Bioplastics reduce CO2 emissions
Part 13 of our interview series on Circular Economy: Interview with Prof. Dr. Hans-Josef Endres, head of IKK Institute for Plastics and Circular Economy at Leibniz University of Hanover
Plastics have a bad image. Can bioplastics contribute to changing attitudes?
Prof. Hans-Josef Endres: Bioplastics can have an impact on the image because they have advantages as regards the raw material as well as their disposal. Plastics have their bad image not only because they are related to petrochemistry, but also on account of their longevity. From the product point of view this is an advantage, but in terms of waste it is seen as a drawback. In truth, the situation of bioplastics is no better. On the contrary: In the public, the negative image of petrol-based plastics is often transferred to bioplastics, although they have advantages as they are compostable and also recyclable. Consumers do not differentiate.
Bio-based plastics are criticised because they use up food resources.
Prof. Endres: This criticism is too sweeping. The greenhouse effect also consumes acreage, and renewable raw materials are also used in the energy sector. Moreover, when we talk about raw materials for bio-based plastics we do not only mean those that are the basis for food but also cotton, rubber or linoleum as well as increasingly agricultural waste materials. But let's set that aside for the moment. If you manufactured the 350 million tons of plastics produced every year completely from bio-based materials, you would need about 5 per cent of the available acreage.
There are bio-based plastics and bio-degradable plastics. Which are better?
Prof. Endres: It depends on their application. Bio-based describes only the origin of the raw material used to produce the polymer. Plastics are bio-degradable when micro-organisms can metabolise the polymer structure in biological processes, completely independently of the raw material origin. For example, you can also make biodegradable plastics from crude oil and durable plastics from renewable raw materials. The very first plastics people made were all bio-based because back then we did not have crude oil.
Why should you produce bio-based plastics if it is not biodegradable?
Prof. Endres: One might also ask why produce bio-based plastics if you can make them petrochemically? The benefit is a reduction in CO2. Every plastic material is disposed of at the end of its useful life – by burning or, in case of many bio plastics, by composting. Bio-based plastics are climate-neutral as each plant absorbs as much CO2 in its lifetime as it emits when it is burned or it decomposes. In addition, the demand for plastics is rising. Soon we will no longer need 5 but perhaps 10 per cent of the crude oil reserves to produce plastics. For this reason, the mineral oil industry could more easily do without the plastics industry as a customer than vice versa; at present plastics still need petrochemical raw materials.
What is the current focus in the research of bio plastics?
Prof. Endres: A major research area is the development of so-called drop-ins. These are bio-based plastics which are identical in structure with their petrochemical counterparts, for example, polyethylene or PET made from bio-alcohol. Technically they offer the same properties as conventional plastics but ecologically they are better as they are bio-based, that means renewable.
In their plastics strategy, the EU focuses on recycling. Is that a problem for bioplastics?
Prof. Endres: Bioplastics can also be separated in the waste stream, recycled and made into new products. If they are composted or even burned, it is still natural recycling of the carbon by means of photosynthesis. When we recycle petrochemical plastics, the carbon is recycled technically. Drop-ins can also be recycled easily together with their petrochemical counterparts. Apart from this we have novel bioplastics, such as PLA. PLA must – just like any other plastics material – be separated from the waste stream. That means recyclability depends on the amount of available material. PLA is easily identifiably in the waste stream; it can be recycled, but due to the small amount it is currently not worthwhile to include a special sorting stage for PLA. Recycling of PET, for example, only developed with the rising amount of PET.
Research is also taking place in the field of bio-composites. What is their advantage over other material composites?
Prof. Endres: The case of carbon fibres shows the dilemma of composite materials. CFK has been optimised over many years, but researchers did not take into account the end of the life cycle. Carbon-fibre materials have very good performance characteristics, but it is difficult to dispose of them. In addition, the production of carbon fibres is very energy intensive. A car made of CFK components weighs clearly less and consequently consumes less fuel or energy. But the car needs to drive 150,000 kilometres for the CO2 resulting in its production to be offset. In the case of CFK the environmental pollution is shifted to the phase of fibre production and its unresolved disposal. This is where the advantages of bio-composites come in. They are also suited to produce light-weight materials. But here we have a material component with a bio-based raw material origin. At the same time, a natural fibre can be burned much more easily, CO2 neutrally. At the end of its life cycle the situation is much better than in the case of carbon fibres.
What is your view of German circular economy in the international context?
Prof. Endres: Several countries are moving in the same direction. Canada, for example, is also increasingly geared towards circular economy and wants to reduce the multitude of approved packaging plastics. But there, waste disposal logistics systems have not yet been properly established. In some Asian countries awareness of circular economy is also rising. However, in the US most plastic waste is dumped. Some European countries including Germany have a certain pioneering role in the field of recycling of plastics packaging. Germany already introduced dual systems more than 20 years ago. Germany has a technological edge in this field but has so far not really made use of it. Only now, with growing political and public pressure is the sector coming to life.