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| 2. |
- Ahlgren, Serina, et al.
(författare)
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Consequential Life Cycle Assessment of Nitrogen Fertilisers Based on Biomass – a Swedish perspective
- 2012
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Ingår i: Insciences Journal. - : Insciences Organization. - 1664-171X. ; 2, s. 80-101
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Tidskriftsartikel (refereegranskat)abstract
- The production of mineral nitrogen represents a large fossil energy input in Swedish agriculture. However, mineral nitrogen can be produced in the Haber-Bosch synthesis, with input from renewable energy. This could lower the dependency on fossil energy and the emissions of greenhouse gases in agricultural production. The aim of this study was to investigate the land use, energy use and greenhouse gas emissions from the production of ammonium nitrate based on biomass, using consequential life cycle assessment methodology. Three scenarios are studied. In one scenario the Haber-Bosch synthesis is integrated in an existing forest residue fired combined heat and power plant. In another two scenarios thermochemical gasification of biomass in combination with Haber-Bosch synthesis is studied, using either straw or short rotation coppice (Salix) as raw material. The results showed that the greenhouse gas emissions and use of fossil energy can be significantly lowered. The size of emission reductions compared to using fossil fuels as raw material is dependent on choice of data, but also choice of functional unit and if e.g. indirect land use change is included. The study also showed that using green nitrogen in rapeseed production substantially can lower the carbon footprint. Further, we argue that production of nitrogen based on renewables should be a high-priority activity, as nitrogen is one of the pillars for a secure food and bioenergy supply for a growing world population.
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| 3. |
- Ahlgren, Serina, et al.
(författare)
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Det svenska jordbrukets framtida drivmedelsförsörjning
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Syftet med detta arbete är att visa på möjligheter för det svenska jordbruket att bli försörjt med drivmedel även i en framtid, när oljan har blivit för dyr eller sällsynt för att kunna användas i tillräcklig omfattning. Detta projekt studerar möjligheterna att ersätta fossil diesel med första och andra generationens förnybara drivmedel, och omfattar drivmedel från råvaror med ursprung i både jord- och skogsbruk. De drivmedel som studeras är etanol, rapsmetylester (RME), biogas, Fischer-Tropsch diesel (FTD), dimetyleter (DME) och metanol. Arealbehov, energibalans och kostnader har beräknats. Studien visar att det finns tillräckligt med arealer i Sverige för att lantbruket ska kunna bli självförsörjande med drivmedel. För de drivmedel som baseras på grödor framförallt första generationens drivmedel) kommer dock mängden mat som är möjlig att producera att minska. Andra generationens drivmedel kan med fördel produceras från biprodukter som halm och matproduktionen behöver då inte minskas
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| 4. |
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| 5. |
- Ahlgren, Serina, et al.
(författare)
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Nitrogen fertiliser production based on biogas - Energy input, environmental impact and land use
- 2010
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Ingår i: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 101, s. 7181-7184
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present paper was to investigate the land use, environmental impact and fossil energy use when using biogas instead of natural gas in the production of nitrogen fertilisers The biogas was assumed to be produced from anaerobic digestion of ley grass and maize. The calculations showed that 1 ha of agricultural land in south-west Sweden can produce 1.7 metric ton of nitrogen in the form of ammonium nitrate per year from ley grass, or 3 6 ton from maize The impact on global warming, from cradle to gate, was calculated to be lower when producing nitrogen fertiliser from biomass compared with natural gas Eutrophication and acidification potential was higher in the biomass scenarios The greatest advantage of the biomass systems however lies in the potential to reduce agriculture's dependency on fossil fuels In the biomass scenarios, only 2-4 MJ of primary fossil energy was required, while 35 MJ/kg N was required when utilising natural gas (C) 2010 Elsevier Ltd All rights reserved
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| 6. |
- Ahlgren, Serina, et al.
(författare)
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Tractive power in organic farming based on fuel cell technology : Energy balance and environmental load
- 2009
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Ingår i: Agricultural Systems. - : Elsevier BV. - 0308-521X .- 1873-2267. ; 102:1-3, s. 67-76
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Tidskriftsartikel (refereegranskat)abstract
- This study analysed a future hypothetical organic farm self-sufficient in renewable tractor fuel. Biomass from the farm was assumed to be transported to a central fuel production plant and the fuel returned to the farm, where it was utilised in fuel cell powered tractors. The land use, energy balance and environmental impact of five different scenarios were studied. In the first two scenarios, straw was used as raw material for production of hydrogen or methanol via thermochemical gasification. In the third and fourth scenarios, short rotation forest (Salix) was used as raw material for the same fuels. In the fifth scenario, ley was used as raw material for hydrogen fuel via biogas production. The straw scenarios had the lowest impact in all studied environmental impact categories since the Salix scenarios had higher soil emissions and the ley scenario had comparatively large emissions from the fuel production. The energy balance was also favourable for straw, 16.3 and 19.5 for hydrogen and methanol respectively, compared to Salix 14.2 and 15.6. For ley to hydrogen the energy balance was only 6.1 due to low efficiency in the fuel production. In the Salix scenarios, 1.6% and 2.0% of the land was set aside for raw material production in the hydrogen and methanol scenarios respectively. In the straw scenarios no land needed to be reserved, but straw was collected on 4.3% and 5.3% of the area for hydrogen and methanol respectively. To produce hydrogen from ley, 4% of the land was harvested. The study showed that the difference in environmental performance lay in choice of raw material rather than choice of fuel. Hydrogen is a gas with low volumetric energy density, which requires an adapted infrastructure and tractors equipped with gas tanks. This leads to the conclusion that methanol probably will be the preferred choice if a fuel cell powered farm would be put into practice in the future. © 2009 Elsevier Ltd. All rights reserved.
