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Item type:Publication, Access status: with files , Biocatalytic strategies for sustainable epoxy polymer degradation and synthesis(2026); Epoxy resins are widely used for their excellent mechanical properties. In contrast, they pose significant sustainability challenges due to their petrochemical origin and highly crosslinked, non-degradable structure. Within the framework of this dissertation two primary challenges in the context of sustainable epoxy thermosets were addressed. First,the investigation ofthe enzymaticdegradation ofhighly crosslinked epoxy resins cured with aromatic amines. By employing a laccase-mediator system inspired by lignin degradation, the normally inert, densely crosslinked polymer network was rendered susceptible to oxidation. This approach paves the way for a mild, environmentally benign breakdown of an otherwise robust thermoset. Second, a bio-based synthesis route was developed for epoxidized thermoset monomers using the renewable resource linseed oil. Through a chemoenzymatic epoxidation of the unsaturated plant oils, sustainable epoxy precursors were produced as alternatives to conventional petroleum-derived monomers. The purification and curing performance of these monomers were evaluated, demonstrating that fully bio-based epoxy matrices can be achieved. Both strategies share the overarching goal of improving the sustainability of epoxy materials. By addressing end-of-life degradation and the utilization of renewable feedstocks, this work contributes to advancing thermoset polymers with reduced environmental impact.Publicationtype: Doctoral Thesis15 20 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Development of scalable solutions for the valorization of brewer’s co-products(2025); With the growing importance of sustainable industry transformation, the valorization of once considered waste streams is gaining traction. In this study, scalable strategies for the valorization of the brewing industry by-products brewer's spent grain and brewer's spent yeast were investigated and experimentally validated. Following biorefinery approaches and industrially relevant technologies, the results enable an informed decision about upscaling potentials and limitations of the proposed processes.Publicationtype: Doctoral Thesis63 49 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Untersuchung der Elektromethanogenese als eine mögliche Speichertechnologie für erneuerbare Energien(2025); Electromethanogenesis is a technology for converting carbon dioxide into methane. In the case of direct electromethanogenesis (-300 mV vs. SHE), without abiotically produced hydrogen, no significant methane production could be measured. In the case of indirect electromethanogenesis (-700 mV vs. SHE), with abiotically produced hydrogen, a daily methane production of 61 mmol/(m² d) with a coulombic efficiency of 73 % could be achieved using Methanococcus maripaludis. The simulation of a day-night cycle of a photovoltaic system demonstrated the flexibility of electromethanogenesis, which is essential for future storage technologies.Publicationtype: Doctoral Thesis38 39 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Inline analytical supported process development towards alternative bio-based plasticizers(2021); Polyvinyl chloride (PVC) is nowadays the third most applied polymer with approximately 41 million tons produced in 2017. Plasticizers are added to the PVC polymer to increase the flexibility. The most common class of plasticizers are ortho-phthalic acid esters (phthalates). In the last years, the application of some of the latter was restricted due to health concerns. Therefore, the need for non-harmful alternatives arises. Additionally, bio-based plasticizer are a promising approach, since these will decrease the overall carbon footprint of the plasticized polymer. In this thesis, a three-step process is developed to produce bio-based plasticizers in a multi-gram scale using renewable resources as basis. Starting from 2-methylfuran and maleic acid anhydride, in a Diels-Alder reaction, a cyclic 6-membered ring intermediate for the plasticizing building block (1st step) is synthesized. This instable intermediate tends to undergo a retro-Diels Alder reaction and need to be stabilized via hydrogenation prior to further reaction steps avoiding the backwards reaction (2nd step). In a 3rd step, the cyclic plasticizer building block was successfully esterified at its acid groups in ortho-position. Here, 2-ethylhexanol, a standard alcohol applied in the synthesis of various plasticizers, is used. Additionally, the applicability of more than 80 enzymes for a biocatalytic esterification step was investigated. Throughout this work, inline analytic was employed for the characterization of the respective reaction steps. In detail, Fourier-transformed Infrared spectroscopy (FTIR) equipped with Attenuated Total Reflection (ATR) probes was implemented. These probes enable a non-destructive analysis directly inside the reactor vessel. To derive the respective concentrations from the recorded vibrational spectra, chemometric models were developed. In this work, the Indirect Hard Modeling (IHM) as a physically motivated hard modeling approach was applied. Besides using these established inline analytical methods in terms of process characterization, the inline measured data were used to set up kinetic