The aim of this study was to identify the most sustainable way to produce char from sewage sludge that later can be used as a coal substitute for the steel industry. For this purpose, a literature review was conducted on the latest technological developments for the production of char, which were subsequently simulated in Aspen Plus to obtain process-specific details. The results of the process simulation are then combined with the Life-Cycle-Assessment (LCA) database EcoInvent to assess the environmental impact of the entire value chain for all countries of the European Union using the LCA methodology according to the ISO 14040 framework and the environmental footprint impact family. This family consists of 19 impact categories of which five relevant categories were chosen: (I) climate change, (II) acidification, (III) freshwater ecotoxicity, (IV) freshwater eutrophication and (V) marine eutrophication. In a second analysis the LCA is combined with the integrated assessment model REMIND, which represents the technological evolution in the future. This allows to evaluate the environmental impact in the years 2030 and 2040.
From the literature review, two technology developments that significantly can reduce the overall electricity consumption of the process were identified: an industrial dryer that can dry sewage sludge at 90% efficiency and a heat pump that can convert moist exhaust air into process heat with an efficiency of 400%. Furthermore, the Torwash process was identified, as a pre-processing step for sewage sludge, which increases the efficiency of the filter process and the subsequent drying of the sludge. Based on the results of the literature research, three different technology scenarios were defined. (I) In the baseline scenario, the gases and bio-oils formed during the slow pyrolysis reaction are burned to produce sufficient process heat for the pyrolysis unit and the drying step. (II) In the Torwash scenario, the feedstock is thermally treated before the filtration, which allows a higher solid content in the filter cake and thus reduces the energy consumption in the drying step. (III) The bio-oil scenario considers the condensation of bio-oils and provides the missing process heat with electric heaters.
The process simulation in Aspen Plus was used to determine several process-specific details, including the energy content of the combustion process and the resulting CO2 emissions. Moreover, the overall energy balance of the different scenario was calculated and the need for external heat was determined. The process simulation additionally revealed a factor not described in the literature yet that influences the energy consumption of the pyrolysis reaction. The higher the ash content of the feedstock, the less energy is required for the pyrolysis process.
In the LCA, the simulation results were combined with further background processes and environmental information from the LCA database EcoInvent and compared against a business-as-usual alternative. In this alternative, the sludge is incinerated and coal with a comparable heating value to the produced char is provided. The results show that the baseline scenario performs better than the business-as-usual alternative in all impact categories. The Torwash scenario, due to the high energy requirements of the pretreatment, performs worse than the baseline scenario in all impact categories and in all but freshwater eutrophication also worse than the business-as-usual alternative. For the bio-oil scenario, the type of heat supply and the CO2 intensity of the electricity grid is of great importance. If an inefficient resistant heater is used, the bio-oil scenario performs better than the baseline scenario in only half of the European countries, depending on the specific CO2 intensity of the national electricity mixes. If, instead, a highly efficient heat pump is used, the environmental impact is lower for all EU member states for all impact categories. The difference between the baseline and the bio-oil scenario becomes even larger when the environmental impact is determined for 2030 or 2040. If a conservative integrated assessment model which leads to 2.5°C warming by 2050 is used as the basis for technological change, the emissions of the bio-oil scenario are 3.020 kg CO2eq per ton of char, more than 9% lower than the baseline scenario and almost 42% lower than the business-as-usual alternative. In addition, to the ton of char, 120 l of bio-oil are produced, with an economic value that offsets the additional cost of electricity.
Therefore, the strong recommendation is expressed to produce char of sewage sludge according to the bio-oil scenario, with includes the latest drying and heat-pump technologies as well as the co-production of bio-oil.

