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Sökning: WFRF:(Björnsson Lovisa)

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  • Prade, Thomas, et al. (författare)
  • Introduction of grass-clover crops as biogas feedstock in cereal dominated crop rotations. Part I: Effects on soil organic carbon and food production
  • 2014
  • Ingår i: Proceedings of the 9th International Conference on Life Cycle Assessment in the Agri-Food Sector. - : ACLCA, Vashon, WA, USA. - 9780988214576 ; , s. 1032-1040
  • Konferensbidrag (refereegranskat)abstract
    • Changes of soil organic carbon (SOC) ontent can have a substantial effect on greenhouse gas emissions, but are rarely included in cropproduction LCAs. SOC content strongly influences soil fertility and therefore crop yields, but is declining in many European soils. The present study investigated if integration of 1-2 years of grass-clover crops in a cereal-dominated crop rotation can increase the SOC pool and how this would impact food production. Results show that when grass-clover crops are integrated, the potential SOC content at steady state will be 41 to 52% higher than in the conventional cereal-dominated crop rotation. The net increase of wheat yields based on SOC improvements indicate that for a crop rotation with one year of grass-clover crops, the initial loss of food production can be counterbalanced due to the impact on fertility of the SOC increase.
  • Selling, Robert, et al. (författare)
  • Two-stage anaerobic digestion enables heavy metal removal.
  • 2008
  • Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223. ; 57:4, s. 553-558
  • Tidskriftsartikel (refereegranskat)abstract
    • To fully exploit the environmental benefits of the biogas process, the digestate should be recycled as biofertiliser to agriculture. This practice can however be jeopardized by the presence of unwanted compounds such as heavy metals in the digestate. By using two-stage digestion, where the first stage includes hydrolysis/acidification and liquefaction of the substrate, heavy metals can be transferred to the leachate. From the leachate, metals can then be removed by adsorption. In this study, up to 70% of the Ni, 40% of the Zn and 25% of the Cd present in maize was removed when the leachate from hydrolysis was circulated over a macroporous polyacrylamide column for 6 days. For Cu and Pb, the mobilization in the hydrolytic stage was lower which resulted in a low removal. A more efficient two-stage process with improved substrate hydrolysis would give lower pH and/or longer periods with low pH in the hydrolytic stage. This is likely to increase metal mobilisation, and would open up for an excellent opportunity of heavy metal removal.
  • Sipos, Balint, et al. (författare)
  • Steam pretreatment of dry and ensiled industrial hemp for ethanol production
  • 2010
  • Ingår i: BIOMASS & BIOENERGY. - : Elsevier. - 1873-2909 .- 0961-9534. ; 34:12, s. 1721-1731
  • Tidskriftsartikel (refereegranskat)abstract
    • Biomass can be converted into liquid and gaseous biofuels with good efficiency. In this study, the conversion of industrial hemp (Cannabis sativa L.), a biomass source that can be cultivated with a high biomass yield per hectare, was used. Steam pretreatment of dry and ensiled hemp was investigated prior to ethanol production. The pretreatment efficiency was evaluated in terms of sugar recovery and polysaccharide conversion in the enzymatic hydrolysis step. For both materials, impregnation with 2% SO2 followed by steam pretreatment at 210 degrees C for 5 min were found to be the optimal conditions leading to the highest overall yield of glucose. Simultaneous saccharification and fermentation experiments carried out with optimised pretreatment conditions resulted in ethanol yields of 163 g kg(-1) ensiled hemp (dry matter) (71% of the theoretical maximum) and 171 g kg(-1) dry hemp (74%), which corresponds to 206-216 l Mg-1 ethanol based on initial dry material. (C) 2010 Elsevier Ltd. All rights reserved.
  • Svensson, Mattias, et al. (författare)
  • Biogas production from crop residues on a farm-scale level: Scale, choice of substrate and utilisation rate most important parameters for financial feasibility
  • 2005
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • Anaerobic digestion would enable the energy potential of agricultural crop residues such as ley crops, sugar beet tops and straw to be harnessed in Sweden. These residues are so spread out that full utilisation of the potential by centralised slurry-based technology is difficult, its appearing that simple but effective high-solids reactor systems have a better chance of being economically viable on a farm-scale level (30-300 kW). In the present study, the financial prospects of single-stage fed-batch high-solids digestion on three different scales, 51, 67 and 201 kW, were calculated, on the basis of experimental results and observations on a laboratory- and pilot-scale. The biogas was disposed as heat, combined heat and power or as vehicle fuel. The results indicate the importance of choosing substrates with a high methane yield and a high nitrogen content, and the necessity of fully utilising both the capacity of the equipment installed and the energy carriers produced.
