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Sökning: WFRF:(Björnsson Lovisa)

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21.
  • Björnsson, Lovisa, et al. (författare)
  • Förbehandling av lignocellulosarika råvaror vid biogasproduktion - Nyckelaspekter vid jämförande utvärdering
  • 2014
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • I biogassektorn finns ett ökande behov av och en ökande konkurrens om råvaror, och intresset för användning av odlingsrester, vall, mellangrödor mm som biogasråvara ökar. Gemensamt för dessa råvaror är att de är fiberrika, dvs. har ett högt innehåll av lignocellulosa, vilket gör att det är osannolikt att de skulle användas för biogasproduktion utan förbehandling. Ett antal förbehandlingstekniker har introducerats på marknaden under senare år, och både företagsdrivna projekt och forskningsprojekt kring utvärdering av en eller flera förbehandlingstekniker pågår. Utvärderingarna läggs dock upp med olika utgångspunkter och metoder så att utkomster från olika projekt blir omöjliga att jämföra. Att utreda frågan om hur man utvärderar och jämför olika förbehandlingsmetoder ur teknik-, ekonomi-, energi- och miljöperspektiv är därför angeläget. Syftet med denna förstudie är att peka ut nyckelaspekter som är viktiga för att möjliggöra jämförande utvärdering av olika förbehandlingsmetoder samt att inspirera aktörer till att vilja medverka till att ta ett samlat grepp i frågan. Ett förslag till upplägg för vidare forskning, utveckling och demonstration presenteras. Arbetet med förstudien har finansierats genom Energimyndigheten.
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23.
  • Björnsson, Lovisa, et al. (författare)
  • Grass biomass as biofuel feedstock –sustainable or not?
  • 2017
  • Ingår i: European Biomass Conference and Exhibition Proceedings, 25thEUBCE, June 2017. - 2282-5819. - 9788889407172 ; 2017, s. 39-40
  • Konferensbidrag (refereegranskat)abstract
    • Low carbon input due to increasing specialization, intensification and reduced use of bio-fertilizer, leads to soil organic carbon (SOC) decreases in arable land. This is an emerging problem in Europe in general, where 45% of the EU soils have low and declining SOC content. SOC losses from agricultural soils influence soil fertility, putting food security at risk, and contributes to greenhouse gas (GHG) emissions. An agricultural practice rendering loss of SOC is thus not sustainable in the long term, and measures must be taken to reverse this trend. However, existing policies for agriculture and biofuels address these issues in isolation, SOC impact is not considered when sustainability criteria for biofuels are defined in the EU renewable energy directive (RED). The aim of this study was to illustrate the relevance of SOC impact on integrated production of food and grass as energy crop for biofuel production. This diversification of current cereal dominated crop rotations proved an efficient tool to reverse SOC losses, simultaneously producing a grass-based biofuel with low climate impact. Since SOC-related aspects are excluded in EU RED, the GHG reduction calculated according to the directive does, however, not meet the 60% GHG reduction demand. This narrow perspective causes potentially interesting double benefits to be missed.
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26.
  • Björnsson, Lovisa, et al. (författare)
  • Integrating bio-oil production from wood fuels to an existing heat and power plant - evaluation of energy and greenhouse gas performance in a Swedish case study
  • 2021
  • Ingår i: Sustainable Energy Technologies and Assessments. - : Elsevier. - 2213-1388 .- 2213-1396. ; 48
  • Tidskriftsartikel (refereegranskat)abstract
    • Combined heat and power (CHP) production in combination with a district heating (DH) grid gives an energy efficient use of wood fuels. The heat demand in the DH grid will, however, decline in the coming decades, and operators are seeking additional heat sinks. In this case study, the integration of a pyrolysis unit into an existing CHP plant was investigated as a possible solution. The retrofitted pyrolysis unit makes use of excess heat and yields a liquid bio-oil. Pyrolysis integrated with CHP production was shown to give a net energy yield of at least 80%, and to decrease the net heat output to the DH grid. The carbon footprint of the delivered heat was very low at maximum 1.6 g CO(2)eq/MJ. Prolonging the operation of the pyrolysis unit to periods without heat delivery to the DH grid would increase the use of existing installations, but at the cost of energy yields decreasing to 63-70%. Up to 2.8 PJ(LHV)/yr crude bio-oil could be produced at the investigated CHP plant. The bio-oil was shown to have a low carbon footprint, 1.7-4.0 g CO(2)eq/MJ(LHV), which makes it attractive for the rapidly expanding transport biofuel market.
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27.
  • Björnsson, Lovisa (författare)
  • Intensification of the biogas process by improved process monitoring and biomass retention
  • 2000
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The utilisation of energy in the form of biogas is one of the environmentally sound alternatives available using renewable energy sources. Biogas is formed by anaerobic degradation of organic material, the main consistuent being energy-rich methane. There is a large unused potential of organic waste that is suitable for biogas production and the anaerobic digestion process has the potential of becoming an important waste treatment and bioenergy generating method in the future. Laws, government grants, taxes and an increasing environmental concern are presently directing developments in a favourable direction for the increased use of the biogas process, but the implementation of anaerobic digestion technology is not straightforward and there is a need for further efforts to develop reliable, economically feasible technology. Anaerobic degradation is performed by a well-organised community of several microbial populations, and is a complex process. Some of the microbial groups involved are slow-growing and sensitive to changes in operating conditions. This can cause instability during both the start-up and operation of the anaerobic process. To make the biogas process more attractive from a commercial point of view, and to facilitate increased integration into our energy supply systems, these instability problems must be overcome in an economically viable way. The purpose of the present work was to investigate different methods of improving the performance and efficiency of the anaerobic digestion process. Based on the knowledge concerning microbial and physical events in the anaerobic digestion process, two main strategies were applied; biomass retention and improved process monitoring. Support materials were utilised to facilitate the retention of slow-growing organisms in biofilms, thereby stabilising the process. It was shown that the protected environment of a biofilm in combination with a long adaptation period made the treatment of toxic wastewater possible. A support material was also successfully used when treating waste containing a high concentration of insoluble particles. No clogging problems occurred, and the retention of important bacteria resulted in a change in metabolic flow and increased process stability. In a two-phase process, a protected environment can be created for the sensitive methanogens. A biosensor that could be used for monitoring of the flow of organic compounds reaching the methanogens was developed. The sensor was able to measure the biochemical oxygen demand (BOD) in a few minutes, making it suitable for on-line monitoring. More efficient operation can be achieved by improving process monitoring, which allows waste treatment at a higher rate. Traditional off-line monitoring methods used in anaerobic digestion were investigated; the results indicating that the present monitoring strategy is not adequate if the process is to be operated at a higher rate. The very rapid response to overload indicates that on-line monitoring is necessary to make suitable process control possible. A new method for utilising a semiconductor sensor for the monitoring of dissolved hydrogen on-line was described. The method was evaluated together with other traditional and new monitoring methods, and proved to be a useful tool in on-line anaerobic digester process monitoring.
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28.
  • 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. - 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.
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29.
  • Björnsson, Lovisa (författare)
  • Jordbruk och bioenergi
  • 2024
  • Ingår i: Perspektiv på bioenergi : Biomassans framtida roll i en föränderlig värld - Biomassans framtida roll i en föränderlig värld. - 1102-3651. - 9789186961596 ; :Rapport Nr 133, s. 29-38
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)
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