As the world grapples with the escalating challenges of climate change, Carbon Capture and Storage (CCS) emerges as a crucial solution, especially for decarbonizing dominant industries such as steel, cement, and petrochemicals. The Intergovernmental Panel of Climate Change (IPCC) and the International Energy Agency (IEA) have highlighted the potential of CCS in addressing the pressing need for large-scale decarbonization. However, the widespread adoption of CCS is hindered by various challenges, including financial, organizational, technical, and governance aspects. Within this context, the research delves into the central question: "How can an evaluation framework combining both project- and policy-related factors provide a better understanding of the deployment of full-chain CCS projects, and how is it developed and implemented?"

To address this pivotal question, the study employs a multifaceted methodology. Literature research, semi-structured expert interviews, the Best-Worst Method, and a project maturity table are utilized to derive comprehensive insights. Factors influencing CCS projects are systematically categorized into six groups: political-legal, economic, social, technical, ecological, and organizational. Additionally, the research presents two in-depth case studies, ROAD and Longship, offering a practical lens into the challenges and triumphs of real-world CCS projects. The culmination of the research is a robust evaluation framework that provides a systematic approach to assess various facets of CCS projects. This framework emphasizes critical areas for resource allocation, stakeholder communication, legal clarity, and financial stability. In essence, this research not only addresses its foundational question but also crafts a multifaceted tool that stands to benefit stakeholders, guiding informed decision-making and enhancing the prospects of CCS projects' success and longevity.

The primary objective of this study was to address the lack of understanding of the commercial- scale implementation of novel CO2 based carbon nanomaterial (CNM) production and its comparison with status quo CNM production processes using unsustainable fossil resources. To accomplish this objective, first, a literature review was performed on the status quo commercial- scale CNM production, the lab-scale CO2 based processes and the CNM market. In regards to the status quo processes, the literature review yielded mainly chemical vapor deposition (CVD) processes of carbon nanotubes (CNTs) and graphene production. With respect to the lab scale CO2 based processes, the literature review involved categorising the identified processes into four different approaches based on their working principles - CO2 based CVD, molten salt based electrochemical CO2 reduction, liquid metal catalyst aided CO2 reduction and metal reductant enabled CO2 reduction. With regards to the CNM market, CNT materials were found to have the highest market share followed by that of graphene. Startup spinoffs working on the graphene and CNT production from CO2 were identified with origins to university-based research groups.

Following such literature review, a framework was developed to select one process each from the status quo CVD processes and the novel CO2 based processes, which produced comparable CNM. This framework was applied to the processes obtained from the literature review, which led to the selection of a methane-based CVD process and a molten salt-based electrochemical CO2 reduction process for small-diameter multi-walled (MW) CNT production. The methane-based CVD process involved the use of Ni-Mo catalyst on MgO support and high-temperature operating condition of 975°C. The molten salt-based electrochemical CO2 reduction process involved the use of Ni and steel electrodes, pure molten Li2CO3 electrolyte and high-temperature operating condition of 750°C. These selected processes were designed and simulated in Aspen Plus at a commercial-scale production level of 5000 tonnes per operating year. The mass balance, energy balance, and equipment cost data obtained from the simulations were used to assess the technical, economic, and environmental performance of the ex-ante CO2 based production process and the status quo CVD production process.

The technical performance assessment involved the estimation of resource intensity and energy efficiency indicators of the two processes, wherein the CVD process outperformed the electrochemical process in both indicators. The economic performance assessment involved the estimation of total capital investment, operational expenditure, net present value, and payback period. The CVD process performed better than the electrochemical process in all the indicators except total capital investment. Both processes indicated positive net present values and short payback periods, indicating the realisation of commercial scale plants of both processes to be profitable. The environmental performance assessment was carried out using the life cycle assessment methodology in the CMLCA software. The climate change impact indicators at scope 1 and 2 levels along with the net avoided impact from using CO2 were estimated using the CML 2001 impact assessment family. The electrochemical process was shown to perform considerably better than the CVD process in all the climate change impact indicators. Overall, the technical and economic performance of the CVD process was better than that of the electrochemical process. However, the environmental performance of the electrochemical process was shown to outperform that of the CVD process.

