Bio-based plastics are aimed at sequestering carbon. But at what price?

It’s the year 2050, and humanity has made tremendous progress in decarbonisation. This is due in large part to the negligible price of solar and wind energy, which even collapsed in 2022. warned would happen, it happened tripled production from 2016 levels. By 2050, humans will produce trillions of kilograms of plastic per year, emitting the greenhouse gas equivalent of more than 600 coal-fired power plants. In three decades we will have stopped using so much oil and gas as fuel, but much more plastic.

Here in 2022, people are trying to counter that nightmare scenario with a much-hyped concept called “biobased plastics.” The backbone of traditional plastics are chains of carbon derived from fossil fuels. Instead, bioplastics use carbon extracted from crops such as corn or sugar cane, which is then mixed with other chemicals, such as plasticizers, found in traditional plastics. Growing those plants removes carbon from the atmosphere and locks it into the bioplastic.if it is used for a permanent purpose, such as building materials, instead of single-use cups and bags.

At least, that’s the theory. In reality, biobased plastics are problematic for several reasons. It would take an astonishing amount of land and water to grow enough plants to replace traditional plastics, plus energy to produce and ship everything. Bioplastics can be loaded with the the same toxic additives who make a plastic plastic, and still shattering into micro-sized pieces 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 “environmental friendliness,” while scientists and environmentalists agree that the only way to stop the crisis is to simply stop producing so much damn plasticregardless of the source of carbon.

But let’s say there was a large-scale shift to bioplastics – what would that mean for future emissions? That’s what a new paper in the journal Nature started estimating and found that if a whole bunch of variables connected — and that’s a very theoretical one if—bioplastics can become carbon negative.

The modeling considered four scenarios for how plastic production – and the life cycle of those products – could unfold up to the year 2100, modeling even beyond those previous projections of production up to 2050. The first scenario is a base case scenario, in which business continues as usual. The second adds a tax on CO2 emissions, which would make it more expensive to produce plastics from fossil fuels, encourage a shift to bioplastics, and reduce emissions through the end of the century. (It would also be an incentive to use more renewable energy to produce plastic.) The third envisions developing a more circular economy for plastics, making them easier to reuse or recycle, reducing both emissions and demand be reduced. And the last scenario imagines a circular bioeconomy, in which much more plastic has its roots in plants and is used over and over again.

“Here we combine all of this: we have the CO2 we have circular economy strategies, but in addition we push more biomass into the sector by giving it a certain subsidy,” says lead author of the study, Paul Stegmann, who now works at the Netherlands Organization for Applied Scientific Research, but did the work at Utrecht University, in collaboration with PBL Netherlands Environmental Assessment Agency. If all three conditions are met, he says, it’s enough to make emissions negative.

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