Humanity’s Plastic Footprint (II)
By: Gail Kulisch
[As a graduate student in Virginia Tech’s Executive Master of Natural Resources (XMNR), Gail Kulisch has applied her 28 years of experience in the US Coast Guard protecting the maritime environment from harmful materials that degrade the health of our waters. In Part I of this four-part series, Kulisch introduced the Great Pacific Garbage Patch and its impact on the aquatic food chain. In this installment, she’ll discuss why plastics are a such a persistent waste problem.]
Plastics – Engineered to Last
An important development in recent years is the invention and widespread distribution of plastic material. It was only about 60 years ago when science fielded the first commodity thermoplastic (Andrady 2015). Plastics entered the mainstream of an increasingly consumptive society in the 1950’s as chemical knowledge and processes advanced.
Heralded as a technological breakthrough, the variety of monomers and polymers that make up plastics resulted in manufactured materials with qualities ranging from flexible thru rigid. They make everyday objects more durable, lighter, and cheaper as well as less expensive to transport. Environmental benefits were noted almost immediately as the lighter containers saved transportation fuel and reduced emissions (Plastics Industry Association 2016). There are now over 80,000 different plastic compounds or mixed plastic formulations available commercially.
Plastic is the common name for chemical polymer that can be molded or shaped, usually by applying heat and pressure. This results in a material that has low density, low electrical conductivity, transparency, and toughness. In addition, they are lightweight yet strong, can be molded into complex shapes, durability is designed in, biologically and chemically inert, can be used as electrical and thermal insulators, are good thermal insulators, and can be manufactured into an insulation material (Andrady 2015). They are highly competitive as a material in the marketplace and the volume and variety are expected to increase.
Plastics can be made into a large variety of products. The more common products include polyethylene terephthalate (PET) beverage bottles, and objects made from polyvinyl chloride (PVC) such as lightweight plumbing tubes and pipes. Plastics can be engineered for high durability and flexibility, functional capabilities that are used in many household and industrial products.
Insulating food containers are made of foamed polystyrene and shatterproof windows often contain polymethyl methacrylate. Industrial processes have evolved such that multiple layers of plastic, each with a unique composition designed for a specific function, can be fused together to form flexible multilayer packaging.
While effective for transportation, storage, and use, multilayer packaging presents a challenge. Once in the waste stream, it is difficult to disaggregate the layers into their component layers for recycling or reuse. Multilayer, multi-component plastics that cannot be recycled or reused find their end use as additional waste material in landfills and incinerators. They also accumulate in natural habitats worldwide (Hopewell et al. 2009).
Labels and adhesives on packaging also create issues with recycling. This affects approximately 30% of polyethylene terephthalate (PET) packaging collected for recycling in the U.S. (Walmart 2016). A more challenging source of plastic pollution is the increase over the last few decades in synthetic garments. Synthetic garments shed plastic fibers through a normal wash cycle with the resulting microfibers moving into sewage systems or wastewater systems which in turn work their way to water bodies such as rivers and ocean. This aspect of plastic pollution has “become a major source of concern to environmentalists and marine-life researchers” (Cernansky 2016).
Biodegradation is also not one-size-fits-all; plastics biodegrade at highly variable rates. PVC-based plumbing biodegrades very slowly which makes it the best choice for sewage conduits. A wide range of oil-based polymers used in packaging applications are virtually all non-biodegradable, and some complex composites with various levels of contamination (Song et al. 2009). These are more difficult to recycle or reuse due to being complex composites having varying levels of contamination.
The wide range of oil-based polymers used in packaging applications makes the challenge even greater. These are virtually all non-biodegradable, and some are difficult to recycle or reuse. The majority of plastic packaging is made with one of six resins: polyethylene terephthalate (PETE), high density polyethylene (HDPE), polyvinyl chloride (PVC or vinyl); low density polyethylene (LDPE), polypropylene (PP), or polystyrene (PS) (Plastics Industry Trade Association 2016).
Synthetic polymers have been engineered and produced such that they biodegrade more quickly and degrade upon exposure to the environment. The more common ones are cellulose acetate, poly-3-hydroxybutyrate, celluloid, and polylactic acid (PLA). They have chemical bonds that can be broken by water.
Much hope is being placed on biodegradation of plastics with the suggestion that natural organisms can be found to resolve the environmental concerns of discarded plastics in the environment. This has yet to emerge at scale and exists in isolated cases and with limited applicability. “Specific enzymes have developed over billions of years to aid rapid degradation of natural polymerization yet for most of the plastics developed over the last 80 years, no such enzymes exist” (Essential Chemical Industry – Online 2013).
Progress is being made to improve biodegradability. Synthetic polymers have been engineered and produced such that they biodegrade more quickly and degrade upon exposure to the environment. Most conventional plastics, however, such as polyethylene, polypropylene, polystyrene, poly(vinyl chloride) and poly(ethylene terephthalate), are non-biodegradable. Their increasing accumulation in the environment is an environmental threat (Tokiwa et al. 2009). Starch-based plastics degrade within two to four months in a home compost bin, while polylactic acid needs higher temperatures to degrade. Polycaprolactone and polycaprolactone-starch composites decompose slower. While their decomposition may be relatively faster, it still takes months.
[In Part III of this four-part series, available on May 7th, Kulisch presents the path plastics take from production to accumulation in the world’s oceans.]
Gail Kulisch is an alumni of the Executive Master of Natural Resources program at Virginia Tech and the Owner and Managing Principal of BTG Ventures LLC, which supports development and implementation of safety and security initiatives, provides leadership and technical expertise to disaster response operations, and advances environmental stewardship. A retired Coast Guard Officer, Kulisch served 28 years on Active Duty, including assignments in marine environmental protection, response, and remediation before retiring from military service and forming her own consulting organization. She is a 1983 graduate of Holy Cross College (B.A. in Chemistry) and earned a Master of Science in Chemical Engineering from UCLA in 1990.
The Center for Leadership in Global Sustainability thanks the following photographers for sharing their work through the Creative Commons License: MajorMalfunction; Chesapeake Bay Program; Vince Alongi; mbeo; and IIP Photo Archive.
- Andrady, AL. 2015. Plastics and Environmental Sustainability (First edition). John Wiley & Sons
- Cernansky, R. 2016. Are synthetic fleece and other types of clothing harming water? The Washington Post, November 2016, ppE1-E5.
- Essential Chemical Industry – Online. 2013. <http://www.essentialchemicalindustry.org/polymers/degradable-plastics.html>, accessed November 2016.
- Hardcastle, JL. 2017. Lightweight food & beverage packaging saves money, reduces carbon emissions. Environmental Leader, <https://www.environmentalleader.com>, accessed April 2018.
- Hopewell, J., R Dvorak, and E Kosier. 2009. Plastics recycling: Challenges and opportunities. Philosophical Transactions of the Royal Society, 364(1526):2115-2126.
- Plastics Industry Trade Association. 2016. <http://www.plasticsindustry.org>, accessed November 2016.
- Song, JH, RJ Murphy, R Narayan, and G Davies. 2009. Biodegradable and compostable alternatives to conventional plastics. Philosophical Transactions of The Royal Society, 364(1526):2127-2139.
- Tokiwa, Y, BP Calabia, CU Ugwu, and S Aiba. 2009. Biodegradability of Plastics. International Journal of Molecular Sciences, 10:3722-3742.
- Walmart. 2016. Walmart Sustainable Packaging Playbook: A Guidebook for Suppliers to Improved Packaging Sustainability.