The limitations associated with modeling decisions taken in the two processes and with the uncertainty associated with the lack of data were highlighted. Further, the relevance of this study was discussed with respect to the industrial symbiosis potential of using waste CO2 from industries leading to GHG emission reduction and subsequent deceleration of climate change impacts. Finally, future potential studies were highlighted that could build on the research and insights generated in this study. One of these studies involved a case study on the implementation of a commercial-scale electrochemical process for MWCNT production in Port of Rotterdam region. Another study involved a techno-economic and environmental assessment of atmospheric CO2 capture and conversion to carbon nanomaterials for applications that can potentially achieve net negative emissions.

When it comes to the modification of a fossil- to bio-refinery, the reuse of a standardized design is unprecedented. Factor in the presence of stakeholders with varying interests and opinions equates to a highly complex system. Alignment of the stakeholders is therefore recognized to be necessary. The possibilities on how to make such a refinery modification less complex through the alignment of the relevant stakeholders became the goal of this study. To achieve it, a framework has been developed, and the necessary data to construct it shall come from interviews with experts from the field and literature reviews. The findings show that alignment of the stakeholders on the requirements that need to be considered for
modification projects can help in increasing the success of the implementation of a
standardized refinery modification design. To test the framework, it was implemented in an engineering company’s refinery modification project. Out of the framework implementation advice has been formulated on how to further help the engineering company to become successful in aligning their stakeholders and to effectively implement a standardized refinery modification design.

Improving sustainability in industrial processes is a key topic for the welfare of the environment. One of the major environmental problems caused by industrial processes is industrial waste production. In the automotive industry, the use of polymers such as PA12 for prototyping produces tons of waste per year which are generally destined to incineration. Recycling could help reduce waste, but recycling procedures can be resource-consuming, therefore it might not always be efficient or more sustainable than traditional practices. In most cases, recycling involves extra steps in the process value chain, including finances, transportation, workforce, as well as machinery. To make sure recycling has positive effects in terms of sustainability on industrial processes, a framework to assess the sustainability of recycling procedures is needed.

In this study, it is proposed an assessment framework which considers four pillars of sustainability: (1) technical, (2) environmental, (3) economic, and (4) social. While the environmental, economic, and social pillars are usually considered in sustainability assessments, the technical pillar has been neglected and should be considered in understanding the sustainability of recycling procedures. This framework can be applied to gain insights into recycling procedures’ sustainability and help as a tool to decide which procedure to adopt. Likewise, it considers the company’s needs and objectives, as fundamental factor for the evaluation. In recycling procedures, the technical pillar should include indicators related to resource efficiency but also recycled material quality, an essential factor when evaluating their effectiveness. Such a framework, consisting of a ten steps approach, aims to facilitate the adoption of recycling procedures, through qualitative and quantitative assessments, on the basis of a set of indicators, selected within the four pillars of sustainability.
From the analysis of the current system, to the definition of objectives, design of the pathways, and the evaluation of sustainability indicators, the framework aims to allow companies to systematically assess and select a sustainable pathway in terms of defined objectives and environmental regulations.

The framework was applied to the case study of mechanical recycling of PA12 waste from automotive prototyping. The aim is to reduce plastic parts waste, to be turned into filament for Additive Manufacturing technologies for use as jigs and fixtures. Following systematically the assessment framework, ten potential recycling pathways were identified and compared. Major differences among them include the ratio of waste parts to virgin material, and filament extrusion location. The sustainable recycling pathway that resulted from the evaluation features the shortest transportation distances (connected to lower carbon footprint and energy consumption, and higher flexibility). The application of the framework provided a trade-off analysis, where not only the interests on the environment are considered, but particular attention is given to companies’ needs and opportunities.

