Plastics are ubiquitous materials in our economy. The aim of this article is to understand the extent of their use, the environmental problems associated with them, their recyclability, and alternatives made from renewable resources.
Abstract:
- Humanity uses around 400 million tons of plastics annually, mainly for packaging, which quickly becomes waste.
- Plastic recycling presents technical and economic challenges. In practice, the use of recycled plastics by European industry remains low (7% incorporation in 2017).
- We identify several potential risks associated with the use of these materials: a risk of resource depletion and a climate risk, linked to the use of fossil resources (oil) for their production and the difficulties of recycling; a risk of toxicity and pollution, linked to the presence of chemicals and fragmentation into microplastics.
- In the final section, we present alternatives to petrochemical-based plastics, namely plastics made from renewable raw materials.
- Research into the impact of plastic use on health and the environment, the development of more environmentally friendly recycling and plastic production techniques, and efforts to reduce plastic use must be stepped up.
Materials are the basis of the value chain. Their availability is essential for the production of goods and services. Materials have different physical and mechanical properties, which give them different industrial applications. In this article, we focus on plastics, which are used in most of the goods sold today.
Since the mid-20th century, humanity has produced some 8.3 billion tons of plastics, according to a 2017 study by Geyer et al.: 6.3 billion tons have already become waste, and the authors estimate that about 9% of this waste has been recycled, 12% incinerated, and 79% accumulated in landfills or the environment. The authors estimate that at this rate, landfills and nature will contain approximately 12 billion tons of plastic waste by 2050. Why haven’t we recycled this plastic, and could we do without it altogether?
1) Plastics, ubiquitous materials in our economy
1.1 Characteristics of plastics
Plastics are mainly derived from crude oil and natural gas (AP, 2020). We will see in section 4 that they can also be synthesized from renewable raw materials.
Plastics are made up of polymers, a set of large carbon molecules (polymer chains), whose subunits are called monomers. Depending on the chemical nature of the monomers and their possible combinations, different types of polymers can be produced. Additives —various chemical compounds—are then added to improve the properties of the material. For example, plasticizers can be added to reduce rigidity, or dyes to change the color, etc. These manipulations can therefore produce different plastics, each with distinct properties.
Plastic = [polymer] + [additives]
The creative possibilities are almost endless, and many plastics have properties that are interesting enough for commercial applications.
By misnomer, the name of the polymer that makes up the plastic is used to refer to the plastic material in question, as can be seen in Figure 1 (from the 2020 Plastics Atlas), which shows the share of each plastic in global production in 2015. Within the same category, the additives used will therefore vary depending on the application. The main plastic produced is polypropylene (PP), which is used for food packaging, but also for banknotes and surgical masks.
Figure 1: Share of each plastic in global production (2015), according to European recycling codes.
Source: Infographic from the Atlas of Plastics (2020)
1.2 Applications and industrial use
Figure 2 shows that plastics are mainly used for packaging (36% of total use), buildings (16%), and textiles (14%). For example, PET, which is impermeable to gases and liquids, is particularly used for beverages (AP, 2020). PP is resistant to high temperatures and can therefore be used for hot liquids (AP, 2020). The construction industry makes extensive use of PVC (rigid and durable) and HDPE for pipes (AP, 2020).
Plastics, being lightweight and insulating, also have many applications in electronics. Electrical and electronic equipment is composed of approximately 26% plastics on average (in terms of weight) (Berthoud, 2016). It now seems difficult to imagine the digitization of the economy without plastics. Due to their resistance to vibration and durability, they are also used in transportation (bumpers, seats, dashboards, etc.) (AP, 2020). Their lightness also allows for energy savings compared to heavier materials. In the renewable energy sector, plastics also seem to be gaining ground in photovoltaic panels and wind turbines (Plastics Europe, 2021; Jensen, 2019).
Disposable plastic is also widely used in the medical sector, particularly to reduce the risk of infection. In the United States, hospitals generate up to 3,500 tons of plastic waste per day[2]. With the pandemic, this use has spread to the general population: the production of masks (FFP2 and surgical, made of polypropylene) has increased 30-fold in France[3].
