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  • 1.
    Larsson, Anneli
    Linköping University, The Tema Institute.
    Profile and perceptions of biogas as automobile fuel: A study of Svensk Biogas2008Independent thesis Advanced level (degree of Master), 20 points / 30 hpStudent thesis
    Abstract [en]

    From an environmental- and health perspective, biogas and other biomass-based fuels have several advantages; nevertheless the majority of motorists fill their cars with petroleum-based fuels. This thesis is designed to explore the profile of biogas in relation to its perceptions. It is a study concerning the communication between the biogas producing company Svensk Biogas and their biogas users and non biogas users. To obtain a thorough understanding of the profile and perceptions of biogas a qualitative approach was considered appropriate. Biogas users and non-users were interviewed at gasoline stations, while Svensk Biogas was interviewed as a group.

    The three interview segments were analyzed and compared in order to identify patterns, similarities and differences. Based on research data the thesis concludes that the profiling arguments of biogas correlates to that biogas is the most environmentally friendly fuel, the least expensive fuel, and locally produced. Furthermore, the company profile of Svensk Biogas is equal to sustainable alternative, locally produced, trustworthy, environmentally friendly and climate smart [klimatsmart]. Given the arguments of the company profile, environmental values seem to be the core communicating value. Profiling Svensk Biogas happens through events and by using communication material such as company logotype.

    Motorists have an overall positive perception of biogas. Biogas users states environmental benefits as the key argument behind their commitment. Non-users are positive toward biogas although expressing a lack of knowledge confusing biogas with ethanol and bio-fuels in general. According to motorists the negative perceptions, in addition to the prerequisites of biogas, are connected to insufficient infrastructure of biogas filling stations, a short range of the biogas tank, a high investment cost of a biogas car, a biogas price increase, scarcity of cars, and information (lack of information and misleading information).

    The overall perception of Svensk Biogas among biogas users is positive. Biogas users express a negative perception concerning the Svensk Biogas filling stations and also wish for a lower biogas price. Non-users express modest perceptions of the company. This research also concludes that perceptions of the biogas producer are correlated to the perceptions of biogas. Furthermore, biogas producer, users and non-users wish to be directed by political decisions, guiding them toward environmentally friendly fuel alternatives.

  • 2.
    Warth, Benedikt
    Linköping University, The Department of Physics, Chemistry and Biology.
    Design and Application of Software Sensors in Batch and Fed-batch Cultivations during Recombinant Protein Expression in Escherichia coli2008Independent thesis Advanced level (degree of Master), 20 points / 30 hpStudent thesis
    Abstract [en]

    Software sensors are a potent tool to improve biotechnological real time process monitoring and control. In the current project, algorithms for six partly novel, software sensors were established and tested in a microbial reactor system. Eight batch and two fed-batch runs were carried out with a recombinant Escherichia coli to investigate the suitability of the different software sensor models in diverse cultivation stages. Special respect was given to effects on the sensors after recombinant protein expression was initiated by addition of an inducer molecule. It was an objective to figure out influences of excessive recombinant protein expression on the software sensor signals.

    Two of the developed algorithms calculated the biomass on-line and estimated furthermore, the specific growth rate by integration of the biomass changes with the time. The principle of the first was the application of a near infrared probe to obtain on-line readings of the optical density. The other algorithm was founded on the titration of ammonia as only available nitrogen source. The other two sensors analyzed for the specific consumption of glucose and the specific production of acetate and are predicted on an in-line HPLC system.

    The results showed that all software sensors worked as expected and are rather powerful to estimate important state parameters in real time. In some stages, restrictions may occur due to different limitation affects in the models or the physiology of the culture. However, the results were very convincing and suggested the development of further and more advanced software sensor models in the future.

  • 3.
    Micael, Karlberg
    Linköping University, Department of Physics, Chemistry and Biology, Biotechnology. Linköping University, The Institute of Technology.
    Soft sensor application on lactate controlled fed-batch cultivation for monoclonal antibody production2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Monoclonal antibody producing cells are of great interest and used frequently in the field of biomedical research, diagnostics and therapy with increasing need for better systems to more efficiently produce antibodies at a lower costs. In this project three fed-batch cultivations of hybridoma cells (HB-8696) were cultured in a stirred tank reactor with the use of a soft sensor to monitor the lactate concentration and as well as a dielectric probe for biomass measurements. In addition, a protocol for growing the inoculum was also successfully produced and a previous batch cultivation was also analyzed which gave crucial information about stoichiometrically relation in the feed medium which was used in the fed-batch cultivations. The BioSenz Analyzer was used for on-line lactate concentration monitoring and was later used to control the feed profile to avoid overflow metabolism in two of the three fed-batch cultivations. However, nothing conclusive could be said about the lactate controller as of yet which needs further research.

  • 4.
    Lindgren, Lina
    Linköping University, The Tema Institute. Linköping University, Faculty of Arts and Sciences.
    Including Additional Land Use, Land Use Change and Forestry-activities under the Clean Development Mechanism: Discussions in the United Nations Climate Negotiations2011Report (Other academic)
    Abstract [en]

     

    Land use, land use change and forestry activities (LULUCF) can help mitigate climate change by creating a terrestrial carbon sink, removing carbon dioxide from the atmosphere, while at the same time help increasing adaptive capacity and reduce poverty. Still, carbon stored in biomass or soils are only stored temporary since natural or human induced disturbances can cause a total or partial loss of stored carbon.

    LULUCF-activities under the clean development mechanism (CDM),  one of the flexible mechanisms under the Kyoto protocol, have been limited to afforestation and reforestation (A/R) projects under the first commitment period. Joint implementation projects and national accounting  of  greenhouse  gas  reduction  can  in  addition  to  A/R-project  also  include deforestation,  revegetation,  forest  management,  cropland  management  and  grazing  land management. The exclusion of these types of activities from CDM has been questioned and debated recently.

    This briefing tracks the United Nations (UN) climate negotiations in regards to the possibility of including additional LULUCF-activities under CDM, mainly the negotiations occurring after the adoption of the Bali Road map.

    LULUCF under CDM has been discussed mainly in the Ad Hoc Working Group on Further Commitments for Annex I Parties under the Kyoto Protocol (AWG-KP). There are diverging ideas on whether a more holistic approach should be applied to the treatment of LULUCF under CDM or whether current structure should be kept. Costa Rica, Colombia, Mexico, Panama, El Salvador, New Zealand, Norway, Canada, Australia and several of the Least Developed Countries have been positive towards including additional LULUCF-activities. Some of the arguments brought up are that the LULUCF-sector holds a large potential to mitigate climate change that is lost with the current structure and that a broader inclusion of LULUCF-activities would lead to an inclusion of all parts of the world in the benefits from CDM. China, Brazil and  Alliance of Small  Island States  have, on the other hand, been sceptical towards including additional activities arguing that there are too large uncertainties and that it creates an offset allowing developed nations to delay emission reduction in other sectors. The EU supports the current structure and rules but is open to discuss alternatives.

    The  AWG-KP  has  been  negotiating  a  new  LULUCF-decision,  which  has  not  yet  been adopted. In the draft LULUCF-decision from the Conference of Parties in Copenhagen 2009, the possibility of expanding LULUCF under CDM was however opened. In the draft decision the Subsidiary Body for Scientific and Technological Advice (SBSTA) is requested to initiate a work programme on additional LULUCF-activities. Since the LULUCF-decision is not yet adopted, SBSTA cannot initiate this work programme and whether they will be able to do so is dependent upon the outcome of the negotiations on the LULUCF-decision. LULUCF- activities under CDM have so far received little negotiation time.

    LULUCF and CDM have also been discussed outside the formal UN climate negotiations. Several  side events,  for  example,  have treated these questions,  both  for and  against  the inclusion of additional activities.

  • 5.
    Wiréhn, Lotten
    Linköping University, The Tema Institute, Tema Environmental Change. Linköping University, The Tema Institute, Centre for Climate Science and Policy Research . Linköping University, Faculty of Arts and Sciences.
    Climate Suitable Energy Crops and Biomass Energy Potentials: Assessment of the Current and Future Prospects in Estonia2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Development of biomass energy plantations is one approach to mitigate and adapt to climate change and the energy challenges related to it; however, climate change will affect the climate conditions and in turn the selection of crops and trees suitable for renewable energy sources. In Estonia, electricity is mainly based on oil shale but since their integration in the European Union they are required to increase the share of energy from renewable sources. In this study, the possible changes of suitable species are assessed by examining the current and the future prospects and potentials with biomass energy derived from energy plantations in Estonia, taking climate change into consideration. The biomass energy potentials for the species that are climate suitable in current and future time are manually estimated, using a case study approach when determining the yields. The study result suggests that biomass energy from crops and trees have great development possibilities and that climate is not a key limitation for the selection of suitable species; in addition, the energy crops and trees appear to suit the future climate conditions better than the current. The results indicate that the established national target of 25% of energy from renewable sources in gross final consumption of energy by 2020 could be achieved to a large extent by putting energy plantations into practice.

  • 6.
    Haglund, Emelie
    Linköping University, Department of Management and Engineering, Environmental Technology and Management. Linköping University, The Institute of Technology.
    Systematisk bedömning av våtmarksväxter som substrat för biogasproduktion2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Two environmental problems today are the increased concentrations of greenhouse gases in the atmosphere and eutrophication.  Therefore, two challenges are reducing greenhouse gas emissions and fluxes of nutrients. Another challenge is to secure the energy supply in a world where energy demand is increasing. New renewable energy sources need to be developed both to secure the energy supply, but also to reduce the use of fossil energy. A renewable energy source is biogas that can be used for electricity, heating and as vehicle fuel. It is predicted that substrate for biogas production will be a limitation in the future, therefore, new substrate need to be evaluated. Wetland plants are an alternative substrate for biogas production and evaluated in this study.  Wetlands and it is plants are interesting to study because they can reduce the concentration of nutrients and therefore help to reduce the problem of eutrophication.  The study was performed within a project at Biogas Research Center and was a literature study with the study of a case. The method used has been developed in the project and is a Multi Criteria Assessment (MCA), which means that there are several different areas being studied. Areas taking into account the biological, economic, chemical, environmental and technological aspects. In order to structure the data, a matrix consisting of the different key areas was used. To clarify the opportunities and obstacles a semi-qualitative assessment was done for each key area. The case studied was a wetland in an agricultural landscape. The wetland is 5 ha and was constructed a few years ago to work as nitrogen and phosphorous trap. There is no vegetation in the wetland because it is relatively new. The plants that were studied during the study was therefore plants that are potential to grow in the wetland in the future. The studied plants were reed, reed canary grass and cattail. In the wetland it is possible to regulate the water and thereby drain the water to facilitate harvesting.   The results showed that the technology available today for the harvesting and chopping needs to be developed because it does not meet the required standards. There are various techniques for digestion, but since the dry matter is high for the plants dry fermentation is preferable, or a two-stage system in which the first step is dry digestion. A wetland provides a relatively small amount of biomass and therefore it is better to co-digest the plants on a farm biogas plant.  Wetland plants are not approved substrates for certification of bio fertilizer, which can be an obstacle. The bio fertilizer also has a low value because the plants contain low levels of nutrients.Wetlands reduce the amount of nutrients and harvest of wetland plants contributes to the retention of phosphorus increases. Wetlands emit methane and nitrous oxide that affect global warming.Today, there is no economic viability of harvesting wetlands. A system in which compensation is obtained for the environmental benefit that harvest provides is an option to increase profitability.

