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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
431

Sustainability certification for deforestation-free supply chains: the cases of palm oil and soy

Hinkes, Cordula Verena Maria 25 March 2021 (has links)
No description available.
432

Barkpressning : Underlag till körstrategi på Kvarnsvedens Pappersbruk

Eriksson, Andreas, Sköld, Jonas January 2020 (has links)
På Kvarnsvedens Pappersbruk används gran som vedråvara för mekanisk massatillverkning. Bark är en biprodukt och används som bränsle vid ångproduktion. Innan barken eldas behöver den avvattnas för att öka det effektiva värmevärdet. Detta sker i roterande barkpressar från Saalasti. Torrhalten på barken efter pressarna varierar från ca 37–48 % beroende på många parametrar. Medeltorrhalten under perioden år 2018–2019 var 42 %. En tumregel säger att varje % ökad torrhalt på barken innebär en besparing på 1 MSEK per år eftersom mindre skogsbränsle och kol behöver köpas in. Då torrhalterna efter barkpressarna varierar mycket så var syftet i den här studien att ta fram ett underlag för lämplig körstrategi genom att undersöka och utvärdera i vilken grad parametrarna påverkar utfallet av barkpressningen. Detta gjordes genom omfattande mätningar före och efter barkpressningen på de parametrar som gick att mäta. Resultat från studien visar att olika torrhalter erhölls beroende på vilken barkpress som användes och kan kopplas till slitaget på utrustningen. Vidare är kaktjocklek den parameter som tydligast visar korrelation med torrhalten. Brist på mätdata gjorde att övriga resultat blev svårtolkade. För bästa torrhalter bör låg tjocklek på barkkaka och låg pressvalshastighet eftersträvas, samt att körning i den barkpressen med minst slitage bör prioriteras. För vidare analys och slutsatser krävs ytterligare undersökning. / At Kvarnsveden Paper Mill, spruce is used as a raw material for mechanical pulping. Bark is a by-product and is used as a fuel for steam production. Before the bark is burnt, it needs to be dewatered to increase the effective heating value. This is done in rotating bark presses from Saalasti. The dry content of the bark after the presses varies from around 37–48 % depending on many parameters. The average dry content during the period 2018–2019 was 42 %. A rule of thumb says that every % of increased dry content on the bark means a saving of 1 MSEK per year, since less hogged fuel and coal need to be purchased. Since the dry contents of the bark presses vary widely, the aim of this study was to develop a basis for a suitable operating strategy, by examining and evaluating how different specific parameters affect the outcome of the bark pressing. This was done through extensive measurements before and after the bark pressing, on the parameters that were measurable. Results from the study show that different dry contents were obtained depending on which bark press was used and can be linked to the wear of the equipment. Furthermore, the bark bed thickness is the parameter that most clearly shows correlation with the dry content. Lack of measurement data made other results difficult to interpret. For best dry contents, low thickness of bark and low rotational speed of the press roll should be sought and operating in that bark press with least wear should be prioritized. For additional analysis and conclusions, further research is required.
433

From Food to Fuel: The Swedish Resource Efficiency Dilemma.

Lundgren, Monia January 2014 (has links)
The EU has embarked on a resource efficiency trajectory in order to solve resource scarcity and general sustainability issues. The conversion of food waste into fuel is considered resource efficient as it makes use of resources that would otherwise be discarded. On the other hand, the food sector affects the environment substantially as it is inherently resource intensive and excessive. The purpose of the study was to assess how resource efficient the food waste substrate (feedstock for energy production) is from a life-cycle perspective. The study also aimed to determine if associated Swedish incentives and current market signals promote resource efficiency in Sweden. The food waste substrate has a complex life-cycle and current analyses neglect crucial life-cycle impacts. This makes resource efficiency difficult to determine in absolute terms. The first resource efficiency principle, that promotes the use of fewer inputs, becomes questionable as the food waste substrate has twice as many input stages in comparison to the food crop substrate. The second principle, stating that the food waste substrate should contribute to a low-carbon economy, also falls short due to a calculation method that neglects crucial emission stages. Due to the absent life-cycle perspective, crucial environmental impacts associated with food production are neglected. This affects the achievement of the Swedish Generation Goal and environmental quality objectives. The study concludes that the food waste substrate should undergo a thorough life-cycle analysis. Furthermore, it should be compared to other biofuel options in order to determine degree of resource efficiency. Only then can an appropriate set of EU and national policy measures be instated to safeguard scarce resources and promote a sustainable agriculture and energy sector.
434

