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Sökning: WFRF:(Björnsson Lovisa)

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  • Föregående 123[4]567...9Nästa
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  • Björnsson, Lovisa, et al. (författare)
  • Introduction of grass-clover crops as biogas feedstock in cereal-dominated crop rotations. Part II: Effects on greenhouse gas emissions
  • 2014
  • Ingår i: Proceedings of the 9th International Conference on Life Cycle Assessment in the Agri-Food Sector. - : ACLCA, Vashon, WA, USA. - 9780988214576 ; , s. 134-141
  • Konferensbidrag (refereegranskat)abstract
    • In an analysis of climate effects, increased soil organic carbon will have a dual effect due to both increased soil fertility and carbon sequestration. Even so, soil carbon changes are neglected in many crop production LCAs. In the present study, the introduction of grass-clover crops in cereal-dominated crop production was evaluated. The grass-clover crops were used for biogas production, and the digested residue was recycled to the farm as biofertilizer. A shift from the cereal-dominated crop rotation to integrated production of food crops and one or two years of grass-clover crops used as biogas feedstock would result in avoided emissions of 2-3 t CO2-eq. ha-1 a-1. Integrated food and energy crop production would in this case improve soil organic carbon content at the same time as resulting in considerably decreased greenhouse gas emissions from the cultivation system.
  • Björnsson, Lovisa (creator_code:cre_t)
  • Pretreating non-wood lignocellulosic material (e.g. bagasse) to produce ethanol, comprises adding organic acid or organic acid-producing bacteria to lignocellulosic material, and storing and heating the organic acid-impregnated material
  • 2012
  • Patent (övrigt vetenskapligt)abstract
    • NOVELTY - Pretreating non-wood lignocellulosic material containing less than 5 wt.% starch or sugar for producing ethanol from lignocellulose, comprises: (a) adding organic acid or organic acid-producing bacteria to the lignocellulosic material; (b) storing the lignocellulosic material in presence of organic acid for at least 2 weeks in an atmosphere of less than 5% oxygen to obtain organic acid-impregnated material; and (c) heating the organic acid-impregnated material at a temperature of at least 190 degrees C for at least 5 minutes to obtain pretreated lignocellulosic material. USE - The method is useful for pretreating non-wood lignocellulosic material to produce ethanol, where the non-wood lignocellulosic material is bagasse (preferably sugar cane bagasse or sweet Sorghum bagasse), sugar cane trash, wheat straw, rice straw, Sorghum species, Arundo, Miscanthus or agricultural residues (all claimed). ADVANTAGE - The method: avoids the need of inorganic acid or base (sulfur dioxide), and utilizes containers which are less corrosion resistant, hence economical; has higher net energy gain; utilizes organic acid which is biodegradable, and produces degradation products (e.g. 5-hydroxymethylfurfural and furfural which acts as inhibitory substances in the subsequent fermentation process), thus environmentally friendly. DETAILED DESCRIPTION - Pretreating non-wood lignocellulosic material containing less than 5 wt.% starch or sugar for producing ethanol from lignocellulose, comprises: (a) adding organic acid or organic acid-producing bacteria to the lignocellulosic material; (b) storing the lignocellulosic material in the presence of organic acid for at least 2 weeks in an atmosphere of less than 5% oxygen to obtain organic acid-impregnated material; and (c) heating the organic acid-impregnated material at a temperature of at least 190 degrees C for a period of at least 5 minutes to obtain pretreated lignocellulosic material, where no inorganic acid or base including sulfur dioxide is added in the method.
  • Björnsson, Lovisa, et al. (författare)
  • Supports made from recycled glass as biofilm carriers in anaerobic packed bed treatment of high-strength wastewaters
  • 1997
  • Ingår i: Resource and Environmental Biotechnology. - : ABA. - 1358-2283. ; 1, s. 243-256
  • Tidskriftsartikel (refereegranskat)abstract
    • The possibility of using carriers made of recycled glass in anaerobic packed bed reactors has been studied in laboratory-scale experiments. Two types of carrier were studied: a porous bead of glass foam and an open ring of a smoother, sintered glass. The performance of processes with these carriers was compared with a conventional upflow anaerobic sludge blanket (UASB) process. The treatment of wastewater from a pulp and paper mill, and from a pharmaceutical plant was studied. Both carrier types were found to be suitable for supporting biofilm growth. With the porous beads, however, suspended sludge accumulated between the carriers, which caused clogging of the process. This, together with the low mechanical strength of the material, makes this carrier less suitable for full-scale processes. The sintered rings showed no signs of clogging and had better mechanical qualities and the maximum loading rate for pulp and paper processing wastewater was 10 kg COD m-3 d-1. This is similar to processes with commercially available plastic carriers, but with the UASB process, the maximum load with this wastewater was around 20 kg COD m-3 d-1, which makes the sintered ring process non-competitive. An anaerobic packed bed process with glass carriers could, however, find applications where the UASB process is not applicable. For example, the wastewater from the pharmaceutical plant could not be treated with conventional suspended sludge methods due to the toxicity of the effluent. Instead, treatment in a packed bed with porous glass beads was tested with good results.