  • 7.
    Moestedt Hellman, Jan
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Evaluation of magnetic biomass carriers for biogas production2013Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis evaluates a novel technique to increase the active biomass inside continuously stirred tank biogas reactors with possible benefits of shorter retention times, higher degree of degradation, higher methane yield and tolerance of higher organic loading rates. The technique includes addition of magnetic biomass carriers to the process which, after adhesion of active microorganisms, can be magnetically separated at reactor outflow and reintroduced to the process.

    The evaluation of magnetic biomass carriers included methods such as batch experiments, quantitative real-time polymerase chain reaction and continuous reactor experiments with different organic loading rates and addition of volatile fatty acids. The results show that reintroduction of magnetic biomass carriers does indeed work: an accumulated biomass of microorganisms is achieved inside the reactor during a continuous process. Magnetite was selected as the most promising biomass carrier, microbiological studies of the particles show that microbiological colonization of magnetite is present with preferential adhesion of hydrogenotrophic methanogens, important for the methanogenesis. The anaerobic digestion with magnetite as biomass carrier present increased process stability and elevated degrading potential of volatile fatty acids, as well as leading to higher methane content when subjected to increased organic load. Thus, the total gas production is increased in certain situations when using magnetic biomass carriers, why further studies of appropriate hydraulic retention times, organic loading rates and substrates are warranted.

  • 8.
    Wang, Yu
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Pretreaments of Chinese Agricultural residues to increase biogas production2010Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    Development of biological conversion of lignocellulosic biomass to biogas is one approach to utilize straw comprehensively. However, high lignin contents of lignocellulosic materials results in low degradation. The main aim of this study was to investigate the appropriate pre-treatment to increase biogas production from Chinese agricultural residues. In this study, Chinese corn stalk, rice plant and wheat straw were evaluated as substrates by applying three different pre-treatments. The investigated pre-treatment were mechanical pre-treatment (cut whole straw into 1-1.5cm) combination of thermal and alkali pre-treatment (1M/L NAOH, 80℃,15 hours) and biological pre-treatment(enzymes provided by Scandinavian Biogas Fuels AB). Biogas production of these substrates was evaluated by batch digester; Sewage sludge from Nykvarn treatment plant and current digesters (Scandinavian Biogas Fuels AB )was the co-digestive substrate which seeded in batch with straw of all pre-treatments.

    The results indicate that at least 50% of organic contents in Chinese agricultural residues could be converted to biogas by these pre-treatments. The optimizing biogas yield is achieved from Chinese corn stalk with combination of thermal and alkali pre-treatment, Chinese rice plant and wheat straw from pre-hydrolysis pre-treatment respectively .Chinese wheat straw has the most biogas potential from combination of thermal and alkali pre-treatment.

  • 9.
    Hiding, Camilla
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Diversity of birds in relation to area, vegetation structure and connectivity in urban green areas in La Paz, Bolivia2012Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    With a   growing human population, cities keep growing worldwide altering ecosystem   and thereby affecting the species living in these areas. Most studies of   urbanization and its effect on ecosystem have been conducted in the western   world and little is known about its effect in the neotropical part of the   world. I examined effects of fragment size, vegetation structure and   connectivity of urban green areas on bird species richness, mean abundance,   diversity and biomass in La Paz, Bolivia. Additionally, the effects of   different disturbance variables on bird community were evaluated. In total,   36 bird species were found in 24 fragment of varying size, connectivity and   level of disturbance. Bird species richness decreased with increasing   disturbance while connectivity and fragment size did not contribute   significantly to explain the variation in species richness at count point scale (p>0.005, multiple linear regression). At fragment   scale, however, species richness increased with fragment sizes,   which has been shown in other studies from neotrophical regions. Variation in   abundance, diversity or biomass could not be explained by connectivity,   fragment size or disturbance.     Furthermore, coverage of construction had a negative effect on species   richness while coverage of bushes and coverage of herbs were negatively   related to biomass and diversity, respectively. The composition of bird   species differed with size and disturbance of the fragments, so that more   omnivorous and granivorous species such as Zonotrichia capensis, Turdus chiguanco and Zenaida auriculata, were present in areas highly affected by human activities. Larger fragments,   less affected by human presence held a larger proportion of insectivorous   species.

  • 10.
    Mettupalli, Dhanunjaya Reddy
    Linköping University, Department of Physics, Chemistry and Biology, Molecular genetics. Linköping University, The Institute of Technology.
    Impact of Arbuscular Mycorrhiza symbiosis on photosynthesis in Medicago truncatula2011Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    The Arbuscular mycorrhiza (AM) symbiosis is a mutual association formed by plant roots and soil fungi. Most vascular flowering plants have the ability to form AM associations, which show significant impact on ecosystem function and plant health. This association is based on the mutual exchange of nutrients between plant and fungus. Therefore, AM association leads to increased demands for photosynthesis. The main aim of this study was to investigate the pathway used by plants during AM to increase the photosynthetic performance. To achieve this aim, we used the model legume Medicago truncatula. We have found out that AM symbiosis develops in roots, where AM fungi colonize the roots, leading to better plant growth and more biomass. Furthermore, AM symbiosis increases chlorophyll content and photosynthetic electron transport rate in leaves. Based on these results we suggest that AM symbiosis increases both efficiency and capacity of photosynthetic apparatus in Medicago truncatula

  • 11.
    Calmunger, Mattias
    Linköping University, Department of Management and Engineering, Engineering Materials.
    Effect of temperature on mechanical response of austenitic materials2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Global increase in energy consumption and global warming require more energy production but less CO2emission. Increase in efficiency of energy production is an effective way for this purpose. This can be reached by increasing boiler temperature and pressure in a biomass power plant. By increasing material temperature 50°C, the efficiency in biomass power plants can be increased significantly and the CO2emission can be greatly reduced. However, the materials used for future biomass power plants with higher temperature require improved properties. Austenitic stainless steels are used in most biomass power plants. In austenitic stainless steels a phenomenon called dynamic strain aging (DSA), can occur in the operating temperature range for biomass power plants. DSA is an effect of interaction between moving dislocations and solute atoms and occurs during deformation at certain temperatures. An investigation of DSA influences on ductility in austenitic stainless steels and nickel base alloys have been done. Tensile tests at room temperature up to 700°C and scanning electron microscope investigations have been used. Tensile tests revealed that ductility increases with increased temperature for some materials when for others the ductility decreases. This is, probably due to formation of twins. Increased stacking fault energy (SFE) gives increased amount of twins and high nickel content gives a higher SFE. Deformation mechanisms observed in the microstructure are glide bands (or deformations band), twins, dislocation cells and shear bands. Damage due to DSA can probably be related to intersection between glide bands or twins, see figure 6 a). Broken particles and voids are damage mechanisms observed in the microstructure.

  • 12.
    Ojong, Pascal
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Investigation of the effects of co-digesting of biodegradable waste and swine manure on the biogas process2011Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    Biomass and biomass-derived waste are important renewable energy sources which plays a vital role in greenhouse gas reduction from fossil fuel.  Biomass can be degraded in a process known as anaerobic digestion (AD) to produce biogas. Biogas is a mixture of methane and carbon dioxide which is utilized as a renewable source of energy. This project was based on the investigation of AD process in Nordvästra Skånes Renhållnings AB (NSR) a biogas facility in Helsingborg Sweden. A lab simulation of NSR digesters was conducted to evaluate the effects of swine manure on AD using two continuously stirred tank reactors (CSTR) R1 (control) and R2 with a working volume of 4L for 21 weeks. The study was divided into 4 periods and the investigation was carried out by increasing the organic loading rate (OLR) step wise from 2.5 to 3.6 gVSL-1day-1. To assess the effects of swine manure, the performance and stability of the reactors were monitored by collecting data from process parameters. These process parameters included biogas production, pH, volatile fatty acids, methane yield, methane content and organic solids (total and volatile solids). Increase in OLR resulted in increase biogas production in both reactors, however R2 with additional swine manure (15%) produced more biogas than R1. Methane yield was fairly stable during the experiment and had a similar trend in both reactors, but however R2 had a slightly higher average yield (730±60 mLCH4 gVS-1) than R1 (690±60 mLCH4 gVS-1) during the entire experiment. Increase OLR resulted in increase VFA in period 2; R2 with additional swine manure had a lower peak VFA concentration of 25 mM as compared to 33mM in R1.  The characteristics of NSR substrate mix and swine manure provided a good buffering system (stable pH), and reactors were still running stably at 3.6 gVSL-1day-1. Furthermore swine manure was investigated to contain macro-nutrients and trace metals which might have enhanced the AD process in R2 containing more Co, Zn, Ni and Mo than R1. Since this investigation was a simulation, the waste mix used at NSR contained 7% swine manure, this made it difficult to give clearer conclusions about the effects of co-digestion of swine manure on the biogas process since the control (R1) had 7% swine manure.

    Keywords: Anaerobic digestion, co-digestion, swine manure, substrate mix, organic loading rate, biogas production, methane yield, VFA, process parameters, CSTR.