Fields of Dreams: Scenarios to Produce Selected Biomass and Renewable Jet Fuels that Fulfill European Union Sustainability Criteria

van Slyke, Torry January 2019 (has links)
Aviation greenhouse gas (GHG) emissions have risen faster than any other transport sector to double between 1990 and 2005. Such emissions from aviation could increase another 700 percent globally, and at least 150 percent in the European Union (EU), by 2050 due to continuously increasing consumer demand. To reverse the trend of rising emissions writ large, the EU has set 2030 climate goals of reducing its GHG emissions by 40 percent (relative to 2005) and having 32 percent of gross final energy consumption from renewables. The EU’s recast Renewable Energy Directive (RED-II) calls for 14 percent of transport energy from renewables, gives multipliers to advanced biofuels, and restricts biomass that is from ecologically valuable lands or that causes land use change. Energy security and energy independence are also long-term EU goals. Many of these goals and targets have also been adopted by the European Free Trade Area (EFTA). Despite these efforts, options are limited to reduce aviation emissions compared to other transport sectors, leaving aviation biofuels, also known as renewable jet fuels (RJFs), as currently the only commercialized option. Against this backdrop, in this thesis scenario analyses were conducted to produce biomass from EU+EFTA lands, project RJF yields from this biomass, and estimate emissions savings of these RJFs compared to petroleum jet fuel. Particular effort was devoted to identifying biomass, biofuels, and EU+EFTA lands that comply with RED-II criteria. The two RJF pathways selected were hydroprocessed esters and fatty acid (HEFA) conversion of Camelina sativa vegetable oil and Fischer-Tropsch (FT) synthesis of forestry residue lignocellulosic biomass. Over 117 million hectares in the EU+EFTA was identified as available for Camelina sativa cultivation, which could yield over 64 Mt of RJF each year, or 113 percent of the total jet fuel consumed in the EU+EFTA in 2017. Conversely, if 50 percent of the forestry residues generated as by-products from EU+EFTA roundwood harvesting operations in 2017 were extracted from harvest sites, 40 Mt of forestry residues would be available as biomass, which would yield almost 7.6 Mt of RJF annually (13% of 2017 jet fuel consumption). If all 144 million hectares of EU+EFTA forest lands deemed available for wood supply were logged, 1,772 Mt of forestry residues would be produced in total (at 50 percent extraction), which could result in almost 337 Mt of RJF, or 590% of the jet fuel consumed in the region in 2017. Hence, RJF can be feasibly produced from biomass from EU+EFTA lands, in amounts that meet or exceed the annual jet fuel consumption of the EU+EFTA, and in ways that meet or exceed RED-II sustainability criteria. However, the proportion of these RJF yields to total annual EU+EFTA jet fuel consumption will decrease over time as the number of flights and their resulting emissions increase. The two RJFs also emit 67 percent and 91 percent fewer GHG emissions, respectively, than petroleum-based jet fuel, showing them to be important tools for the EU to meet its 2030 renewables and emissions reductions targets. Producing the biomass feedstocks and RJFs in these quantities will require the EU to make serious decisions on land use trade-offs, such as whether livestock production is more important than biofuel production.
435

Heterogeneous catalytic conversion of biomass-derived carbohydrates to furanic biofuel additives and chemicals

