Plastics have the potential to play a crucial role in emission-saving technologies – from the advanced polymer composites making ever-bigger wind turbine blades feasible, to the lightweight parts which will allow electric vehicles to push to greater distances with each charge. However, society’s reliance on plastics also presents a monumental challenge in meeting COP26’s ambitious targets, due to the emissions associated with their production, use and disposal. To reach a truly green future, we must reshape our relationship with plastics, innovating to minimise the impact of emissions from plastics across their lifecycle.
Where to start?
At present, a huge portion of the plastics we use are born from fossil fuels. As we push to keep fossil fuels in the ground, we will need to find bioplastic alternatives which have a lower carbon footprint.
Strides are already being made in this process. For example, polyethylene – the most widely used plastic in the world – is the subject of attention from a number of companies seeking to develop green biopolyethlyene (bio-PE for short). Brazilian company Braskem already markets “I’m greenTM” bio-PE produced through dehydration of sugarcane-derived ethanol. Dow has also been active in the area, teaming up with Finnish company UPM Biofuels to produce bio-PE from naphtha derived from a residue of paper pulp production.
It is a similar story with polyethylene terephthalate (PET)- the workhorse polyester which finds applications in everything from bottles, to carpets, to clothes. PET is made from two components – terephthalic acid and monoethylene glycol. In conventional PET, both components are sourced from petroleum. Some modest inroads in improving the green credentials of the material have been made using biomassderived monoethlyene glycol - for example, in Coca Cola’s PlantBottleTM in 2009. However, producing a 100% biomass-derived PET is problematic due to the difficulties of arriving at a commercially viable “green” terephthalic acid. Thus, interest is growing in replacing PET with alternative polymers. A prime candidate in this regard is sugar-derived polyethylene furanoate or “PEF”, in which terephthalic acid is replaced with furandicarboxylic acid, where multiple innovations over the past decade have brought this material closer to commercial reality.
Reduce, reuse and recycle
Once we have our starting materials, it is important that we get maximum value from those materials, through feeding them into a circular plastics economy. To do this, we must incentivise design and behaviours which avoid single use where possible, foster reuse, and ensure that materials can be and are efficiently and repeatedly recycled.
Some pressure in this direction is already being applied through legislation.
For example, the EU Single Use Plastics (SUP) Directive 2019/904, which came into force in July this year, seeks to ban or phase out the sale of a specific range of fossil-fuel derived single use plastic items across the EU. Certain EU countries have extended the list of prohibited items even further, for example, with France banning plastic toys with children’s meals and plastic party confetti. However, to make this fit with broader targets to cut emissions, it is vital to ensure that the alternatives which fill the gap left by single-use plastic items actually reduce emissions. To this end, the EU have set up the European Platform on Life Cycle Assessment to develop methods for carrying out life cycle analysis, weighing up the impact from single use items against reusable alternatives (for example, the impact of having to wash non-sanitary multi-use items).
In the UK, a Plastic Packaging Tax is due to come into force in April 2022, which will impose a tax on plastic packaging having a recycled content below 30%. At an EU level, industry is calling for similar measures to be introduced, through revision of the longstanding Packaging and Packaging Waste Directive.
Alongside legislative efforts, we must refine and deploy recycling technology to allow plastics to “loop” through the circular economy as many times as possible. In particular, we must try to minimise downcycling of plastics - that is, degradation in the quality of a polymer during recycling, which causes recycled materials to shift to use in ever less demanding applications. In other words, we want bottles to be reborn as bottles – a continuous circle instead of a downward spiral.
“To reach a truly green future, we must reshape our relationship with plastics, taking into account the emissions impact of plastics across their lifecycle.”
To tackle downcycling, there is a push towards developing technologies which break polymers into their constituent components, so that they can be rebuilt from scratch. One approach is so-called “chemical recycling”, in which chemicals are used to break polymers into their constituent monomers, such as the technology developed by Loop Industries to break apart PET. Another approach showing promise is enzymatic degradation, in which enzymes chew threw the bonds holding the polymer together, as exemplified by Carbios’ work on PET degradation.
To complement the development of recycling technology, we must also amplify the importance of recycling (and waste-management more generally) at the product design stage. Advances are already being made in this regard. For example, as of 2024 it will be mandatory in the EU for beverage containers with capacity of up to 3 litres to have a tethered cap or lid, to avoid the closure falling through the gaps of the recycling system. There is also a drive to avoid the use of pigments that can complicate recycling, and a push to redesign composite packaging (made of multiple materials) to simplify waste processing, such as the all polyethylene food pouches developed by Nova Chemicals to replace pouches which previously included a mixture of metal and plastic.
Recycling is not the only part of the picture, however: we must also reassess our reliance on incineration as a plastic waste management solution. In this regard, whilst there have been positive increases in recycling uptake in recent years, there has been a similar uptick in the growth of energy-from-waste incinerators. For example, in the UK local authorities burnt 3610 million tons of waste in 2009-2010, but this grew to nearly 11500 million tons in 2019-2020, with many new incinerators being built in spite of COP26’s goals. The waste burnt in incinerators still includes a large fraction of plastic, and we will need to work hard to ensure that this plastic is instead directed to recycling streams.
Powering plastics
Leaving aside the specific ingredients in our plastics, a vital consideration is how we fuel the plastics economy. The methods used to produce and process plastics are energy intensive, and to decrease the overall impact on the environment it is important that we maximise use of renewable energy sources at every step. Indeed, in a 2019 study by Zheng and Suh , the authors suggested that using renewable energy in the plastics economy could be the greatest overall contributor to reducing emissions from the plastic lifecycle.
Conclusions
From all of the above, it is clear that the impact of plastics on the climate is extremely complex, and there is no quick fix. What is clear, however, is that to have a meaningful impact on reducing emissions we must push on all fronts – sourcing starting materials from sustainable sources, processing those materials using renewable energy, and seeking to maximise the value of those starting materials through incentivising reuse and recycling. This is not only a huge challenge, but also a huge opportunity for innovators to develop new technologies to play their part in stemming climate change.
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