refinery. 

Some of the biggest players in the industry have thrown their support behind facilities with the Cat-HTR HTL platform at their core, including Shell Catalysts & Technologies, Dow Chemicals, KBR, Mitsubishi Chemicals and LG Chem.

HTL vs pyrolysis 

Pyrolysis works by pyrolyzing plastic – heating it in the absence of oxygen. Heating plastic from the outside is an energy intensive process that results in the formation of a ‘char’ or waste carbon. 

Using water makes hydrothermal liquefaction a more controlled reaction. The water more efficiently transfers heat, meaning that HTL operates at significantly lower temperatures than pyrolysis. 

A more controlled reaction also means that more carbon is retained from the plastic into the product oil. Essentially, this helps keep more plastic in circulation and reduces the demand for virgin plastic from fossil resources. 

Another major advantage of HTL is its proven ability to handle a wider range of plastics and contaminants, including PVC. Undesirable chemicals, like the chlorine from PVC, are removed with the water. 

It all counts

Compared to older advanced recycling approaches, HTL keeps more carbon from plastic in circulation, meaning we need to take less fossil carbon from the ground. It also uses less energy, therefore creating less emissions. 

In Licella, Australia has the world’s leading hydrothermal liquefaction advanced recycling technology, and an unprecedented opportunity to support local technology that reduces emissions and keeps more plastic in circulation.

In 2021, Licella, supported by Amcor, Coles, iQ Renew, LyondellBasell, and Nestlé, released a report highlighting the potential for establishing an advanced recycling facility using HTL.

The report followed a feasibility study that demonstrated a circular economy for plastic is not only possible but is essential for Australia to meet its National Waste Policy commitments.

The report highlighted significant economic and environmental benefits using advanced recycling with HTL to enable a local circular economy for plastic. It found that compared to imported conventional crude, Cat-HTR oil delivers a 64 per cent CO2 reduction.

The study identified Altona in Victoria as the location best placed for an advanced recycling facility, given the area’s existing infrastructure and manufacturing capabilities.

The advanced recycling facility would be an Australian first and presents the opportunity to divert up to 120,000 tonnes, or 24 per cent, of the waste plastics sent to landfill every year in Victoria alone.

The project is at the fundraising stage and well advanced with site approval and community consultation.

For more information, visit: www.licella.com 

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