Around 3.3 million tons of plastic waste are incinerated in Germany every year, releasing more than 10 million tons of harmful carbon dioxide into the atmosphere. In addition, almost one million tons of plastic waste are exported abroad every year. In line with the vision of an energy transition, as also prescribed in the “Circular Economy Action Plan” adopted by the European Commission, there is an urgent need to leave behind the linear “take-make-waste” mentality of a throw-away society and to move towards a circular economy where value is added by recycling and resources are spared by reusing materials. Countries with an efficient circular economy will have clear advantages in the global marketplace. Compound recycling processes are already established for unmixed or easily processed plastic waste. The situation is entirely different when it comes to non-homogeneous or problematic plastic waste where the only solutions to date have been disposal or incineration. In the interests of economic and circular management, this waste must also be recycled – ideally into marketable recycled materials.
Thermolysis and pyrolysis are suitable processes for feedstock recycling and for the provision of recycled resources in gas, liquid and solid form. The organic source material is broken down into several products in the heating process. Problematic plastic waste, such as production residues and mixed fractions with impurities, can be turned into carbon-neutral hydrogen in high-temperature rotary kilns at temperatures of up to 1000 degrees. The process could be used primarily for packaging waste, such as multilayer packaging films which contain PVC or added fillers and reinforcing materials. A figure of 1.5 million tons per year is put on the volume of this packaging waste in Germany.
In addition to carbon-neutral, non-electricity-based hydrogen, it is thought that the process will be used to produce a versatile recycled carbon / recycled coke which could also be sequestered more easily than CO2 as a solid using “carbon capture and storage (CCS)” technology. If this process is successfully developed and scaled up to industrial proportions, it would be possible to sidestep existing incineration emissions which amount to up to three tons of CO2 per processed ton of plastic waste.
The ZSW has expertise in pyrolysis, gasification and high-temperature process engineering, as applied in reactor technology and its integration in the existing high-temperature test environment. There are plans to extend the existing high-temperature test environment in the ZSW laboratory by mid-2023 to include a high-temperature rotary kiln facility. The engineering team is currently designing a high-temperature rotary kiln reactor for this purpose. The aim is to develop a competitive, versatile and commercially scalable high-temperature rotary kiln system for plastic waste fractions which are difficult to process. This is an important step for the future generation of climate-neutral hydrogen and on the way to a circular economy without further use of fossil resources and resulting CO2 emissions.