Science to Enable Sustainable Plastics
More sustainable plastics are within our grasp but more research is needed.
In November, experts from China, Germany, Japan and the UK came together at the Chemical Sciences and Society Summit (CS3) held at the Royal Society of Chemistry in November 2019.
Over the course of the three day summit, they developed a plan for how to create a circular economy for plastics, preserving the crucial function they serve in society while introducing much better recyclability and reusability into their design.
About the Chemical Sciences and Society Summit (CS3)
The CS3 brings together leading researchers to discuss how the chemical sciences can help to tackle some of the most daunting challenges that our world faces. Previous summits have tackled topics as diverse as water resources, human health, and sustainability.
This White Paper, Science to enable sustainable plastics, summarizes the presentations, discussions and outcomes of the 8th CS3 meeting, held in London, UK, on 10–13 November 2019. More than 30 scientists from four participating countries gathered to discuss four major themes in sustainable plastics: their impact on the environment; new sustainable plastics; the recyclability of plastics; and the degradation of plastics.
Their goals were to assess the current status of sustainable plastics, identify the most pressing research challenges in this area, and make recommendations about how the field should progress.
The CS3 initiative is a collaboration between major international chemical societies. For this report, the collaboration involved the Chinese Chemical Society (CCS), the German Chemical Society (GDCh), the Chemical Society of Japan (CSJ), and the Royal Society of Chemistry (RSC). Support was also given by National Science Foundation of China (NSFC), the German Research Foundation (DFG), the Japan Science and Technology Agency (JST), and the UK Engineering and Physical Sciences Research Council (EPSRC). The CS3 summits are held every two years, and rotate among participating nations.
Science to Enable Sustainable Plastics – Summary & Recommendations
Plastics have helped to build the modern world. They keep our food fresh and safe. Plastics build our cities, homes and the mattresses we sleep on; they power the green revolution, producing light-weight electric vehicles and solar cells; they are essential components of mobile phones and computers; and they enable medical advances, from masks, contact lenses and heart diaphragm pumps to artificial tissues.
Plastics are essential to create a more sustainable society, and to ensure that future technologies develop rapidly and cost effectively. Plastic packaging reduces food waste by prolonging its shelf life, and has an important role to play in detecting food quality. Recent developments in plastic composites mean that plastic can form 50% of the primary structure of aeroplanes, resulting in significant greenhouse gas emissions savings.
Future technologies central to reducing our reliance on fossil fuels will also require plastics. In electric vehicles, for example, it is possible to replace even more metal components than in petrol cars, and to use light-weight plastics in energy recovery devices, cooling pipes, pumps, fans and casings. The use of plastics in electric vehicles is already growing rapidly. Wind turbine blades require plastic composites and adhesives, while batteries rely on plastics in their housing and may even apply them as electrolytes and other components.
Plastics are also widely used in home insulation, reducing energy usage, and they play critical roles in the construction sector as pipes and conduits, cladding, seals, adhesives and gaskets. In future, plastic composites could replace metals in load-bearing structures and will likely be important in intelligent buildings as components of detection and monitoring systems. Plastics are essential as the active layer in water purification systems and deliver efficiencies in agriculture, such as reducing water usage and increasing productivity. Future technology sectors such as robotics, drones, electronics, personalized healthcare and diagnostics each rely on the development of better plastic materials.
Despite these benefits, the use of plastics is also causing major environmental challenges. Plastic manufacturing consumes significant quantities of petrochemicals: in Europe, for example, it accounts for roughly 4%–6% of all oil and gas use, according to industry group Plastics Europe. Since plastics are interwoven with the petrochemical industry, they are subject to its fluctuations, geo-politics and contributions to CO2 emissions.
Discarded plastic pollutes the natural world, with microplastics and nanoplastics being detected in many ecosystems.
The majority of plastic waste is generated and emitted on land, but research on plastic pollution initially focused mainly on the marine environment, where plastic particles are reported to occur from tropical to pristine polar areas, and from beaches to deep-sea sediments. Later, river and lake systems were examined, where plastic particles were found even in remote mountain lakes. Plastic particles have more recently been found in the atmosphere and in terrestrial ecosystems, especially in urban and agricultural soils. The ingestion of plastic particles together with food has already been investigated in a variety of organisms from aquatic and terrestrial habitats, and the resulting effects on organisms and human health are still under discussion.
Possible risks associated with plastic particles cannot be generalized because microplastics and nanoplastics comprise a very heterogeneous group of particles that vary in polymer composition, additive content, size, shape, ageing state, and consequently in their physicochemical properties. However, the ubiquitous contamination of the environment with microplastics and nanoplastics, along with the possible associated risks to ecosystems and ultimately to human health, has recently attracted a great deal of public and scientific attention.
For many members of the general public, plastics now epitomize a disposable way of life and are associated with cheap, low-quality and low-value products. The visible evidence of plastic pollution and as yet unknown impacts of these materials are driving a reconsideration of their life cycles, designs and uses. Technical solutions will be needed to ensure that in future plastics combine useful properties with better end-of-life options, and chemistry will play a central role in delivering these.