Figure 2: Globaluse of plastics by industrial sector (2017)
Distribution of 438 million tons
Source: Figures from the Atlas of Plastics (2020), Figure by the author
2) Recycling plastics: is it possible?
Much of the plastic waste collected comes from packaging( 60% of household plastic waste collected each year in the EU; Plastics Europe, 2019). In this section, we will see that the issue of plastic recycling remains complex.
2.1 Technical challenges: producing high value-added materials without skyrocketing economic and environmental costs
We have seen that there are many different types of plastic, and they are often used in combination with each other and/or with other materials. For example, a computer can contain around 20 different types of plastic (Berthoud, 2016). The sorting and separation of materials is a complex and costly process. The intensity of the sorting process will depend on the desired final quality (Chaumonnot, 2021). We present two recycling techniques that come after collection and sorting.
Mechanical recycling is the most widely used and least expensive technique, but requires intensive sorting (Chiappinelli, O. et al., 2020). It exposes the material to high temperatures in order to remelt it, which accelerates its aging (IFP, 2020). The decontamination phase (removal of additives and impurities) is often not possible, which can prevent the plastic from returning to food-grade quality (IFP, 2020). As a result, this recycling process often produces materials of lower quality than virgin materials, and the number of times the material can be recycled is limited (Ragaert et al., 2017).
Chemical recycling [5] makes it possible to transform plastic, for example to recover monomers (depolymerization) decontaminated of additives (IFP, 2020). In some cases, it is therefore possible to produce polymers from monomers that are identical in every way to virgin polymers. However, the economic model is sometimes difficult to apply on an industrial scale, and the environmental balance sheet is sometimes disputed (Euractiv, 2020). In particular, depending on the reaction temperatures required and the number of purification steps, this technology can be very energy-intensive compared to mechanical recycling (Marty et al. 2019; Euractiv, 2020).
Not all plastics can be remelted (mechanical recycling), depolymerized, or recycled more widely. The most appropriate technique will therefore be chosen on a case-by-case basis, depending on the waste to be treated (type and quantity), taking into account the economic and environmental costs and the desired quality. One way to facilitate recycling would be to limit the diversity of plastics (particularly the additives used) in order to enable the development of more standardized techniques (Chiappinelli, O. et al., 2020; Chaumonnot, 2021).
2.2 Economic incentives: imperfect substitutability and price competition between recycled and virgin substitutes.
If recycled plastic is of lower quality, economic agents will be willing to pay less than for virgin plastic, which is of higher quality.[6] Virgin plastic is often added to recycled plastic to ensure that the final product has the desired properties. For certain applications, such as food packaging, where product standards are most stringent, producers sometimes prefer virgin resin to avoid any risk of contamination from recycled material (Euractiv, 2020).
In addition, it is difficult for recycled resin to compete with cheap virgin resins. Thus, when oil prices are low, virgin resins can be priced lower than their recycled substitutes (Fédérec, 2015; Milios, 2018; Joltreau, 2019; Aydel 2020). Recyclers are therefore faced with a cost-quality trade-off exacerbated by this competition with virgin materials. Recently, however, demand for certain plastics and grades has risen sharply and has been constrained by supply.[7]
Figure 3: Consumption of plastic materials by European industry by sector (2018)
Comparison of virgin versus recycled resin consumption
Source: Plastics Europe data (2019, 2020), Figure by the author
Note: « Other » includes the medical sector, furniture, household appliances, etc.
Figure 3 shows that the consumption of recycled plastics remains low in European industry compared to the volumes of virgin resins used. Recycled plastics account for 7% of European plastics consumption across all sectors. The main applications are in the agriculture sector (23% incorporation) and construction (15% incorporation), while most of the waste collected comes from packaging. This is referred to as open-loop recycling[8] or, if it is due to a loss of quality, downcycling.