Elsayed, Islam 13 December 2019 (has links)
Increasing energy demand and various problems associated with fossil fuels such as environmental pollution, global warming and diminishing petroleum reserves have greatly stimulated production of fuels and chemicals from renewable sources. Lignocellulosic biomass has been considered as one of the potential sources for a variety of fuels and industrial chemicals. 5-Hydroxymethylfurfural (HMF) has been identified as an excellent platform molecule because it is a flexible intermediate for the synthesis of bio-renewable fuels and materials. HMF can be easily obtained from acid-catalyzed hydration of biomass-derived carbohydrates (hexoses) in various media. HMF can be converted to energy products such as 2,5-bis(alkoxymethyl)furans (BAMFs), monomers for high-value polymers such as 2,5-bis(hydroxymethyl)furan (BHMF), and valuable intermediates for fine chemicals. Recently, magnetic nanoparticle based catalysts attracted more attention due to their good stability and easy separation from the reaction mixture by a permanent magnet. This unique magnetic separation property makes MNPs more effective than conventional filtration or centrifugation as it prevents loss of the catalyst. This dissertation work focuses on, firstly, studying the effectiveness of silica coated magnetite (Fe3O4) nanoparticles MNPs supported with sulfonic acid groups (Fe3O4@SiO2-SO3H) on the dehydration of glucose to HMF. Secondly, preparing a cost-effective catalytic transfer hydrogenation system for the selective transformation of HMF into BHMF via Meerwein-Ponndorf-Verley (MPV) reaction over the copper iron magnetic catalyst supported on activated carbon in ethanol solvent with the absence of molecular hydrogen. Thirdly, producing alkoxymethylfurans (AMFs) which are considered a potential biofuels by using two-step sequential reactions with cheap heterogeneous zinc-iron oxides magnetic nanocatalyst for the hydrogenation of HMF to furfuryl alcohols in various alcohols solvents in the absence of molecular hydrogen followed by solid Brønsted acid catalyst for the etherification reaction of furfuryl alcohol derivatives. All prepared heterogeneous catalysts were characterized by FTIR, XRD, H2-TPR, XPS, ICP-OES, HRTEM-EDX, and N2 adsorption-desorption isothermal analyses (BET and BJH) and were tested for recyclability. The chemical products were identified by high performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), and products quantities were calculated by using calibration curves of chemical standards. Various reaction conditions such as reaction temperature, reaction time, catalyst amount, and alcohol type were optimized.
436

Grön uppvärmning av gröna hus : Hållbara uppvärmningsalternativ för växthusföretaget Svegro / Biofuel heating for greenhouses : Sustainable heating options for the greenhouse company Svegro

Hägvall, Kristoffer, Järn, Martin January 2014 (has links)
I takt med stigande oljepriser har ett av Sveriges största odlingsföretag Svegro bestämt sig för att byta ut sitt nuvarande värmesystem. Svegro består idag av växthus på ca 50 000 m2 på Thorslunda gård, Färingsö. Uppvärmningen sker idag med hjälp av oljeeldning samt den värmeenergi som omvandlas från växthuslampor. Det nya värmesystemet kommer att använda sig av ett annat förbränningsalternativ än mineralolja. Detta kommer göra det möjligt för Svegro att sänka sina energikostnader och minska miljöpåverkan genom reducerat koldioxidutsläpp. Kraven som ställs är att det nya värmesystemet ska kunna integreras med det befintliga värmesystemet och samtidigt leva upp till dagens ekologiska krav. Målet med bytet av värmesystem är att sänka energiförsörjningskostnaderna men också att klara av framtida högre ställda krav och miljömålsättningar. För att avgränsa rapporten har tre olika förbränningsalternativ behandlats där alla passar bra med den nuvarande vattenburna värmelösningen. Alternativen består av bioolja, pellets och flis. För att bestämma det bästa alternativet har en jämförelsestudie mellan de olika bränslena gjorts där faktorer som investeringskostnader, miljöpåverkan och bränsleeffektivitet beaktats. Utifrån analyserna av resultaten i rapporten föreslås pellets som det bäst lämpade systemet för Svegros anläggning. Enligt livskostnadsanalysen i rapporten kommer det nya systemet att ha betalat av sig efter 1,5 år och efter det kommer besparingar på ca 5,5 miljoner kr göras per år jämfört med om det befintliga systemet skulle bevaras. Det nya bränslet kommer utöver ekonomiska besparingar även minska CO2-utsläppen med ca 2300 ton per år. Konsekvenserna av att välja pellets som förbränningsalternativ är att man måste kombinera pelletsförbränningen med en biooljeuppvärmning, detta för att växterna ska klara av att överleva extremt kalla vinterdagarna. / While the oil price continues to increase, one of Sweden’s largest indoor growing companies Svegro has decided to replace their existing heating system. Svegro is a large green house with an area of approximately 50 000 m2 and is located at Thorslunda gård, Färingsö.The heating system today uses mineral oil and the heat from assimilation lamps. The new system will be using an alternative combustion fuel to the expensive mineral oil. This will make it possible for Svegro to lower their energy costs and reduce their environmental effect by lowering the emissions of carbon oxide.The requirements are that the new heating system should be able to be integrated with the already existing system and at the same time live up to today´s ecological requirements. The goal of replacing the heating system is to reduce the energy costs but also to manage future demands and environmental ambitions. In order to define some limitations for the reports we have chosen three different combustion options where all alternatives fit with the present heating distribution. The combustion options are biological oil, wood pellets and wood chips. To determine the best option a comparison between the different fuels has been done considering factors such as investment costs, environmental impact and fuel efficiency.Based on the analyzed results we suggest that wood pellets will be the most suitable fuel for Svegros facility and heating system. According to the lifecycle cost the new system will have paid off itself after 1,5 years. The savings made each year from changing fuel will be approximately 5,5 million SEK per year compared if the oil still was used. The new fuel will in addition to the financial savings also reduce the carbon dioxide emissions by 2300 tons per year.The consequence of choosing wood pellets as combustion fuel is that you have to combine the pellet burning with biofuel combustion. The combination will make it possible for the plants to survive extremely cold weather conditions during the winter.
437

