The widespread use of bioplastics, which are plastics derived from renewable biomass sources such as corn, straw and food waste, appear to not have as much an effect on mitigating climate change as was first surmised.
This letdown was made public in a study from the University of Bonn in Germany that examined the potential implications of transitioning to plant-based plastics. The study suggests that shifting to plant-based plastics might have less than positive effects on easing climate change.
It also said an increased consumption of bioplastics will likely generate more greenhouse gas (GhG) emissions from cropland expansion on a global scale.
Plastics, which are usually made from petroleum, contribute heavily to global warming. Their production emits some 400 million metric ton of carbon dioxide per year worldwide. This amount is almost half of the total GhG that Germany emitted into the atmosphere in 2017.
It is estimated that by 2050, plastics might account for 15 percent of global CO2 emissions.
In principle, bioplastics are climate-neutral since they're made from renewable raw materials such as wheat or sugarcane. These plants absorb the CO2 from the air through their leaves.
This means producing bioplastics consume CO2. The net greenhouse gas balance of bioplastics is assumed to be zero. Bioplastics are often consumed as an environmentally friendly alternative.
The study notes that with the current level of technology, this issue of bioplastics playing a key role in mitigating climate change is probably not as clear-cut as is often assumed.
The production of bioplastics in large amounts will change land use globally, according to Dr. Neus Escobar, who works for the University of Bonn at its Institute of Food and Resource Economics. This fact will potentially lead to an increase in converting forest areas to arable land.
But forests absorb much more CO2 than wheat or sugar cane annually, mainly because of their larger biomass. Dr. Escobar said experience with biofuels has shown that this effect is not a theoretical speculation.
And, unfortunately, the increasing demand for green energy sources has brought massive deforestation to some tropical countries.
The team simulated the effects of an increased demand for bioplastics in major producing countries. They used a computer model to calculate the impacts of biofuel policies.
The team concluded it takes a lot of time for the switch to bioplastics to prove beneficial. They estimate the societal costs of this policy to decrease one metric ton of CO2 at more than $2,000 -- a large sum as compared to biofuel mandates.
They conclude that consuming bioplastics from food crops in greater amounts does not seem to be an effective strategy to protect the climate. Doing so will trigger many other negative effects such as more expensive food prices.
This grim scenario, however, will probably look different if other biomass resources such as crop residues were used for production, noted Dr. Escobar. The team recommends concentrating research efforts on advanced bioplastics and bringing them to market.
The belief that bioplastics will reduce the amount of waste in the oceans might not even be realized, said the study. Just because plastics are made from plants does not automatically make them easily degradable in marine environments, according to Escobar.
Bio-PE and Bio-PET are not biodegradable, which is the same disadvantage their petroleum-based counterparts possess.
Bioplastics and biomaterials, however, possess one clear advantage: they help to reduce the fossil fuel dependency of highly industrialized regions. The study finds that if governments really want to protect the environment, they should pursue a different strategy.
It also makes more sense to use plastic sparingly and to ensure it is actually recycled.