  • Björnsson, Lovisa, et al. (författare)
  • Utilisation of a Pd-MOS sensor for on-line monitoring of dissolved hydrogen in anaerobic digestion
  • 2001
  • Ingår i: Biotechnology and Bioengineering. - : John Wiley and Sons Inc.. - 1097-0290. ; 73:1, s. 35-43
  • Tidskriftsartikel (refereegranskat)abstract
    • The use of a hydrogen-sensitive palladium-metal oxide semiconductor (Pd-MOS) sensor in combination with a membrane for liquid-to-gas transfer for the detection of dissolved hydrogen was investigated. The system was evaluated with known concentrations of dissolved hydrogen in water. The lowest concentration detected with this set-up was 160 nM. The method was applied to monitoring of a laboratory-scale anaerobic digestion process employing mixed sludge containing mainly food/industrial waste. Pulse loads of glucose were added to the system at different levels of microbial activity, and the microbial status of the culture was reflected in the dissolved hydrogen response. Simultaneous headspace hydrogen measurements were performed, and at the lower levels of dissolved hydrogen no corresponding headspace hydrogen could be detected. When glucose was added to a resting culture the dissolved hydrogen response was rapid and the first response could be detected 9 min after addition of glucose, whereas headspace hydrogen concentrations increased only after 80 to 110 min. This indicates limitations in the liquid-to-gas hydrogen transfer and illustrates the importance of hydrogen monitoring in the liquid. The sensor system developed is flexible, the membrane is easily replaceable, and the probe for liquid-to-gas hydrogen transfer can be adjusted easily to large-scale applications.
  • Bohn, Irene, et al. (författare)
  • Effect of temperature decrease on the microbial population and process performance of a mesophilic anaerobic bioreactor
  • 2007
  • Ingår i: Environmental Technology. - : Selper Ltd. - 1479-487X. ; 28:8, s. 943-952
  • Tidskriftsartikel (refereegranskat)abstract
    • The effect of a temperature decrease from 33 degrees C to 12 degrees C was investigated for anaerobic digestion of crop residues. A laboratory-scale reactor (R,) was inoculated with mesophilic sludge and operated as continuously stirred fed-batch system at temperatures of 12 degrees C, 18 degrees C and 33 degrees C. Changes in the microbial populations of the sludge were followed by means of fluorescence in situ hybridization analysis. Methane was produced in R, at all temperatures. Stable long-term operation at 18 degrees C was achieved yielding 151 mlCH(4) gVS(added)(-1) at a rate of 108 mlCH(4) l(R)(-1)d(-1) once the microbial populations of the sludge had adapted to this temperature. After operation at 18 degrees C, the contents of R-0, was mixed and distributed into three smaller reactors, which were operated at 18 degrees C (R-18), 25 degrees C (R-25) and 37 degrees C (R-37) respectively. Methane production rates for R-37 and R-25 were 366 and 310 mlCH(4) l(R)(-1)d(-1), respectively, which were higher than the 215 mlCH(4) l(R)(-1)d(-1) obtained in R-0 when this was operated at 33 degrees C. Hydrolysis was found to decrease when temperature was decreased and especially below 25 degrees C. At temperatures below 16 degrees C, acidogenesis and methanogenesis were the rate-limiting steps. Adaptation of the mesophilic sludge to 18 degrees C was indicated by an increase in the ratio of Bacteria to total prokaryotes (sum of Archaea and Bacteria). This was thought to be caused by enrichment of Bacteria in the sludge, which appeared to be an important adaptation mechanism. During the adaptation, the Methanomicrobiales and Methanosarcinaceae populations increased relative to the total Archaea population whereas the Methanosaeta population decreased. The population changes were reflected by reactor performance.
