THE CARBON FOOTPRINT OF BIOPLASTICS
Bioplastics have a bad reputation when it comes to climate impact? Wrongly so! The carbon footprint of bioplastics is already lower than that of their fossil counterparts. And thanks to technological advances, we expect even further improvements. Even the EU has now classified bioplastics as sustainable in its taxonomy.
What are we talking about when we use the term carbon footprint?
The carbon footprint calculates, e.g. for a product, all the climate-damaging emissions it causes. However, the carbon footprint can also be calculated for an entire company, countries or one's own lifestyle. For the footprint, everything is considered that can be directly attributed to the product. This means that not only the energy consumption during use is considered, but everything from the extraction of raw materials to production, transport and disposal. This approach is also known as "cradle-to-grave".
The carbon footprint should not be confused with the life cycle assessment, short LCA, or an environmental footprint.
For these, many other impact categories are assessed, such as eutrophication, toxicity for ecosystems and humans, or the consumption of fossil resources.
And how do you calculate the carbon footprint of special materials like bioplastics?
In this particular case, one usually considers only the processes up to the finished material. This is called from the cradle to the factory gate or "cradle-to-gate". The reason for this is that the use phase, the manufacturing of the final product and the disposal are very dependent on the final product. By excluding these steps, a largely universal comparison of the materials becomes possible. The carbon footprint of bioplastics therefore usually includes the steps from the cultivation of the plants, or extraction of the oil in the case of fossil plastics, to the finished plastic granulate.
The steps from cradle to gate in detail:
Plants bind CO2 while growing. In the carbon footprint of bioplastics, this amount is credited proportionally to the amount of biocarbon. In the ideal case, the production of bioplastics releases less CO2 than is absorbed by the corn or sugar cane. This leads to climate-positive materials.
In the next step, the biopolymer is produced from the plant-based raw materials. This is done either directly, e.g. via bacterial fermentation, or via several intermediate steps. In this case, the individual building blocks, so-called monomers, are synthesised from precursors and then connected to polymer chains. Frequently, additives or fillers are added to the polymers in order to obtain the desired properties such as colour or elasticity (more info). The finished bioplast has the form of pellets or granules and is ready for further processing into a final product.
Bioplastics also save energy during further processing into plastic products. This is because many bioplastics have a lower melting point than conventional plastics. However, since the footprint depends on the manufacturing process and thus on the end product, this step, like the use, cannot be calculated to be generally applicable.
Although most bioplastics are still relatively young materials, manufacturers have already achieved great improvements. Since the beginning of the industrial production of PLA 20 years ago...
the carbon footprint has dropped to a quarter of its original value!
But not only manufacturing is relevant.
Today, plastic products are usually incinerated at the end of their life. This releases CO2. With fossil plastics, it comes from deposits millions of years old. With bio-based plastics, however, only the amount of CO2 that was bound during cultivation is released. If the incineration is omitted, e.g. through material recycling, bio-based plastics even store atmospheric CO2 in the long term.
In a Nutshell
That bioplastics have a worse CO2 balance is a myth. They are already in most cases more climate friendly than fossil plastics with similar properties. The carbon footprint of bioplastics usually includes the cradle to gate process steps, i.e. from the cultivation of the raw materials to the finished bioplastic. This also includes a credit for the CO2 stored by the plants. But the disposal must also be considered.
And best of all, further technological development can be expected to bring additional improvements to the carbon footprint.
Do you want to delve deeper into the subject?
The BioPolyDat tool goes into detail about the scientific background of the carbon footprint and life cycle assessment. It was created by the Institute for Bioplastics and Biocomposites at the Hanover University of Applied sciences and Arts (ifBB) and the Fachagentur Nachwachsende Rohstoffe e.V. (FNR).