models describing the each single reaction step. For this reason, the inline data were fitted to inline measured concentration profiles yielding the respective reaction rate constants. Concluding, in this thesis a promising approach for inline analytical-supported process development towards bio-based plasticizer is presented. Moreover, this approach can be transferred to other potential plasticizer candidates helping to reduce the time needed for the process development.Publicationtype: Doctoral Thesis208 912 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Treatment and substance recovery in landfill leachate permeates : an alternative sustainable approachIn this Doctoral work, landfill leachate is viewed as a RESOURCE without ignoring the environmental problems link to it. Substances including CaCO3-Rich Solids and Concentrated (NH4)2SO4 Solutions (≈20%) were recovered form a landfill leachate permeate generated in a treatment facility located at a landfill site in Northern Germany. Also more than 99% of the inorganic-N was removed from the treated permeates through Nitrification/Denitrification in FBBs. Additionally, explored applications for the reutilization of the recovered substances included pH correction of Acid Soil and Ammonium Sulfate Crystallization.Publicationtype: Doctoral Thesis591 934 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Investigation of a desiccant assisted geothermal air conditioning systemPublicationtype: Doctoral Thesis163 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Kultivierung der Mikroalge Chlorella sorokiniana zur Gewinnung von Naturwertstoffen im Rahmen eines BioraffineriekonzeptsPublicationtype: Doctoral Thesis109 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Development of an in situ extraction process of fatty acids from microalgae cultures(2018); In this work micellar extraction was investigated in order to develop an alternative process for the in situ extraction of hydrophobic substances from microalgae cultures. The main requirements for an in situ extraction process such as biocompatibility, phase separation behavior and partitioning of the hydrophobic target substance between micellar- and aqueous phases were studied for a number of surfactants. The cloud point temperatures (CPT) as well as the biocompatibility of the nonionic surfactants with the microalgae C. reinhardtii, C. vulgaris, and S. obliquus was determined as a function of time. It was shown that algae cells are concentrated in the aqueous phase, whereas the hydrophobic compounds (fatty acids) are enriched in the micellar phase. Significant differences in growth and the photosynthetic activity of different algae strains after exposure to surfactants were determined. Thus, besides extraction, surfactants might be applied to control the growth of certain algae enabling the monoalgal culturing in outdoor cultivation of microalgae since the growth of the less surfactant-tolerant microalgae could be suppressed. For the most biocompatible surfactant under study, Triton X-114 with a biocompatibility of 98%, the kinetics of phase separation in the temperature range between 30 and 40°C have been investigated. The fastest phase separation took place at a Triton X-114 concentration of 3%wt at 40°C. The partitioning of representative hydrophobic substances between the both phases was predicted using the model COSMO-RS, the results were compared to experimental data with satisfying agreement (LogPcalc. palmitic acid: 0.82; LogPexp. palmitic acid: 0.75). Based on these results the extraction of valuable compounds from the microalgae Scenedesmus obliquus was realized on a pilot plant and compared to the lab scale experiments. Overall, the results indicate that a continuous micellar extraction with nonionic surfactants offers the opportunity for an in situ extraction of hydrophobic substances directly from the culture medium and is a promising alternative to a classic solvent extraction of dried algal biomass.Publicationtype: Doctoral Thesis773 1242 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Material flow analysis of the urban water system in Tepic Mexico: Integral evaluation and improvement optionsA Material Flow Analysis (MFA) was carried out for the integral assessment of the urban water system In Tepic, Mexico by means of a computer model and scenarios representing the city in year 2007, 2011 and 2030. Based on the results of the MFA, following improvement options were investigated and evaluated: consumption control and reduction, infiltration reduction and improved rain water management. Additionally, a concept to measure the sewer infiltration and exfiltration in Tepic was developed and the safe reuse of treated wastewater in the city was discussed.Publicationtype: Doctoral Thesis648 3659 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Bioressourceninventur – Analyse von Stoffströmen zur Bestimmung urbaner Biomassepotenziale in einem Geoinformationssystem (GIS)For the efficient energetic and material utilisation of bioresources from urban areas the knowledge of their amounts, origin and composition is very important. In this work the specific spatial dependencies between geographic data and the characteristics of the bioresources are investigated. Influencing factors and parameters for their determination for a bioresources inventory based on geographical data in a GIS are developed.Publicationtype: Doctoral Thesis772 1345