7 min. read
Fantastic plastic! Cheap, light and versatile, plastics have literally invaded our lives with a total of almost 9 billion tons produced since its industrial expansion in the 1950s. The word ‘plastic’ only recently became associated with a category of materials: polymers. Polymers are long chains of atoms composed of repeated single units called monomers. It is the variation in length and in the nature of monomers that accounts for the exceptional diversity of plastics. While polymers can be found in nature most of them today are synthetic and made from crude oil. The first commercialized and mass-market synthetic polymer derived from natural polymers was developed in 1869 by John W. Hyatt as a response to a project that aimed to find a substitute to ivory. In 1907, to help with the rapid spread of electricity in the USA, the first fully petroleum-based plastic was created by Leo Baekeland as a substitute for natural insulators. Bakelite, in addition to being a good insulator, was suitable for mass production and easily shaped into anything. Important breakthroughs followed suit, like the development of polyvinyl chloride (PVC) and polystyrene (PS) and the global production increased during World War II – by 300% in the USA – to compensate for the scarcity of natural resources. The plastic revolution was born … 
Origins of plastics – a little bit of chemistry
Plastics are manufactured via the polymerisation process of natural materials: cellulose, coal, natural gas or crude oil. The last two are the most commonly used today, with the global plastic production now accounting for approximatively 4% of the annual total use of oil and gas (compared to 45% and 42% respectively for transportation and heating and energy).
Different types of additives are then used to modify the base polymers in order to confer specific properties to the final plastic, e.g. colorants, protective agents (to prevent plastic degradation by heat or light), lubricants (to reduce rigidity and simplify moulding), plasticisers (to make the final plastic more flexible), flame retardant (to enhance resistance to fire) or mineral charges (mainly to reduce the price of the final material). The final polymers are usually found in the form of resin pellets ready to be processed into plastic products. 
Plastic production process from crude oil
The process starts with distillation in order to separate the heavy crude oil into groups of lighter components: gasoline and kerosene, heating fuel and naphtha (the crucial compound to produce plastics). Naphtha then undergoes a cracking process – heating to 800°C and sudden cooling – to separate molecules based on their molecular weight. The small isolated molecules, i.e. monomers, are further refined and constitute the basis of plastic material production. They are finally chemically bonded into polymers.
“The material of a thousand uses”
Plastics can be grouped into two categories: thermosets and thermoplastics. Thermosets are plastics that retain their shapes and cannot return to their original form once cooled and hardened. They are hard and durable. Polyurethanes (PUR), polyesters and epoxy / phenolic resins are well-known thermosets. They are used for auto parts, aircrafts and tires. Thermoplastics are less rigid than thermosets, they soften when heated and may return to their original form. They are easily moulded and extruded into films, fibres and packaging. Thermoplastics include polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC).
In 2017, almost 350 million of tons of plastic have been produced worldwide – 11,4 tons per second – 20% of which are in Europe. In Europe, packaging accounts for approximatively 40% of the total plastic demand (mainly polyolefins), construction accounts for almost 20% (e.g. PVC, widely used for pipes and PUR, used for foam insulation) and automotive follows with 10% of the demand (the EU estimates that 16% of an average car is composed of plastic). Remaining applications are in the electronic & electrical sectors, household, leisure & sport sectors, agriculture and other minor sectors. 
End of life: the factsIncreasing plastic production inevitably comes with increasing plastic waste. This is exacerbated by the fact that packaging, the dominant sector using plastic, also has the lower product lifetime – less than 6 months in average, compared to 35 and 13 years for construction and transportation respectively. Thus, packaging is today responsible for almost half of global plastic waste.
In 2016, most of the plastic waste was accumulated in ‘official’ landfills (40%) or was simply littered in the environment / ended up in unmanaged dumps (20%), while 25% was incinerated (see chart below). Finally, only a mere 12% was recycled, mainly via mechanical processes. Many challenges therefore still need to be addressed in order for recycling to be a sustainable solution, e.g. polymers’ sensitivity to mechanical / thermal stresses, inhomogeneity of plastic waste (more than 50 types of plastics with different shape, size, density, etc.) and of plastic products itself often composed of more than one polymer type. 
