Plastic has permeated every corner of the planet, from the highest mountains to the deepest ocean trenches, from the stomachs of whales to the rock strata itself.
More than 300 million tonnes are produced every year, and these will eventually break down into nanoscale particles that will never go away. But since many aspects of modern life rely on plastic, a great deal of research is focused on creating biodegradable and eco-friendly alternatives.
In the latest advance, researchers in China say they have developed a fabrication method to produce a strong, bio-based material. The study, published in the journal Nature Communications, describes a simple and efficient “directional deforming assembly” method, capable of producing tough, stable structural materials.
“The bioinspired structural material possesses better mechanical and thermal properties than petroleum-based plastics, making it a high-performance and eco-friendly alternative structural material to substitute plastics,” the authors write.
Currently, plastics are made from oil, gas and their by-products. Most that exist today were created in the past decade, partially as a result of the US fracking boom, which has made these raw materials much cheaper.
As we attempt to wean the world off fossil fuels, oil and gas companies seem to be hedging their bets on a future in plastic, ramping up their production by injecting billions into new projects. Petrochemicals – which include plastic – account for 14% of oil use today and are expected to drive half of all oil demand growth by 2050, according to a report by the International Energy Agency (IEA).
But there is growing global awareness that petroleum-based plastics present a great threat to the environment and to human health, from carbon dioxide emissions to air pollution to the creation of microplastics.
As Australian environmental scientist Paul Harvey explains, recycling is also unable to deal with the millions of tonnes being produced.
“The problem is mostly related to the molecular structure of the plastic,” he says. “It is very difficult to break the structure once it has been formed and then recreate that structure for another use.”
This means a large proportion of plastics can’t be recycled back into “virgin-use” materials, so either end up in tertiary products like road surfaces, in landfill, or in places we don’t want them – choking rivers, strangling sea turtles or contaminating Antarctic ice.
While there are some plastics we can’t do without – single-use plastic in medicine has revolutionised infection control, for example – as a society we are realising we need to greatly curb our use. Generally, cost-effective solutions fall into three categories: reduce demand; improve recycling; and substitute more sustainable materials.
Until now, potential replacement materials suffered from limited mechanical properties and complex manufacturing processes, which pushed up their price tag and made them difficult to produce on a large scale.
But in recent years, researchers have made breakthroughs by taking inspiration from nature. One particularly effective model emulates nacre: the strong, resilient coating of pearls and on the inside of many mollusc shells. Nacre is made up of nanoscale slabs of aragonite glued together with organic material. This “brick-and-mortar” structure is highly desired in synthetic materials, as it gives them mechanical properties that can outperform many plastics.
Fabricating this structure involves incorporating small “filler” particles into polymers, although these particles are difficult to arrange in the uniform orientation necessary to provide strength.
The new study, led by materials scientist Qing-Fang Guan from the University of Science and Technology of China, demonstrates a method to assemble such a microstructure from bio-based materials – namely, cellulose nanofibre and mica microplatelet.
This means a large proportion of plastics can’t be recycled back into “virgin-use” materials, so either end up in tertiary products like road surfaces, in landfill, or in places we don’t want them…
The process uses pressure to reduce the thickness of the material, forcing the particles to align. The result is a tough structure that remains stable at high temperatures, as opposed to most plastics, which become brittle or soft. The researchers used it to fabricate a phone case, showing that the process can be easily scaled up.
“Mass production, good processability, and tuneable colouration allow it to be used to fabricate a series of advanced, beautiful, and durable structural materials to replace plastics,” Guan and colleagues write in their paper.
But don’t expect bio-based plastics to solve our problems, cautions Harvey.
“We have to be really careful when we start looking into these new types of materials – what are they made from, how stable are they, how do they degrade?” he says.
Harvey points out that this bio-based material is largely composed of titanium oxide (the mica microplatelet), which has been shown to pollute soils. The material’s very high heat tolerance is also a potential warning sign, as it may not break down easily unless processed in specialised recycling facilities.
“As this plastic is a new concept, we know very little about how it will behave in the environment or in animals or humans – if ingested – once it starts to break down,” he says. “We could be replacing a problematic product with something just as problematic.”
The bottom line is this: we need to kick our addiction to plastic. Unless we reduce our use, any efforts to stop plastic flooding the environment – including creating bio-based alternatives – will be insufficient.
This study, however, is still a step forward.
“We absolutely need to be moving away from oil-derived plastics and this study shows that we are moving in that direction,” Harvey says.
“We need to learn from the mistakes of the past and move forward with developing thoroughly researched and tested plastic replacements that don’t create a new or greater environmental burden.”
Lauren Fuge is a science journalist at The Royal Institution of Australia.
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