| 1. |
- Hammar, Torun, et al.
(författare)
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Climate impact and energy efficiency of woody bioenergy systems from a landscape perspective
- 2019
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Ingår i: Biomass and Bioenergy. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0961-9534 .- 1873-2909. ; 120, s. 189-199
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Tidskriftsartikel (refereegranskat)abstract
- The climate impact of bioenergy is debated, especially due to potential land use change effects and biogenic carbon fluxes. This study assessed the climate impact and energy efficiency of conventional long-rotation forest residues (branches, tops and stumps) and short-rotation forestry (willow) from a landscape perspective. A time-dependent life cycle assessment method, which considers the timing of biogenic carbon fluxes and the impact on global temperature over time, was combined with GIS mapping to assess the impact for a specific Swedish region (Uppsala County), i.e. a 'real' landscape. The results showed that harvesting forest residues decreased the forest carbon stocks over the landscape, while growing willow on previous fallow land increased the total carbon stocks. On average, energy ratios of 49 MJ MJ(-1) for branches and tops, and 30 MJ MJ(-1) for stumps and willow was found. Harvesting forest residues from the studied landscape resulted in climate impacts of around 0.8.10(-15) K MJ(-1) heat for branches and tops, and 1.3.10(-15) K MJ(-1) heat for stumps. Willow energy gave the lowest climate impact of about -0.6,10(-15) K MJ(-1) heat. The landscape analysis showed that spatial variations in the region had an effect on energy efficiency and climate impact, but that this effect was relatively small. A more important factor was the time frame chosen for the analysis, especially for long-rotation forest systems. Methodological choices such as spatial scale (stand or landscape perspective), allocation method and functional unit also influenced the results.
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| 2. |
- Kimming, Marie, et al.
(författare)
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Biomass from agriculture in small-scale combined heat and power plants - A comparative life cycle assessment
- 2011
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 35, s. 1572-1581
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Tidskriftsartikel (refereegranskat)abstract
- The results show that the biomass-based scenarios reduce greenhouse gas emissions considerably compared to the scenario based on fossil fuel, but have higher acidifying emissions. Scenario 1 has by far the best performance with respect to global warming potential and the advantage of utilizing a byproduct and thus not occupying extra land. Scenario 2 and 3 require less primary energy and less fossil energy input than 1, but set-aside land for willow production must be available. The low electric efficiency of scenario 3 makes it an unsuitable option. (C) 2011 Elsevier Ltd. All rights reserved.
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| 3. |
- Nilsson, Daniel, et al.
(författare)
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Pellet production from agricultural raw materials - A systems study
- 2011
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 35, s. 679-689
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Tidskriftsartikel (refereegranskat)abstract
- The demand for biofuel pellets has increased considerably in recent years, causing shortage of the traditional raw materials sawdust and wood shavings. In this study, the costs and energy requirements for the production of pellets from agricultural raw materials were analysed. The materials studied were Salix, reed canary grass, hemp, straw, screenings, rape-seed meal, rape cake and distiller's waste. Four production scales were analysed, having an annual output of 80,000, 8000, 800 and 80 tonnes of pellets per year. It was concluded that the raw materials of greatest interest were Salix and reed canary grass. They had competitive raw material costs and acceptable fuel properties and could be mixed with sawdust in existing large-scale pelleting factories. Straw had low production costs but can cause serious ash-related problems and should, as also is the case for screenings, be avoided in small-scale burners. Hemp had high raw material costs and is of less commercial interest, while distiller's waste, rape-seed meal and rape cake had higher alternative values when used as protein feed. The scale of production had a crucial influence on production costs. The machinery was used much more efficiently in large-scale plants, resulting in clear cost savings. Small-scale pelleting, both static and mobile, required cheap raw materials, low labour costs and long utilisation times to be profitable. In most cases, briquetting would be more commercially viable. The energy use in manufacturing pellets from air-dried crops was generally no higher than when moist sawdust was used as the raw material. (C) 2010 Elsevier Ltd. All rights reserved.
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| 4. |
- Porsö, Charlotta, et al.
(författare)
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Time-dependent climate impact of heat production from Swedish willow and poplar pellets - In a life cycle perspective
- 2014
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 70, s. 287-301
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Tidskriftsartikel (refereegranskat)abstract
- Sweden has the potential to increase fuel pellet production from alternative raw materials, such as willow and poplar, and also to use former agricultural land for energy crop production. This study used a life cycle perspective to investigate district heat production from pellets produced from willow or poplar cultivated on fallow land in Sweden. The energy efficiency and global warming potential of the systems was evaluated, additionally was the climate impact, expressed in global mean surface temperature change, evaluated from annual greenhouse gas data, including the most relevant fossil and biogenic sources and sinks. The systems were also compared with a fossil fuel alternative in which coal was assumed to be used for heat production. The results showed that the systems investigated had a cooling effect on both global mean surface temperature and global warming potential within the 100-year study period owing mainly to an increase in live biomass and a more long-term increase in soil organic carbon (C), which shows the importance of land use. At the same time, the systems produced renewable energy. The poplar system contributed to a larger cooling effect than the willow system due to more C being sequestered in live biomass and soil in the longer growth periods between harvests and to higher yield. The energy efficiency of the willow and poplar systems used for pellet fuel production was about 11 times the energy input. (C) 2014 Elsevier Ltd. All rights reserved.
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