  • Bohn, Irene, et al. (författare)
  • The energy balance in farm scale anaerobic digestion of crop residues at 11-37 degrees C
  • 2007
  • Ingår i: Process Biochemistry. - : Elsevier. - 1873-3298. ; 42:1, s. 57-64
  • Tidskriftsartikel (refereegranskat)abstract
    • Crop residues can be used for biogas production in farm scale reactors. Use of a process temperature below mesophilic conditions reduces the need for heating as well as investment and operating costs, although it may also reduce the methane yield. In the present study the effect of temperature on net energy output was studied using sugar beet tops and straw as substrates for two pilot-scale reactors. Digestion was found to be stable down to 11 degrees C and optimal methane yield was obtained at 30 degrees C. The methane yield and process performance was studied at 15 degrees C and 30 'C as organic loading rates were increased. It was found that the highest net energy production would be achieved at 30 degrees C with a loading rate of 3.3 kg VS m(-3) day(-1). Running a low-cost process at ambient temperatures would give a net energy output of 60% of that obtained at 30 degrees C. (c) 2006 Elsevier Ltd. All rights reserved.
  • Bohn, Irene, et al. (författare)
  • Torrötning av rejekt från förbehandling av matavfall.
  • 2011
  • Rapport (övrigt vetenskapligt)abstract
    • När källsorterat matavfall från hushållen rötas i en biogasanläggning av modellen omrörd tank behövs en förbehandling för att göra materialet pumpbart och ta bort orenheter. En typ av förbehandling innebär att avfallet passerar genom en skruvpress som delar avfallet i en pumpbar fraktion och en torr fraktion, så kallat rejekt. På NSR förbehandlas matavfallet med denna teknik och rejektet skickas idag till förbränning. Tidigare studier har visat att ca 30% av metanpotentialen i matavfallet finns kvar i rejektet. Syftet med detta projekt var att undersöka möjligheterna att utvinna den kvarvarande metanpotentialen genom att testa satsvis torrötning med efterföljande kompostering som alternativ till förbränning. Vid satsvis torrötning i lakbädd läggs materialet i en reaktor (lakbädd) som översilas med vätska. Det är därför viktigt att lakbädden har en porös struktur som gör att vätskan fördelas jämt i materialet. Rötning av enbart rejekt och rejekt blandat med strukturmaterial testades för att undersöka om inblandning av strukturmaterial gav någon effekt. För att undersöka flödesegenskaperna i lakbädd, med och utan inblandning av strukturmaterial, genomfördes två spårämnesförsök. Efter rötningen komposterades den fasta rötresten, och färdiga kompostens kvalitet utvärderades. Porlukten i rötresten och i komposten under komposteringsprocessen och efter siktning av komposten utvärderades dessutom. Spårämnesförsöken och rötningsförsöken visade att inblandning av strukturmaterial påverkade flödesmönstret och rötningsprocessen i lakbädden i positiv riktning. Tillsats av strukturmaterial var nödvändigt för att rötningsprocessen skulle fungera. Tekniken med spårämnesförsök visade sig vara lämplig för att indikera graden av homogen perkolering av bädden. Vid rötning av rejekt uppblandat med strukturmaterial uppnåddes ett metanutbyte på 100 Nm3 metan per ton blandning vilket motsvaradedet förväntade metanutbytet. Vid kompostering av materialet uppnåddes kraven på hygienisering och halt av tungmetaller. Däremot var halten synliga orenheter över 2 mm för hög, och den siktning med 15 mm såll som genomfördes visade sig inte vara tillräcklig som efterbehandling av komposten. Luktpotentialen i den siktade komposten var runt 300 OUE/m3 vilket kan beskrivas som oproblematisk, medan luktpotentialen i rötresten och under komposteringsprocessen var högre.
  • Börjesson, Pål, et al. (författare)
  • Energy Crop-Based Biogas as Vehicle Fuel: The Impact of Crop Selection on Energy Efficiency and Greenhouse Gas Performance
  • 2015
  • Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 8:6, s. 6033-6058
  • Tidskriftsartikel (refereegranskat)abstract
    • The production of biogas from six agricultural crops was analysed regarding energy efficiency and greenhouse gas (GHG) performance for vehicle fuel from a field-to-tank perspective, with focus on critical parameters and on calculation methods. The energy efficiency varied from 35% to 44%, expressed as primary energy input per energy unit vehicle gas produced. The GHG reduction varied from 70% to 120%, compared with fossil liquid fuels, when the GHG credit of the digestate produced was included through system expansion according to the calculation methodology in the ISO 14044 standard of life cycle assessment. Ley crop-based biogas systems led to the highest GHG reduction, due to the significant soil carbon accumulation, followed by maize, wheat, hemp, triticale and sugar beet. Critical parameters are biogenic nitrous oxide emissions from crop cultivation, for which specific emission factors for digestate are missing today, and methane leakage from biogas production. The GHG benefits were reduced and the interrelation between the crops changed, when the GHG calculations were instead based on the methodology stated in the EU Renewable Energy Directive, where crop contribution to soil carbon accumulation is disregarded. All systems could still reach a 60% GHG reduction, due to the improved agricultural management when digestate replaces mineral fertilisers.
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