Designing a Circular Economy for Plastics: The Role of Chemical Recycling in Germany

Greenhouse gas emissions from human economic activity are causing global warming, leading to numerous impacts, including sea level rise, biodiversity loss, and increases in extreme weather events. For this reason, parties involved in the Paris Climate Agreement agreed to limit global warming to reduce its impacts. The second largest global emitter of carbon dioxide is the industrial production of goods. Within industrial production, the chemical industry with the production of olefins and other high-value chemicals for, among other things, plastic production, has a significant impact. Therefore, the present dissertation addresses designing a circular economy for plastics employing chemical recycling, contributing to the decarbonization and defossilization of the German chemical industry. Five studies published as companion articles address substantial aspects of the chemical recycling of plastic waste as well as barriers to establishing a circular economy. Study A assesses chemical recycling via pyrolysis for lightweight packaging waste and shows that combining the currently predominant mechanical recycling with chemical recycling has economic and environmental advantages over employing these technologies individually. At the same time, more carbon can be recycled, reducing the dependence on fossil resources. Study B shows the importance of integrating the quality of secondary materials in assessing recycling routes. The preferable recycling technology can change based on the quality metrics and their integration into the assessment. Study C conducts pyrolysis experiments for automotive plastic waste and includes the generated data in an economic and environmental assessment of a chemical recycling route. Different economic and environmentally preferable waste handling options are identified when comparing chemical recycling with waste incineration with energy recovery. Study D examines the economics of automotive plastic waste pyrolysis and identifies the minimum plant input capacity at which the pyrolysis is economically feasible in German framework conditions. Study E combines the collected findings in a facility location optimization model for pyrolysis plants treating lightweight packaging and automotive plastic waste in Germany\u27s current waste treatment network. Political steering strategies are analyzed to align economic and environmental objectives in the waste treatment sector. In addition to the detailed results of the individual studies, four overarching implications are derived: First, waste containing primarily polyolefins and engineering plastics can be technically pyrolyzed and are a suitable feedstock for chemical recycling. However, the most significant waste quantities studied are generated in short-lived lightweight packaging. Second, chemical recycling is environmentally preferable over waste incineration with energy recovery for all assessed waste streams. Economically, chemical recycling is not preferable compared to waste incineration with energy recovery for automotive plastic waste resulting in a conflict of economical and environmentally preferable waste handling options. Third, the quality of the secondary materials must be considered when assessing waste recycling options, as this strongly influences economic and environmental assessment. Fourth, political steering strategies like the extension of CO$_{2}$ certificate trading and introducing recycling rates for waste that is a feedstock for waste incineration with energy recovery can align economical and environmentally preferable waste treatment options. Consequently, the present dissertation provides valuable insights into the role of chemical recycling when designing a circular economy for plastics. Therefore, it has the potential to significantly contribute to closing the circularity gap of plastics

Regional rotor blade waste quantification in Germany until 2040

Worldwide, wind turbine stocks are ageing and questions of reuse and recycling particularly of rotor blades become urgent. Especially, rising rotor blade wastes face lacking good recycling options and exact quantification is difficult due to information gaps on the rotor blade size, mass and exact material composition. In a combined approach, the expected rotor blade waste is quantified and localized on a national level for Germany until 2040. Fibre-reinforced plastics (FRP) from rotor blades are in focus and differentiated into two material classes: glass-fibre reinforced plastics (GFRP) and glass- and carbon-fibre reinforced plastics (GFRP/CFRP). The quantification approach is based on a national power plant stock database (Marktstammdatenregister) and regression models, combined with a power class-based estimation for missing datasets. As a result, between 325,726 and 429,525 t of waste from the GFRP material class and between 76,927 t and 211,721 t of waste from the GFRP/CFRP material class arise from obsolete rotor blades in Germany until 2040. This corresponds to a share of between 11% and 32% of wind turbines with GFRP/CFRP rotor blade material in Germany. For GFRP, waste peaks in 2021, 2035 and 2037 are expected with around 40,000 t of waste per year. For GFRP/CFRP, waste peaks in 2036 and 2037 will induce more than 20,000 t/a. Mostly affected federal states are Lower Saxony, Brandenburg, North Rhine-Westphalia and Schleswig-Holstein. The methods are applicable and transferable to other countries, particularly with ageing wind turbines fleets

Designing a Recycling Network for the Circular Economy of Plastics with Different Multi-Criteria Optimization Approaches