Developments in chemistry will be key to understand and mitigate the impact of plastics in the environment.
Chemistry can help to develop efficient ways to recycle the plastics we use today and, in the longer term, create replacements that are made from sustainable starting materials, are more amenable to recycling at end-of-life, and have reduced environmental persistence or impact.
Sustainability across the entire plastics life cycle must be a core design feature of the polymers of the future. It is also clear that a suite of materials will be required to meet the myriad of applications, just as different plastics are applied today.
This means that underpinning investment is recommended in a range of different technologies and options. It is also essential to emphasize that no single solution is suitable for all scenarios, geographies or products. Different countries already employ a wide range of waste management practices, with varying degrees of environmental impacts. As such, the most sustainable option for a particular location is not necessarily a global solution.
In some scenarios, improved sustainability will arise from deployment of polymers built entirely from renewable, biologically-derived feedstock chemicals, or from wastes like CO2 where the raw materials used to produce the polymer are carbon neutral.
For some applications, durable or longer-lasting polymers, which can be reused multiple times prior to efficient closed-loop recycling, will be the best option. In yet other scenarios, it will be important to design polymers to incorporate special chemical and physical features to make them ‘degradable on demand’ – such features will reduce energy use and improve selectivity for closed-loop recycling. Fundamentally, there is a need to design polymers for efficient disassembly. Such an approach has the potential to enable closed-loop recycling over multiple cycles and to reduce, or even nullify, environmental persistence if they escape from waste systems.
We recognize that building this new future for plastics necessitates a major collaboration between sciences, engineering, technology, materials design, humanities, human behaviour, policy, regulation, economics and business. This report focuses only on the contributions and solutions that could be technically feasible, and on the research challenges specific to chemistry and the chemical sciences. It deliberately avoids making recommendations on policies or regulations for recycling, waste management systems, use of financial incentives and taxation (the further reading appendix p45 includes references to recent policy briefings and reports from expert working groups that address some of these important parallel issues).
In coming up with our recommendations, we emphasize that technology alone cannot provide all solutions and that parallel advances in waste management, regulation, economics and behaviour will be needed to deliver the infrastructure and ecosystems for a sustainable plastics future. We signal that experts in chemistry are well placed to provide impartial evidence for policymaking and standardization of plastics, as well as in environmental monitoring and detection.
We propose four major research challenges and their underpinning research priorities. These research challenges are interlinked and symbiotic, as such we do not recommend unbalanced selection or weighting of research in a particular direction. Our philosophy is that plastics should not be deliberately released or dumped into the environment and that efficient closed-loop waste management systems are vital to implement these technological advances and solutions. Meeting the technical challenges necessitates close integration with a range of other technical disciplines, as well as in parallel with the broader considerations outlined above.
To ensure future researchers are able to invent effectively in this space, it is important to offer multi-disciplinary training and education of chemists in areas such as polymer science, materials engineering, process design, eco-toxicology, molecular biology, environmental sciences, life cycle assessment and data science. We, as a scientific community, recognize the benefits of, and urgent need for, outreach, advocacy and public engagement activities to stimulate a public dialogue about the impacts and solutions of future plastics, and to examine material selection choices using a life cycle approach, and in the context of sustainable development goals.
Science to Enable Sustainable Plastics – Research Themes
The Impact of Plastics
Plastics are an essential part of modern life, and an indispensable tool in sustainable development. Some of today’s petrochemical-based plastics also have concerning environmental impacts, from the greenhouse gases involved in raw material extraction and manufacturing to waste plastic pollution in the environment. Chemistry can underpin efforts to understand and mitigate these impacts by developing sustainability tools and, where appropriate, circular economies for plastics.
New Sustainable Plastics
To develop sustainable plastics, researchers are creating polymers that not only have excellent properties during their useful life, but also offer options for end-of-life management. A life cycle assessment approach should underpin these developments, which should improve the efficiency of polymer production and reduce energy inputs. In some contexts, it may be beneficial to use waste plastics, biologically-derived feedstocks or even CO2 as raw materials to make new plastics. Ideally, renewable feedstocks should be suitable as ‘drop in’ substitutes in existing chemical processes.
Recyclability of Plastics
In the transition from a linear to a circular economy, much more of the plastic waste we produce must be recycled. Chemists can help to achieve this goal by finding more efficient ways to recycle the plastics we use. And developing new plastics that can be more effectively recycled in the future. This includes a greater emphasis on chemical recycling technologies. Upcycling waste polymers into valuable chemicals, fed back into polymer manufacturing processes or used in other processes.
Degradation of Plastics
Although some biodegradable and compostable plastics are available. There remains some confusion among the public and in industry regarding what these terms mean. And around the conditions and time scales necessary for these degradation processes. Research is needed to understand exactly how all plastics degrade in different circumstances, and the fate of their degradation products. This knowledge will help chemists to design polymers that are durable in life and degradable on demand. Ensuring that there are not unintended environmental consequences resulting from the degradation products of plastics.
Science to enable sustainable plastics – A white paper from the 8th Chemical Sciences and Society Summit (CS3), 2020, rsc.li/sustainable-plastics-report