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| 7. |
- Ericsson, Niclas, et al.
(författare)
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Climate impact and energy efficiency from electricity generation through anaerobic digestion or direct combustion of short rotation coppice willow
- 2014
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Ingår i: Applied Energy. - : Elsevier BV. - 0306-2619 .- 1872-9118. ; 132, s. 86-98
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Tidskriftsartikel (refereegranskat)abstract
- Short rotation coppice willow is an energy crop used in Sweden to produce electricity and heat in combined heat and power plants. Recent laboratory-scale experiments have shown that SRC willow can also be used for biogas production in anaerobic digestion processes.Here, life cycle assessment is used to compare the climate impact and energy efficiency of electricity and heat generated by these measures. All energy inputs and greenhouse gas emissions, including soil organic carbon fluxes were included in the life cycle assessment. The climate impact was determined using time-dependent life cycle assessment methodology.Both systems showed a positive net energy balance, but the direct combustion system delivered ninefold more energy than the biogas system. Both systems had a cooling effect on the global mean surface temperature change. The cooling impact per hectare from the biogas system was ninefold higher due to the carbon returned to soil with the digestate.Compensating the lower energy production of the biogas system with external energy sources had a large impact on the result, effectively determining whether the biogas scenario had a net warming or cooling contribution to the global mean temperature change per kWh of electricity. In all cases, the contribution to global warming was lowered by the inclusion of willow in the energy system. The use of time-dependent climate impact methodology shows that extended use of short rotation coppice willow can contribute to counteract global warming. (C) 2014 Elsevier Ltd. All rights reserved.
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| 8. |
- Ericsson, Niclas, et al.
(författare)
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Time-dependent climate impact and energy efficiency of combined heat and power production from short-rotation coppice willow using pyrolysis or direct combustion
- 2017
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Ingår i: Global Change Biology Bioenergy. - : Blackwell Publishing Ltd. - 1757-1693 .- 1757-1707. ; 9:5, s. 876-890
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Tidskriftsartikel (refereegranskat)abstract
- A life cycle assessment of a Swedish short-rotation coppice willow bioenergy system generating electricity and heat was performed to investigate how the energy efficiency and time-dependent climate impact were affected when the feedstock was converted into bio-oil and char before generating electricity and heat, compared with being combusted directly. The study also investigated how the climate impact was affected when part of the char was applied to soil as biochar to act as a carbon sequestration agent and potential soil improver. The energy efficiencies were calculated separately for electricity and heat as the energy ratios between the amount of energy service delivered by the system compared to the amount of external energy inputs used in each scenario after having allocated the primary energy related to the inputs between the two energy services. The energy in the feedstock was not included in the external energy inputs. Direct combustion had the highest energy efficiency. It had energy ratios of 10 and 36 for electricity and heat, respectively. The least energy-efficient scenario was the pyrolysis scenario where biochar was applied to soils. It had energy ratios of 4 and 12 for electricity and heat, respectively. The results showed that pyrolysis with carbon sequestration might be an option to counteract the current trend in global warming. The pyrolysis system with soil application of the biochar removed the largest amount of CO2 from the atmosphere. However, compared with the direct combustion scenario, the climate change mitigation potential depended on the energy system to which the bioenergy system delivered its energy services. A system expansion showed that direct combustion had the highest climate change mitigation potential when coal or natural gas were used as external energy sources to compensate for the lower energy efficiency of the pyrolysis scenario.
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| 9. |
- Ericsson, Niclas, et al.
(författare)
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Time-dependent climate impact of a bioenergy system - methodology development and application to Swedish conditions
- 2013
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Ingår i: GCB Bioenergy. - : Wiley. - 1757-1693 .- 1757-1707. ; 5, s. 580-590
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Tidskriftsartikel (refereegranskat)abstract
- The area of dedicated energy crops is expected to increase in Sweden. This will result in direct land use changes, which may affect the carbon stocks in soil and biomass, as well as yield levels and the use of inputs. Carbon dioxide (CO2) fluxes of biomass are often not considered when calculating the climate impact in life cycle assessments (LCA) assuming that the CO2 released at combustion has recently been captured by the biomass in question. With the extended time lag between capture and release of CO2 inherent in many perennial bioenergy systems, the relation between carbon neutrality and climate neutrality may be questioned. In this paper, previously published methodologies and models are combined in a methodological framework that can assist LCA practitioners in interpreting the time-dependent climate impact of a bioenergy system. The treatment of carbon differs from conventional LCA practice in that no distinction is made between fossil and biogenic carbon. A time-dependent indicator is used to enable a representation of the climate impact that is not dependent on the choice of a specific characterization time horizon or time of evaluation and that does not use characterization factors, such as global warming potential and global temperature potential. The indicator used to aid in the interpretation phase of this paper is global mean surface temperature change (T-s(n)). A theoretical system producing willow for district heating was used to study land use change effects depending on previous land use and variations in the standing biomass carbon stocks. When replacing annual crops with willow this system presented a cooling contribution to T-s(n). However, the first years after establishing the willow plantation it presented a warming contribution to T-s(n). This behavior was due mainly to soil organic carbon (SOC) variation. A rapid initial increase in standing biomass counteracted the initial SOC loss.
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