  • 13.
    Choudhury, Md. Maidul Islam
    Linköping University, Department of Physics, Chemistry and Biology, Ecology. Linköping University, The Institute of Technology.
    Does an evolutionary change in the water sowbug Asellus aquaticus L. alter its functional role?2011Independent thesis Advanced level (degree of Master (Two Years)), 60 credits / 90 HE creditsStudent thesis
    Abstract [en]

    The ecology behind evolutionary diversification is a well studied area of research, whereas the effects of evolution on ecosystems get little attention. In line with ecological theory, evolutionary diversification of a species could influence different ecosystem aspects such as food web composition, energy flow, nutrient cycling etc. The main objective of this study was to investigate whether two diverging ecotypes (reed and chara) of Asellus aquaticus differ regarding their role in two aquatic ecosystem processes: decomposition of terrestrial leaves and grazing of periphyton. Their role in ecosystem process as well as treatment effects on fitness, measured as growth and survival, were investigated in a laboratory experiment with various levels of intra-specific competition and inter-specific interactions with the amphipod Gammarus pulex. The isopods were collected from two Swedish lakes: Lake Tåkern and Lake Fardume. These two lakes represent different history of ecotype divergence. The experimental design consisted of 2-L aquaria, each providing elm leaves (Ulmus glabra), oak leaves (Quercus roburleaves) and periphyton as food sources. Ten treatments with five replicates were applied for each lake and the experiment lasted for four weeks. The study showed that there was no significant difference between chara and reed ecotype in their functional role. However, the rate of ecosystem processes per individual decreased in competitive interactions. In high density, decomposition per dry weight consumer was low and total algae biomass was high at the end of four weeks due to intra-specific competition. Moreover, ecosystem processes were lowest in inter-specific competition between Gammarus pulex and each ecotype. Present study also shows that ecotypes from the different lakes, having different history, had different responses to mortality and growth. 

  • 14.
    Jansson, Niklas
    Linköping University, Department of Physics, Chemistry and Biology.
    Biologiska behandlingsmetoder för rening av rejektvatten från biogasproduktion2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this literature review the characteristics of two free-floating macrophytes, water hyacinth   (Eichhornia crassipes) and duckweed (Lemna sp.), and two microalgae, Chlorella and Scenedesmus, have been examined regarding their suitability as efficient nutrient removers in the treatment of wastewater with high levels of nutrients and suspended solids from a biogas plant in Loudden. The needs required for the plants to be able to grow in wastewater and the amounts of biomass they can produce have also been studied. The results show that Chlorella is capable of a very high uptake of nutrients in photobioreactors with high nutrient loadings. With an ammonia uptake maximum value at 10900mg/m2/d Chlorella outshines the other organisms in this study. The test organism that performed the closest to Chlorella in terms of nitrogen uptake was water hyacinth with an uptake about 1602mg/m2/d. One factor affecting nutrient uptake in a positive way is the growth rate. Free-floating macrophytes produce more biomass than algae do, and water hyacinth have been shown to be the most productive. It is important to conduct a regular harvest of the plants if a high production should be maintained. High quantity of biomass per unit area can inhibit the growth, and algae are more sensitive to this than the macrophytes often suffering from self-shading when the density is too high. The high level of nutrients in the wastewater prevents growth and dilution is required to achieve any growth at all. Therefore, conventional treatment methods might prove to be a better option.

  • 15.
    Fraissard, camille
    Linköping University, Department of Physics, Chemistry and Biology, Zoology .
    Experimental release of hand-reared wolf pups in Tver region (Russia): food habits, movement patterns and fear of humans.2011Independent thesis Advanced level (degree of Master (Two Years)), 60 credits / 90 HE creditsStudent thesis
    Abstract [en]

    Studying the reintroduction of hand-raised wolves may embrace several interests such as deepening knowledge on wolf biology and allowing a controlled release in isolated populations in need of genetic influx. Studies on hand-raised wild animals, showing successful reintroduction, suggested that young released wolves might be able to survive in the wild without previous fastidious training. Most of their survival behaviours would be instinctive. In this study, nine young wolves were reintroduced in Tver region (Russia) and followed in order to evaluate their fear of humans, their movement patterns, thanks to GPS-Argos collars fitted to three of the animals, and assess their diet via four methods of scats analysis. We analyzed 46 wolf scats collected from August 2010 to January 2011. We determined the frequency of occurrences of items per scats and per items, and used the Relative Estimated Bulk to estimate the biomass of prey species consumed. Statistics were conducted to test for significance of method comparisons. The results showed that half of the wolves remained near the enclosure weeks to months after release, occasionally leaving the vicinity. The individual wolves behaved differently, they adopted various movement patterns and had diverse home ranges (from 15 km2 to 40 km2). Released wolves preyed more on ungulates, especially moose and on other wild mammals such as mountain hare. They also sporadically hunted domestic animals and regularly consumed vegetal matter along with smaller animals as alternative prey. Finally, all scat-analysis methods significantly assessed (p < 0.01) the relative importance of the main food types.

  • 16.
    Sandstedt, Cecilia
    Linköping University, Department of Physics, Chemistry and Biology.
    Phenotypic characteristics during early growth of Equisetum arvense originating along a 1000 km north-south gradient in Sweden2011Independent thesis Advanced level (degree of Master (Two Years)), 60 credits / 90 HE creditsStudent thesis
    Abstract [en]

    Equisetum arvense is an evolutionary old species that is common as a perennial weed in Europe, North America and Australia. It reproduces vegetatively via rhizomes and tubers and due to this it spreads efficiently below ground after initial establishment. The aim of this study was to increase the knowledge of performance during early growth of the species. This included differences between clones along a gradient throughout Sweden, development of tubers and rhizomes, local adaptation and the overall variation within the species. Rhizomes of E. arvense were collected from three different places in each of four regions, up to 1000 km apart, in Sweden. Clones from the twelve places were planted in spring for a common garden study. During summer the plants were watered when needed and during late summer the plants were harvested every second week until late autumn. Data recorded were tuber and rhizome biomass, aboveground biomass, number of tubers and three different tuber characteristics. The results showed clone specific phenotypes, but no gradient response or adaptation to regions, e.g. the clone with the highest and the clone with the lowest tuber biomass in relation to the rhizome biomass were from the same region. During early growth, the plants developed continuously with rapid increase of belowground biomass after development of aboveground photosynthetic parts. Tuber productions differed a lot between clones. The relationship between tubers and rhizomes may affect the clone’s possibility to be competitive in different environments. Management advice may need to be based on clone specific knowledge.

  • 17.
    Liu, Yang
    Linköping University, The Tema Institute, Department of Water and Environmental Studies.
    Greenalgae as a substrate for biogas production - cultivation and biogas potentials2010Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    Algae is regarded as a good potential substrate for biogas production, due to high cells productivity, low cellulose and zero lignin content. Two parts were included in this study: first, cultivations of micro-algae (Chlorella sorokiniana and Tetraselmis suecica) at two different nitrate concentrations, also the effect of addition of CO2 on algae grow was investigated in this first part. Second, batch fermentations of the cultivated micro-algae as well as a powder Chlorella (obtained from Raw Food Shop) and a dry mix filamentous algae (collected in the pounds in the park at the back of the Tema-building and then dried) were performed. In this part also effects of thermo-lime pretreatment (room temperature, 80oC, 105oC and 120oC) on the algae biogas potentials was investigated.

    Both strains of micro-algae cultured at low nitrate gave more CH4 yield: 319 (±26) mL and 258 (±12) mL CH4 per added gVS was obtained during the degradation of Chlorella sorokiniana grown at 0.4mM-N and 2mM-N level, respectively. For Tetraselmis suecica 337 (±37) mL and 236 (±20) mL CH4 per added gVS was obtained at 2.4mM-N and 12mM-N level, respectively. Powder Chlorella gave the highest biogas production (719 ±53 mL/added gVS) and CH4 yields (392 ±14 mL/added gVS), followed by the dry filamentous algae (661 ±20 mL biogas and 295 ±9 mL CH4 per added gVS) and Tetraselmis suecica (12 mM-N; 584 ±7 mL biogas and 295 ±9 mL CH4 per added gVS).

    A negative effect of lime treatment at room temperature on CH4 yield of algal biomass was obtained. Lime treatment at 120oC showed the fastest degradation rate for Tetraselmis suecica and powder Chlorella during the initial 5 days of incubation.

    Chlorella sorokiniana and Tetraselmis suecica cultures flushed with biogas containing 70% and also CO2 enriched air (5% CO2) did not increase cells growth (measured as OD600) if compared to references grown under air. On the contrary, a clearly inhibition effect on the algal cells growth was observed in some cultures.

  • 18.
    Karlsson, Andreas
    Linköping University, Department of Management and Engineering.
    Produktionsintegrerad ORC / kraftvärme i ett småskaligt befintligt fjärrvärmesystem2010Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A part of reducing the increased greenhouse effect is to reduce emissions of carbon dioxide.Much of the carbon dioxide emitted by the energy sector comes from electricity produced incondensing power plants. These emissions can be reduced by the development ofcogeneration, i.e. simultaneous production of heat and electricity. One way to do this is tocomplement the existing, small-scale heat plants with electricity production via a productionintegrated ORC (Organic Rankine Cycle). The purpose of this study is to give an idea of thetechnical and economical conditions, when installing a production integrated ORC. Thepurpose is also to compare these conditions with the conditions for the alternative flashtechnology.An Organic Rankine Cycle (ORC) works as a conventional Rankine Cycle (steam poweredcycle), with a steam turbine and generator that generates electricity. The difference is that thefluid in the circuit is organic, instead of water. Examples of organic fluids are CFCs,refrigerants, ammonia and hydrocarbons. Which fluid is chosen depends on the temperaturesand flows.The study was based on a typical district heating systems of size 20 MW, with a biomass firedboiler of 10 MW, a flue gas condenser with size 20% of the biomass fired boiler power tipand an oil boiler to meet remaining needs.Three system concepts were studied.Load integrated ORC: Is the traditional way of connecting ORC units (condensation mode), inthis case it is connected as an ordinary district heating customers. The downside of thisconcept is that a large amount of heat is lost to the atmosphere, via the ORC device coolingsystem.Production integrated ORC: The idea here is that the ORC unit is installed directly after theboiler. Residual heat from the ORC unit is then fed back into the system and can be used aspaid heat in the district heating system, instead of cooling it off.Flash Technology: In this concept steam is produced from hot water in a steam generator. Thesteam then goes through a steam turbine and generates electricity. After the turbine, the steamis used to heat the water for the district heating system.The study has shown that the load integrated ORC generates a loss each year and is a conceptwhich is, under the assumptions being made, not profitable. Production integrated ORC andflash technology both generates a profit every year. Flash technology is more profitable,primarily for the efficiency is slightly higher compared to the ORC. Further, flash technologyseems to have lower investment costs because the components are fewer and simpler. Thisgives an indicated pay-off time between eight and 12 years for ORC, and between five andnine years of Flash technology.

