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| 2. |
- Lantz, Mikael, et al.
(författare)
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The prospects for an expansion of biogas systems in Sweden - Incentives, barriers and potentials
- 2007
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Ingår i: Energy Policy. - : Elsevier BV. - 1873-6777 .- 0301-4215. ; 35:3, s. 1830-1843
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Forskningsöversikt (refereegranskat)abstract
- Biogas is a renewable, high-quality fuel, currently produced at more than 200 locations in Sweden. The present production is some 5 PJ/year but the potential is approximately 10 times higher. Biogas can be produced from a wide range of raw materials, from organic waste to dedicated energy crops, and can be utilised for various energy services such as heat, combined heat and power or as a vehicle fuel. Biogas systems are therefore affected by a number of different incentives and barriers, including energy-, waste treatment- and agricultural policies. In this paper, different policies and policy instruments, as well as other factors, which influence a potential expansion of Swedish biogas systems, are identified and evaluated. Existing incentives and barriers can be divided into those affecting the production of biogas, and those affecting the utilisation of the biogas. Only a few types of biogas systems are competitive in Sweden today, while the majority needs increased incentives of different kinds to reach profitability. Such incentives are often motivated from an energy and environmental point of view. Due to the complexity of the biogas systems and the many actors involved, all with different interests, the process of implementing adequate policy instruments will require concerted efforts. (c) 2006 Elsevier Ltd. All rights reserved.
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| 3. |
- Svensson, Mattias, et al.
(författare)
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Biogas production from crop residues on a farm-scale level: is it economically feasible under conditions in Sweden?
- 2005
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Ingår i: Bioprocess and Biosystems Engineering. - : Springer Science and Business Media LLC. - 1615-7605 .- 1615-7591. ; 28:3, s. 139-148
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Tidskriftsartikel (refereegranskat)abstract
- Anaerobic digestion would enable the energy potential of agricultural crop residues such as sugar beet tops and straw to be harnessed. Sweden is so spread out that full utilisation of this potential by centralised slurry-based technology is difficult. It appears that simple but effective high-solids reactor systems have a better chance of being economically viable on a farm-scale level (50500 kW). In the present study, the financial prospects of high-solids digestion, using either single-stage fed-batch or two-stage batch reactor systems, are compared on a farm-scale level (50 kW) with those of conventional slurry digestion, on the basis of experimental results and observations on a laboratory- and pilot-scale. The gas produced can be used for heat, combined heat and power or as vehicle fuel. The results indicate high-solids single-stage fed-batch operations to stand the best chances of being competitive, particularly in connection with organic farming. The methane yield, degree of gas utilisation, and operational costs were found to have the strongest impact on the financial success of the process.
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| 4. |
- Svensson, Mattias, et al.
(författare)
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Biogas production from crop residues on a farm-scale level: Scale, choice of substrate and utilisation rate most important parameters for financial feasibility
- 2005
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)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.
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| 5. |
- Svensson, Mattias, et al.
(författare)
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Enhancing performance in anaerobic high-solids stratified bed digesters by straw bed implementation
- 2007
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Ingår i: Bioresource Technology. - : Elsevier BV. - 1873-2976 .- 0960-8524. ; 98:1, s. 46-52
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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.
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| 6. |
- Svensson, Mattias, et al.
(författare)
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Straw bed priming enhances the methane yield and speeds up the start-up of single-stage, high-solids anaerobic reactors treating plant biomass
- 2006
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Ingår i: Journal of Chemical Technology and Biotechnology. - : Wiley. - 0268-2575 .- 1097-4660. ; 81:11, s. 1729-1735
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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.
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