Bio-based plastics aim to capture carbon… but at what cost?

Humans have made huge progress in decarbonizing. It was thanks to the negligible price of solar and wind power that it was able to rise. The fossil fuel industry has tripled production from 2016 levels despite the World Economic Forum warning. Humans are making trillions of pounds of plastic a year, and in the process emitting over 600 coal-fired power plants. We will no longer use so much oil and gas as fuel in three decades.

People are trying to head off that nightmare scenario with a concept called bio-based plastic. Chains of carbon derived from fossil fuels are the basis of traditional plastic. Carbon from crops such as corn or sugarcane is mixed with other chemicals to make bioplastics. If it is used for a permanent purpose, like building materials, instead of single-use cups and bags, carbon can be pulled out of the atmosphere and locked inside the bioplastic.

At least, that’s the theory. In reality, bio-based plastics are problematic for a variety of reasons. It would take an astounding amount of land and water to grow enough plants to replace traditional plastics—plus energy is needed to produce and ship it all. Bioplastics can be loaded with the same toxic additives that make a plastic plastic, and still splinter into micro-sized bits that corrupt the land, sea, and air. And switching to bioplastics could give the industry an excuse to keep producing exponentially more polymers under the guise of “eco-friendliness,” when scientists and environmentalists agree that the only way to stop the crisis is to just stop producing so much damn plastic, whatever its source of carbon. Advertisement

What would happen to emissions if there was a large shift to bioplastics? A paper in the journal Nature estimated that if a bunch of variables were to align, bioplastics could go carbon-negative.

The modeling took into account four different scenarios for how the life cycle of plastic products might unfold in the future. Business goes on as usual in the baseline scenario. The second adds a tax on CO 2 emissions, which will make it more expensive to produce fossil-fuel plastics, which will encourage a shift toward bio-based plastics and reduce emissions through the end of the century. It would encourage people to use more renewable energy. The third assumes that the development of a more circular economy for plastics will make them more easily reused or recycled. The last scenario imagines a circular bio-economy in which a lot of plastic is used over and over.

Paul Stegmann is the study's lead author and he says that the study combines all of the above. It's enough to push emissions into the negative if all three conditions are met.