If plastics cannot be contained within the industrial cycle, they will eventually end up in the environment, either in the form of emissions (with or without energy recovery) or as solid waste (in regulated or « unregulated » landfills).
3) The environmental and health challenges of plastics
We identify two main risks associated with plastics: (i) their chemical risks and fragmentation into microplastics; and (ii) their risk to the climate. The risks of using plastic objects to human health and the environment have not yet been clearly identified.
3.1 Toxic risk: additives and microplastics
Certain chemical additives contained in plastics can migrate and accumulate in food, indoor air, and building dust, posing a health risk (AP, 2020; Michalowicz, 2014). For example, many plasticizers are considered endocrine disruptors, meaning they mimic the body’s hormones (AP, 2020). In 2011, Cirillo et al. showed that phthalate (plasticizer) concentrations in schoolchildren’s food increased by more than 100% as a result of food packaging. More studies are needed on long-term exposure to these additives and their migration conditions in order to identify hazardous substances and uses. Product standards could then be adapted in line with eco-design for recycling, which would also be facilitated by simplified chemical compositions.
It is estimated that around one-third of the plastics produced each year end up in soil or inland waters (AP, 2020). When dumped or buried in the environment, plastics fragment[9] into tiny particles that can pass through the barriers of living organisms (Gontard, 2020) and act as magnets for toxic substances (AP, 2020). Microplastics[10] are found everywhere in our environment, even in polar regions (Obbard et al., 2014). In the oceans, bacteria that attach themselves to their surface can be biological contaminants (ANSES, 2020). Furthermore, plastic pollution in soil could be 4 to 23 times higher than ocean pollution, with an ecological impact that has yet to be assessed (AP, 2020).[11]
Having safe materials is essential. In the future, we will need to better understand the ecological and health impact of microplastics, which do not seem to be linked solely to the end of a product’s life. For example, synthetic textiles lose microfibers during machine washing, and some cosmetics contain microplastics, which are used as such. Researchers analyzed 259 plastic water bottles (unused) and found that 93% were contaminated with microplastics (Mason, 2018).
3.2. Incineration of plastics: a risk to the climate
Plastic waste is often incinerated for energy recovery because of its high calorific value and the difficulties of recycling it. In 2018, this treatment was used for 34% of plastic packaging in the EU[14]. Furthermore, once plastics have reached the limit of their recyclability, incineration (with or without energy recovery) seems to be the last option to avoid landfill.
The incineration of plastics, with or without energy recovery, poses a climate challenge given that 90% of them are derived from fossil fuels (EMF, 2017).[15] When burned, they release carbon dioxide (CO2) that was fossilized in the ground, increasing the greenhouse effect. The Ellen MacArthur Foundation estimates that by 2050, plastics could account for 15% of our carbon budget[16] by 2050 (EMF, 2017).[17]
4) What are the alternatives to plastics made from fossil resources?
Plastics accounted for 6% of global oil consumption in 2014, a percentage that could reach 20% by 2050 (EMF, 2017). Can we reduce our dependence on fossil resources and replace petrochemical-based plastics with bio-based plastics? Bio-based plastics are made from renewable raw materials, such as plants, and store carbon as they grow. In this section, we present some possible alternatives.
4.1 The use of bio-based plastics may increase pressure on land use and have a negative environmental impact
Hydrocarbons, the material from which plastics are made, are extracted from the ground. To produce plant-based resources, land must be freed up for cultivation. Increasing pressure on land use and forests is difficult to sustain in a context of global population growth, climate change, and biodiversity crisis. Agriculture already uses five billion hectares, or 38% of the world’s land area (FAO, 2020). According to the 2020 Plastic Atlas, 0.37 hectares of land are needed to produce one ton of polylactic acid (PLA), a plastic resin that can be produced from corn. Thus, to achieve an annual production of 400 Mt, the equivalent of 148 million hectares, or 1.1% of the Earth’s land area, would need to be freed up.[19]
According to S. Pasquier of ADEME, the environmental impact of bio-based plastic will depend on the method of cultivation. Monoculture, the use of pesticides, and deforestation will lead to a negative environmental impact. In particular, forests absorb much more carbon than corn crops.[21] However, manufacturing bio-based plastics from plant waste could offer a real advantage, as it will not change land use.
