English edit by Marina Botana and Carla Elliff
Illustration by Joana Dias Ho
Plastic is an organic synthetic material made of either a single type or a mixture of polymers (macromolecules made of repeated units of single smaller molecules). The type of plastic, its characteristics and chemical properties are defined by the polymers used in each case. In addition to the polymer structure, lots of different additives can be included to the final composition, such as plasticizers, chemical stabilizers, and dyes. The main raw material used for building plastic is petroleum. However, polymers can also be made from plant-based sources, such as plant oils and fats, corn starch, hay, etc. These kinds of polymers are called bioplastics. Another way to produce plastic is by combining polymers from these two sources [1].
Great durability is one of the characteristic that makes plastic such an attractive material. However, it also turns the use of plastic into an environmental problem. Plastic debris are found in ecosystems all around the world, including at the bottom of the oceans, over 6,000 m below the surface [2]. When plastic debris reach the ocean environment, they can cause the death of many species by smothering them, making it difficult to swim and causing a false feeling of fullness once they are ingested [3]. A specific group called microplastics (debris smaller than 5 mm) are not only a physical threat to the marine biota [4], they might also work as vectors for spreading out other contaminants that can adhere to their surface (e.g. pesticides and trace metals) and even lead to higher organic matter sedimentation, which impacts the oceanic biological pump (responsible for uptaking CO2 from the atmosphere to marine sediments) [5]. Moreover, the degradation of plastic debris is slow and releases methane, a greenhouse gas capable of warming the Earth’s atmosphere even more than CO2 [6].
Aiming to reduce the length of time that plastic remains in the environment and mitigate the associated environmental problems, new technologies and raw materials started to be explored for polymer production. You might have heard about them – the oxo-degradable, biodegradable, bioplastics and compostable plastics. However, while sometimes they are used as synonyms, they can be quite different from each other!
The word biodegradable, for instance, might be misleading. All organic material, including plastic will eventually biodegrade, but the required amount of time for that can vary from a few days to thousands of years. This can lead to the idea that the term biodegradable could be used for any type of plastic, regardless of the amount of time it lasts in the environment. To avoid that, there are some international protocols that define the specific uses of this term, such as the definition given by the American Society for Testing and Materials (ASTM):
A biodegradable plastic must have all its organic carbon converted into biomass, water, carbon dioxide and/or methane through the natural action of microorganisms naturally present in the environment (i.e. fungi and bacteria) over a period of time that is consistent with the given environmental conditions (ASTM D883-18 [7]).
Another definition, given by the Federal Trade Commission [8], considers a product as biodegradable if it can be completely fragmented and return to nature by decomposing itself entirely into elements naturally found in nature, over a reasonably short period of time (1 year) after disposal.
In the pursuit of increasing the degradability of plastics, oxo-degradable options started to become very popular in the 2000s as an alternative for faster plastic degradation in the environment. This was achieved by adding chemical additives to conventional plastic to increase oxidation processes. Thus, when exposed to UV light, oxygen, and heat, the material fragments into smaller pieces (microplastics) more quickly and the problem “vanishes” from sight. However, today it is known that microplastics are a huge environmental concern, as discussed here before. Therefore, the use of oxo-degradable plastic is no longer accepted as a sustainable alternative [9]. There are also concerns about other environment consequences from the use of these additives in the polymer to accelerate fragmentation.
In Brazil there is a policy (ABNT PE-309.01) created in 2004 regarding the use of oxo-degradable plastic. However, nowadays we have a lot more information about this issue and some updates are necessary. And even with this policy, some companies operate according to the methods described in another norm, ASTM D6954-4 [10], to test if their plastic products are indeed oxo-degradable. However, this norm, which is also from 2004, has since been replaced by a newer one - ASTM D6954-18 – which considers more recent scientific discoveries. Finally, even the Ministry of the Environment in Brazil does not recommend the use of oxo-degradable plastic because of risks to the environment [11].
If you look carefully at the packages of some brands of straws and plastic bags, you might find some of the characteristics below:
Contains oxo-degradable additives according to the AST-D6954-4 norm, which is the one we mentioned above from 2004 that has been suspended;
36 months (=2.5 years) to be totally biodegraded, though even the AST-D6954-4 norm required the product to be biodegraded in 2 years maximum.