  • 19.
    Ström, Emma
    Linköping University, The Tema Institute, Department of Water and Environmental Studies.
    Leachate treatment and anaerobic digestion using aquatic plants and algae2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Phytoremediation as a way to control and lessen nutrient concentrations in landfill leachate is a cheap and environmentally sustainable method. Accumulated nutrients in the plants can then be removed by harvesting and anaerobically digesting the biomass. This study presents two aquatic plants (L. minor (L.) and P. stratiotes (L.)) and one microalgae species (C. vulgaris (L.)), their capacities for growth and nutrient removal in leachate from Häradsudden landfill, Sweden, are investigated. The biogas potential of the two plants is determined via anaerobic digestion in a batch run, followed by a lab-scale reactor run for L. minor only. Results show that growth in leachate directly from the landfill is not possible for the selected species, but at a leachate dilution of 50% or more. Nutrients are removed in leachates with plants to a higher extent than in leachates without, yet the actual amounts do not differ notably between plant species. L. minor proves a better choice than P. stratiotes despite this as growth is superior for L. minor under the experimental conditions of this study. Considering biogas production, L. minor gives more methane than P. stratiotes according to the results from the batch run. The former is however not suitable for large-scale anaerobic digestion unless as an additional feedstock due to practical cultivation issues.

  • 20.
    Rehman, Ateeq ur
    Linköping University, Department of Physics, Chemistry and Biology, Molecular genetics .
    Does arbuscular mycorrhiza symbiosis increase the capacity or the efficiency of the photosynthetic apparatus in the model legume Medicago truncatula?2010Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    The Arbuscular mycorrhiza (AM) is an endosymbiont of higher plant roots. Most land plants and cultivated crops are concerned to AM symbiosis. This endosymbiosis is based on the mutual exchange of nutrients between plant and fungus. Therefore, AM symbiosis leads to an increased demand for photosynthetic products. The aim of this study was to investigate the pathway used by plants during AM symbiosis to increase photosynthetic performance. Therefore, we have carried out a systematic characterization of photosynthesis in Medicago truncatula (M. truncatula), which is a model legume. We observed colonization by the fungus in roots and that AM symbiosis increases the fresh and dry plant biomass. This could be attributed to an increase in both photosynthetic efficiency and capacity in AM plants. Consistent with these observations, AM symbiosis enhanced phosphorus uptake from the soil into roots, stems and leaves, as based on analyses of phosphorus content. Based on equal chl loading, no differences were found regarding D1, Lhcb1 and Lhcb2 protein content in four plant groups. This indicates similar ratio between chl and PSII proteins. Furthermore, AM symbiosis increases the amount of chlorophyll, steady state oxygen evolution activities, maximum quantum yield (Fv/Fm), and photosynthetic electron transport rate (about 5 fold). Nevertheless, photoprotection was not affected by AM symbiosis. We observed an increase in weight of seed/fruit and weight of seed/plant in AM plants (about 2 fold). Based on these results, we propose that AM symbiosis increases both the efficiency and the capacity of photosynthetic apparatus in the M. truncatula.

  • 21.
    Smith, G
    et al.
    Chalmers Univ Technol, Dept Radio & Space Sci, S-41296 Gothenburg, Sweden Swedish Def Res Estab, FOA, Dept Surveillance Radar, Linkoping, Sweden.
    Ulander, LMH
    Chalmers Univ Technol, Dept Radio & Space Sci, S-41296 Gothenburg, Sweden Swedish Def Res Estab, FOA, Dept Surveillance Radar, Linkoping, Sweden.
    A model relating VHF-band backscatter to stem volume of coniferous boreal forest2000In: IEEE Transactions on Geoscience and Remote Sensing, ISSN 0196-2892, Vol. 38, no 2, 728-740 p.Article in journal (Refereed)
    Abstract [en]

    A physical model is presented describing the backscatter from coniferous boreal forests in the lower VHF-band in terms of Stem volume. By using measurements of mean amplitude in high-resolution SAR images (rather than intensity), a linear dependence on stem volume can be obtained. The model fits well with the measurements made using the coherent all radio band sensing (CARABAS) SAR in the southern boreal forest, indicating the possibility of retrieving stem volume, and hence biomass, with an accuracy similar to that reached by standard ground-based measurements. No saturation of the scattering is seen up to biomasses of 550 m(3)/ha.

  • 22.
    Fransson, JES
    et al.
    Swedish Univ Agr Sci, Dept FOrest Resource Management & Geomat, S-90183 Umea, Sweden Swedish Univ Agr Sci, Ctr Image Anal, Uppsala, Sweden Swedish Def Res Estab, Div Sensor Technol, Linkoping, Sweden.
    Walter, F
    Swedish Univ Agr Sci, Dept FOrest Resource Management & Geomat, S-90183 Umea, Sweden Swedish Univ Agr Sci, Ctr Image Anal, Uppsala, Sweden Swedish Def Res Estab, Div Sensor Technol, Linkoping, Sweden.
    Ulander, LMH
    Swedish Univ Agr Sci, Dept FOrest Resource Management & Geomat, S-90183 Umea, Sweden Swedish Univ Agr Sci, Ctr Image Anal, Uppsala, Sweden Swedish Def Res Estab, Div Sensor Technol, Linkoping, Sweden.
    Estimation of forest parameters using CARABAS-II VHFSAR data2000In: IEEE Transactions on Geoscience and Remote Sensing, ISSN 0196-2892, Vol. 38, no 2, 720-727 p.Article in journal (Refereed)
    Abstract [en]

    The use of airborne CARABAS-II VHF (20-90 MHz) SAR data for retrieval of forest parameters has been investigated, The investigation was performed at a test site located in the southwest: of Sweden consisting mainly of Norway spruce forests. Regression models predicting forest parameters from radar backscattering amplitude were developed and evaluated. The results showed a linear relationship between backscattering amplitude and forest stem volume, stem diameter, and tree height. The analysis also showed that the radar signal is strongly affected by ground slope conditions. The root mean square errors from the regression analysis, restricted to forest stands on near-horizontal ground, were found to be 66 m(3) ha(-1), 3.2 cm, and 2.3 m for stem volume, stem diameter, and tree height respectively. No saturation of the backscattered signal was observed up to the maximum stem volume of 625 m(3) ha(-1), corresponding to a biomass of 375 tons ha(-1). The results imply that VHF SAR data have significant potential for operational use in forestry.

  • 23.
    Carlson, A
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Energy systems and the climate dilemma - Reflecting the impact on CO2 emissions by reconstructing regional energy systems2003In: Energy Policy, ISSN 0301-4215, Vol. 31, no 10, 951-959 p.Article in journal (Refereed)
    Abstract [en]

    Global warming is one of the most important environmental issues today. One step for the European Union to fulfil the Kyoto protocol, stating a worldwide decrease of emissions of greenhouse gases, is to treat the environment as a scarce resource by attributing costs for environmental impact. This accompanied with considering the European electricity market as one common market, where coal condensing power is the marginal production, lead to the possibility to reduce CO2-emissions in Europe by reconstructing energy systems at a local scale in Sweden. A regional energy system model is used to study possibilities to replace electricity and fossil fuel used for heating with biomass and how a reconstruction can affect the emissions of CO2. An economic approach is used where cost-effective technical measures are analysed using present conditions and by including monetary values of externalities. The analysis shows that, by acting economically rational, a large amount of electricity and fossil fuel should, in three Out Of four cases, be replaced leading to a substantial reduction of CO2 emissions. (C) 2002 Elsevier Science Ltd. All rights reserved.

  • 24.
    Carlson, A
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Energy system analysis of the inclusion of monetary values of environmental damage2002In: Biomass and Bioenergy, ISSN 0961-9534, Vol. 22, no 3, 169-177 p.Article in journal (Refereed)
    Abstract [en]

    This is an analysis of the effect on the technical solution when monetary values of externalities are included in a model for optimising energy systems. The focus of the study is on heating in domestic houses, non-residential premises, multi-dwelling buildings and district heating systems. The included monetary values of damage to the environment and health are those resulting from atmospheric emissions Of CO2, NOx, SO2 and particulates. The estimates are taken from the literature. An optimising method based on linear programming is used and the result is an optimal mix of energy carriers as well as new and existing heating plants that minimise the costs of satisfying a demand for heat. Furthermore, a calculation is made of the externality cost resulting from the energy system. The analysis makes it possible to compare the technical and economic differences of an energy system based on business economics to a system with greater emphasis on socio-economics. Generally speaking, it is cost-effective to take externality costs into consideration at the planning stage instead of correcting the damage later. The results show that by considering externality costs the total discounted cost of the energy system would be approximately 30% lower than today. Furthermore, the use of pellets and wood chips should be substantially larger in all of the studied regions. (C) 2002 Elsevier Science Ltd. All rights reserved.

  • 25.
    Melon, P.
    et al.
    Centre d'Etudes Spatiales de la Biosphère (CESBIO), Toulouse, France.
    Martinez, J.-M.
    Centre d'Etudes Spatiales de la Biosphère (CESBIO), Toulouse, France.
    Le, Toan T.
    Le Toan, T., Centre d'Etudes Spatiales de la Biosphère (CESBIO), Toulouse, France.
    Ulander, L.M.H.
    Beaudoin, A.
    L3S Cemagref-ENGREF, 34039 Montpellier Cedex 05, France, Aerospace and Navigation Radar Section/Defense Research Establishment, Ottawa, Ont. K1A 0K2, Canada.
    On the retrieving of forest stem volume from VHF SAR data: Observation and modeling2001In: IEEE Transactions on Geoscience and Remote Sensing, ISSN 0196-2892, Vol. 39, no 11, 2364-2372 p.Article in journal (Refereed)
    Abstract [en]

    The objective of this paper is to investigate the relationships between VHF data and forest biomass using data acquired by the Airborne Imaging Radar CARABAS over two different pine plantation forests in southern France. Data are analyzed using detailed ground truth measurements available on both sites. The backscattering coefficient is strongly correlated to characteristics of the tree trunk. Signal saturation is not observed up to 900 m3/ha. However, the sensitivity to the volume is high in the range of 0-500 M3/ha (e.g., 1 to 1.5 dB for 50 m3/ha), whereas it is reduced beyond 500 m3/ha (< 0.5 dB for 50 m3/ha). The experimental analysis is supported by theoretical modeling using a coherent backscatter model based on the distorted Born approximation coupled with a tree growth model giving a fine and precise description of the trees at both sites. The modeling results show that the trunk is the main scatterer, but that, when the branch dimensions are not insignificant compared to trunk dimension, branch scattering needs to be accounted for. However, since the two species under study are both coniferous, branch dimensions are relatively small compared to trunk dimension. This explains no significant differences observed in the backscatter behavior between both sites, except for mature stands with low stem density. Finally, the effect of topography is investegated both experimentally, using using a digital elevation model (DEM), and theoretically with the coherent model. The loss of sensitivity to stem volume due to slope is clearly demonstrated and explained by the decrease of the dihedral trunk-ground interaction as the slope increases.

