For those guilt-ridden about the environmental damage caused by everyday consumer purchases, there are myriad paths toward forgiveness. Stick your bottles, cans and Amazon cartons into the recycling box. Buy the organic cold brew that is made with 100 percent renewable power. Minimize the carbon from your ski holiday flight with Peruvian rainforest offsets.
Then there are biodegradable plastics. It is hard to cut polymers from your life when boxed blueberries are so temptingly cheap and so healthy — but perhaps the effects can be mitigated if they are bought in a box that can turn into compost.
Chemicals companies are paying attention. Production capacity for plant-derived and biodegradable products is likely to triple over the next five years to 6.3 million metric tonnes, industry association European Bioplastics said.
Illustration: Tania Chou
That sounds like a drop in the ocean next to the about 400 million tonnes a year plastics market, but it could grow rapidly. Project Drawdown, a climate think-tank, estimates 92 million tonnes to 357 million tonnes of bioplastics production by 2050.
If the only problem posed by plastics is waste management, we should be welcoming this trend. Biodegradable plastics are meant to break down in the environment in weeks or months, rather than the decades or centuries that conventional ones can hang around.
However, with consumption of polymers predicted to double by 2040, another issue ought to come into focus: emissions.
Like gasoline, Vaseline and asphalt, most of the world’s plastics are byproducts of the oil refining industry, accounting for about 8 percent of total oil consumption. That proportion is likely to rise drastically in the coming decades as electric vehicles displace combustion engines in road transport, reducing the share of the oil barrel going into fuel.
However, they differ from fossil fuels in a crucial way. Using a tonne of jet kerosene pumps more than three tonnes of carbon dioxide into the atmosphere, as burning pulls apart its hydrocarbon molecules. A plastic pipe, on the other hand, is only useful if it remains chemically stable. Its carbon must remain locked tight inside its chemical structure, or it would weaken and shatter.
Biodegradable plastics change that dynamic. In breaking down, they release their carbon back into the environment — particularly as methane, one of the most potent greenhouse gases.
As a result, life-cycle emissions could end up being greater than those from conventional alternatives. A 2020 US study of polylactic acid derived from cornstarch and commonly used in disposable food containers, found that its total emissions were greater than those of conventional plastics, except in cases where it remained inert after being trashed.
Not all bioplastics are created equal. The same study found that bio-polyethylene, a plant-derived polymer that does not break down, could suck up more carbon than it emits. That calculation demonstrates that biodegradability is just one of a series of good and bad factors relating to different varieties of plastics, rather than a simple and absolute positive.
The greatest risk is that we allow the virtuous glow of compostable polymers to blind us to their potential downsides. While most biodegradable plastics are made from biomass such as starches and crop residues, they can also be made from fossil fuels. That is a worst-of-all-worlds situation, in which the emissions released in landfill are not even offset by carbon sucked out of the atmosphere by the plants used as feedstock.
It could also be the segment of the bioplastics market that grows fastest over the coming years. Polybutylene adipate terephthalate — a fossil-derived alternative to the polyethylene used in plastic wrapping, bags and bottles — appears to be winning the race in China, with a government-commissioned study forecasting production to hit 7 million metric tonnes in 2025, compared with 1 million tonnes for polylactic acid.
One advantage of the mountains of waste created by the voracious appetite for plastics is that it is a highly visible problem. That means there is motivation to tackle it.
If the dozen developing countries that generate nearly nine-tenths of the world’s marine plastic could lift their waste management to developed-economy levels, the oceans would be drastically cleaner. Improving recycling rates worldwide from current levels of less than 10 percent to those of more than 40 percent common for packaging in Europe would help even more.
Emissions from plastic degradation — an invisible process taking place deep underground, and producing no emotive imagery of floating debris, tangled turtles or overflowing waste dumps — could be far more insidious.
Bioplastics “are not permanent solutions because they still reaffirm the take-make-waste linear economy mindset,” said Alice Zhu, a researcher of plastic pollution at the University of Toronto.
To businesses, the green aura surrounding bioplastics is an advantage, helping to reconcile busy consumers to the polymers used every day. In environmental terms, that is precisely the problem: They risk absolving the need to carry out the basic work of reducing, reusing and recycling. Ultimately, that is the only way to deal with the plastics addiction.
David Fickling is a Bloomberg Opinion columnist covering energy and commodities. Previously, he worked for Bloomberg News, the Wall Street Journal and the Financial Times. This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.
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