Downregulation of Cinnamyl Alcohol Dehydrogenase or Caffeic Acid O-Methyltransferase Leads to Improved Biological Conversion Efficiency in Brachypodium distachyon

Trabucco, Gina M 01 January 2012 (has links) (PDF)
Lignin is a significant recalcitrant in the conversion of plant biomass to bioethanol. Cinnamyl alcohol dehydrogenase (CAD) and caffeic acid O-methyltransferase (COMT) catalyze key steps in the pathway of lignin monomer biosynthesis. Brown midrib mutants in Zea mays and Sorghum bicolor with impaired CAD or COMT activity have attracted considerable agronomic interest for their altered lignin composition and improved digestibility. We identified candidate genes encoding CAD and COMT enzymes in the grass model species Brachypodium distachyon and developed transgenic plants overexpressing artificial microRNA designed to silence BdCAD1 or BdCOMT4. Both transgenes caused altered flowering time and stem count and weight. Downregulation of BdCAD1 caused a leaf brown midrib phenotype, the first time this phenotype has been observed in a C3 plant. While acetyl bromide soluble lignin measurements were equivalent in BdCAD1-silenced and wildtype plants, histochemical staining and thioacidolysis indicated a decrease in lignin syringyl units and reduced syringyl/guaiacyl ratio in the transgenic plants. BdCOMT4-downregulated plants exhibited a decrease in total lignin content, a significant reduction of guaiacyl lignin, and a modest reduction of syringyl lignin. Ethanol yield by microbial fermentation was enhanced in both BdCAD1- and BdCOMT4-downregulated plants. These results have elucidated two key genes in the lignin biosynthetic pathway in B. distachyon that, when perturbed, may result in greater biomass yield and bioconversion efficiency.
438

Tillbaka till framtiden? : Gengas som ett alternativ till höga priser på el, bensin och diesel

Algotson, Gabriella, Hy, Sandra January 2023 (has links)
Första och andra världskrigen medförde stora importrestriktioner för bensin och diesel och Sverigestod inför en potentiell kris. Lösningen till drivmedelsbristen var gengas som produceras genom attförbränna träd eller kol i en syrefattig miljö. Med dagens kontinuerligt stigande bensin, diesel ochelpriser står Sverige inför en liknande situation och nya lösningar för att kompensera för de högapriserna söks. Detta kandidatarbete undersöker potentialen med att använda gengas som ett alternativ för attbedriva fordon och småhus för att sänka kostnaden. Arbetet tittar på hur gengas kan användas i treolika fall; i en taxi, lätt lastbil samt ett småhus över ett års tid där kostnadsvinsten beräknas genom attbestämma hur mycket ved som krävs utifrån hur mycket energi som krävs vid användning. Resultatettyder på att med dagens elpriser är el det billigare alternativet för bostäder. Däremot går det att se attdet kan vara ekonomiskts fördelaktigt att använda gengas istället för flytande bränsle när vedprised är billigt. / The First and Second World Wars imposed major import restrictions on gasoline and diesel andSweden faced a potential crisis. The solution to the fuel shortage was producer gas, which isproduced by burning trees or coal in a low-oxygen environment. With today's continuously risinggasoline, diesel and electricity prices, Sweden faces a similar situation and new solutions tocompensate for the high prices are being sought.This bachelor thesis examines the potential for using producer gas as an alternative to power vehiclesand small houses to reduce the cost. The thesis looks at how producer gas can be used in threedifferent cases; in a taxi, light truck and a small house over a years time where the cost benefit iscalculated by determining how much wood is required based on how much energy is required in use.The results indicate that with current electricity prices, electricity is the cheaper option for poweringhouses. However, it can be seen that it can be economically advantageous to use producer gas instead of liquid fuel when the price of wood is cheap.
439

