EDITORIAL OPEN The future of plastic

Plastic, a highly useful and convenient material, is also one of the world’s greatest environmental problems, yet both industry and society are still heavily reliant on its usage. On World Environment Day, Nature Communications asks: will biodegradable polymers alleviate plastic’s environmental impact?

rom initial conception, plastic was problem, a new plastic future is also hailed a wondrous material. Fol- required. lowing 80 years of innovation Reduce, reuse and recycle have been Finvolving disciplines spread across embraced as the common approach to industry and academia, mass pro- combat the escalating plastic waste pro- duction of plastic became successful and blem. The dream is to create a circular revolutionised consumerism in a post-World plastic economy where products are 100% War II generation1. Plastic, although a simple recyclable, used for as long as possible, and 3,6

1234567890():,; synthetic polymer consisting of small mole- their waste is minimised . Until recently cules (monomers) linked together in a repe- this strategy has lacked success, but with an titive formation, is extremely versatile; with increasing number of new initiatives, sup- properties ranging from, resistance to corro- port from governments and leading man- sion, light weight, high strength, transpar- ufacturers committing to achievable ency, low toxicity to durability. Used by targets, change is being accomplished6. For almost every industry in the world, from food now, progress remains slow despite packaging to space exploration, plastic is the advances in molecular level recycling, ultimate commodity of convenience. House- which enables different plastics to be hold names in the plastic industry include recycled together7,8. Recycling is costly, polyethylene terephthalate (PET), poly- reliant on human behavioural changes and ethylene (PE), polypropylene (PP), poly- produces lower quality materials, in terms styrene (PS) and polyvinyl chloride (PVC).1 of both thermal and mechanical proper- Although the ease of ties7. Additionally, recycling does not curb plastic production gen- our plastic addiction; if we want to main- “Durability, one of plastic’s erates cheap goods, the tain our current lifestyles modification to greatest assets is now its curse linear plastic economy plastic manufacture needs to go hand in adopted sees 90% of hand with effective recycling. —its robustness means that products used once and Recent success in reducing carrier bag (PE) then discarded, thus and drinks bottles (PET) waste in Europe plastics stay in our creating a global envir- suggests lifestyle adjustments are possible, but onmental crisis. Since plastic is ingrained in modern society and a environment for hundreds of the plastic revolution, future free from plastic seems unlikely. years.” 6.3 billion tonnes of Complete alteration of human behaviour is plastic waste has been difficult to attain, as indicated by the fact that produced worldwide2. We store roughly only 9% of plastic waste is recycled3.There- 79% of plastic waste in landfills, which fore in addition to these three solutions to the results in up to 2.41 million tonnes of plastic waste problem (reducing, reusing and plastic waste entering oceans via rivers recycling), we need a fundamental change in every year3,4. Durability, one of plastic’s order to make a noticeable impact on the greatest assets is now its curse–its robust- plastic waste seeping into our environment. A ness means that plastics stay in our envir- new plastic future in which biodegradable onment for hundreds of years. Even when polymers replace conventional plastics could degraded, plastic never truly leaves the be the answer. environment but is present as smaller Biodegradable polymers can break down pieces invisible to the naked eye (micro- into smaller molecules, such as CO2,CH4 plastics) that are choking marine life and and H2O, by microorganisms under aerobic propagating up the food chain5. Alongside or anaerobic conditions. Although not always a solution to the existing plastic waste required, abiotic chemical reactions like

NATURE COMMUNICATIONS | (2018) 9:2157 | DOI: 10.1038/s41467-018-04565-2 | www.nature.com/naturecommunications 1 EDITORIAL NATURE COMMUNICATIONS | DOI: 10.1038/s41467-018-04565-2

AbdulRaheemMohamed/EyeEm/Getty photodegradation, oxidation and hydrolysis degradation time compared to current the environment, but further developments can also aid the degradation process9.There plastics (~12 months), which is believed to are still required before PLA or other biode- are many examples of biodegradable poly- prevent its accumulation in our environ- gradable polymers can replace existing plas- mers, some are produced from plants, ani- ment if implemented on an industrial tics10,15. Cost is not the only roadblock for mals or micro-organisms, others are purely scale12. However, specific micro-organisms such materials. Governments, society and synthetic (man-made). The most commonly present in composting plants at slightly industry have learnt from past mistakes and known synthetic biodegradable polymers are elevated temperatures are required for this realise that production of new materials must polylactide (PLA), polyglycolide (PGA), process; if not available the degradation consider their source and end of life together polycaprolactone (PCL), polyhydroxyalk- time can be longer. The small molecules with the essential criteria of production scal- anoates (PHA), poly(butylene succinate) formed during biodegradation do not ability and material properties. In order to (PBS) and poly(butylene adipate-co-ter- impact the environment in the same way as successfully substitute current plastics with ephthalate) (PBAT)9. microplastics, but there are concerns that biodegradable polymers, we not only need PLA is considered the most promising they will add to our greenhouse gas (GHG) industry and academia to work together but candidate to replace current plastics. Unlike emissions. That said, life cycle analysis has also different disciplines (chemistry, engi- other synthetic biodegradable polymers and found that less net GHG generation occurs neering, materials science, biogeochemistry even conventional plastics, which are pro- during PLA production compared to cur- and climate science) to collaborate. Similar to duced from petrochemicals, PLA is formed rent petroleum-based plastics13. the current plastics we use, this process will from sustainable resources (lactic acid in Although biodegradable polymers and in take time and key multi-disciplinary devel- corn)9,10. However, if such biodegradable particular PLA have been the focus of much opments will be required. We hope polymers were produced on an industrial research and patents over the last decade, Nature Communications provides the inter- scale, competition for land with food crops their production has still not reached the level disciplinary, open-access platform to dis- maybecomeanissue.Goodmechanical of PE, PET and PP due to cost10,11,14.Lactic seminate this research to all relevant stake- strength and low toxicity have already led acid is not as readily available compared to holders. We have begun the journey towards to PLA’s successful implementation in the starting materials used for current plastics a new plastic future involving biodegradable packaging and biomedical applications9. (e.g. ethylene for PE). Additionally, lactic acid polymers; we need to persevere together to Unfortunately, PLA has one important is converted to lactide before PLA can form reach the finish line in order to protect our downside–its poor thermal properties limit its andthisextra-stepaddstothefinal environment. applicability at high temperatures (above expenditure11,14. 60 °C)11. Biodegradable polymers along Despite PLA’s shortcomings, interest in with reducing, reusing and recycling this material has not waned due to its faster could impact the accumulation of plastics in

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