Refine
Document Type
- Doctoral thesis (4)
- Master thesis (2)
Has Fulltext
- yes (6)
Is part of the Bibliography
- no (6)
Keywords
- Biomasse (6) (remove)
Determination of specific metabolic activities of anammox bacteria and their sensitivity to oxygen
(2013)
The discovery of Anammox bacteria has bridged our knowledge gap in the nitrogen cycle. This is because it explained the direct conversion of nitrite and ammonium to nitrogen gas in many reducing natural environments. However, it has been found that the presence of oxygen is an important determinat factor for certain biochemical processes and distribution of organisms in the environment. In this work, two methodological approaches were used to investigate the specific metabolic activities of Anammox bacteria and their sensitivity to oxygen using a mixed biomass culture. Two laboratory-scale bioreactors were maintained and the biomass in the reactors served as the inoculum for the investigations. The molecular characterization of the biomass was done using the Fluorescence in situ hybridization (FISH) technique. The specific Anammox activity (SAA) and important inhibition kinetic parameter characterization were estimated while monitoring activities of the biomass using several batch experiments.
The results of the biochemical characterization revealed that several microbial activities such as denitrification, nitrification, dissimilatory nitrate reduction to ammonium and Anammox processes were competing in the bioreactors. These were observed in the analysis of effluent recirculation of the feed solutions in the bioreactors, however, the Anammox process was predominant. An optimum sonication time top of eight minutes was established used to determine the average optical density to dry mass (OD: DM) ratio of 0.87 in the biomass. The FISH characterization estimated 60.4 % ± 14.6% (mean ± standard deviation) Anammox bacteria concentration in the biomass of Bioreactor 1. The Anammox bacteria were made up C. Kuenenia Stuttgartiensis (̴ 78%) and the remaining C. Brocadia Fulgida.
The maximum SAA of 0.025 mgNH4-N (TSSAnammox-1. d-1) and 5.4 mgNH4–N (1011 CellAnammox-1. d-1) for ammonium, and 0.04 mg N2-N (TSSAnammox-1. d-1) and 9.4 mgN2–N (1011 CellAnammox-1. d-1) for nitrogen gas were found in the biomass. While a binding affinity constant Ki = 0.07 mgO2 /l, maximum half inhibition concentration IC50 ̴ 0.2 mg O2 /l and KM = 50 mg/l were estimated for the inhibition kinetics of oxygen in the biomass. The low Ki value found in this study indicates that oxygen is an efficient inhibitor for Anammox activities and concentrations between 0.4 - 0.64 mg O2 /l can lead to complete inhibition of Anammox activity. However, this process is reversible. Finally, the implication of this inhibition kinetic results might be important in tracing the distribution of Anammox processes in natural environments where fixed nitrogen is present.
An empirical and simulation-based assessment of tree growth in temperate alley-cropping systems
(2020)
The potential of biomass generated from dedicated energy crops, used in short-rotation coppices (SRC), progressively grows recognition as a flexible primary source for the generation of energy, heat, fuel, and bio-based materials and chemicals. The alley-cropping systems (ACSs), which can integrate tree strips managed as SRC into agriculturally managed fields, are often regarded as an adaptable multi-crop land-use strategy that can provide ecological and economic benefits. The research aim of the present dissertation has focused on investigating the prospective implications of different site-specific conditions and scenarios on tree growth in ACSs with SRC, thus incorporating several experimental and simulation-based studies. For this, the ability of a process-oriented, eco-physiological tree growth model was investigated in order to (i) impute missing empirical data, thus securing a reliable repository of tree growth characteristics, (ii) simulate the tree growth in terms of woody biomass production in strong relation to the interactions with adjacent crops and their respective resource capture, (iii) predict and evaluate the tree growth sensitivity to prospective climate changes, thus performing risk assessments for the near and distant future, and (iv) derive and assess the land equivalent ratio (LER) and gross energy yield for different climatic, soil, and management scenarios. The findings have corroborated the potential tree growth vulnerability to prospective climatic changes, particularly to changes in water availability, and have underlined the importance of coping management strategies in SRC for forthcoming risk assessments and adaptation scenarios. Both LER and gross energy yields had resulted in a convex curve where the maximum values were achieved when either the tree or crop component was dominant (>75% of the land area) and minimum when these components shared similar proportions of land area. Collectively, the implications of different site-specific conditions and scenarios on tree growth in ACSs with SRC have been investigated in order to improve the decision-making, optimization, and adaptation of such systems. Last but not least, this dissertation has emphasized the considerable potential of modelling approaches in ACSs, as they can impute missing data from scarce available data and simulate tree and crop yields for specific site-conditions in a non-intrusive, inexpensive, and prompt way while supporting early site-setup planning.
The Electric power crisis is one of the major problems in Bangladesh, the gap between demand and generation is increasing day by day. Moreover, most of the power plants are gas based which will be phased out in future. An alternate electric supply is an essential part for electrifying the developing countries, in this context an innovative approach of rural electrification including DC microgrid, mini-grid and nanogrid would be technically and economically feasible. The thesis draws also attention on the development of technology which enables community owned power system to emerge in the rural areas based on distributed SHS and demand of that community.
Firstly, the electric status and renewable potential in Bangladesh are studied and considered those data into the software based simulation to analysis the technical feasibility to implement DC microgrid by Homer pro tools. The distributed RES (Renewable Energy sources) considered solar PV and biomass. The booming of a large number of individual SHS (Solar Home System) in Bangladesh, bottom-up energy sharing concept would have studied to configure the optimal design of microgrid system and different configuration including grid connected and DC and AC system studied.
