“Plastics are a not only an environmental problem but have also revolutionised society and will continue to do so,” said Harm-Anton Klok from the Institute of Materials of the Ecole Polytechnique Fédérale de Lausanne (EPFL). “The word plastic is often associated with waste, environmental pollution and excessive use of fossil resources. The development and emergence of synthetic polymers over the past century, however, has been key to a vast number of technological advances, and it’s hard to envision our society without this class of materials.”
He explained that people usually only focus on the devil in plastics – namely pollution, with plastic waste a big and complex issue. The long-term consequences are multiple including that micro particles of plastic can enter the food-chain causing health issues for both animals and humans. “However, I believe, plastics, and materials more generally, will be key to making the planet more sustainable for future generations.”
Tracing some highlights in the history of plastics, Klok pointed to the development of the first synthetic plastic namely Bakelite which was patented in 1907 and found use in telephones, among other things.
Wallace H. Carothers, a chemist at DuPont, is credited with the invention of nylon plastic in 1935. This lightweight material has multiple uses in clothing and other items we use daily.
Klok then highlighted the work of Karl Ziegler and Giulio Natta who shared the 1963 Nobel Prize in Chemistry for the establishment of catalytic processes for the preparation of polyethylene and polypropylene, which now represent the most widely produced plastics.
A next substantial, breakthrough was the discovery of conductive polymers which led to the 2000 Nobel Prize in Chemistry being awarded to Alan J. Heeger, Alan G. MacDiarmid and Hideki Shirakawa. “Up to then plastics were considered electrical insulators” explained Klok. “The discovery of conductive polymers opened the way to a new range of applications requiring materials that were flexible but could carry a charge. It meant you could make plastics that could harness energy in solar cells and stretchable batteries. It also meant plastics could be used to interrogate the human body – soft, flexible conductors to non-invasively place electrodes in the human brain. This was not possible before.”
Need for radical change
“However,” said Klok, “the current use of synthetic polymers is not sustainable, and needs to be radically revisited.”
Much of the problem lies in the way we utilise materials in a linear-economy model. “For example, we start with petroleum-based feedstocks which are turned into plastic packaging materials (at a rate of just under 80 million tonnes per annum) – of this, 40% ends up on landfills, 32% is lost to leakage and only 14% is recycled.”
“We need to change to a circular economy – starting from renewable or biologically sourced feedstocks to prepare plastics, and design plastic products that are designed for re-use instead of single use.”
Klok pointed out that a one contribution towards a more sustainable polymer economy would be to expand the range of renewable, biological resources available to produce polymer materials. Lignocellulosic biomass, which is one of the areas of interest of his research group, is one example of a biological feedstock that has not yet been fully exploited to produce materials, and that could complement other biosourced polymers or replace fossil-resource based plastics.
Lignocellulosic biomass comes from plants and trees, and is comprised of three components – cellulose, lignin and hemicellulose with lignin comprising 5 to 30% of biomass. One 100 million tonnes of lignin are isolated per annum but only 2% is used for low value-added applications. Most is just burnt. Lignin is a challenging material to work with as it has limited solubility, and a complex structure. The use of refined pathways to isolate lignin from biomass allows to overcome some of these challenges, and provides access to lignin with improved properties. Klok highlighted recent work from his group which showed that these new lignins can be used to prepare films that are optically transparent, and flexible and offer UV barrier and antioxidant properties which can be used for food-packaging films. Tests thus far have shown that lignin-based films can be as good as polyethylene-based packaging films at preserving broccoli.
“But,” he warned, “there isn’t a single biosourced feedstock for all plastics.” Different renewable feedstocks allow access to plastics with different properties. Another important factor to consider is that land that is used to produce feedstock for plastic materials of course is not available to produce food or to construct housing, and we need to be thoughtful how to best use the limited space on our planet.
Plastics for sustainable agriculture
Sustainable agriculture is another of Klok’s research interests. He explained that revolutionary changes during the past century in agricultural production like fertilisers, mechanised tools, irrigation, agrochemicals and GMOs have all increased food production but some of these methods are harming the environment because they are inefficient or energy inefficient. For example, with traditional fertilisers – 50% are lost due to wash off and leaching. “We need efficiency, sustainability and resilience in agriculture,” he said.
His STIAS project looks at the concepts and methods that have driven the development of polymer nanomedicine, to provide a starting point for the development of polymer-based ‘nano-agrochemicals’, tailored to address key agricultural challenges. He is specifically looking at challenges in the African context that could benefit from these technologies. Klok’s research group’s work using Arabidopsis thaliana (a plant from the mustard family) is showing that it might be possible to develop materials that are able to interact with plants, and for example facilitate nutrient uptake in nutrient-scarce environments.
“It would be a small contribution to a huge problem,” he said.
Science, politics and society
However, even if technological solutions are available, they are useless if governments and people don’t buy into them and we therefore have to strengthen the science, political and social interface.
“If you can’t get society and decision makers on board nothing will happen. COVID-19 showed us the importance of that and that such collaboration is possible,” said Klok. “Often the social and political hurdles are bigger than the scientific.”
He pointed out that the 2023 Global Sustainable Development Report (Global Sustainable Development Report (GSDR) 2023 | Department of Economic and Social Affairs (un.org), which looks at progress on the 17 Sustainable Development Goals (SDGs), specifically emphasises the need for science backed by political leadership to accelerate transformation.
“The SDGs challenge us to transfer technical solutions into societal change,” he said. “There has only been progress on two or three of the SDGs, most are going backward. It’s time for action. We need to transform science for sustainable development – through multidisciplinarity, inclusiveness, equity and sharing. This means more implementation-orientated research while also not eroding curiosity-driven research.”
“To solve complex problems, we need to think across disciplines, cultures and continents – STIAS embodies that philosophy, and we need to pass that on to our students.”
Michelle Galloway: Part-time media officer at STIAS
Photograph: Noloyiso Mtembu