The great upswing of bio-plastics
Companies are increasingly looking at bio-plastics as the solution to reducing climate impact and littering. As a result, there is a growing variety of bio-plastics on the market today. There are bio-plastic alternatives for almost every conventional plastic material and application. But many questions remain: What are the things to look out for when considering a bio-plastic alternative? And in what cases can bio-plastics offer a climate-related solution to fossil-based plastics?
But first – what is considered a bio-plastic?
Bio-plastics are a diverse family of materials with varying properties. Europe Bioplastics distinguishes three main groups:
- Biobased or partially biobased non-biodegradable plastics: According to the European norm EN16575 these plastics are fully or partly developed from biological materials (biomass). Examples are biobased PE, PP, or PET. Also included in this group are biobased technical performance polymers such as PTT or TPC-ET;
- Plastics that are both biobased and biodegradable: a plastic that is fully developed from biological materials and that eventually decomposes into carbon dioxide, biomass or water. Examples of such plastics are PLA and PHA or PBS. The product has to meet the European Norm EN13432 or the US Standard ASTM D6400 to be considered industrially compostable;
- And then there are plastics that are based on fossil resources and are biodegradable. Such plastics, like PBAT, decompose into carbon dioxide, biomass, or water. Again, generally under industrial circumstances.
The properties of bio-plastics have greatly improved in recent years and can compete with conventional plastics on the basis of flexibility, transparency, heat resistance, and gloss. Biobased or partially biobased non-biodegradable plastics are even technically equivalent to their fossil-based counterparts, therefore also known as drop-in plastics.
Production of bio-plastics is increasing but still small for most varieties
Although the demand is rising, the production of bio-plastics is still limited. In 2019, bioplastics represented about 1% of the 359 million tonnes of plastic produced annually. For most bio-plastics, there are only several suppliers. As a result, on a weight basis, bio-plastics are currently more expensive than fossil-based plastics. But when the economy-of-scale of production, conversion into products and logistics improve, the prices of bio-plastics may decrease. And the advantage that bio-plastics have over their fossil-based counterparts is that they do not depend on fluctuating oil prices.
Bioplastics show great potential for greenhouse gas emission reductions
Although the climate impact varies per bio-plastic type, from a cradle-to-grave perspective their greenhouse gas (GHG) emissions are generally lower than fossil-based plastics. In contrast to what is sometimes thought, the GHG emissions of bio-plastics are not zero due to their ‘natural origin’ and are not a carbon sink as a result of the carbon uptake of the biomass. The overall cradle-to-grave GHG reduction varies between 14% and 65% depending on the type and life cycle of the bioplastic. A number of factors play a critical role in the potential size of GHG reduction:
- Choice of raw material: The bio-plastics made from fermentable sugars, like sugar cane and sugar beet, are preferable to cereal crops, like maize. Mainly because sugars, by-products, or product waste can be used and there is no competition with food production. This is also the case for other waste types, like used cooking oil as a basis for the bio-plastic. Therefore, the GHG emission savings in comparison to fossil-based plastics is not as high if maize starch is used. In the raw material choice, care should also be given to maintaining the soil quality at a sustainable level.
- Accurate reflection of treatment at end-of-life (EoL): For bio-plastics the EoL varies, depending on the material and application chosen. In general, mechanical recycling is the most environmentally friendly EoL option. It can reduce the GHG emissions of EoL by 60% to 80% compared to incineration, depending on the type of bio-plastic material. Especially for drop-in bioplastics, that can be recycled in existing recycling schemes, the GHG reduction is high. However, for some of the popular bio-plastics, like PLA, recycling is not commercially available and sometimes even adds complexity to the separation process. Mechanical recycling is then followed by incineration or digestion as the second-best option, and the composting of biodegradable bio-plastics is the lesser favorable option.
Currently not a solution for the reduction of environmental littering
Although in most cases, bio-plastics can reduce GHG emissions, when handled correctly at EoL, the potential of reducing environmental pollution when plastics end up in the environment is currently limited. Various studies have revealed that bio-plastic items, including biodegradable ones, are still intact after years in the sea or buried underground, thus causing great impacts on aquaculture, marine ecosystems, habitats, and biodiversity.
Some common non-biodegradable polymers, such as oxo-degradable bio-plastics, can even be deemed worse than fossil plastics, as they fragment rapidly, causing an increased rate of microplastic formation. According to the EU Single-use Plastic Directive, bio-based and biodegradable plastics are therefore also seen as single-use plastics and do not solve the plastic pollution issue.
So, are bio-plastics a good alternative to fossil-based plastics?
There are quite some critical elements to take into account when determining the climate impact reduction of bio-plastics compared to fossil plastics. When considering climate impact from a GHG reduction perspective bioplastics are more a climate “friend” than “foe”. But it is not that simple. To ensure a real climate impact improvement the type of the chosen bio-plastic(resource material) and its end-of-life (treatment type and avoidance of littering) are crucial. Therefore, understanding the life cycle of the biobased material as well as how the carbon emissions are released throughout the product life cycle is essential for appropriate environmental emissions accounting.
 Biobased Plastics in a Circular Economy, Ministry of Infrastructure and Environment & CE Delft, September 2017; Environmental impact assessments of innovative bio-based products, European Commission &COWI, December 2018; Bio-based and biodegradable plastics – Facts and Figures, Wageningen University Research (WUR), April 2017.
 Since there are technical challenges for all end-of-life options, depending on the material, country, etc, in practice it is less straightforward to be able to choose to recycle or digestion/composting freely.