Over the last 30 years, plastic product manufacturing has increased globally by over 70%. Single-use products such as plastic bags, bottles, and product wrappings currently comprise the largest sector of plastic manufacture—and plastic waste. While the flexible, unyielding nature of plastic makes it ideal for use in previously shatter-prone items like bottles and jars, the enduring nature of traditional plastic also means that it takes years for plastic products to breakdown in landfills. With an estimated 55% of plastics sent to landfills over the last half century, management of plastic waste is a growing challenge.
How long does it take for plastic to degrade?
Organic waste products like food scraps undergo decomposition, biodegradation, or composting once they are discarded. Traditional plastic products, on the other hand, do not decompose—nor do they biodegrade or compost. All three of these processes are highly dependent on the ability of microscopic organisms such as bacteria to consume and thus breakdown landfill organic waste into simpler organic matter. Plastic products are typically made with synthetic chemical ingredients like polyethylene terephthalate (PET) that biodegradation organisms cannot consume. As such, plastics cannot be readily degraded.
Traditional plastics do eventually breakdown in landfills during the process of photodegradation. Instead of living organisms, ultraviolet (UV) radiation from the sun undoes the chemical structure of plastic to breakdown a large plastic unit into smaller and smaller pieces over time. Given the resistant nature of chemicals like PET, this gradual breakdown process can take years to complete. Plastic bottles, for instance, are estimated to require approximately 450 years to decompose in a landfill.
What happens to plastic in landfills?
Once plastic waste arrives at a landfill, it can be subjected to photodegradation—provided that sunlight can reach the plastic. Landfills are constructed to maximize daily fillable area and longevity of the landfills. To accomplish this, areas of the landfill are compacted, covered with a layer of soil, and compacted again each day to make room for the next day's refuse. Ultimately, this creates an environment where little sunlight can reach discarded plastics to encourage photodegradation and contributes to the persistence of plastic waste in the environment.
Not all plastic waste ends up in landfills, however. Due to regional landfill mismanagement and littering, an estimated 3% of plastic waste annually reaches the world’s oceans. In warm, ocean water plastics can undergo photodegradation more quickly—though not without causing environmental harm. As plastics breakdown into smaller pieces, they produce small pieces of plastic (i.e., less than 5mm in length) known as “microplastics” that can be mistaken for food by aquatic life and birds and potentially reaching drinking water sources.
An additional problem posed by plastic decomposition in the ocean is the release of potentially toxic chemicals such as bisphenol A (BPA) into water sources and within the animals that have consumed plastic. BPA and related chemical components of plastics are a current concern for human and wildlife as they have the potential to disrupt normal hormone function and can cause reproductive harm.
How effective is plastic recycling currently?
Over the last 50 years, environmentally conscious movements have encouraged consumers to “Reduce, Reuse, Recycle” one-time use products like plastics and glass. A study conducted in 2015, however, found that only 20% of plastic waste is recycled.
Despite consumers' best efforts, some plastics intended for recycling are ultimately directed to landfills for a variety of reasons including: contamination of recycling streams, inability to meet plastic recycling demand, quality of recycled plastics.
1. Contamination of Recycling Streams
“Contamination” of the recycling process chain with food waste, non-recyclable items or packaging components causes a fraction of all plastics intended for recycling to be rejected at local or regional waste handling facilities. The difficultly and economic costs of separating poorly-sorted and/or contaminated plastics encourages subsequent diversion to landfill.
2. Inability to Meet Recycling Demand
Plastic codes—also known as the "chasing arrows" symbol—found on plastic products indicate what type of plastic was used to produce the product. Contrary to popular belief, this symbol does not necessarily indicate that a product is recyclable. For instance, plastics found in clear food packaging (polyvinyl chloride; PVC), frozen food and grocery bags (low density polyethelene; LDPE), and disposable diapers (polypropylene; PP) are not readily recycled.
Until 2018, China was the world’s largest plastic importer and accepted over half of global post-consumer plastic waste for processing. This policy ended due to recurrent management issues posed by contaminated materials. As a result, large exporters of post-consumer plastic like the United States and Australia are struggling to address the demand for plastic recycling. Many domestic recycling facilities do not accept mixed plastics due to associated economic challenges. Instead, some waste management operations have opted to automatically divert mixed plastics to landfills, incinerators, or stockpiles.
3. Quality of Recycled Plastics
Most recyclable plastic waste is suitable for only one round of recycling. This is because the recycling process degrades overall plastic integrity. Thus, most recycled plastic ultimately ends up in a landfill or incinerator regardless of whether it experiences another use cycle or not.
How can we address the plastic waste crisis?
Given the current environmental and health hazards posed by plastic waste and the recycling challenges associated with plastic waste, it is clear that the world is in the midst of a crisis. Plastic waste is projected to increase by approximately 20% over the next 30 years, with almost half reaching landfills or the environment. Moving forward, responsible plastic use is critical for effectively addressing plastic waste.
Reduction and replacement of traditional plastic use will likely form the core of plastic waste reduction strategies. Updated consumer practices like swapping out plastic shopping bags for reusable tote bags and carrying reusable water bottles instead of plastic, single-use bottles can help reduce traditional plastic use.
Replacing traditional plastics with biodegradable materials also offers a promising opportunity to reduce the environmental burden of plastics waste. Biodegradable plastics (BDPs) are designed to break down into the environment into natural components, allowing them to be composted. Presently, BDP prototype materials have been developed from plant materials like the hardy Miscanthus (i.e., Elephant grass) plant. Early work developing BDP technology suggests that—depending on the approach and materials—it could be possible to produce biodegradable plastics durable enough for use in car parts.