A recent study had discovered a new technique will simultaneously break down the most widely used plastic form and synthesise useful, widely used molecules, allowing plastic waste recycling to be more desirable and realistic.
Every year, about 300 million metric tonnes of plastic waste are produced, with almost 12 billion metric tonnes of plastic waste projected to pollute the earth by 2050. The molecule polyethylene, mostly found in containers and shopping bags, is the largest portion of plastic waste and can take several centuries to decompose.
One issue with plastic is that it is quicker and simpler to produce new ones than it is to recycle it. Recycled plastic items also have inferior properties to freshly manufactured ones, and breaking plastics down to their initial building blocks is often difficult and needs a lot of resources or additives, but such costs are often not recovered by the resulting goods. It is basically converting a low-value commodity into a product of high value.
To “upcycle” plastic waste — to turn it into useful chemicals — is one possible route to overcome this economic barrier. However, before synthesising the desired chemicals, this also requires the energy-intensive, laborious process of breaking the plastic down to its simple components.
The study established a simple , low-energy technique to transform polyethylene into alkylaromatic compounds, which are the source of a significant variety of detergents, lubricants, paints, solvents, pharmaceuticals and other industrial and consumer goods.
According to Bert Weckhuysen, a chemical engineer at the University of Utrecht in the Netherlands, ‘Polyethylene is one of the most commonly produced and processed plastics in the world — there is a large waste stream available.’
Only moderate temperatures are needed, while traditional alkylaromatic processing processes usually need temperatures of 500 to 1,000 degrees C (approximately 930 to 1,830 degrees F), this latest process requires only around 300 degrees C (approximately 570 degrees F). Water or some other solvent is also not required — it simply needs cooking polyethylene with a typical form of catalyst produced from platinum nanoparticles on aluminium grains that have long been used in oil refining.
This latest approach depends on the tandem activity of two separate chemical reactions. To split polyethylene apart into smaller parts, one uses hydrogen, splitting the tight molecular bonds binding the plastic intact, while the other synthesises alkylaromatic compounds. Hydrogen is created by the latter reaction which may help push the former reaction. Just a limited amount of by-products are produced — light gases, such as methane, that can be burned to help supply the process with electricity.
The most interesting result is that polyethylene is probably a stronger starting point than the normal starting point for producing alkylaromatic molecules, which are molecules that come directly from gasoline.
The usage of plastic is not second-best in this context but is really favoured. Plastics are highly developed and manufactured products, the energy and chemical quality of which is an opportunity rather than a detriment.
One downside to this modern method is that when matter gloms onto it, the catalyst loses activity with time. However, heating the catalyst in the presence of air to burn off everything trapped on the surface, one could refresh it.
While the catalyst itself is pricey, the price is amortised over the immense quantity of output it will manufacture over several years. Future research could explore the production of cheaper alternatives.
In addition to investigating ways to render this catalyst more effective, potential research might also explore various catalysts that can break down other plastics or produce other useful goods. This could help lead the path to a world where plastic is not deemed waste but rather a desirable raw material.