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Item type:Publication, Access status: with files , Ammonia emission from field-applied synthetic fertilizer – processes, methods and mitigation(2026); Ammonia emissions affect environment, climate and health, mainly originating from agricultural sources, especially mineral fertilizers. To evaluate suitable mitigation measures and monitor emissions reliable analytical methods are needed. Thus, firstly the mitigation effect of different incorporation approaches and inhibitors was identified in lab scale. Secondly, different small plot suitable measurement techniques were assessed under realistic conditions in field trials.Publicationtype: Doctoral Thesis63 19 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Einflussfaktoren auf die Sammlung von Biogut und Restmüll – Preview zur Dissertation „Household food waste management: Bridging current and new practices“ (vsl . 2025). Kapitel “Status quo of biowaste collection in Germany”(2024-02-24); Diese Präsentation und deren Inhalt ist eine Vorschau auf das Kapitel „Status quo of biowaste collection in Germany” der Dissertation „Household food waste management: Bridging current and new practices” von Steffen Walk. Sie dient einer ersten Übersicht der Datenauswertung zum Stand des Bioabfallmanagements im Jahr 2022 mit Fallbeispiel Deutschland. Hierzu wurden Leistungsindikatoren (engl. Key Performance Indicators) und deren Einflussfaktoren (engl. Influencing Factors) miteinander korreliert und eine statistische Auswertung vorgenommen. Im Weiteren wurde ein besonderer Fokus auf Lebensmittelabfälle gelegt, welche über die Abfallsysteme entsorgt wurden.Publicationtype: Conference Presentation35 49 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Valorization of deinking sludges from wastepaper recycling: Biogas production and calcium carbonate recovery(2024); Deinking sludges are residues generated from deinking operation during wastepaper recycling. The common treatment option in Europe includes dewatering steps followed by incineration. Incineration of deinking sludge is capital intensive and not sustainable hence it was investigated if it can be valorized energetically by anaerobic digestion and materially by calcium carbonate recovery. Investigations were carried out by characterisation of substrates and execution of experiments. The dry matter of deinking sludges depends on the dewatering stage in treatment plant and is in the range of 2 to 40% fresh mass. The pre-dewatered deinking sludge has a dry matter content of 5 - 16% fresh mass. The organic dry matter of deinking sludges is in the range of 29 to 33% DM. Calcium carbonate and ash contents have the highest fraction of dry matter in deinking sludges and are 47 - 52% DM and 67 - 71% DM respectively. Deinking sludges showed good digestibility with common inocula and their biogas yield was observed to be about half of that of cellulose under similar anaerobic conditions. Pre-dewatered deinking sludge from the mixture of high and medium wastepaper grades showed the highest specific biogas yield (417 ± 0 NL/kg·oDM) followed by those with a mixture of medium wastepaper grades (275 ± 14 NL /kg·oDM) and lastly those from ordinary wastepaper grades (250 ± 21 NL /kg·oDM). A carbon to nitrogen ratio in the range of 29 and 34 is recommended to improve the efficiency of a semi-continuously operated anaerobic digestion of deinking sludge. Within the scope of this study, a hydraulic retention time of 19 days which corresponds to an organic loading rate of 1.6 ± 0.42 kg oDM/m3·d was observed as optimal for anaerobic digestion of deinking sludge using a semi-continuous system. Deinking sludge settles quickly in bioreactors, hence an efficient mixing mechanism during semi-continuous process is recommended. The two-step first order kinetics showed the best fitting for the anaerobic digestion of raw and pre-dewatered deinking sludges from ordinary wastepaper grades. The modified Gompertz model showed the best fit for pre-dewatered deinking sludges from high and medium wastepaper grades. The ashes of deinking sludges and its digestates are rich in calcium carbonate and contain some elements found in portland cement but in different proportion. The ashes contribute to flexural and compressive strength which make them suitable as supplementary building materials. Results obtained from the study show that biogas production from deinking sludges combined with calcium carbonate recovery is a sustainable approach.Publicationtype: Doctoral Thesis28 80 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Optimization of anaerobic digestion: influence of trace elements on methanization processes(Gesellschaft zur Förderung der Forschung und Entwicklung der Umwelttechnologien an der Technischen Universität Hamburg e.V. (GFEU), 2014-07); Optimization of Anaerobic Digestion: Influence of Trace Elements on Methanization Processes Nickel, cobalt, selenium and molybdenum are trace elements (TEs) and activators of enzymes that produce CH4 from carbon sources; thus can be used to optimize methanization processes. Batch experiments and multivariate techniques were used to identify and quantify the main effects and interaction of these TEs during methanization for the purpose of optimizing volatile fatty acids degradation (VFA) and CH4 production. Optimal supplementation ranges were derived; supplementation approaches were evaluated and the mechanisms by which the TEs improve methanization were determined in batch methanization. Results of the batch operations were validated in semi-continuous methanization, with the additional task of increasing organic loading rate without inducing process instability and digester failure. As in the batch process, process stability and optimization aims were achieved in the semi-continuous process using our experimentally and statistically derived optimum TEs configuration.Publicationtype: Doctoral Thesis138 293 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , A decision support model for waste management in support of developing low carbon, eco region : case studies of densely populated kampung setllements in urban areas in Jakarta(2014); Due to the various types of waste disposal, treatment, utilization and technologies, decision support model for waste management is needed to assist planners and decision makers in finding most suitable way to manage municipal solid waste efficiently. Many planners and decision makers in the area of municipal solid waste have a lack of thorough understanding of the complex chains of waste management system. Therefore the impact for the environment quality and the public health can only be judged at the rudimentary level. However, most existing models are primarily focusing on cost or environmental analysis. Only few consider other crucial factors such as the demographic condition, the characteristics of urban form and urban infrastructure, land transformation aspects due to urban development. Consequently, such models often meet difficulties to cope with cultural requirement. Based on those reasons, a decision support model to set up alternatives of most appropriate technology for sustainable waste management towards a low carbon eco-city on a regional basis is developed in this PhD study. The Low Carbon- and Eco-Region, in particular the contribution of waste management sector, is a vision of living in low rate of carbon generation, using fewer natural resources, and encouraging energy recovery and/or waste reduction at source by improving the used material quality (up-cycling). This decision support model is constructed mainly based on the cultural requirement and local context of a region and synergize the geographic, environmental, social capital and economics aspects in order to fulfill the needs of the respective region and its society. The method employed in this model is not solely a new developed model, but also an advanced model in material flow analysis (STAN), and life cycle assessment on solid waste system (EASEWASTE) and Geographic Information System (GIS). At the same time the model also assists the stakeholders in improving the environmental quality and the public health by promoting waste separation at source and reducing the greenhouse gas emission potential from waste sector.Publicationtype: Doctoral Thesis778 500 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Prozesssimulation biologischer Abbauprozesse im Bereich der Abfallwirtschaft(2014)1453 5371