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Chemical recycling could facilitate the transition from a linear to a circular carbon economy, where carbon-containing waste is channeled back into the production cycle as a chemical feedstock instead of being incinerated or landfilled. However, the predominant focus on technological aspects of chemical recycling for plastic waste narrows evaluations of its potential in contributing to such a transition. Moreover, it leads to significant controversy about its role in the waste hierarchy as a possible competitor to mechanical recycling. To address these gaps in the literature, this study assesses ecological and economic impacts associated with chemical recycling of residual municipal solid waste in Germany. Combining approaches of life cycle assessment and techno-economic analysis, chemical recycling and conventional incineration-based treatment pathways are comparatively evaluated in terms of global warming potential and economic performance (i.e. fixed capital investment, net present value, dynamic payback period, and levelized cost of carbon abatement). Results indicate that compared to incineration-based conventional pathways, chemical recycling can contribute to reducing greenhouse gas emissions in low-emission energy systems. However, the economic performance of chemical recycling is highly dependent on its scale of operation. Additionally, a price premium for recycling products as well as economic instruments for penalizing CO2 emissions are identified to play important roles in the economic performance of chemical recycling.

Process metallurgy is a key enabler and the heart of the Circular Economy (CE). This paper shows the state-of-the-art approach to understanding the resource efficiency of very large-scale CE systems. Process simulation permits system-wide exergy analysis also linked to environmental footprinting. It is shown that digital twins of large CE systems can be created and their resource efficiencies quantified. This approach provides the basis for detailed estimation of financial expenditures as well as high-impact CE system innovation. The cadmium telluride (CdTe) photovoltaic technology life cycle, which brings several metal infrastructures into play, is studied. The results show that considerable work remains to optimise the CdTe system. Low exergy efficiencies resulting specifically from energy-intensive processes highlight areas with the greatest renewables-based improvement potential. This detail sheds light on the true performance of the CE and the inconvenient truth that it cannot be fully realised but only driven to its thermodynamic limits.

The chemo-enzymatic epoxidation of Lallemantia iberica seed oil (LISO), a novel plant oil characterized by its exceptional high content of alpha-linolenic acid (> 60%), was developed using an immobilized lipase from Pseudozyma antarctica and hydrogen peroxide as oxidant. A statistical approach was used to study the effect of enzyme amount, temperature, time, and solvent amount on the oxirane oxygen content obtained during epoxidation. An oxirane oxygen content of 8.6 ± 0.2% corresponding to a yield of 82% was obtained under optimized conditions that were identified to be at an enzyme load of 8.2 g/mol of double bonds, a solvent amount of 56.4 wt.%, a temperature of 33 deg C, and an incubation time of 17 h. In addition, the experimental investigation was combined with a techno-economic and ecological assessment gaining detailed information regarding cost structure and environmental impact for the chemo-enzymatic epoxidation of the novel plant oil.

Minerals and metals required to produce renewables and everyday electric and electronic technologies are extracted from both geological (primary) and urban (secondary, recycling) mines. Extraction and recycling process complexity is often neglected in impact assessments. Treatment of interconnected components in isolation is physically impossible, and should be reflected in impact assessments. Claims of completely closed loops neglect irreversible losses governed by the thermodynamics. Aggregation of complex processes into average “black boxes” reduces resolution, removing the ability to allocate impacts and optimise circular economy systems that are often geographically and temporally dispersed. We aim to expand and integrate existing frameworks, models and tools, including fundamental thermochemistry, process simulation, life cycle inventory and impact assessment, costing and thermoeconomics, and to utilise multi-criteria optimisation to conduct holistic assessments and optimisation of resource efficiency, losses and impacts of entire circular economies at high resolution. This will benefit stakeholders from operational through to policy-making levels.

For assessing and calculating biomass value chains the costs for transportation are the most important factor the economic performance as they form the largest share of the overall production cost. The objective of this work is to develop a methodology that includes not only the distance in the calculation of transportation costs. The main purpose is to also optimize the choice of transport mode depending on the given circumstances. These are especially the distance from the harvesting site to the subsequent processing or storage unit, the transported biomass with its distinctive properties (moisture content, bulk density etc.) and the required harvesting method. To achieve this, a model is elaborated that calculates the minimal overall transportation costs of a biomass-based supply chain comprising fixed and variable costs of the chosen transportation method. This could extend existing supply chain models for the elaboration and assessment of biomass-based value chains by a more comprehensive transportation modelling., Proceedings of the 22nd European Biomass Conference and Exhibition, 23-26 June 2014, Hamburg, Germany, pp. 170-177

The described work investigated ethanol-water fractionation of beech wood as the basic technology for a lignocellulose biorefinery. The main products were glucose, lignin and xylose. The fractionation technology was studied, scaled-up and successfully implemented on pilot scale. Based on an Aspen process simulation of an industrial production plant, the process was assessed economically and ecologically, pointing out the potential benefits of a "lignocellulose biorefinery" and the importance to valorize all the obtained fractions. The process assumptions of the assessment have been tested at the pilot plant and its feasibility was verified.

The aim of this study is to model and assess different biomass-to-liquid (BtL) pathways for the production of fuels and chemicals via dimethyl ether (DME) synthesis as well as via Fischer-Tropsch (FT) synthesis. The conversion of lignocellulosic biomass, such as residual wood or straw, to synthetic fuels and chemicals is currently under development at the Karlsruhe Institute of Technology (KIT). Within the considered bioliq® concept, so-called slurry is produced by multiple decentralized fast pyrolysis plants and is then processed in a single centralized pressurized entrained flow gasifier. The resulting syngas has to be conditioned and cleaned before it is converted in a DME or FT synthesis in order to complete the biomass-to-liquid (BtL) production. This two-stage concept allows the economic transportation of biomass over long distances, due to the relatively high energy density of the slurry produced in the first stage. In addition, reductions in specific investments and costs for further processing in the second stage are enabled by economies of scale. This study addresses possibilities for further process development and presents an outlook for a commercial implementation of biomass-derived fuels and chemicals., Proceedings of the 21st European Biomass Conference and Exhibition, 3-7 June 2013, Copenhagen, Denmark, pp. 1975-1983

This assessment focuses on the gasification process step which converts a biomass-derived intermediate called slurry into synthesis gas (syngas) for subsequent synthesis of fuel and chemicals. The slurry is produced by fast pyrolysis plants and is processed in a pressurized entrained flow gasifier. The resulting syngas is conditioned and cleaned before it is converted in a Fischer-Tropsch or dimethyl ether synthesis in order to complete a biomass-to-liquid (BtL) production such as the considered bioliq® concept which is currently under development at the Karlsruhe Institute of Technology (KIT). This two-stage concept allows economic transportation of biomass over long distances due to the relatively high energy density of the slurry produced in multiple decentralized plants and economies of scale in the centralized gasification and synthesis stage. Different process configurations regarding operating pressure, gasification agent, syngas conditioning and feedstock composition of a commercial scale gasification plant for the production of clean syngas are analyzed from an energetic and economic point of view., Proceedings of the 20th European Biomass Conference and Exhibition, 18-22 June 2012, Milan, Italy, pp. 942-947

An amendment to this paper has been published and can be accessed via a link at the top of the paper.