Etanol som drivmedel : En analys av etanolbränslets minskade användning och dess framtidsutsikter / Ethanol as a fuel : An analysis of the reduced use of ethanol fuel and its future prospects

Nordhammer, Caroline, Stenberg, Amanda January 2019 (has links)
The use of biofuels within the Swedish transport sector has increased, although the use of ethanolhas decreased considerably since 2011. The purpose of this report is to examine why and onwhat grounds this decrease has occurred. Furthermore the report aims to discuss whether thisdevelopment is beneficial to reaching the climate goals of Sweden. The study focuses solely onethanol as a high proportion blend of E85 for road transportation and its future within theSwedish transport sector. The following questions have therefore been formulated: Why has thesale of ethanol (E85) decreased? Can ethanol (E85) be a tool for Sweden in order to reach itsclimate goals? In order to answer these questions, 12 interviews were conducted with different stakeholdersrelated to ethanol fuel. Stakeholders represented in this report are: organizations, authorities, fueldistributors, car manufacturers, scientists and purchasers. From the interviews, a number offactors that are assumed to have impacted the use of E85 were identified. The identified factorswere: the debate around the land use for ethanol production and its connection to increased foodprices and climate benefit, technical problems, increased operating costs, political means ofcontrol and pricing, and limited sales of new cars. It is probable that no single factor caused thedecrease in the use of E85, but that it was rather a combination of all of the aforementionedfactors over a certain period of time that lead to the decrease. In order for Sweden to reach its climate goals, three factors are significant: energy efficiency, adecrease in transportation and increased usage of renewable fuels must be implemented. E85could be part of the solution in order to reach these goals. There currently exists an infrastructurefor E85, which means that the goals can be reached in the short term, compared to electrification,which is considered to be a long term solution. Political means of control are crucial to the roleof the biofuel in the transition that is required to reach the goals, since they decide how E85 willbe able to compete on the fuel market going forward. / Användningen av biodrivmedel inom den svenska transportsektorn har ökat, däremot haretanolanvändningen minskat kraftigt sedan 2011. Syftet med denna rapport är att undersökavarför och på vilka grunder denna minskning har skett. Därutöver ämnar även rapporten attredogöra för en diskussion kring huruvida denna utveckling är gynnsam för att nå Sverigesuppsatta klimatmål eller inte. Studien avser endast att studera etanol som höginblandning i E85för vägtransporter och dess framtid inom den svenska transportsektorn. Följande frågeställningarhar formulerats: Varför har försäljningen av etanol (E85) som drivmedel minskat? Kan etanol(E85) utgöra ett medel för att Sverige ska nå sina uppsatta klimatmål? För att besvara frågeställningarna genomfördes 12 intervjuer med olika aktörstyper som ärrelaterade till etanolbränsle. Aktörstyper som representeras i denna rapport är:intresseorganisationer, myndigheter, drivmedelsdistributörer, biltillverkare, forskare samtupphandlare. Utifrån intervjuerna identifierades faktorer som antas ha påverkat användningen avE85. De faktorer som identifierades var: debatten kring etanolproduktionens markanvändningoch dess koppling till höjda livsmedelspriser samt klimatnytta, tekniska problem, högredriftkostnader, politiska styrmedel och prisbildning samt begränsad nybilsförsäljning. Det ärsannolikt att det inte var en enskild faktor som gav upphov till minskningen utan att det iställetrörde sig om en kombination av samtliga påverkansfaktorer under en viss tidsperiod. För att Sverige ska kunna nå landets klimatpolitiska mål är en förutsättning att det sker enenergieffektivisering, en minskning av transporter samt en ökad användning av förnybaradrivmedel. E85 kan utgöra en del av lösningen för att nå målen. Idag finns en tillgängliginfrastruktur för E85 vilket medför att målen kan nås på kort sikt i jämförelse med enelektrifiering som anses vara en långsiktig lösning. Politiska styrmedel är avgörande förbiobränslets roll i omställningen som krävs för att nå målen. Detta eftersom dessa avgör hur E85kommer att kunna konkurrera på marknaden för drivmedel fortsättningsvis.
440

Ignition and Combustion Characteristics of Nanoscale Metal and Metal Oxide Additives in Biofuel (Ethanol) and Hydrocarbons

Jones, Matthew January 2011 (has links)
No description available.

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