Due to the heavy dependence on fossil-fuels as raw materials, the defossilization of feedstocks in the petrochemical industry represents a challenge. A large number of possible process routes that use alternative carbon sources (ACS) like CO2, biomass, and waste are being developed for the feedstock replacement. For instance, to produce ethylene, more than 40 ACS process routes were identified. These multiple options make the selection of the promising process route a complex task. By replacing feedstocks, a process can change significantly and the impacts related to these changes in a highly interconnected industrial cluster can create cascading effects due to system interdependencies. This work aims to understand the cascading impacts in carbon flows and prices of implementing an ACS production process in an ethylene cluster. The results show that PVC will be the highest impacted and defossilizing one value-chain can have cascading effect on other value-chains as observed for PET.@en

Ambitious decarbonization targets are introduced to combat climate change. According to the European Commission, sector coupling is required to achieve these targets. This includes the inclusion of renewables into sectors that are difficult to decarbonize, but also using resources more efficient, and introducing new clean fuels. Recent research has examined the increased integration of renewables into the energy system, or the coupling with other sectors, such as the heating industry. However, a paucity of studies investigated the integration of the transportation sector with the power sector based on different configurations of hydrogen supply chains, with hydrogen as a nodal connector. Some studies looked into the decarbonization of the transportation sector but diminished to explore how the coupling based on hydrogen supply chains including hydrogen storage could support the grid by providing balancing services. Therefore, the aim of this study was to examine potential designs for renewable hydrogen supply chains to provide joint applications, which are satisfying a hydrogen mobility demand, as well as providing balancing services to the power grid. However, the interconnection of the hydrogen system within the mobility sector, as well as the functioning power grid, based on the supply chain, poses multiple challenges on different levels. This complex problem requires solving in an integrated manner. In that regard, this thesis proposes a modelling approach for the optimal functioning of hydrogen generation and storage supply chains. Hereby the objective of the function is to maximize the profit of the supply chains through the supply of hydrogen fuel to the mobility sector and the contribution of balancing services to the power grid. The proposed optimization model is employed to perform a techno-economic comparison of two supply chain configurations: a distributed on-site supply chain, in which the hydrogen is generated at the fuelling stations, and a centralized off-site supply chain, where the hydrogen is centrally produced and afterwards transported to the dispersed fuelling stations. Both scenarios are quantitatively studied under two operating conditions, which are only selling to the mobility demand, and providing ancillary services to the power grid concurrently. It was found that both distributed and centralized hydrogen generation and storage supply chains can be used to offer hydrogen fuel to the transportation sector as well as provide different ancillary services to the grid. Furthermore, the numerical findings show that when both supply chains are planned and run concurrently for various ancillary services, the highest improvement in terms of financial parameters can be observed. The results also indicate that the profitability of the distributed and centralized supply chain is comparable under various operating conditions. However, while the distributed supply chain system presents better economic performances than the centralized supply chain system under the performed conditions, the centralized hydrogen supply chain has greater
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technological benefits than the distributed supply chain in terms of flexibility. Whereas the decentralized supply chain is more beneficial for smaller demands and a more isolated operation, the centralized supply chain can provide higher values to investors who must deal with larger demands and more interconnected systems. Because the majority of these systems will be operated by larger system operators, and the supply chain, including fuelling stations, will be increasingly connected to the energy sectors rather than operating independently, the centralized alternative is likely to be the most beneficial investment. The analyses reported in this study are useful to interconnected investors or system operators for assessing the technical and economic viability of the widespread deployment of distributed and centralized hydrogen generation and storage supply chains integrated with the power grid. Future research might investigate other system configurations, such as including the hydrogen backbone into the operation or integrating the hydrogen supply chain with diverse industries, such as the heating sector. Different renewable energy sources, such as biomass or hydropower, might also be included. Other research might involve dynamic hydrogen pricing or the engagement of various distribution modalities with global demand points. Finally, for the supply chain systems to be successful, the social aspect must be considered, in which numerous market regulatory and governance impediments must be identified and exploited.