4.2. Recycling organic waste to produce bioplastics means that land use does not need to be changed.
A. Moores and his team at McGill University in Canada have found a new process for making biodegradable plastic from shrimp shells and other crustacean shells (i.e., bio-based) (AP, 2020). According to the researchers, this material could be used in the medical sector, but also for packaging. Every year, 6 to 8 million tons of crustacean waste are generated, which is still a long way from our 400 million tons of plastic per year.
However, according to N. Gontard et al., we could replace 50% of the petrochemical plastics consumed in Europe with bio-based plastics derived from agricultural residues, using less than 30% of agricultural residues (Gontard, 2018).
4.3. Bio-based and then what?
Bio-based does not necessarily mean recyclable and/or biodegradable. Less than 20% of bioplastics[23] were considered biodegradable in 2019 (EEA, 2018). In addition, some will be considered biodegradable in industrial composting, but not easily in the natural environment, such as PLA[24].
N. Gontard’s teams are also working on the recyclability and biodegradability of their materials under natural conditions. In addition, researchers are still exploring the possibilities of substituting controversial additives (Gontard, 2018).
For A. Chaumonnot, the priority will be to recycle plastic that has already been produced (from petrochemicals) and possibly consider adding a bio-based virgin supplement[25] to improve the properties of the recycled material, while reducing our use wherever possible and bearing in mind that there will be multiple solutions for reducing our environmental impact (Chaumonnot, 2021).
Conclusion
Plastics are now everywhere, in our objects and in our environment. It is difficult to imagine being able to « do without » them, both in the new technology sector and in the medical sector. And yet, given the difficulties involved in recycling them, plastics end up leaving the industrial cycle in the form of greenhouse gas emissions (incineration) or solid waste, which then fragments. One way to facilitate recycling would be to limit the diversity of plastics. However, this would also restrict product design possibilities.
Most plastics are produced from fossil fuels, a finite resource. So, if we cannot obtain renewable materials, either through recycling or from natural sources, we will inevitably be forced to « do without » them one day. Furthermore, with a view to saving resources and preventing certain ecological risks that are awaiting assessment (notably microplastics), reducing plastic use must be prioritized, in accordance with the waste treatment hierarchy (reduce, reuse, recycle).
New studies on the impact of plastic use on health and the environment, as well as research into recycling techniques and bio-based and biodegradable alternatives, are needed to better understand the challenges that lie ahead.
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Endnotes
[1]Made from virgin polymer resins, i.e., not derived from recycled plastic waste.
[2]Sarah Gibbens, for National Geographic, « Can medical care exist without plastic? » https://www.nationalgeographic.com/science/2019/10/can-medical-care-exist-without-plastic/
[3] Julien Cottineau for Usine Nouvelle, « From scarcity to abundance… Production of FFP2 and surgical masks increased 30-fold. » https://www.usinenouvelle.com/article/de-la-penurie-a-la-profusion-voici-ou-sont-produits-les-masques-chirurgicaux-et-ffp2-en-france.N1042104
[4]We can assume that this is due to their high plastic consumption, short lifespan, and the collection and sorting systems that have been put in place.
[5]According to ISO 15270, chemical recycling is the transformation of plastic waste into secondary raw materials or products without significantly altering the chemical structure of the material.
The technologies involved include depolymerization, conversion, and possibly dissolution. Dissolution uses solvents and depolymerization uses reagents. These techniques are detailed in the article by IFP Energies Nouvelles (2020). It should be noted that the dissolution option for recovering the polymer is often considered mechanical (rather than chemical) recycling, as it does not affect the polymer chains in the process. However, due to a misuse of language, dissolution, which involves chemistry, is sometimes considered chemical recycling.