Plastic straws are a common item found during beach cleanups (Source: Bate-Papo com Netuno/Chat with Neptune, CC BY-SA 4.0 licence).
The production of bioplastics has increased recently. The plastic industry is exploring more and more the use of plant-based sources as a solution to the environmental problem created by the use of plastic. So, what is a bioplastic? As explained before, it is a plastic made of polymers synthesized from a biological matrix, such as sugar cane, cassava, etc.
It is extremely important to highlight that bioplastic is not necessarily a synonym for biodegradable plastic.
However, bioplastics present two advantages: a) they are not generated from a matrix connected to several socio-political-economic and environmental problemas (petroleum, remember?) and b) their production may release less carbon than what was assimilated by the plants used to create the polymer, an important step towards decreasing greenhouse gas emissions.
However, two important questions remain:
1) Can bioplastic be considered biodegradable? and
2) What are the other possible associated impacts related to the use of plant-based sources, such as deforestation, food security and the use of land?
To cover these points, let’s talk about the case of the I’m Green bioplastic produced by Braskem from sugar cane. Recently, the Carbon Trust (a company that helps governments, organizations and other companies to reduce carbon emissions) recognized that the production of I’m Green plastic consumes more carbon than it releases [12], which is a good thing! However, it is polyethylene just like any other plastic of this category, with the same characteristics of regular plastic made from petroleum. This means that if it is not discarded properly for recycling, it can end up in the environment where it will last for hundreds of years. Although there are some bioplastics which are indeed biodegradable, we cannot use these words as synonyms because this leads to wrong assumptions about the environmental benefits of each one. An example of biodegradable bioplastic is the polylactic acid made from corn starch, sugar cane or cassava [13].
Regarding the second important question, Braskem has pledged to only use sugar cane grown in areas that expanded over exhausted pasture lands. However, this can still contribute to deforestation because farmers will then have to look for other areas for pasture. Deforestation not only contributes to global warming, but it can also change the rain seasonality of a specific region. This is a particularly important aspect to consider, especially in view of the creation of environmental laws (PLS 626/2011) aiming to regulate the production of sugar cane in the Amazon [14].
Finally, there are also the compostable plastics. According to ASTM 6400 [15], these are materials that when sent to a composting plant should degrade through biological processes and during composting should produce CO2, water, inorganic compounds and biomass at a consistent rate with other known compostable materials, without leaving any visible, distinguishable or toxic residues, over the course of up to 180 days. According to this definition, not all biodegradable plastics are compostable. To avoid confusions, in California, for instance, the use of the term biodegradable in plastic bags, cups and food containers was prohibited and only products that are indeed compostable can be indicated as such [16].
When evaluating the best option, you should not only consider the composition of polymers, but also which chemical additives are present in the final product and the environmental conditions required for the decomposition of the material [17].
For instance, some plastics will only decompose in specific conditions of temperature and oxygen, which might only be found inside composting plants. Therefore, if this material does not reach its proper destination and ends up in a landfill, it might take much longer to decompose. The way plastic is discarded is another problem associated with the amount of time that plastic debris last in the environment. For example, compostable plastics should be separated from conventional recycling materials and from the waste that goes into a landfill.
After all these considerations you might be a little confused with so many options and lack of standardization. How can we then figure out what is the best option in environmental terms?
First, we must pay a lot of attention to the greenwashing practices used by some companies. Greenwashing consists on announcing a product as having more advantages towards the environment than they actually have. It is common to find packages using the color green or with drawings of leaves followed by the words “green”, “eco” and “bio”, with no proper explanation as to what they refer, but sending the message that this product is less harmful to the environment.
Similar to the belief of two decades ago that oxo-biodegradable plastics were the best alternative, today there is a trend towards bioplastics because of their potential for lowering impacts during production. However, if you want to guarantee a lower impact to the planet, the best option is to avoid the consumption of plastic whenever possible!
