Study Looks at Potential Implications of Shifting to Plant-Based Plastics

Usually, bioplastics are promoted as a climate- and eco-friendly alternative to traditional plastics based on petroleum. However, according to a new study conducted by the University of Bonn, transitioning to plant-based plastics may have less positive impacts than anticipated.

Most significantly, on a global scale, a growing consumption of bioplastics in the coming years can possibly lead to increased emissions of greenhouse gas from cropland expansion. The study has been reported in the scientific journal “Environmental Research Letters.”

Often made from petroleum, plastics are known to have the related impacts in terms of the depletion of fossil fuels as well as climate change: burning or degradation causes the carbon contained in fossil resources to abruptly discharge into the atmosphere, thus contributing to global warming. This, in turn, corresponds to approximately 400 million metric tons of CO₂ each year across the globe, nearly 50% of the total greenhouse gases emitted into the atmosphere by Germany in 2017. It has been projected that plastics may already account for 15% of the global CO₂ emissions by the year 2050.

On the other hand, bioplastics are based on renewable raw materials like sugar cane, maize, or wheat, and hence are technically climate-neutral. Such plants receive their required CO₂ from the air via their leaves. Therefore, the production of bioplastics consumes CO₂, which offsets the amount that is subsequently discharged at end of life. On the whole, their net greenhouse gas balance is believed to be zero. Hence, bioplastics are usually consumed as an eco-friendly alternative.

However, at least with the present level of technology, this problem is perhaps not as clear as usually believed.

The production of bioplastics in large amounts would change land use globally. This could potentially lead to an increase in the conversion of forest areas to arable land. However, forests absorb considerably more CO₂ than maize or sugar cane annually, if only because of their larger biomass.

Dr Neus Escobar, Institute of Food and Resource Economics, University of Bonn.

An understanding of biofuels has demonstrated that this impact is not a hypothetical speculation. The growing demand for the “green” energy sources has led to considerable deforestation to certain countries across the tropics.

Together with her colleagues Prof. Dr Jan Börner, Dr Wolfgang Britz, and Salwa Haddad, Dr Neus Escobar successfully simulated the impacts of the ubiquitous demand for bioplastics in top producing countries. They applied and extended a computer model that had already been used for determining the effects of biofuel policies. The model is based on a database depicting the economy of the entire world.

For our experiment, we assume that the share of bioplastics relative to total plastic consumption increases to 5% in Europe, China, Brazil and the USA. We run two different scenarios: a tax on conventional plastics compared with a subsidy on bioplastics.

Dr Neus Escobar, Institute of Food and Resource Economics, University of Bonn.

The tax scenario presents the most major effects: As plastics based on fossil fuels become substantially more costly, the demand for them reduces dramatically. Globally, 0.08% fewer greenhouse gases will be emitted every year. Yet, part of this reduction is because of economic distortions, since the tax also slows down economic development.

More fields, fewer forests

Simultaneously, the forest area reduces by 0.17%, while the land area used for agriculture rises in the tax scenario. This translates into huge amounts of CO₂ being released into the atmosphere.

This is considered to occur as a one-time effect. Nevertheless, according to our calculations, it will take more than 20 years for it to be offset by the savings achieved by fossil substitution.

Dr Neus Escobar, Institute of Food and Resource Economics, University of Bonn.

All things considered, the shift to bioplastics will take a lot of time to pay off. Moreover, the scientists estimate the societal expenses of this policy to reduce one ton of CO₂ at over 2000 US dollars—which is a significant amount as compared to biofuel mandates. Although subsidizing bioplastics would have an entirely different impact on the worldwide economy, the costs for climate change mitigation a well as the compensation period would stay nearly the same as with the tax.

“Consuming bioplastics from food crops in greater amounts does not seem to be an effective strategy to protect the climate,” stated the researcher, particularly because this would set off several other negative effects, like increasing food prices. “But this would probably look different if other biomass resources were used for production, such as crop residues,” stated Escobar. “We recommend concentrating research efforts on these advanced bioplastics and bring them to market.”

The assumption that bioplastics will decrease the amount of waste present in the oceans may not even come true. Just the fact that plastics are made from plants does not essentially make them easily degradable in marine settings, Escobar emphasized. “Bio-PE and Bio-PET are for example not biodegradable, same as their petroleum-based counterparts.”

However, biomaterials and bioplastics have one distinct benefit: They aid in reducing the dependency of highly industrialized regions on fossil fuels. The researchers surmise that if governments truly wish to safeguard the environment, then they must implement a different approach: Using plastics sparingly and ensuring that it is really recycled make a lot more sense.