  • 26.
    Biswas, Rajib
    Linköping University, The Tema Institute, Department of Water and Environmental Studies.
    Biomethanation of Red Algae from the Eutrophied Baltic Sea2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In the semi-enclosed Baltic Sea, excessive filamentous macro-algal biomass growth as a result of eutrophication is an increasing environmental problem. Drifting huge masses of red algae of the genera Polysiphonia, Rhodomela, and Ceramium accumulate on the open shore, up to five tones of algae per meter beach. During the aerobic decomposition of these algal bodies, large quantities of red colored effluents leak into the water what are toxic for the marine environment. In this study, feasibility of anaerobic conversion of red algae Polysiphonia, rich in nitrogen and phosphorous, was investigated. Biogas and methane potential of Polysiphonia, harvested in two different seasons [October and March], was investigated through three different batch digestion experiments and laboratory scale CSTR [continuous stirred tank reactor] at mesophilic (37oC) condition. Autoclavation [steam and heat] and ultrasound pretreatments were applied in order to enhance the biodegradation. In STR, anaerobic codigestion of algal biomass with SS [sewage sludge] was applied with a gradual increase in organic loading rate [1.5-4.0 g VS/L/day] and operated for 117 days at 20days HRT [hydraulic retention time]. Reactor digestate was analyzed four times over the period to determine the nutrients and heavy metals content. It is concluded that the methane potential of algae harvested in October is almost two-fold than that of algae harvested in March, probably due to it’s higher [more than double] nitrogen richness. An increase in biogas yield was observed upto 28% and VS reduction was increased from 37% to 45% due to autoclave pretreatment. Ultrasound pretreatment had no effect on digestion. In batch digestion, maximum methane yield 0.25 m3/kg VS added at 273oK, was obtained from algae [harvested in October] pretreated in autoclave. Codigestion of algae with SS worked well in STR with a comparatively lower OLR. At a higher OLR, methanogens were inhibited due to increased VFAs accumulation and decreased pH. A maximum biogas yield 0.49 m3/kg VS added at 310oK , was obtained from algae [harvested in October] pretreated with autoclave. The methane content of the produced biogas was 54%. Average [over a short period, day 99-107, reactor showed steady performance] maximum biogas yields from untreated algae obtained 0.44 m3/kg VSadded at 310oK and the VS reduction was calculated 32%. Digestate, to be used as a fertilizer, was found NH4-N, N, P, K, S and Na rich and only Cadmium level was above the maximal limit among the heavy metals. The sand content in algae during harvesting was considered as a factor to disrupt the operation. Codigestion of Polysiphonia algal biomass with substrate with higher C:N ratio like paper mill waste should be more appropriate to increase the methane and biogas yield. It is inconclusive whether AD process is a good method to dewater redalgae or not but large scale harvesting of algae will definitely contribute to curb eutrophication of the Baltic Sea through decreasing N and P level.

  • 27.
    Kuruvilla, Jacob
    Linköping University, Department of Physics, Chemistry and Biology.
    Localization, functional analysis and physiological role of Anion Transporter 3 (Arabidopsis Thaliana)2009Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    In this project, the maintenance of dynamic cycling of inorganic phosphate is discussed in terms of a phosphate transporter, ANTR3. Reverse genetics are applied with the help of bioinformatics and other web based tools which provided valuable initial information. The model organism Arabidopsis thaliana, both wild-type and mutants was cultivated hydroponically. Screening for homozygotes proceeded standardization of a protocol for isolation of plastids from the roots of these plants. Presence and absence of protein in root plastids was confirmed by western blotting in wild-type and mutants respectively. This was followed by functional and biochemical analysis of the protein by transport experiments using radioactively tagged phosphate.

    The development of a protocol for isolation of root plastids from roots of Arabidopsis thaliana with high yields has been successful. In-vitro studies by radioactive phosphate transport experiments were possible with the help of knock out mutants. It has been concluded that transport of Pi via ANTR3 is dependent either on an H+ or a Na+ gradient. Back exchange experiments have aided us in establishing its activity in export and import of Pi. Last but not the least, phenotypic analysis have observed larger biomass in mutants leading to the conclusion that even though other transporters are present the sink (roots) – source (leaves) balance is disturbed.

  • 28.
    Karlsson, Christian
    Linköping University, Department of Physics, Chemistry and Biology.
    En jämförelse mellan får- och nötkreatursbetade hagmarker med avseende på populationsstorlek samt artsammansättning hos dagfjärilar och örter2009Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    Many of Europe’s day-living butterflies have shown decreasing populations during the last decades and many species are threatened. Many butterflies are dependent on managed semi-natural grasslands because of their richness in nectar sources and host plants for the butterfly larva. Swedish pastures are mostly managed through grazing. The number of cattle in Sweden have been decreasing while the number of sheep in the country increased by 30%. I examined if there was any differences in the butterfly and herb species diversity between pastures grazed by cattle or sheep. During the fieldwork, ten structurally similar pastures in the vicinity of Linköping, Östergötland were studied. Grazing by cattle was favourable both for butterfly and herb species with respect to species richness. Larger amounts of grass biomass and ground coverage by grass were in this study linked to sheep grazing. There have earlier been proposed that sheep graze more selective on herbs in favour of grass, with decreasing amounts of herbs and increasing amounts of grass in sheep grazed pastures, as a result. This theory is confirmed in this paper. The hypothesis that lower amounts of herbs give lower supply of larval host plants, which result in declining populations of day-living butterflies was strengthened by this study.

  • 29.
    Gudmundson, Sara
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology . Linköping University, Department of Physics, Chemistry and Biology, Ecology .
    Stabilizing factors in spatially structured food webs2009Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    Ecological models have problems showing the positive relationship between diversity and stability found in nature. Theory states that complex food webs have high extinction risks and low stability. However, persistent food webs found in nature are large and complex containing many interconnections between species. There are many possible mechanisms enabling persistent food webs such as; complex interaction patterns, asynchronous fluctuations of species densities, environmental fluctuations and spatial distribution. These factors have not been used in classical models. In this study, coloured environmental 1/f noise and dispersal between subpopulations were incorporated into a diamond shaped food web based on a model by Vasseur and Fox 2007. Contradictions between theoretical and empirical results regarding food webs can be resolved by detailed analyses of models, withholding stabilizing mechanisms. Weak environmental 1/f noise generated an increased coefficient of stability but the stabilizing effect of noise can be questioned because of a decreased mean food web biomass and reduced stabilizing effect when reddened. However, detailed studies of the food web revealed that noise can redistribute density proportions between species, evading lowest species density and thereby increase food web resistance to demographic stochasticity and catastrophes. Noise induced density proportion shifts imply that large population sizes are no insurance towards future increase in environmental variance. Synchrony of species environmental responses and dispersal between subpopulations can both have major influences on stability and extinction risk of smaller food webs indicating that spatial structure could be one of the dominating factors stabilizing complex food webs found in nature.

  • 30.
    Larsson, Anneli
    Linköping University, The Tema Institute, Department of Water and Environmental Studies.
    Profile and Perceptions of Biogas as Automobile Fuel: A Study of Svensk Biogas2008Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    From an environmental- and health perspective, biogas and other biomass-based fuels have several advantages; nevertheless the majority of motorists fill their cars with petroleum-based fuels. This thesis is designed to explore the profile of biogas in relation to its perceptions. It is a study concerning the communication between the biogas producing company Svensk Biogas and their biogas users and non biogas users. To obtain a thorough understanding of the profile and perceptions of biogas a qualitative approach was considered appropriate. Biogas users and non-users were interviewed at gasoline stations, while Svensk Biogas was interviewed as a group.

    The three interview segments were analyzed and compared in order to identify patterns, similarities and differences. Based on research data the thesis concludes that the profiling arguments of biogas correlates to that biogas is the most environmentally friendly fuel, the least expensive fuel, and locally produced. Furthermore, the company profile of Svensk Biogas is equal to sustainable alternative, locally produced, trustworthy, environmentally friendly and climate smart [klimatsmart]. Given the arguments of the company profile, environmental values seem to be the core communicating value. Profiling Svensk Biogas happens through events and by using communication material such as company logotype.

    Motorists have an overall positive perception of biogas. Biogas users states environmental benefits as the key argument behind their commitment. Non-users are positive toward biogas although expressing a lack of knowledge confusing biogas with ethanol and bio-fuels in general. According to motorists the negative perceptions, in addition to the prerequisites of biogas, are connected to insufficient infrastructure of biogas filling stations, a short range of the biogas tank, a high investment cost of a biogas car, a biogas price increase, scarcity of cars, and information (lack of information and misleading information).

    The overall perception of Svensk Biogas among biogas users is positive. Biogas users express a negative perception concerning the Svensk Biogas filling stations and also wish for a lower biogas price. Non-users express modest perceptions of the company. This research also concludes that perceptions of the biogas producer are correlated to the perceptions of biogas. Furthermore, biogas producer, users and non-users wish to be directed by political decisions, guiding them toward environmentally friendly fuel alternatives.

  • 31.
    Oni, Stephen Kayode
    Linköping University, The Tema Institute, Department of Water and Environmental Studies.
    Modeling Chloride Retention in Boreal Forest Soils - synergy of input treatments and microbial biomass2007Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis
    Abstract [en]

    The hypothetical assumption that chloride is conservative in the soil has been debated for the last decade. The results of the recent years of study in chlorine biogeochemistry show that chloride is non-conservative but rather participates in complex biogeochemical reactions in the soil. These interactions in nature inform the development of simplified hydrochemical model of chloride dynamics in the soil that is driven on soil routine component of HBV hydrological model. This novel attempt affords the opportunity to explore chlorine biogeochemistry further by evaluating the biological processes such as microbial biomass that predominate chlorine cycles in the same order of magnitude as earlier studied abiotic factors. Data from soil lysimeter experiment with different inputs treatments were used in the calibration and validation of both the hydrological and biogeochemical model. The results show that (1) model efficiency reduces with decreasing water residence and with increasing soil organic matter. (2) Longer water residence time (low water input), high chloride and high nitrogen input loads relatively enhance maximum biomass accumulation in a shorter time span. (3) Chloride retention time reduces with increasing chloride loads under short water residence. (4) Microbial biomass growth rate is highest under high chloride input treatments. (5) Biomass death rates shows reducing trend under short water residence (High water input). Further researches are therefore suggested for possible model expansion and to make the results of this model plausible under field conditions.

