Catalytic pyrolysis succeeds against the threat of plastic bags

Employees sort piles of plastic waste at African Recycling, one of the few recycling companies in Tunisia – Copyright AFP / File FRANCOIS GUILLOT

Mankind has lived without plastic for a hundred years and the substance is part of everyday life, despite efforts to reduce its use. Plastics reduction processes are often offset by manufacturers looking to utilize the inexpensive and quick nature of the material. Too many consumers depend on plastics, and this dependence will only be corrected through fundamental changes in infrastructure and lifestyle.

The environmental risks of plastics are well documented, and the planet is grappling with more than seven billion tonnes of plastics, most of which are indestructible. Disposal is a major concern and less than 10 percent of global plastic waste is recycled and less than 1 percent will be recycled more than once.

In addition, 24,400 billion pieces (82,000 to 578,000 tonnes) of microplastics are believed to be present in the world’s oceans.

One of the main sources of plastic pollution comes from plastic bags. A new initiative aims to partially address the issue of disposal. Scientists are reporting the success of using the process of catalytic pyrolysis (using a dewaxing catalyst) to turn plastic waste into a valuable fuel source (a substance with properties similar to diesel).

To do this, researchers at California State Polytechnic University focused on recycling plastic and turning the plastic into other products, or converting it into vapor with heat, to create a fuel-like product.

At the heart of the pyrolytic process is the transformation of primary organic waste into sustainable fuel or other valuable chemicals. The term pyrolysis refers to the thermochemical decomposition of carbonaceous material in the absence of oxygen. Such a process can be used on plastic bags.

According to researcher Mingheng Li, the catalyst is the most important factor in the process: “The catalyst is essential to this particular pyrolysis process because it only requires one step to achieve the desired combustible product at relatively mild temperatures.

The catalyst was made by dipping a zeolite substrate in an aqueous solution containing nickel and tungsten and drying it in an oven at 500 degrees Celsius.

The search appears in the Journal of Renewable and Sustainable Energies, with the research document entitled “Catalytic production of diesel-type oils from plastic waste”.

In related news, another team of scientists (from RMIT University) has developed a new approach to plastic recycling that offers a sustainable alternative for the production of carbon nanotubes (which are used for hydrogen storage, composite materials, electronics, fuel cells and biomedical technologies.).

The process first converts agricultural or organic waste into biochar (a carbon-rich form of charcoal often used to improve soil health), and then uses biochar to remove toxic contaminants like polycyclic aromatic hydrocarbons, as the plastic is broken down into gas and oil. The process removes contaminants and converts plastics into high quality liquid fuel.

Bryce K. Locke