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From campaigns against microplastics to the news of the big dump in the Pacific, the public is becoming more and more aware of the disproportionate effect of plastic on the world's oceans. However, its effect on the air is much less obvious. The production, use and disposal of plastics all produce prodigious amounts of greenhouse gases, but scientists have not yet grasped the scope.
Researchers at the University of Santa Barbara have now determined to what extent plastic is contributing to climate change and what should be done to reduce these emissions. The results appear in the log Nature Climate change.
"It is, to our knowledge, the world's first life-cycle badessment of greenhouse gas emissions from all plastics," said author, Sangwon Suh, a professor at Bren School of Environmental Science & Management at the University of Santa Barbara. "It's also the first badessment of various strategies to reduce plastics emissions."
Plastics have life cycles that are surprisingly rich in carbon. The vast majority of plastic resins come from oil, which requires extraction and distillation. Then, the resins are transformed into products and transported on the market. All these processes emit greenhouse gases, directly or through the energy required to accomplish them. And the carbon footprint of plastics continues even after they are eliminated. Rejection, incineration, recycling and composting (for some plastics) all release carbon dioxide. In total, emissions from plastics in 2015 were equivalent to nearly 1.8 billion tonnes of CO2.
And researchers expect this number to increase. They predict that global demand for plastics will increase by about 22% over the next five years. That means we will have to reduce emissions by 18% just to break even. According to new findings, plastics emissions will reach 17% of the global carbon budget by 2050. This budget estimates the maximum amount of greenhouse gases we can emit while preventing global temperatures from rising. more than 1.5 degrees Celsius.
"If we really want to limit the rise in global average temperature from the pre-industrial era to below 1.5 degrees Celsius, we can not increase greenhouse gas emissions, let alone reduce greenhouse gas emissions. Substantial increase in greenhouse gas emissions, as we had expected for the life cycle of plastics, "said Suh.
In addition to diagnosing the problem, Suh and lead author Jiajia Zheng, a graduate student at Bren School, evaluated four strategies to reduce the carbon footprint of plastics.
Recycling may offer the simplest solution. Emissions reductions resulting from the elimination of the need for new plastic exceed the slightly higher emissions resulting from the processing of scrap. Currently, 90.5% of the plastic is recycled worldwide, a figure calculated by Roland Geyer, industrial ecologist of the University of Santa Barbara, who published the statistics for the year 2018. Clearly , There is still a lot to do.
Increasing the percentage of biobased plastics could also reduce emissions. Bio-based plastics are made from plants that capture atmospheric CO2 during their growth. If they are composted, the carbonaceous matter contained in the bioplastics is released into the atmosphere in the form of CO2. This makes the material itself carbon neutral, although manufacturing still generates a small amount of greenhouse gases.
Slowing down the growing demand for plastics could also limit their emissions, but Suh admits it would be a difficult task. Plastics are versatile, cheap and ubiquitous. Scientists are working on alternatives, but nothing has yet dethroned the plastic. What's more, as developing countries modernize, more and more people will enjoy a modern, plastic-rich lifestyle.
In the end, Suh and Zheng found that replacing fossil fuel energy with renewable sources had the biggest impact on greenhouse gas emissions from plastics. The switch to 100% renewable energy – a purely theoretical scenario, concedes Suh – would reduce emissions by 51%.
Unfortunately, the growing demand for plastic means that this situation always ends up producing more carbon than what we are currently producing. In fact, Suh was surprised to see how difficult it was to reduce emissions given this trend.
"We thought each of these strategies should have significantly reduced greenhouse gas emissions from plastics," said Suh. But they did not do it. "We tried one and it did not really have any impact, we combined two, but the shows were still there, and we combined them all together. 39, while we may see a reduction in future greenhouse gas emissions compared to the current level. "
The results of the study highlight the scale of efforts needed to significantly reduce greenhouse gas emissions. "The public really needs to understand the magnitude of the challenge we face," Suh said.
To that end, Suh is focused on the best way to take advantage of the renewable energy we produce. "The question is, what is the biggest blow for the kilowatt-hour of renewable energy?" he said. For example, does 1 kWh of renewable energy offset more emissions when it is intended for home use, transportation or some other application?
After working with so many people, one thing became clear to Suh: "What I'm seeing is that reducing greenhouse gas emissions will only be possible if we actually deploy efforts of unprecedented scale. "
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