  • Svensson, Mattias, et al. (författare)
  • Enhancing performance in anaerobic high-solids stratified bed digesters by straw bed implementation
  • 2007
  • Ingår i: Bioresource Technology. - : Elsevier. - 1873-2976. ; 98:1, s. 46-52
  • Tidskriftsartikel (refereegranskat)abstract
    • Anaerobic high-solids single-stage stratified bed digesters have been found to be simple and flexible design candidates for small-scale reactors located in medium- to low-technology environments. In the present study, wheat straw was used as the starter material for the stratified bed. Upon green mass feeding, the anaerobically stabilised straw bed functioned both as a biofilm support and as a particulate filter. It enabled a direct onset of 7 kg VS m(-3) batch loads, added twice a week, and permitted a low but consistent bed permeability during feeding at an average superficial flow velocity of 1 m d(-1) to be achieved. Fed-batch tests with sugar beet tops in pilot- and laboratory-scale setups at an average loading rate of 2 kg VS m(-3) d(-1) resulted in average biogas production rates of 1.2-1.4 m(3) m(-3) d(-1) and methane yields of 0.31-0.36 m(3) kg(-1) VSadded. At the end of the laboratory-scale feeding trial, the 200 day old straw bed had compacted to 50% of its initial volume, without any negative effects on performance being detectable. (c) 2005 Elsevier Ltd. All rights reserved.
  • Svensson, Mattias, et al. (författare)
  • Startup of an anaerobic single stage digester with a fixed wheat straw bed
  • 2001
  • Ingår i: 9th World Congress, Anaerobic Digestion 2001, Anaerobic Conversion for Sustainability, Proceedings. - : Technologisch Instituut vzw. - 9076019169 ; , s. 549-551
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • The most common form of technology for energy utilization via anaerobic treatment is slurry digestion with a low solids contents, such as sewage sludge or manure. Process control and maintenance are relatively simple, but costs involved with liquid handling and heating favour large, centralised plants. Raising the solids content of a digester to 30% significantly improves the economy of anaerobic digestion, increasing the methane production per volume unit reactor, and avoiding the handling and heating of large volumes of process water. One simple and potentially cheap method of high-solids reactor implementation is a single stage fixed bed reactor, with a solid substrate as the bed and a recycled leachate stream One potential problem with this design is an initial organic acid production during reactor startup, which originates from the easily degradable substrate. A low initial loading rate gives a safer but prolonged startup, and decreases gas production in this period. The choice of substrate strongly influences the probability of clogging. A more careful choice of carrier material allows quicker startup, and reduces the risk of clogging. The material should degrade slowly, to avoid overload during startup, and have a rigid structure in order to avoid clogging. This bed can then be fed from the top with more easily degradable substrate, e.g. crop residue. In this study, we demonstrate startup of a single stage wheat straw (low biodegradability) reactor in a fixed bed.
  • Svensson, Mattias, et al. (författare)
  • Straw bed priming enhances the methane yield and speeds up the start-up of single-stage, high-solids anaerobic reactors treating plant biomass
  • 2006
  • Ingår i: Journal of Chemical Technology and Biotechnology. - : Wiley-Blackwell. - 0268-2575. ; 81:11, s. 1729-1735
  • Tidskriftsartikel (refereegranskat)abstract
    • A simple and potentially inexpensive implementation of a high-solids reactor is a single-stage, stratified bed reactor, in which the bed is made up of the plant biomass fed into the system. In the present study, the stratified bed was started up for a period of four weeks by either direct feeding of sugar beet leaves at four different feeding rates, or by introducing a straw bed primer which was batch digested without feeding. During weeks five to six both systems were fed with sugar beet leaves at such a rate that the total amount of beet leaves added at the end of week six was the same in each of the four corresponding pairs of straw and 'no-straw' reactors. Straw bed priming enhanced the methane yield of the sugar beet leaves, with 0.33-0.37 in 3 kg(-1) VSadded (volatile solids) accumulated at average solid retention times as short as 11-25 days, while the 'no-straw' reactors had lower yields at longer average solid retention times. The levels and speciation of the organic acids suggested that both the rate and extent of the anaerobic digestion of the sugar beet leaves added in the straw reactors were improved. At the highest loading rate, the straw reactor failed, while the 'no-straw' reactor did not. It is hypothesised that the microbial biomass was better established in the straw reactors than in the 'no-straw' reactors.
  • Svensson, Mattias, et al. (författare)
  • The effect of packing density on the startup and operation of an anaerobic single stage fixed wheat straw bed digester
  • 2002
  • Ingår i: Proceedings of 3rd International Symposium for Anaerobic Digestion of Solid Wastes. - : Technische Universität München. ; , s. 14-14
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • In Southern Sweden, production of renewable energy from crop residues digestion is viewed as a worthwhile alternative. Also, the process gives valuable mineralised nitrogen as a by-product, which when produced at farm-scale can be recycled for ecological farming. It is difficult to achieve economic utilisation of crop residues in centralised slurry digestion, mainly because of the greater transport costs. Traditional reactor designs have a too low cost efficiency on farm-scale level, and therefore it is essential to introduce technologies and practices leading to economically viable reactor systems on this scale. One very simple reactor design being considered is the vertical column fixed bed digester. This allows relatively high loading rates, combined with a low maintenance requirement. Plant material can be used as a biofilm carrier, and is an inexpensive and highly efficient alternative to traditional support materials, and wheat straw, with its rigid structure and low biodegradability, is a good candidate. In this study, the influence of packing density on startup and single stage semi-batch operation of vertical column fixed bed digesters was examined in one laboratory-scale and three pilot-scale systems.
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