But how? With small changes to your daily habits:
1. Choosing reusable options (cups, mugs, straws and cutlery, for example) and, of course, remembering to always carry these items with you;
2. Using reusable bags when you go shopping;
3. Bulk buying, to decrease packages;
4. Choosing fruits and vegetables that are not wrapped in clingfilm and other plastics;
5. Replacing plastic trash bags for paper bags (you can even reuse newspaper or paper grocery bags for that);
6. Replacing your single-use tampons by menstrual cups or any other option available in the market that you might like;
7. Rethinking your overall habits: before buying something, stop and ask yourself “do I really need this?”;
8. Sharing these ideas.
And, if you cannot avoid plastic, your best option is to separate it and send it off to recycling accordingly after its use.
Do you have any other ideas to add to our list? Let us know!
Suggested literature:
1. Álvarez-Chávez, C. R.; Edwards, S.; Moure-Eraso, R.; Geiser, K. (2012) .Sustainability of bio-based plastics: general comparative analysis and recommendations for improvement. Journal of Cleaner Production 23:47-56.
2. Chiba, S.; Saito, H.; Fletcher, R.; Yogi, T.; Kayo, M., Miyagi, S.; Ogido, M.; Fujikura, K. (2018). Human footprint in the abyss: 30 year records of deep-sea plastic debris. Marine Policy, 96:204-212.
3. Law. K.L. (2017). Plastics in Marine Environment. Annual Review of Marine Science, 9:205-229.
4. Cole, M.; Lindeque, P.; Halsband, C.; Galloway, T.S.(2011). Microplastics as contaminants in the marine environment: a review. Marine Pollution Bulletin, 62:2588-2597.
5. Cole, M.; Lindeque, P. K.; Fileman, E.; Clark, J.; Lewist, C.; Halsband, C.; Galloway, T. S. (2016). Microplastics Alter the Properties and Sinking Rates of Zooplankton Faecal Pellets. Environmental Science and Technology, 50:3239–3246.
6. Royer, S-J.; Ferrón, S.; Wilson, S. T.; Karl, D. M. (2018). Production of methane and ethylene from plastic in the environment. PLoS ONE 13(8):e0200574. https://doi.org/10.1371/journal.pone.0200574
7. ASTM Standard D883, 2018. Standard Terminology Relating to Plastics, ASTM International, West Conshohocken, PA, DOI: 10.1520/D0883-18, www.astm.org
8. Federal Trade Commission, “Proposed Revisions to Green Guides: Summary of Proposal,” Washington, DC: October 10, 2010, (http://www.ftc.gov/os/2010/10/101006greenguidesproposal.pdf) - acessado em 02/11/2018.
9. Report to the European Parliament and the Council on the impact of the use of oxo-degradable plastic, including oxo-degradable plastic carrier bags on the environment. European Commission. January, 2018. (http://ec.europa.eu/environment/circular-economy/pdf/oxo-plastics.pdf) - acessado em 02/11/2018.
10. ASTM Standard D6954-4, 2004, Standard Guide for Exposing and Testing Plastics that Degrade in the Environment by a Combination of Oxidation and Biodegradation, ASTM International, West Conshohocken, PA, DOI: 10.1520/D6954-04, www.astm.org
11. http://www.mma.gov.br/component/k2/item/7660-saiba-mais - acessado em 10 de março de 2019.
12. https://www.biobasedworldnews.com/carbon-trust-endorses-braskems-carbon-negative-claims-for-its-bio-based-plastic - acessado em 02/11/2018
13. Hammad, K.; Kaseemb, M.; Ayyoob, M.; Joo, J.; Deri, F. (2018). Polylactic acid blends: The future of green, light and tough. Progress in Polymer Science, 85:83-127
14. Ferrante, L.; Fearnside, P. M. (2018). Amazon sugarcane: a threat to the forest. Science. DOI: 10.1126/science.aat4208
15. ASTM Standard D6400, 2004, Standard Specification for Compostable Plastics, ASTM International, West Conshohocken, PA, 2004, DOI: 10.1520/D6400-04, www.astm.org
16. Compostable Plastics 101: An overview of compostable plastic sponsored by the California organics recycling council. https://compostingcouncil.org/wp-content/plugins/wp-pdfupload/pdf/8095/Compostable%20Plastics%20101%20Paper.pdf – accessed on 11/02/2018.
17. Kubowicz, S.; Booth, A. M. (2017). Biodegradability of Plastic: Challenges and Misconceptions. Environmental Science and Technology, 51:12058-12060.