As the extent of plastic pollution continues to surpass expectations, a variety of possible solutions have been emerging. One area that has received a lot of focus is creating new forms of plastic that are more recyclable or not fossil-fuel based. Bioplastics have become a popular topic and choice for packaging. They are commonly considered a sustainable solution due to the reduced use of fossil fuel resources, producing a smaller carbon footprint, decomposing faster, involving less toxic materials, such as Bisphenol A (BPA). On the other hand, the production of bioplastics does not address all the virgin plastic being created and the already existing amounts of plastic waste. When comparing life cycle assessments, post-consumer recycled plastic has a lesser environmental impact than most bioplastics when considering the amount of land, water, energy, and chemicals that are required to produce bioplastics. Additionally, existing infrastructure is mostly geared towards plastic recycling and though it is in need of numerous improvements, turning to bioplastics would require completely new infrastructure and would perhaps be a better approach in the future once virgin plastic production is reduced, the existing plastic is utilized, and the technology and infrastructure have been developed to truly make it a more sustainable alternative.
It is important to distinguish between “degradable” bioplastics, which means they don’t return to nature; they just break down in the same way that virgin plastic would over time. However, they may do so at a faster rate and release less toxic byproducts, but they still require proper disposal or they still contaminate the natural environment. Bioplastics can also be considered “biodegradable”, which means they will eventually be broken down completely into water, carbon dioxide, and compost by microorganisms through a process of decomposition that can take anywhere from weeks to months. A bioplastic that is “compostable” on the other hand, will biodegrade at a compost site into carbon dioxide, water, inorganic compounds, and biomass, leaving no toxic residue.
There are mainly two types of bioplastics; the first one is PLA (polylactic acid), which is typically made from sugars found in cornstarch, cassava, or sugar cane. PLA is biodegradable, carbon-neutral, and edible. This type of bioplastic can look and behave like PE (polyethylene), PS (polystyrene), and PP (polypropylene). The other common bioplastic is PHA, which is made by microorganisms that are sometimes genetically engineered to produce plastic from organic materials. PHA is also biodegradable and it won’t harm living tissue thus is often used for medical purposes such as for sutures, slings, bone plates, and skin substitutes. It is also commonly used for single-use food packaging.
In order to discern what kind of material is most sustainable for the environment and a better solution towards the plastic pollution crisis, one must consider all the factors that go into the production, manufacturing, and disposal of these materials. Life cycle assessments are commonly used to gauge the complete environmental impact of a material throughout its lifecycle. A study in 2011 from the University of Pittsburgh found that the life cycles of bioplastics are in reality not as sustainable as they are often made out to be. The results of the assessment showed that bioplastic production in fact resulted in greater amounts of pollutants due to fertilizers and pesticides that had to be used to grow the crops to produce these plastics in addition to the chemical processes that are required to convert the organic materials into the plastic material. Additionally, an important factor to consider is the large amount of land needed to grow these crops, which end up being used for plastic instead of food. This contributes to deforestation and may lead to increased fertilizer runoff, affecting water supplies and eventually also affecting the ecosystems in the ocean and other bodies of water it reaches. To meet the demand there is for plastic, the land required for bioplastic production would compete with that for food production. Around 3.4 million acres would be needed to meet the current demand, this amounts to an area that is larger than Belgium, the Netherlands, and Denmark combined. This total switch of plastic production that amounts to approximately 250 million tonnes to bio-based plastics would require as much as 5% of all arable land, which could potentially undermine the carbon benefits of bio-based plastics. In 2014, almost a quarter of grain production in the United States was for biofuels and bioplastics production. Taking agricultural land out of production for food and utilizing it for bioplastic production could cause a significant rise in food prices, which would hit the poorest communities the hardest. Another aspect to consider is the potential greenhouse gas emissions that would result from the petroleum that is needed to run the farm machinery and harvest this corn, cassava, or sugarcane if renewable energy is not used. However, bioplastics do produce significantly fewer greenhouse gas emissions over their lifetime and produce no net increase in carbon dioxide when they break down because the plants absorbed the same amount of carbon dioxide while they were growing. A study from 2017 found that switching from traditional plastic to corn-based PLA (without taking into account time and resources to implement the necessary infrastructure) could reduce the US greenhouse gas emissions by 25% or even 50 to 75% if they were produced using renewable energy sources.
