Scientists give another reason to scorn plastics: They emit greenhouse gases
Clogging landfills, trashing beaches and fouling the oceans — in part via a massive junk ball off the coast — have been key reasons for the war on plastic bags, straws and bottles. Now, a researcher from UC Santa Barbara has added one more: They make the planet warmer.
In one of the first-ever evaluations of greenhouse gas emissions from plastics, Professor Sangwon Suh found that production and post-use of plastics — including composting and recycling — emit a substantial amount of carbon dioxide into the atmosphere.
A growing problem
In 2015, carbon dioxide emissions from plastics were equivalent to nearly 1.8 billion metric tons, according to a study published in the journal Nature Climate Change released Monday.
That number will increase if the demand for plastics grows an expected 22% over the next five years, the study found. This would make the emissions from plastics about 17% of the world’s total carbon budget by 2050.
Carbon dioxide contributes to the warming of the earth’s atmosphere by trapping heat, a phenomenon supported by evidence and upheld by 97% of atmospheric scientists from around the world.
While plastics emissions are fewer than those produced from other sources, such as transportation, Suh said the amount is “sizable” and largely ignored in global efforts to slow rising temperatures.
Countries around the world have pledged to reduce carbon emissions to keep global temperatures from increasing more than 1.5 degrees Celsius (2.7 Fahrenheit). Without intervention, scientists predict warmer oceans which would cause sea levels to rise, potentially flooding coastal neighborhoods in New York and Florida, for example.
Plastic emission sources
Carbon is released from plastics in two forms: in production and after they are used. Suh’s life cycle measurements include both.
In making plastics, the amount of greenhouse gases released is only 5% less than from electricity production worldwide, he said. Plastics are made from drilling and processing crude oil and the heating of resins, plus the transportation of the finished products — all steps that produce carbon emissions.
Second, used-up plastics will release carbon dioxide when exposed to ultraviolet light, according to Furya Prakash, professor of chemistry at USC and director of the school’s Hydrocarbon Institute. “It does degrade over time when exposed to sunlight,” he said, sometimes releasing methane, a very potent greenhouse gas.
It is a myth that plastic stays the same for thousands of years, Suh said, adding that even scientists know little about the breakdown of plastics in the environment.
The most carbon is released when plastics are tossed in the trash and then incinerated. The Sanitation Districts of Los Angeles County operate the Southeast Resource Recovery Facility in Long Beach where municipal waste is incinerated and turned into electrical energy. Very few incineration plants are located in Southern California because of strict air quality rules.
However, composting and recycling of plastic waste also produces carbon dioxide, Suh said. For example, plastic waste is shredded by machines and then heated up into a molten form to make other products. This process uses energy most often from combustion of fossil fuels that releases greenhouse gases, he said.
As restaurants switch to plant-based straws, plates and utensils, some of the emissions are eliminated but not all. Even composting plant-based plastics considered environmentally friendly produce some carbon dioxide emissions. Suh said by not using petroleum, the amount of CO2 is reduced but not eliminated.
“There is no free lunch,” Prakash said. “We are all made of carbon. So carbon has to be managed.”
Recycle. but use green fuels
The UC Santa Barbara professor’s study concludes that reducing greenhouse gases from plastics will be very challenging and requires a multipronged approach.
The most effective way is recycling plastics using 100% renewable power, such as wind, solar, biogas, hydro-electric and geothermal.
Recycling rates are low
On the other hand, that change may not have the impact some are expecting — 90.5% of all plastic waste has never been recycled. That calculation made by UCSB industrial ecologist Roland Geyer, was the winning international statistic of the year in 2018 as named by the Royal Statistical Society of Great Britain.
What happens to plastic waste?
According to the RSS and Geyer, about 12 percent gets incinerated, giving off the most greenhouse gases; 79% ends up in landfills or the natural environment. The world’s oceans are the receptacles for 8.8 million tons a year, polluting coral reefs, fish, turtles and even whales, including the swirling Great Pacific Garbage Patch, the size of Texas.
The world’s corporations must reduce plastic packaging, Suh said. Plastic demand is increasing 4% each year, with the bulk of that coming from developing countries, he said.
When examining alternatives to plastics and ways to reduce their emissions load, Suh said using one or two strategies won’t work. The world needs an all-out effort.
“We thought that any one of these strategies should have curbed greenhouse gas emissions of plastics significantly. We tried one, and it didn’t really make much impact. We combined two, still emissions were there.
“When we combined all of them, only then could we see a reduction in future greenhouse gas emissions,” Suh said.