In Part III, we discussed managed plastics emissions. In the final installment, we will be highlighting the unmanaged portion — plastic's climate impact within the natural environment.In July 2021, the San Francisco Chronicle reported that a summer volunteer cleanup had yielded 3,200 pounds of trash from Bay Area beaches. The most common item was cigarette butts, which are mostly plastic. Then came food wrappers, plastic straws, nets, bottle caps, six-pack rings, plastic bottles, and scraps of Styrofoam and plastic. What wasn’t removed probably ended up in the ocean or the bay. According to a 2019 study, a staggering 7 trillion microplastics (pieces of plastic that are less than 0.2 inches long) enter the bay every year.
The problem is global of course. The United Nations Environment Programme reports that the world generates about 300 million tons of plastic waste annually. At least 2 billion people have no access to waste management services and even when discarded plastic is collected, many countries lack the capability to process it using best practices. More than one-fourth of global waste is openly dumped, which leads to unmanaged plastic detritus clogging waterways. On top of that, developed countries export much of the plastic waste they do collect. As a result, once-agricultural villages in Asia and Africa have become plastic dumpsites.
Unmanaged plastic in the environment is not only a trash problem. It also has climate impacts that are still poorly understood but are the focus of a growing body of research.
Plastic in the Environment Releases Methane and Ethylene
In 2018, a startling groundbreaking study at the University of Hawai’i found that plastic litter emits methane and ethylene when exposed to sunlight. The researchers tested multiple types of plastic, all of which produced the two potent greenhouse gases as they degraded. The world’s most frequently discarded plastic, polyethylene (used for shopping bags), is also the most prolific emitter. Scientists are now figuring out how to account for this previously unrecognized source of greenhouse gases As the planet grows hotter, plastic litter breaks down into more methane and ethylene, creating a feedback loop and accelerating climate change. Its impact may be significant.
Microplastics May Be Disrupting the Ocean’s Ability to Sequester Carbon
As for the climate impact of the 99 percent of ocean plastic found beneath the surface, studies have shown that microplastic may be interfering with the ocean’s capacity to absorb and sequester CO2.
Over seventy percent of the world’s surface is covered with water, which acts as a pump for CO2. About 25 percent of all CO2 emissions are absorbed by the ocean. That happens because CO2dissolves in water but also because plankton captures carbon at the surface and transports it to the ocean floor when they die or are eaten.
However, the 8 million metric tons of plastic that enter the ocean annually—in addition to the 150 million metric tons already in the marine environment—could be impeding this process. Scientists have found that the microplastics in toothpaste and beauty products (called microbeads), as well as those that result from the breakdown of larger plastic items, may be reducing the ocean’s capacity for sequestering carbon.
According to a 2020 study by researchers at Hunan University, microplastics in the ocean can disrupt the ability of phytoplankton (planktonic plant life) to fix carbon through photosynthesis. They may also be having toxic effects on the development and reproduction of zooplankton and on the creatures’ capacity for transferring carbon to the deep ocean.
Other critical marine life is also affected. Investigators at the National University of Ireland (Galway) recently examined the effect of microplastics on salps, tiny jellyfish-like animals that feed on algae on the ocean’s surface. These algae contain CO2taken in during photosynthesis. The salps’ CO2-rich fecal matter transports the greenhouse gas to the ocean floor. However, when salp ingest microplastics, their fecal matter lingers at the surface, where it breaks down, causing the release of some CO2 back into the atmosphere.
As with emissions from plastic litter, more research is needed. Plastic’s impact on the ocean as a CO2 sponge is a wild card in the climate crisis. However, it’s already clear that the more microplastics enter the ocean and put pressure on the plankton population, the more they disturb one of the planet’s most critical natural processes.
In Conclusion
Through this series, we’ve explored the multi-faceted issue that is plastics. The material’s versatility and low cost drive the modern economy, and it is this ubiquity and dependence that make the problem so pernicious.
As the world gains some traction on renewable energy and cleaner transportation, the petrochemical industry is pivoting to plastic, vastly ramping up production, often in the form of single-use throwaway items. If output grows as the industry is planning, plastic could consume between 10 and 17 percent of allowable carbon emissions by midcentury—allowable if warming is to stay below 1.5 degrees Celsius. Thus, scientists are sounding the alarm on soaring emissions from plastic. After a sweeping study of plastic and the climate, the Center on International Environmental Law, for one, sees “a grim picture: plastic proliferation threatens our planet and the climate at a global scale.”
Want to join in the effort to stop the plastics catastrophe? Learn more about 350 Silicon Valley’s work to regulate plastics and/or join our team. Email plastics@350siliconvalley.org.