Mechanical recycling process
This method consists in several manual and automated (infrared spectroscopy, laser or X-ray techniques) sorting processes to identify and separate the different material types which are then cleaned, grinded, re-melted and re-granulated. The resulting materials can then be used as “new” secondary raw materials. 
king process – heating to 800°C and sudden cooling – to separate molecules based on their molecular weight. The small isolated molecules, i.e. monomers, are further refined and constitute the basis of plastic material production. They are finally chemically bonded into polymers.
Plastic waste: a growing global concern
Current plastic waste management systems are facing multiple environmental, health and economic issues (see details below) which are amplified by the global trade in plastic waste. Lack of capacity, important maintenance efforts of facilities, social disapproval and high building costs of new infrastructures, expensive treatment cost of dirty, damaged and unsorted waste streams are among some of the intertwined reasons why it is cheaper for high-income countries to export plastic waste. In 2017, Europe exported almost 1.5 million of tons of plastic waste. China was historically the biggest importer but a ban, which came in force in 2018, redirected the streams to predominantly India and South East Asia (Malaysia, Thailand, Indonesia).
Importing countries have poor waste treatment infrastructures most of the time, which enhance the negative environmental, health and social impacts in those countries. 
In high-income countries, landfills are regulated (waste handling / storage is done according to quality and safety norms) whereas in low-income countries landfills are often mismanaged resulting in wide open-air dumping areas often close to habitations. Leaking chemicals, if not correctly contained, contaminate soils, groundwaters and waterways. Uncontrolled landfills near coastal areas and rivers are a major vector of plastic waste into oceans (more than 150 million of tons today).
The direct externality is the greenhouse gas emission. Another important drawback is the production of toxic carbon monoxide and dioxin emissions from incomplete combustions. Technologies exist (selective catalytic reduction, inhibitors) and regulations can be implemented to minimize toxic emissions, but this is generally not the case in low-to-middle income countries, which results in unsafe open-air burning areas.
Plastic can hardly be recycled more than one time because the process degrades its quality. This fact combined with the raising health concerns of the use of recycled materials – namely for food packaging (impossible traceability of toxic substances coming from the original utilization) – negatively impacts the recycled plastic market.
Negative environmental, health and social impacts of plastic waste end-of-life sectors
Towards a “new plastic economy”
In order to overcome the challenges and negative impacts of the current plastic economy, it is necessary to rethink the entire plastic lifecycle and to switch from a linear model to a circular economy. Rethinking the plastic system implies going beyond recycling and considering ‘reduce’ and ‘reuse’ concepts as fundamentals across the whole lifecycle.
To reach this common goal, every stakeholder has an important role to play. From a technical perspective, new promising technologies of materials and recycling processes are being developed. Bio-based and biodegradable plastics (currently, bio-based plastics are mostly mixed with fuel-based plastics and are not systematically biodegradable or under certain conditions), chemical recycling (conversion of plastic waste into monomers and other valuable chemicals that can be used to produce new virgin materials) or innovative technologies to remove plastics out of the oceans (e.g. The Ocean Cleanup project) can be mentioned. Companies have to rethink the design of their products and go beyond the performance criteria by integrating the recyclability and reparability aspects from the very start. In parallel, we need to develop new business models enabling the reuse of raw materials or packaging through deposit systems for example, repair / maintenance services, industrial symbiosis, etc. Through appropriate legislations and regulations, institutions and governments need to drive the transition toward the new plastic economy. Important steps forward have been made during the last years; several complete or partial bans on plastic bags, straws and other utensils have been implemented across the world. As an example, the EU parliament approved in 2018 a bill banning a list of 10 single-use plastic items which should be enforced as of 2021. Regarding plastic waste, governments amended the Basel Convention in 2019 (an international treaty designed to limit hazardous waste streams between nations) to include plastic waste. Consumers have also an important role to play, namely by changing their consumption habits.
As seen, actions and changes are being undertaken and will have to be intensified and pursued at a global scale in order to overcome the numerous challenges of the current plastic system with the goal of creating an economy ‘in which plastics never become waste’. 
Elisabeth Trofimoff – Consultant at Greenfish
Michèle Uhring – Consultant at Greenfish
Nassim Daoudi – Chief Executive Officer at Greenfish
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