As for all materials, the disposal process for bioplastics must also be examined. Simply because a material is sourced biologically does not necessarily mean it will break down and disappear in the natural environment. In fact, only around 50% of bioplastics are actually biodegradable. PLA is commonly labeled as biodegradable but as a number of other bioplastics, it will only break down in an industrial composting facility. Most bioplastics need high-temperature industrial composting facilities in order to totally break down and currently, few countries and cities have this infrastructure in place. This misconception leads to a sort of greenwashing in terms of using bioplastic packaging with the idea that if it ends up in a landfill it will biodegrade completely and there will be no harm. However, in reality, if it does end up in a landfill, it is deprived of oxygen and in turn, releases methane which is 23 times more potent than carbon dioxide as a greenhouse gas. Eventually biodegradable plastic does break down through photooxidation, but in reality, it just breaks down into smaller pieces which can then leach into water sources in the way that microplastics do.
Some forms of bioplastics are compostable, but unless they are certified for home compost, compostable synthetic materials such as PLA “7”, require the microorganisms in a professionally-managed compost facility to consume them within a relatively short period of time. These facilities are also lacking in most places, for example in the United States less than 1% of the country has a curbside collection of mixed compost. Therefore if consumers are using compostable packing, they are most likely responsible for getting this to the correct facility. Additionally, most compost facilities are geared toward organic farmers and organic materials. For this reason, these facilities cannot accept compostable bioplastics because they’re considered synthetic materials, and they are not currently set up to process large amounts of compostable bioplastics. These bioplastics are not yet designed to improve the nutrient content of compost and render it beneficial to soil and are therefore not a very useful addition to composting facilities and their products. Another challenge for biodegradable and compostable bioplastics is that they can harm the recycling stream. If they are disposed of in a recycling container, they will either be sorted out and sent to a landfill or they will contaminate a whole batch of recyclable plastic causing the whole batch to end up being sent to a landfill. Although any material ending up in a landfill is a waste of all the natural resources and energy that went into its development, non-biodegradable materials in a well-managed landfill are fairly benign besides the negative consequences of landfills themselves. On the other hand, biodegradable materials in a landfill will release methane which contributes to greenhouse gas emissions more greatly. For this reason, the recycling of post-consumer plastic waste helps capture the full value of these materials and keep them out of landfills for longer.
Thus, bio-based plastics do have benefits but only keeping sustainability in mind in all the other factors that are involved such as where the base material is grown, how much land is required, how much water is used, and how much fertilizer can potentially end up in the environment, and whether or not renewable energy is used. The production of bioplastics is also a relatively expensive process due to its complexity causing bio-based plastics to be 20 to 50 times more costly than using virgin materials and does not curb the production of virgin plastic and its consequences. Therefore, without the adequate disposal and decomposition infrastructure and the consumer know-how, bioplastic products can end up an example of greenwashing and do more harm than good and impede necessary developments in solutions that could provide a more immediate and effective solution like the recycling of post-consumer plastic. Though these all serve as possible solutions, to truly address an emissions issue, aggressive implementation of renewable energy in these processes and extensive recycling is required.
Sources:
Alaerts, L.; Augustinus, M.; Van Acker, K. Impact of Bio-Based Plastics on Current Recycling of Plastics. Sustainability 2018, 10, 1487 https://www.mdpi.com/2071-1050/10/5/1487/htm
Jiří Jaromír Klemeš, Yee Van Fan & Peng Jiang (2020) Plastics: friends or foes? The circularity and plastic waste footprint, Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, DOI: 10.1080/15567036.2020.1801906 https://www.tandfonline.com/action/showCitFormats?doi=10.1080%2F15567036.2020.1801906&area=0000000000000001
Zheng, J., Suh, S. Strategies to reduce the global carbon footprint of plastics. Nat. Clim. Chang. 9,374–378 (2019). https://doi.org/10.1038/s41558-019-0459-z: https://rdcu.be/ccbOp
http://www.news.pitt.edu/sites/default/files/documents/TaboneLandis_etal.pdf
https://www.bbc.com/future/article/20191030-why-biodegradables-wont-solve-the-plastic-crisis
