Constance Ißbrücker, Head of Environmental Affairs at European Bioplastics e.V.

Life cycle assessment (LCA) has evolved to be the preferred tool to assess the environmental sustainability of certain products and materials. Recently it has also been used with great enthusiasm to compare bio-based with fossil-based plastics. It seems to be an easy instrument to draw conclusions on certain advantages or disadvantages of both material groups. However, there are quite some hurdles to overcome if you do not want to end up comparing apples with oranges again. 

There are several aspects to which attention must be paid in order to guarantee a fair comparative assessment. Fossil-based plastics have experienced many decades of continuous, often heavily subsidised, process improvements, whereas most bio-based alternatives are still at the beginning of their maturity/optimisation curve. Therefore, comparing fossil-based with bio-based plastics is comparing mature and immature production systems. Future improvements in terms of feedstock sourcing, production, conversion, and end-of-life options need to be considered and assessed by appropriate assumptions and modelling approaches.   

Additionally, it is often assumed that the applied inventory data of bio-based and fossil-based materials are comparable, but currently there is in fact no real level playing fieldFossil- and bio-based plastics datasets should be brought to the same level of quality in terms of their completeness, system boundaries, regional scope, and, of course, transparency. 
It is one of the inherent advantages of bio-based materials that they are produced from annually renewable feedstock, such as corn, sugarcane, or wood. Thus, CO2 is taken up from the atmosphere, and the biogenic carbon is locked up in the bio-based product. At the product’s end of life (i.e. when it can no longer be recycled), the carbon re-enters the natural carbon cycle via incineration or composting, thereby closing the material carbon loop. 

Bio-based plastics are independent of fossil resources and do not contribute to harmful environmental effects connected with the exploitation of fossil raw materials such as crude oil. Effects of the latter are, interestingly, hardly considered in LCA data modelling. In contrast to certain possible negative indirect effects connected with the sourcing of renewable feedstockNo doubt, it can make sense to look at factors such as ILUC (indirect land use change) and gain additional information on this subject, but when done, a playing field should be given by also considering indirect effects caused by fossil-based materials and their production. Furthermore, LCAs should not only focus on the negative impacts, but also account for indirect positive impacts, especially where these are of high relevance to a functioning circular economy (e.g. the beneficial effects on biowaste collection by using industrial compostable bio-waste bags).
Bio-based plastics offer multiple end-of-life options, depending on the material chosen and the application at hand. For example, bio-based drop-ins (e.g. bio-PE or bio-PET) can be mechanically recycled in the existing recovery streams. Industrially compostable materials that are certified in line with EN 13432 can be recovered through organic recycling. Any selected end-of-life option needs to be material and product-specific and reflect reality. 

Whatever impact categories are considered in a comparative LCA of fossil- and bio-based materials, a transparent and acknowledged methodology (like ISO 14040/44, or PEF methodology) must be the basis, without neglecting stakeholder involvement. In the end, the interpretation of the results is a crucial aspect and can, when done frivolously, be harmful for the whole bioplastics sector. Especially in policy context