Sustainability in Packaging
Packaging is something that we all see around us. Drinks, food, makeup, clothes, everything that we interact with in our daily lives, are engulfed in layers of packaging. And more often than not, this packaging is made of plastic.
Most things in today's world are packaged using single-use plastics like Polyethylene Terephthalate (PET). This plastic is fossil fuel-based and once used, cannot be reused (without going through a recycling process). More often than not, PET ends up in a water body or landfill, where it takes thousands of years to degrade.
In today’s world, there are two kinds of plastics - fossil fuel-based, and bio
-based plastics. The raw materials used to create fossil-based plastics (like conventional PET) are sourced from crude oil, through a process known as steam cracking (where long polymer chains are ‘cracked’ into shorter ones). Fossil fuels are considered to be a non-renewable resource, therefore making fossil-based plastics unsustainable. Bio-based plastics (like PLA), on the other hand, use materials sourced from plants like sugarcane, or tapioca. These crops are renewable resources as they can be grown in a relatively short period of time (in comparison to fossil fuels). This means that bio-plastics are more sustainable than fossil fuel-based ones.
Often, the term ‘bio-plastic’ is misinterpreted and taken to mean that the plastic is biodegradable. This is not always the case, and not all bio-based plastics are naturally degradable (PLA). The most sustainable plastic would be one that is both biobased and biodegradable. Using such plastics in packaging, instead of PET, would make the process more sustainable.
POSSIBLE ALTERNATIVES TO PET IN PACKAGING
Bio PE is a bio-based form of polyethylene, which is traditionally sourced from naphtha, one of the components of crude oil. Bio PE uses materials sourced from sugarcane and is 100% recyclable. Since it is recyclable and bio-based, the material has a reduced carbon footprint in comparison to fossil-based PE, while having identical properties. According to its Life Cycle Analysis (a process by which the environmental impact of a product over its lifecycle can be measured), bio PE captures 3.09 kg of CO2 per kg produced, thereby acting as a carbon sink and helping in removing excess carbon dioxide from the atmosphere. However, bio PE, like most plastics, is not infinitely recyclable. After a few recycling cycles, the material starts to lose its properties, and can no longer be used. At this stage, bio PE ends up in a landfill, where it does not decompose, thereby making it unsustainable in the long term. Furthermore, compared to fossil-based PET, the material is 50% more expensive to produce, making it unappealing to manufacturers.
BIO POLYETHYLENE TEREPHTHALATE
Bio-based PET is simply PET made from renewable sources rather than fossil fuels, and it is already in the process of being implemented in industry. Coca Cola is working on a PlantBottle, where the monoethylene glycol (MEG) used to produce PET comes from renewable sources. Danone, Nestle, PepsiCo, are also working towards creating a bottle made fully from renewable sources. Like fuel-based PET, these bottles too will be 100% recyclable, and while this sounds good on paper, these bio-based bottles will still not be biodegradable. Therefore, they will eventually end up in landfills, where they will not degrade for thousands of years, making them unsustainable.
RECYCLED POLYETHYLENE TEREPHTHALATE
Since PET bottles are recyclable, used bottles can be sent to recycling plants where they are sorted based on their color and material, then washed, dried, shredded, and turned into pellets which can be converted back into products. However, recycling PET causes it to degrade, due to the multiple heat cycles it goes through. This causes the intrinsic viscosity (which is a measure that provides manufacturers with an idea about the physical properties of the material, like strength) of the material to change, making it unsuitable for use in manufacturing. To be able to use the rPET, many companies use a blend of rPET and virgin material (ex: 35% recycled, 65% virgin). The biggest problem with rPET is that there is not enough supply since most people don’t recycle their PET bottles. In the US for example, only 31% of plastic bottles are recycled. In order to increase recycling, companies, alongside governments, need to work on consumer awareness, promote recycling. Companies like Coke, PepsiCo, and Nestle are pledging to increase their use of recycled materials in the next few years, and while this is certainly a step towards making packaging more environmentally friendly, rPET is not biodegradable and is therefore not ideal as a replacement for virgin PET bottles.
Chemical recycling is another part of the solution which would expand the lifespan of rPET. Chemical recycling breaks the PET down into ethylene glycol and terephthalic acid, which can then once again be made into PET (recycled), which is nearly identical to virgin PET. However, chemical recycling is not vastly used, therefore making it expensive and unappealing to manufacturers. Should it be recognized in the future, however, the price of chemical recycling would theoretically decrease, and it would expand the lifespan of PET, making it a more environmentally friendly alternative to virgin PET.
Polylactic acid is a bio-based polymer made from renewable resources like cornstarch, sugarcane, or tapioca roots. PLA is biodegradable (degrades in 45-60 days), however, the conditions it requires are those of industrial composting (high humidity at 50-60℃), meaning that it cannot be composted at home and that the plastic will not biodegrade if left alone in a landfill or the oceans. PLA is also not as durable as PET, and it softens at 60℃, making it unsuitable for the packaging of hot beverages or reheatable meals. Since PLA has a melting point significantly lower than PET, it cannot be recycled in the same facilities, as PLA would degrade at the relatively high temperatures used to recycle PET. This means that more recycling plants need to be built, causing an increase in costs that manufacturers may not be willing to incur.
PHA is a bio-based plastic, with the ability to biodegrade under natural conditions. This makes it an ideal substitute for PET, however being fairly new in the plastic industry, PHA does not have a lot of demand yet.
PHA is made by microorganisms that are given an excess of carbon dioxide, however, do not have access to enough nitrogen, oxygen, or phosphorus, which are all nutrients needed for the microorganism to reproduce. Since the bacteria do not have sufficient nutrients to grow or reproduce, it reserves this excess carbon as granules of PHA which is then collected by companies and used as a substitute for traditional plastics like PET.
PHA is a thermoplastic, like PET, meaning that it softens at high temperatures, allowing it to be molded into the desired shape (bottles or another packaging). They are UV stable, and unlike PLA, can resist heat up until 180℃.
There are many different kinds of PHA polymers, however, poly(3-hydroxybutyrate) (PHB), seems to be most widely researched and is thought to have the greatest potential in food packaging.