Secondly, The PV module is highly dependent on cell temperature and solar irradiance, the ambient temperature, and solar irradiance mathematical equation have been considered to model and simulate in MATLAB/SIMULINK based environment. Similarly charge controller, battery operation, and performance analysis with respect to the PV model. In the distributed energy sources are mainly SHS including large size and regular also model and simulate in MATLAB/SIMULINK software. For instance, the thesis mainly focuses on an optimal design, planning, sizing of DC hybrid microgrid, the SHS, and biomass-based power system with the goal of maximizing the efficiency and reliability. Homer Pro tool used in the work for design an optimal configuration and sizing for technical feasibility.
Finally, a model of DC microgrid compresses with micro sources like SHS systems, µ-CHP, the household loads model in MATLAB/SIMULINK. Decentralized SHS control strategies (droop control) and operation also design and model in MATLAB/SIMULINK environment, where DC – DC converter needs to couple SHS and DC microgrid.
Lignin ist bereits ein intensives Gebiet der Forschung, allerdings werden Verknüpfungen zwischen Quelle, Aufschlussmethode und Einsatz in der Literatur kaum beschrieben. In der vorliegenden Arbeit werden Lignine von verschiedenen Quellen (Weizenstroh, Buche, Nadelholz) und Aufschlussmethoden (AFEX, Wasserdampfaufschluss, Organosolv, Saure Hydrolyse) analytisch erfasst und hinsichtlich ihres Einsatzes in polymeren Materialien charakterisiert. Eine breite Auswahl an Methoden wurden eingesetzt, FT-IR- Spektroskopie, UV-Vis, 31P-NMR, GPC, Pyrolyse-GC/MS, sowie HPLC zur Bestimmung der Reinheit gemäß des NREL-Standard-Protokolls. Thermische Analysen, wie TGA und DSC zeigten Glasübergangstemperaturen um 120°C, sowie Zersetzungstemperaturen zwischen 340°C und 380°C. Die Ergebnisse weisen für das Organosolv-Buchenholz-Lignin hochreine Fraktionen auf, die bis dato noch nicht erreicht wurden. Die Ergebnisse dieser Arbeit identifizien die Organosolv-Buchenholz-Lignine als ein verwertbares Produkt im Hinblick auf die Anwendung in Polyurethanen sowie Phenol-Formaldehydharzen.
Regular electricity access is a key element for the economic development and social welfare of rural areas. Decentralized energy generation has the advantage of using local resources, increasing employment and reducing transmission and distribution losses. Brazil is a tropical country, endowed with vast arable land, plentiful precipitation levels, and a large supply of human labour. Furthermore, it has strong regional distinctions with geographical, cultural and economical differences. Forestry and agriculture, important activities in the Brazilian economy, are dependent on local people and are deeply connected to traditions, nature and culture. Furthermore, these activities generate a significant amount of residues that could be used in conversion technologies for biomass, based on type, availability and market demand. When biomass were used to generate energy locally, community members could have business opportunities, improving local economy and life quality of individuals while diversifying the Brazilian energy matrix, which is mostly based on hydropower. Alternatives for implementing small-scale decentralized biomass schemes are dependent on the screening of the existing biomass supply chains, the implementation of adapted technologies for local conditions and the exploration of local resources. The present research carried out a detailed field work in order to evaluate the potential of Brazilian biomass in different regions. The author identified crucial needs, usual constraints and possible challenges of rural electrification and economic development in Brazil. Several case studies and social groups were investigated in the Federal States of Minas Gerais, São Paulo and Pará to identify different resource management strategies, which biomass technology was applied and the needs of the local population. It was concluded that the compaction of biomass to generate solid biofuels with uniform properties could be a cost-effective alternative for communities taking advantage of the resources available in the region to produce energy. Nevertheless, each case has to be considered on its own. It was concluded that energy supply and consumption should be addressed through integrated research. Scientific research should be focused on technological solutions for improving living standards and socio-economic development in rural areas. The implementation of new regulatory arrangements and a constant revision of the Brazilian energy policies are crucial for encouraging a national industry for renewables. It was also concluded that the cultural, geographical and socio-economic discrepancies of Brazil could involve challenges for the implementation of future projects, even when their development would provide benefits for Brazil as a whole.
This thesis seeks to enhance a better understanding of the concept of cookstoves and their associated repercussions on health and the environment. A three tier methodological approach was used in this study. Firstly, questionnaires were distributed in the study areas and results analysed. Secondly, a laboratory based water boiling test was conducted using three stoves (open fire, rocket stove and “skirt” stove) to assess the effect of wood moisture content on combustion and heat transfer efficiencies. Lastly, a simulation model was used to understand the behaviour of key players within the system of cookstoves and indoor air pollution such that setbacks are better understood, controlled or mitigated. Results of the questionnaires showed that the majority of the people in the case study area are not aware of the threats posed by indoor air pollution on health; however, they are willing to accept any innovations that will abate the pending related environmental, social and health crises associated to poor cooking techniques. From the water boiling test, results showed that fuel moisture greatly affects combustion efficiency and heat transfer efficiency. Fuel at 15% moisture produced best results with little particulate matter and carbonmonoxide emissions meanwhile emissions at 5% and 30% moisture were relatively high. The sensitivity model laid down the basis for comparism and control mechanisms for indoor air pollution and deforestation.