A growing plastic production increases the pressure on waste management systems, which have to cope with greater volumes of plastic waste. Increased plastics recycling can reduce environmental impacts by lowering the need for primary plastics production and thus fossil resources demand. Current research is mainly focused on identifying environmentally friendly recycling technologies for different waste streams. However, recycling capacities must also be expanded to handle the waste generated. Therefore, this paper develops multiple exemplary multi-criteria optimization models to design an optimal recycling network. The models are deployed in a case study for plastic packaging waste in Europe for an advanced mechanical recycling process. We compare the different multi-criteria optimization approaches, how they balance environmental and economic aspects differently, and how this affects the recycling network design. Finally, we compare the optimization approaches and find goal programming the most promising approach for recycling network design that ensures a balance between economic and environmental objectives

On the combination of water emergency wells and mobile treatment systems: a case study of the city of Berlin

A shortage of water leads to severe consequences for populations. Recent examples like the ongoing water shortage in Kapstadt or in Gloucestershire in 2007 highlight both the challenges authorities face to restore the water supply and the importance of installing efficient preparedness measures and plans. This study develops a proactive planning approach of emergency measures for possible impairments of water supply systems and validates this with a case study on water contamination in the city of Berlin. We formulate a capacitated maximal covering problem as a mixed-integer optimization model where we combine existing emergency infrastructure with the deployment of mobile water treatment systems. The model selects locations for mobile water treatment systems to maximize the public water supply within defined constraints. With the extension to a multi-objective decision making model, possible trade-offs between the water supply coverage and costs, and between the coverage of differently prioritized demand points are investigated. Therefore, decision makers benefit from a significantly increased transparency regarding potential outcomes of their decisions, leading to improved decisions before and during a crisis

Chemisches Recycling von Automobilkunststoffen mittels Pyrolyse

In the past, the amount of plastic waste steadily increased in Germany. Plastic waste from automotive applications challenges existing mechanical recycling processes due to its material heterogeneity and complexity. However, chemical recycling via pyrolysis has the potential to recycle these plastics, obtain a high value recycled plastic with the quality of virgin material, and reduce the use of primary material. To date, no mass and energy balances are available to assess the performance of the pyrolysis process itself nor the process chain it is embedded in. This study conducted experiments with automotive plastic waste from garages in a pyrolysis screw reactor. The resulting pyrolysisproducts‘ mass and elemental compositions were determined and balanced considering reasonable assumptions. It was shown that about 70 % of the automotive waste plastics‘ inherent carbon was transferred to pyrolysis oil. When considering the entire process chain from waste sorting, pyrolysis of the sorted waste, pyrolysis oil upgrading, and subsequent steam cracking producing ethane, propene, butadiene, and pyrolysis gasoline, a carbon efficiency of approximately 55 % was calculated based on the experimental data, assumptions and data from literature. Elsewhere, similar experimental results have been found for the pyrolysis of plastic waste from post-shredder treated automotive shredder residue (ASR) from end-of-life vehicles. With a yearly amount of approximately 68,000 tons of ASR in Germany, the potential of chemical recycling via pyrolysis becomes apparent. Future studies should focus on the economic and ecologic assessment and optimized performance of such a process chain. In addition, a better database for pyrolysis oil upgrading and pyrolysis oil steam cracking is needed to yield more accurate results in the assessment of chemical recycling via pyrolysis

Economic and environmental assessment of automotive plastic waste end‐of‐life options: Energy recovery versus chemical recycling

Most automotive plastic waste (APW) is landfilled or used in energy recovery as it is unsuitable for high-quality product mechanical recycling. Chemical recycling via pyrolysis offers a pathway toward closing the material loop by handling this heterogeneous waste and providing feedstock for producing virgin plastics. This study compares chemical recycling and energy recovery scenarios for APW regarding climate change impact and cumulative energy demand (CED), assessing potential environmental advantages. In addition, an economic assessment is conducted. In contrast to other studies, the assessments are based on pyrolysis experiments conducted with an actual waste fraction. Mass balances and product composition are reported. The experimental data is combined with literature data for up- and downstream processes for the assessment. Chemical recycling shows a lower net climate change impact (0.57 to 0.64 kg CO2e/kg waste input) and CED (3.38 to 4.41 MJ/kg waste input) than energy recovery (climate change impact: 1.17 to 1.25 kg CO2e/kg waste input; CED: 6.94 to 7.97 MJ/kg waste input), while energy recovery performs better economically (net processing cost of −0.05 to −0.02€/kg waste input) compared to chemical recycling (0.05 to 0.08€/kg waste input). However, chemical recycling keeps carbon in the material cycle contributing to a circular economy and reducing the dependence on fossil feedstocks. Therefore, an increasing circularity of APW through chemical recycling shows a conflict between economic and environmental objectives