  • 32.
    Faxälv, Olle
    et al.
    Linköping University, Department of Management and Engineering.
    Nyström, Olof
    Linköping University, Department of Management and Engineering.
    Biomass Briquettes in Malawi2007Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis
    Abstract [en]

    In Malawi 2.5 % of the forest disappears each year. The use of firewood and charcoal, deriving from forest resources,

    accounts for about 99 % of the household energy demand in Malawi and is a cause to the deforestation. The Government of

    Malawi recently launched a programme called Promotion of Alternative Energy Sources Programme (PAESP) with the aim

    to reduce the use of firewood and charcoal. One of the fuels included in the programme is the biomass briquette. The aim

    with this study is to evaluate the viability of biomass briquettes as a sustainable alternative energy source to firewood and

    charcoal for households in Malawi.

    Research for the study was carried out during three months in Malawi. Visits were made to a number of briquette

    production sites to study the manufacturing methods and to collect briquette samples. The briquettes were tested using

    various methods and then compared with results for firewood and charcoal.

    At the moment various production methods are used in Malawi, with a high difference in technical complexity and cost.

    Machines produced from wood using very basic mechanics can apply similar pressure as more advanced metal pressers.

    They also seem to be better suited than those made of metal, in terms of price and availability.

    The majority of the briquette producers in Malawi use waste paper as base material. Although the paper briquettes are good,

    other raw materials will be needed if the production is supposed to be significantly increased.

    The briquettes burn well using the most common stoves in Malawi, including the commonly used charcoal stove. While

    firewood is cheaper to use than other available fuels, the briquettes seem to be able to compete with the fuel costs for

    charcoal.

  • 33.
    Salawu, Lukman
    Linköping University, The Tema Institute.
    Large-scale nutrient pattern in the Gulf of Bothnia with the hydrodynamic of its loads2006Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Eutrophication, which is the most important degradation in water bodies, has been traced to the imposed loading of nutrients. Of interest is the fact that the process is often accompanied with undesirable effects, one of which is primarily the increased algae production at the surface and accumulation of biomass at the bottom and the secondary responses, which include a., change in species composition b. change in the biogeochemical cycle c. shift in the seasonal pattern and magnitude variability.

    The biogeochemical cycle in response to hydrodynamic alterations may occur internally; however external loading often fosters the process over large spatial scales. In the quest of validating the above statement, we hypothesized that there is no difference in the mean concentration of nutrients in the Gulf of Bothnia from the overall mean concentration.

    The analysis was done with a probability mapping method, in which all stations were grouped into a lattice. The cells are constructed using a grid system, i.e. x and y axis (longitude and latitude). Basically the method statistically tested for variables deviating from the over mean concentration. The variables analyzed are DIN, DSi, DIP and DIN: DSi.

    Results of the analysis showed significant spatial variations in the nutrient distribution in the Gulf of Bothnia; such differences were observed in the coastal to the deep zones of the Gulf.

  • 34.
    Pauline, Ekoff
    et al.
    Linköping University, Department of Mechanical Engineering.
    Johanna, Lund
    Linköping University, Department of Mechanical Engineering.
    Absorptionskyla i Linköpings energisystem: kompressorkyla vs absorptionskyla2006Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis
    Abstract [en]

    The main purpose of this thesis has been to look in to the potential of a production of district cooling using heat as the source of power, i.e. absorptions cooling, in the energy system of Linköping. In the light of the fact that many energy companies are looking for new markets for district heating due to the surplus of heat in the summertime in an energy system with CHP (Combined Heat and Power). Furthermore, the price on electricity is expected to continue to rise since Sweden is most likely to follow Europe’s lead and embrace a power dimensioned energy system. As a result of that transition, energy efficient measures will be more important and absorption cooling implies that more electricity can be produced, instead of consumed, in a CHP system.

    There are two different types of absorption cooling machines available in the market, with either district heating or steam as the source of power. A machine using district heating as the source of power is most suitable to produce comfort cooling i.e. the cold does not need to attain such low temperatures. A steam driven absorption cooling machine is able to attain the very low temperatures needed for cooling used in the processing industry. A condition for absorption cooling is the access to low-cost heat/steam. Tekniska Verken (an energy company) has due to waste incineration access to low-cost heat. The steam in the energy system is produced with oil and electricity, which makes it more expensive to generate absorption cooling with steam as the power source.

    A casestudy was preformed at two industries in Linköping, Linköpingsmejeriet and Swedish Meats, where the possibility for connection of district cooling was examined. Mainly the cooling needed in the processing industry has been examined as this is need is considerably larger than the need for comfort cooling. A number of cases with different conditions for producing district cooling have been simulated in MODEST. The following conclusions have been drawn based on the results of the simulations.

    • In the energy system of today there is not enough steam production to fulfil both the current need for steam and the amount of steam needed for cooling production.

    • An investment in new CHP-plants using biomass fuels will generate enough heat and steam to be profitable for cooling production using heat as a source of power.

    • The emission of carbon dioxide will decrease as a result of the transmission from compression cooling to absorption cooling. The emission will decrease further if an investment in new CHP plants with biomass fuels is carried out. This will then replace the use of fossil fuels.

    • An investment in lithium bromide absorptions cooler will not be profitable with such a small demand as the one in question.

  • 35.
    Tynell, Åsa
    Linköping University, The Tema Institute.
    Microbial Growth on Pall-rings: A problem when upgrading biogas with the technique water absorption2005Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis
    Abstract [en]

    Upgrading of biogas performed using the technique absorption with water wash is common in Sweden where eleven biogas plants, comprising a total of fourteen upgrading plants use this technique. However problems with microbial growth on the pall-rings in the absorption column, and in one case in the desorption column, have negative impact on upgrading the raw gas to vehicle gas. Five of the nine biogas plants studied here have experienced problems with microbial growth. The objective of this report was to identify the microbial growth and determine possible factors regulating microbial growth in order to give advice to process management.

    A questionnaire was sent out and visits were made to the upgrading plants to collect information about the plants. A phospholipid fatty acid (PLFA) analysis was performed to determine microbial biomass and community structure, for which PLFA biomarkers are one type of indicator.

    Samples were analysed from four upgrading plants: Jönköping, Kristinstad, Linköping and Uppsala. The cultures collected were visually different, varying from yellow and slimy to reddish brown with the consistency of coffee grounds. In the Linköping and Uppsala samples, biomarkers for methane-oxidising bacteria (type I methanotrophs) were detected. Methanotrophs live in environments with access to methane and oxygen and are inhibited by e.g. acetylene. In the Jönköping samples biomarkers indicating the bacteria actinomycetes common in the water of aeration tanks in sewage treatment plants, were detected. In Kristianstad there was only enough culture for one sample, so no reliable result was obtained. Fungi were detected in all samples and probably established after other organisms.

    Factors affecting development of microbial growth were found to be water quality, pH and temperature of the process water. Clean water (drinking water) contains less organic material than cleaned water from sewage treatment plants. All plants using water from sewage treatment plants have experienced microbial growth. Low pH is beneficial for reducing microbial growth since most organisms prefer a neutral environment.

    Low temperature is beneficial for minimising microbial growth since the solubility of carbon dioxide and hydrogen sulphide increases with decreasing temperature.

  • 36.
    Jansson, Rickard
    Linköping University, Department of Physics, Chemistry and Biology.
    An Assessment of Biofuels and Synthetic Fuels as Substitutions of Conventional Diesel and Jet Fuels2008Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Today, a majority of the world’s energy need is supplied through sources that are finite and, at the current usage rates, will be consumed shortly. The high energy demand and pollution problems caused by the widespread use of fossil fuels make it increasingly necessary to develop renewable energy sources of limitless duration with smaller environmental impact than the traditional energy sources.

    Three fuels – rapeseed methyl ester (RME), Fischer-Tropsch (FT) diesel and FT jet fuel – derived from biomass, coal or gas were evaluated in this project. The fuel properties evaluated are in most cases listed in standards, often with recommendations, developed for biodiesel, petroleum diesel and jet fuel.

    Biodiesel is monoalkyl esters, e.g. RME, produced by transesterification of triglycerides in vegetable oil and an alcohol to esters and glycerin. This produce a fuel that is suitable as a direct substitution for petroleum diesel. Biodiesel may be used in pure form or in a blend with petrodiesel. Oxidative degradation and weak low temperature performance of biodiesel are properties of concern when substituting petrodiesel with biodiesel, as was shown in this project. The experiments show that oxidative stability can be improved with a synthetic antioxidant, e.g. butylated hydroxytoluene (BHT).

    The FT process converts syngas (a mixture of hydrogen and carbon monoxide) to a range of hydrocarbons. Syngas can be generated from a variety of carbon sources, e.g. coal, natural gas and biomass. The high-temperature (300-350 °C) FT process with iron-based catalysts is used for the production of gasoline and linear low molecular mass olefins (alkenes). The lowtemperature (200-240 °C) FT process with either iron or cobalt catalysts is used for the production of high molecular mass linear waxes. By applying various downstream processes, fuels suitable for substitution of petrodiesel and conventional jet fuel can be obtained. The FT fuels have lower densities than the conventional fuels. However, conclusions from this project are that most of the properties of FT fuels are better, or equal, than conventional petroleum fuels.

  • 37.
    Balkmar, Liv
    Linköping University, The Tema Institute.
    Different views of how CDM projects contribute to sustainable development: A study of stakeholder perspectives of two large-scale renewable energy projets in Southern India2008Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Climate change and sustainable development are interlinked in several ways. A global sustainable development with decreased emissions of green-house gases is seen as a prerequisite for mitigation of climate change. Simultaneously a changing climate will put constraints to development endeavours in developing countries. Yet, a sustainable pathway should include both mitigation and adaptation to climate change facilitating social development, economic growth and a stable environment in developing countries. The Clean Development Mechanism (CDM) of the Kyoto Protocol is combining reduced green-house gas emissions with sustainable development in the CDM project’s host country. This so called dual goal has turned out hard to fulfil, especially the local development objective.

     

    This thesis studies how CDM projects contribute to local development and how this development is viewed differently by various stakeholders. This was made through qualitative interviews with actors connected to two CDM projects in Southern India. In addition, a literature review and a document study was made. The projects chosen are in the renewable energy sector, using biomass fuel. Renewable energy is regarded as an important factor to come to terms with increasing green-house gas emissions.

