According to projections, the global production of plastics exceeds 400 million tons each year. About one third of the plastic will be classed as plastic waste shortly after it has been used. There is still far too much plastic waste in the EU and in Germany. The German government and the EU are therefore focusing on reducing single-use plastic and are aiming at sustainable closed-loop processes and the recycling of plastic waste. Less than ten per cent of all plastics is currently recycled.
The different processes for recycling include energy recovery in power plants, emitting on a linear basis around three tons of CO2 per ton of plastic waste incinerated, mechanical recycling of predominantly single-variety plastic waste, and feedstock recycling of mixed plastic waste fractions which are difficult to process. In mechanical recycling, the plastic macromolecules are retained. In feedstock recycling, the macromolecules are converted into their basic chemical building blocks, oils or gases.
The ZSW is pursuing two innovative approaches in feedstock recycling for mixed plastic waste fractions. One is high-temperature pyrolysis leading to the production of turquoise hydrogen, and the other is hydrogasification with electrolysis hydrogen resulting in the production of methane, hydrocarbons and synthesis gases.
Alternatively, plastic waste can also be converted to turquoise hydrogen in a pyrolysis process.
This is another field in which the ZSW is developing new processes in order to find feasible ways of recycling, especially for mixed plastic waste fractions which are difficult to process. A high-temperature pyrolysis process could be used as a conversion technology requiring very little electricity to generate turquoise hydrogen. Carbon will emerge in this process as a valuable resource.
ZSW takes an innovative approach to recycling mixed plastic waste, including residuals containing PVC. Plastic waste is hydrogenated with renewable hydrogen produced by electrolysis. This way, the raw materials may be reclaimed and reused rather than incinerated to produce thermal energy. ZSW is focusing on a highly efficient, direct method of producing methane in a fluidized bed reactor. The infrastructure in place today for natural gas can serve to store, distribute and use the methane – CH4, a natural gas substitute – produced via this method. As an alternative, hydrogenating gasification can produce a syngas suitable for use in other applications, for example, to yet again produce plastics in keeping with the principle of closed-loop, low-CO2 carbon recycling.