Enzymatic recycling is also being developed in Clermont-Ferrand (Carbios company) for PET and, like the chemical alternative for certain polymers, would allow a return to monomers (Tournier et al., 2020), with the advantage of using less energy (low reaction temperature; Marty et al., 2020).
[6]Unless it benefits their image, and therefore their sales; or there is a mandatory incorporation rate for the product in question. For example, Europe has imposed a 25% incorporation rate by 2025 for transparent PET bottles. See the article in Les Echos (next note) for more information.
[7] Myriam Chauvot for Les Echos « Why recycled plastic is becoming a rare… and expensive commodity. » Article available at the following link: https://www.lesechos.fr/industrie-services/energie-environnement/pourquoi-le-plastique-recycle-devient-une-denree-rare-et-chere-1164105
[8] Waste is recycled for a use other than the product from which it originated.
[9] Plastics fragment under the action of the sun’s ultraviolet rays, the physical forces of waves, and hydrolysis. You can refer to the article by Alain-Hervé le Gall, University of Rennes, available at the following link
[10]Plastic smaller than 5 mm. « Nanoplastics » (<100 nm) are also defined.
[11] Researcher Nathalie Gontard (Gontard, 2020) also warns us about our landfills: « The plastics buried in our landfills are therefore destined, in the long term, to join their contemporaries that have escaped directly into the environment, contaminating our fresh water and oceans after passing through our soil. »
[12]The impact on human health also remains to be assessed, yet we are thought to ingest up to 5g of plastic per week. See the article by Kala Senathirajah and Thava Palanisami, 2019, « How much microplastics are we ingesting? Estimation of the mass of microplastics ingested, » available at the following link:
[13] See the Greenpeace article on the subject, https://www.greenpeace.ch/fr/story-fr/25787/les-microplastiques-particules-cosmetiques-et-fibres-textiles/
[14]Eurostat estimate: https://ec.europa.eu/eurostat/, database [env_waspac]
[15] Furthermore, the incineration of plastics generates highly toxic final waste (AP, 2020).
[16]The amount of greenhouse gas emissions that humanity can « afford » to emit in order to stay within the maximum global warming target for 2100 under the Paris Agreement.
[17] Researchers also suspect that microplastic particles in the oceans are impacting the ability of plankton to capture atmospheric CO2 (AP, 2020). Research on this topic is still pending.
[18]According to ADEME, « bio-based » means: obtained from renewable raw materials derived from biomass (e.g., plants).
Plants are considered renewable materials because they can regrow from one period to the next. This assumes that the agriculture practiced respects the maintenance of soil properties.
https://www.ademe.fr/expertises/produire-autrement/produits-biosources
[19]Author’s calculation. The comparison is made for illustrative purposes. As each plastic resin is different, PLA cannot mimic the characteristics of each of them.
[20]From the French Environment and Energy Management Agency (ADEME), speaking on France Inter:
https://www.franceinter.fr/environnement/le-nouveau-plastique-vegetal-est-il-bon-pour-la-nature
[21] Article from the University of Bonn, « More bioplastics do not necessarily contribute to climate change mitigation, » available at: https://phys.org/news/2018-12-bioplastics-necessarily-contribute-climate-mitigation.html
[22]For an article on the subject: https://www.cbc.ca/news/canada/montreal/mcgill-researchers-use-lobster-shells-to-make-biodegradeable-plastic-1.4920820
[23]Bioplastics: biodegradable and/or bio-based plastics (EEA, 2018)
[24]CNRS publication « Polylactic acid (PLA), the base material, » available at the following link: https://www.prc.cnrs.fr/spip.php?rubrique129
Excerpt: « At the other end of the life cycle, PLA biodegrades under the specific conditions of industrial composting, with controlled temperature, humidity, and the presence of microorganisms. It does not easily biodegrade in the natural environment. »
[25] As mentioned in section 2, a virgin additive is often added to the recycled material to ensure the final product has the desired properties.