     

    The results from the literature review and document study show that the expected contribution by CDM projects to local sustainable development is usually expressed in terms of employment, distribution of benefits, social infrastructure, access to energy and technology transfer. The environmental benefit is included in the reduction of green-house gas emissions. In the context of local development, stakeholder participation is brought up as an important factor. The results of the interviews present similar categories of development linked to CDM projects. However, differing views of actual local development assisted by the CDM project was discerned in the answers.

     

    This study points to scale-related problems linked to the global benefit of mitigation of climate change in combination with local development. In conclusion, there is a need for monitoring and evaluation of actual contribution by CDM projects to local sustainable development. To facilitate local sustainable benefits of CDM projects, enhanced stakeholder participation is necessary during the whole project activity period.

     

  • 38.
    Hansson, Cecilia
    Linköping University, Department of Physics, Chemistry and Biology.
    Identification of a butanol tolerant Saccharomyces cerevisiae strain and of a gene associated with enhanced butanol tolerance.2016Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    The most widely used biofuel on the market today is ethanol derived from food crops, such as maize and sugarcane. Ethanol is renewable and environmental friendly but the low energy density makes it unable to compete with fossil fuels. Enlarged focus on replacing fossil fuels with biofuels from renewable biomass have identified isobutanol and 1-butanol as future biofuels, possessing similar capabilities as gasoline e.g. high octane number and energy density. The yeast Saccharomyces cerevisiae can produce butanol through fermentation of carbohydrates but butanol concentrations over 2% is toxic to most strains. To reach the commercial requirements for economic and efficient isobutanol production using S. cerevisiae, higher butanol tolerance is crucial.

    The butanol tolerance of isolated strains of S. cerevisiae from different habitats were examined using spot plating and growth measurements. The results showed variance in butanol tolerance between strains, where the most tolerant strains were able to grow in isobutanol concentration up to 3 %. The expression of genes associated with increased butanol tolerance was investigated by Quantitative Real-time PCR. Data showed an upregulation of RPN4 in strains subjected to butanol induced stress. The study aims to identify butanol tolerant strains that can be engineered for efficient butanol production for sustainable biofuel production.

  • 39.
    Duong, Sutina
    Linköping University, Department of Management and Engineering, Environmental Technology and Management. Linköping University, The Institute of Technology.
    Systematic Assessment of Straw as Potential Biogas Substrate in Co-digestion with Manure2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This work was carried out at Biogas Research Center (BRC) and the company Biogas in Vadstena. The aim was to systematically evaluate new substrates for biogas production. In particular, this case investigated the potential of straw in co-digestion with manure and slurry from pig, chicken and dairy. Straw is interesting to evaluate since it is second generation biomass and available in a large quantity. Also, anaerobic digestion (AD) of manure is beneficial because it deals with the spontaneous methane emission and leads to a better manure handling. Goals within the EU as well as in Sweden have been set up to reduce greenhouse gas emissions from fossil fuel and to produce more renewable energy.

    The methodology used is outlined by BRC in which a number of key areas, such as description of biomass, amount biomass, gas yield, technology, economy, environmental performance and energy system, competing interests and institutional factors, have been evaluated through literature studies and case study Biogas in Vadstena. Based on the results an overall judgment is done to determine the potential of straw.

    The result shows that straw is not appropriate to digest solely because of high TS, high carbon content and lack of nutrients. Straw also has lignocellulosic structures, which are difficult to break down. Especially lignin limits the biodegradability. Mechanical, thermal, chemical and biological pretreatments can increase the availability and biodegradability in the straw. In some cases pretreatment can also increase the methane potential. However, straw works well as a carbon complement in co-digestion with manure, which is a nitrogen-rich substrate. There are technologies available for AD of straw and manure for the whole biogas process, from transportation and pretreatment to digestion and upgrading. Although, there is space for further development of pretreatment and upgrading technology. The economic calculations show that it is profitable to use straw with manure in a farm-based biogas plant for vehicle gas production. Furthermore, the calculations of the energy show that biogas production is energy efficient with energy input/output ratio of 18-23%. Besides production of biogas, the digestate could be used as an environmentally friendly fertilizer.

    In summary, it is possible to produce biogas from straw together with manure, and this is beneficial from both an environmental and economic perspective.

  • 40.
    Hellberg, Kristoffer
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, The Institute of Technology.
    Designkriterier för produktiva våtmarker: hur bör framtidens biogasproducerande våtmarker se ut?2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The aim of this literature review was to identify design criteria for the construction of wetlands whose primary purpose is to produce plant biomass for biogas production. The study deals with aspects that are important for decisions regarding location, design, choice of vegetation as well as the design of the wetlands harvesting and maintenance regime. A conclusion is that other ecosystem services such as nutrient retention and biodiversity can be combined with plant production, by considering alternative pathways during the planning process. The report presents a schematic planning model that will guide the reader through the steps that the planning process involves. The report discusses selected helophytes and hydrophytes that may be suitable production plants. The study also shows conflicting interests which may exist between different interests and secondary production, i.e. how certain changes are not compatible with optimal biomass production. A result of the study is a conceptual planning model that can be used as a decision support tool in the planning process. The model is applied on a test farm in eastern Östergötland to show how a planning process should look like according to the planning model.

  • 41.
    Tran, David
    Linköping University, The Tema Institute, Tema Environmental Change.
    Hydrodynamic cavitation applied to food waste anaerobic digestion2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Innovative pre-treatment methods applied to anaerobic digestion (AD) have developed to enhance the methane yields of food waste. This study investigates hydrodynamic cavitation, which induce disintegration of biomass through microbubble formations, impact on food waste solubilisation and methane production during following AD. Two different sub-streams of food waste (before and after the digestion) pre-treated by hydrodynamic cavitation were evaluated in lab scale for its potential for implementation in a full scale practise. First, the optimum condition for the hydrodynamic cavitation device was determined based on the solids and chemical changes in the food waste. The exposure time was referred to as the number of cycles that the sample was recirculated through the cavitation inducer’s region. The optimal cycles were later tested as a pre-treatment step in a BMP test and semi-CSTR lab scale operation. The tests showed that sufficient impact from the hydrodynamic cavitation was achieved by 20 cavitation cycles. Due to the pre-treatment, food waste solubilisation increased, up to 400% and 48% in terms of turbidity and sCOD measurements, respectively. In the BMP test, the treated samples improved the methane yield by 9-13%, where the digested food waste increased its kinetic constant by 60%. Fresh food waste was then processed in the semi-CSTR operation and the methane yield was increased by up to 17% with hydrodynamic cavitation for two reference periods. These promising results suggest that the hydrodynamic cavitation can be implemented for full scale production with food waste.

  • 42.
    Abrahamsson, Louise
    Linköping University, Department of Thematic Studies, Tema Environmental Change.
    Improving methane production using hydrodynamic cavitation as pre-treatment2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    To develop anaerobic digestion (AD), innovative solutions to increase methane yields in existing AD processes are needed. In particular, the adoption of low energy pre-treatments to enhance biomass biodegradability is needed to provide efficient digestion processes increasing profitability. To obtain these features, hydrodynamic cavitation has been evaluated as an innovative solutions for AD of waste activated sludge (WAS), food waste (FW), macro algae and grass, in comparison with steam explosion (high energy pre-treatment). The effect of these two pre-treatments on the substrates, e.g. particle size distribution, soluble chemical oxygen demand (sCOD), biochemical methane potential (BMP) and biodegradability rate, have been evaluated. After two minutes of hydrodynamic cavitation (8 bar), the mean fine particle size decreased from 489- 1344 nm to 277- 381 nm (≤77% reduction) depending of the biomasses. Similar impacts were observed after ten minutes of steam explosion (210 °C, 30 bar) with a reduction in particle size between 40% and 70% for all the substrates treated.  In terms of BMP value, hydrodynamic cavitation caused significant increment only within the A. nodosum showing a post treatment increment of 44% compared to the untreated value, while similar values were obtained before and after treatment within the other tested substrates. In contrast, steam explosion allowed an increment for all treated samples, A. nodosum (+86%), grass (14%) and S. latissima (4%). However, greater impacts where observed with hydrodynamic cavitation than steam explosion when comparing the kinetic constant K. Overall, hydrodynamic cavitation appeared an efficient pre-treatment for AD capable to compete with the traditional steam explosion in terms om kinetics and providing a more efficient energy balance (+14%) as well as methane yield for A. nodosum.

  • 43.
    Milić, Vlatko
    Linköping University, Department of Management and Engineering, Energy Systems.
    Energy Renovation of an Historic Town Using Life Cycle Cost Optimization: An Assessment of Primary Energy Use and CO2 Emissions2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Historic buildings, buildings built before 1945, represent a third of the total building stock in Sweden. While implementing energy efficiency measures (EEMs) on historic buildings it is important to consider heritage values. This thesis aims to investigate impacts on primary energy use and CO2 emissions while using life cycle cost (LCC) optimization on historic buildings in three studied cases: reference case with no implemented EEMs (case 1), lowest possible LCC (case 2) and a decrease by 50% in energy use (case 3). As a case study 920 historic buildings divided into twelve typical buildings (6 wood buildings, 1w-6w, and 6 stone buildings, 1s-6s) in the downtown area of Visby, Sweden, are used. Within the scope of the thesis, how to achieve the most profitable EEMs and how the profitability of energy renovation varies between the typical buildings in the studied cases will be analyzed also.

    An interdisciplinary method is applied in the thesis that considers both heritage values and energy savings. However, the keystone of the thesis is the use of the program Optimal Energy Retrofit Advisory-Mixed Integer Linear Programming (OPERA-MILP), which is a part of the interdisciplinary method. With the use of OPERA-MILP, the cost-optimal energy renovation strategy is obtained for a building. The program takes into account all energy-related investment costs, as well as the investment and operation costs for the heating system, during a set time period.

    The results show unique packages of EEMs for each of the twelve typical buildings with a potential to lower the total LCC by between 4-11% in the building stock and simultaneously decrease the energy use by more than 50%. The thesis also shows a possible decrease in primary energy use from 24%-57%. The CO2 emissions vary significantly depending on what assumptions are made related to electricity production and biomass use; the results show increases up to 224% in CO2 emissions but also decreases up to 85%. All typical buildings are economically viable to energy renovate. The LCC savings are between 1.4-11.8 SEK with a life cycle set to 50 years for every annually saved kWh, except for case 3 where cost is incurred for every annually saved kWh, 10.0-17.2 SEK, for a number of the typical buildings.

  • 44.
    Broberg, Marina
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    FTIR method for analysis of synthesis gas2013Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    The research institute ETC in Piteå is working with energy technical research and development. Today, much work revolves around research about renewable sources for fuel. In one project, biomass such as wood pellet is heated up while producing synthesis gas. The synthesis gas is then analyzed using three different GC techniques. ETC wanted to be able to make all their analysis on one instrument and with a faster speed. They contacted the company Rowaco in Linköping for help with developing a method on FTIR for analysis of the synthesis gas and that has been the aim for this thesis. A method has been developed for analysis of water, carbon monoxide, carbon dioxide and methane. The results from this thesis show that the concentrations of the molecules in the synthesis gas are outside the calibration curved that has been made and that the high concentrations give much interference to other molecules. The thesis also shows that many areas in the spectrum from the process are roof absorbers and there is also a contamination of water and carbon dioxide in the system. Suggested improvements are to find the source for the contamination, to develop calibration points with higher concentrations, to reduce the length of the gas cell and to dilute the gas before entering the FTIR. 

  • 45.
    Bacos, M P
    et al.
    Office National d'Etudes et de Recherches Aérospatiales, France.
    Josso, P
    Office National d'Etudes et de Recherches Aérospatiales, France.
    Vialas, N
    CIRIMAT––ENSIACET-INPT, Toulouse, France.
    Poquillon, D
    CIRIMAT––ENSIACET-INPT, Toulouse, France.
    Pieraagi, B
    CIRIMAT––ENSIACET-INPT, Toulouse, France.
    Monceau, D
    CIRIMAT––ENSIACET-INPT, Toulouse, France.
    Nicholls, J R
    Cranfield University, United Kingdom.
    Simms, N
    Cranfield University, United Kingdom.
    Encinas-Oropesa, A
    Cranfield University, United Kingdom.
    Ericsson, Torsten
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Stekovic, Svjetlana
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    ALLBATROS advanced long life blade turbine coating systems2004In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, Vol. 24, no 11-12, 1745-1753 p.Article in journal (Refereed)
    Abstract [en]

    The scientific and technological objectives of this program are to increase the efficiency, reliability and maintainability of industrial gas turbine blades and vanes by

    • developing coatings that can warrant a 50 000 h life, i.e. twice that of the usual life, of the hot components (800–1100 °C) even with the use of renewable fuels such as biomass gas or recovery incinerator gas i.e. low-grade fuels with high pollutant levels,

    • characterising advanced existing coatings to assess lifetime and performance of coatings and coated materials,

    • providing material coating data and design criteria to use coating as a design element,

    • increasing the fundamental understanding of the behaviour of coated materials, their degradation, fracture mechanisms and engineering because of the strong need for a mechanism-based modelling of durability.

    These programmes permitted the selection of two reference coatings and the development of two innovative coatings. Concurrently work has been done in order to develop corrosion, oxidation and thermo-mechanical property models. Correlations between coatings development, experimental results and calculations will be discussed.

  • 46. Pedersen Brandt, Anneli
    et al.
    Karlsson, Laila
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Ecology .
    Wennergren, Uno
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology .
    Lettuce grown in silver laden soil at two different activity levels of soil microorganisms2005In: Journal of Applied Botany and Food Quality, ISSN 1613-9216, Vol. 79, no 1, 33-37 p.Article in journal (Refereed)
    Abstract [en]

    Lettuce biomass, silver accumulation in lettuce, and effect of activity of soil microorganisms on these items, were studied in a series of experiments. Lettuce was cultivated in two kinds of soil with different organic matter concentrations. Initially the soil was either sterile or non-sterile, and had been supplied with different silver nitrate concentrations. Lettuce growth was significantly negatively affected by silver, especially in initially sterile soil with a lower organic matter content. There was also a significantly enhanced silver accumulation at larger silver supply in initially sterile soil with the lower organic matter content, otherwise there was no enhanced silver accumulation. There was a significant difference in respiration rate after harvest between the initially sterile soil and the non-sterile soil. In soil with the lower organic matter content, microorganism activity was inhibited by silver. In conclusion, silver accumulation increased and growth decreased in the lettuce grown in soil containing silver when the microorganism community in the soil had been affected by sterilization. The negative effects of silver on both lettuce and microorganisms were more distinct when the soil had a lower organic matter content.

  • 47.
    Nkurunziza, Libère
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Milberg, Per
    Linköping University, Department of Physics, Chemistry and Biology, Ecology . Linköping University, The Institute of Technology.
    Repeated grading of weed abundance and multivariate methods to improve the efficacy of on-farm weed control trials2007In: Weed Biology and Management, ISSN 1444-6162, Vol. 7, no 2, 132-139 p.Article in journal (Refereed)
    Abstract [en]

    We evaluated whether new information could be drawn from additional data collection and unconventional statistical analyses of an on-farm trial. First, we compared a conventional sampling method using a biomass estimate of weed abundance to repeated visual assessment of the percentage ground cover of weeds. The biomass was sampled once after the treatment, whereas the ground cover was repeatedly sampled once before weed control plus several occasions after weed control. Second, we contrasted the outcomes from analysis of variance (ANOVA), taking samples from a single point in time with repeated measures (rm)ANOVA and a multivariate method. As the outcomes and conclusions drawn were relatively similar, we conclude that the ground cover estimate of weed abundance was as reliable as the biomass estimate. The rmANOVA enabled us to follow the temporal trend in response to treatments in the most abundant species, including possible initial differences. Multivariate analysis went even further, by clearly displaying species-wise responses and treatment selectivity.

  • 48.
    Gebremedhin, Alemayehu
    et al.
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Karlsson, Björn
    Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Bjornfot , K
    Shell Raffinaderi AB.
    Sustainable energy system - A case study from Chile2009In: RENEWABLE ENERGY, ISSN 0960-1481 , Vol. 34, no 5, 1241-1244 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents some of the results of a power system analysis for Chile. The two major Chilean electric systems are roughly modelled and optimized using a linear programming method with the option to integrate renewable energy sources like wind power, solar power, mini-hydropower and biomass-fired power and also "municipal waste". A total of four different scenarios are outlined: reference system, new production units, gas and coal price variations and a policy measure to encourage power production based on renewable energy. The objective of the scenarios was to illustrate under what conditions integration of the different energy sources in the existing production system is possible. The study shows that even under current conditions, mini-hydro and waste to energy plants are economically viable. Wind power might be interesting alternatives if policy instrument measures are applied. On the other hand, it is hard for the other energy sources to enter the system even when higher price levels of gas and coal are applied. The system is more sensitive to coal price increases than to gas price increases and this mainly encourages CO2 emission reduction.

  • 49.
    Von Arnold, Karin
    et al.
    Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
    Ivarsson, Maria
    Botanical Institute, Göteborg University, Göteborg, Sweden.
    Öqvist , Mats
    Department of Forest Ecology, Swedish University of Agricultural Sciences, Umå, Sweden.
    Majdi, Hooshang
    Department of Ecology and Environmental Research, Swedish University of Agricultural Sciences, Uppsala, Sweden.
    Björk , Robert G.
    Botanical Institute, Göteborg University, Göteborg, Sweden.
    Weslien, Per
    Botanical Institute, Göteborg University, Göteborg, Sweden.
    Klemedtsson, Leif
    Botanical Institute, Göteborg University, Göteborg, Sweden.
    Can distribution of trees explain variation in nitrous oxide fluxes?2005In: Scandinavian Journal of Forest Research, ISSN 0282-7581, Vol. 20, no 6, 481-489 p.Article in journal (Refereed)
    Abstract [en]

    The impact of distance to tree stems on nitrous oxide (N2O) fluxes was examined to determine whether it is possible to improve the accuracy of flux estimates from boreal forest soils. Dark static chambers were placed along transects between pairs of trees within a Norway spruce stand and fluxes of N2O and carbon dioxide (CO2) were measured during the period 1999-2003. The groundwater table was measured on every sampling occasion along the transects. In addition, radiation transmission, potential diffusion rate and biomass of forest floor vegetation were measured once at each chamber site along one of the transects and soil samples were collected at three depths, from which pH, denitrification enzyme activity, soil moisture, organic matter, and carbon and nitrogen content were determined. There was a high level of variation in the N2O fluxes, both spatially and temporally. However, the spatial variation in the N2O fluxes within the transect could not be explained by differences in any of the measured variables. Sometimes, mainly when no major peaks occurred, N2O fluxes were significantly correlated with CO2 release. It is concluded that distance to stems cannot be used to improve the design of sampling schemes or for extrapolating flux levels to larger scales.

  • 50.
    Krook, Joakim
    et al.
    Linköping University, Department of Management and Engineering, Environmental Technique and Management . Linköping University, The Institute of Technology.
    Mårtensson, Anders
    Linköping University, Department of Management and Engineering, Environmental Technique and Management . Linköping University, The Institute of Technology.
    Eklund, Mats
    Linköping University, Department of Management and Engineering, Environmental Technique and Management . Linköping University, The Institute of Technology.
    Metal contamination in recovered waste wood used as energy source in Sweden.2004In: Resources, Conservation and Recycling, ISSN 0921-3449, Vol. 41, no 1, 1-14 p.Article in journal (Refereed)
    Abstract [en]

    Large amounts of recovered waste wood (RWW) originating from construction and demolition activities (C&DWW) and industrial activities (IWW) are annually generated in Sweden. RWW is also imported for use as an energy source at biofuel boilers. Increased use of biomass is one strategy to decrease environmental impact, in general, and the emissions of green house gases, in particular. This study addresses the environmental and resource implications of metal occurrence in RWW that is used as an energy source at biofuel boilers. RWW contains elevated concentrations of arsenic, chromium, copper, zinc, mercury, nickel, lead and possibly cadmium. The metal composition of Swedish and imported RWW differs in that Swedish RWW contains higher concentrations of arsenic, chromium, zinc, nickel and copper, while imported RWW contains higher concentrations of lead, mercury and cadmium. Ashes from combustion of RWW are nowadays generally disposed in landfills due to their elevated metal concentrations. This practice makes it impossible to use these ashes as filler material thereby replacing extraction of raw materials and decreasing the need for landfill space. Furthermore, landfilling leads to accumulation of hazardous heavy metals that poses a future environmental and health problem. If RWW from construction and demolition should contribute optimally to a sustainable energy system, cleaner waste wood flows are a prerequisite. The elementary measure is to track potential pollution sources in this waste stream and find out which are significant. Furthermore, since most of the RWW is untreated and unpolluted wood, there is a great environmental potential to separate this flow through the waste management system. Such an approach might lead to decreased environmental pollution of heavy metals and an improved resource management.

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