| 1. |
- Berndes, Göran, 1966, et al.
(författare)
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The contribution of biomass in the future global energy supply: A review of 17 studies
- 2003
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Ingår i: Biomass and Bioenergy. - 1873-2909 .- 0961-9534. ; 25:1, s. 1-28
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Tidskriftsartikel (refereegranskat)abstract
- This paper discusses the contribution of biomass in the future global energy supply. The discussion is based on a review of 17 earlier studies on the subject. These studies have arrived at widely different conclusions about the possible contribution of biomass in the future global energy supply (e.g., from below 100 EJ yr-1 to above 400 EJ yr-1 in 2050). The major reason for the differences is that the two most crucial parameters - land availability and yield levels in energy crop production - are very uncertain, and subject to widely different opinions (e.g., the assessed 2050 plantation supply ranges from below 50 EJ yr-1 to almost 240 EJ yr-1). However, also the expectations about future availability of forest wood and of residues from agriculture and forestry vary substantially among the studies. The question how an expanding bioenergy sector would interact with other land uses, such as food production, biodiversity, soil and nature conservation, and carbon sequestration has been insufficiently analyzed in the studies. It is therefore difficult to establish to what extent bioenergy is an attractive option for climate change mitigation in the energy sector. A refined modeling of interactions between different uses and bioenergy, food and materials production - i.e., of competition for resources, and of synergies between different uses - would facilitate an improved understanding of the prospects for large-scale bioenergy and of future land-use and biomass management in general. © 2003 Elsevier Science Ltd. All rights reserved.
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| 2. |
- Berndes, Göran, 1966, et al.
(författare)
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The feasibility of large-scale lignocellulose-based bioenergy production
- 2001
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Ingår i: Biomass and Bioenergy. - 1873-2909 .- 0961-9534. ; 20:5, s. 371-383
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Tidskriftsartikel (refereegranskat)abstract
- Global, large-scale use of bioenergy may replace a significant part of present fossil fuel use. We show that labor availability and water resources are large compared to those required to operate a bioenergy system of such size. The present study contradicts the assertion by Giampietro et al. [Bioscience 47(9) (1997) 587], that labor and water availability provide invincible barriers to a large-scale use of biofuels. We examine water and labor requirements under more reasonable assumptions about bioenergy supply options and demand levels. Bioenergy supplies are based on dedicated plantations of lignocellulosic crops and bioenergy demand is based on the renewable intensive global energy scenarios (RIGES). We find that labor and water requirements are an order of magnitude lower than the estimates by Giampietro et al. For instance, labor requirements do not exceed 1 percent of the estimated total work force in any country. © 2001 Elsevier Science Ltd.
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| 3. |
- Börjesson, Pål
(författare)
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Energy Analysis of Biomass Production and Transportation
- 1996
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Ingår i: Biomass & Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 11:4, s. 305-318
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Tidskriftsartikel (refereegranskat)abstract
- Energy efficiency in the production and transportation of different kinds of biomass in Sweden has been analysed, as well as the change in energy efficiency in a transition from fossil-fuel-based to biomass-based systems. Net energy yields under current production conditions were found to be highest for short-rotation forest (Salix) and sugar beet (about 160 to 170 GJ ha-1 year-1), followed by ley crops (110 to 140 GJ ha-1 year-1), and rape, wheat, and potatoes (50 to 90 GJ ha-1 year-1). The energy input per unit biomass produced is lowest for straw, logging residues and Salix, equal to 4 to 5% of the energy output. Corresponding figures for perennial ley crops are 7 to 10% and for annual crops 15 to 35%. Salix chips can be transported by truck about 250 km before the transportation energ is equal to the production energy. Corresponding distances for tractor, train and boat (coastal shipping) are about 100 km, 500 km and 1000 km, respectively. It is estimated that future increases in yield and technological development will almost double net energy yields for dedicated energy crops within the next two decades. A transition from a fossil-fuel-based energy system to a CO2-neutral biomass-based system around the year 2015 is estimated to increase the energy input in biomass production and transportation by about 30 to 45%, resulting in a decreased net energy output of about 4%.
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| 4. |
- Börjesson, Pål, et al.
(författare)
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Future Production and Utilisation of Biomass in Sweden: Potentials and CO2 Mitigation
- 1997
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Ingår i: Biomass & Bioenergy. - 1873-2909 .- 0961-9534. ; 13:6, s. 399-412
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Tidskriftsartikel (refereegranskat)abstract
- Swedish biomass production potential could be increased significantly if new production methods, such as optimised fertilisation, were to be used. Optimised fertilisation on 25% of Swedish forest land and the use of stem wood could almost double the biomass potential from forestry compared with no fertilisation, as both logging residues and large quantities of excess stem wood not needed for industrial purposes could be used for energy purposes. Together with energy crops and straw from agriculture, the total Swedish biomass potential would be about 230 TWh/yr or half the current Swedish energy supply if the demand for stem wood for building and industrial purposes were the same as today. The new production methods are assumed not to cause any significant negative impact on the local environment. The cost of utilising stem wood produced with optimised fertilisation for energy purposes has not been analysed and needs further investigation. Besides replacing fossil fuels and, thus, reducing current Swedish CO2 emissions by about 65%, this amount of biomass is enough to produce electricity equivalent to 20% of current power production. Biomass-based electricity is produced preferably through co-generation using district heating systems in densely populated regions, and pulp industries in forest regions. Alcohols for transportation and stand-alone power production are preferably produced in less densely populated regions with excess biomass. A high intensity in biomass production would reduce biomass transportation demands. There are uncertainties regarding the future demand for stem wood for building and industrial purposes, the amount of arable land available for energy crop production and future yields. These factors will influence Swedish biomass potential and earlier estimates of the potential vary from 15 to 125 TWh/yr.
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| 5. |
- Hansson, P.A., et al.
(författare)
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Air emissions from the fuel supply system of a Swedish CHP plant and the effects of stricter emission regulations
- 2003
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Ingår i: Biomass and Bioenergy. - 1873-2909 .- 0961-9534. ; 24:1, s. 59-68
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this work was to quantify the energy use and production of air emissions by supply systems for different biofuels used in a typical Swedish combined heat and power plant. In addition, the effects of the future reductions in the total amounts of exhaust gas emissions, as a result of stricter emission regulations for transport and off-road equipment, were studied. A model was developed and used for the calculations. Input data were collected from a plant situated some 100 km from Stockholm in Sweden. Biofuels used by the plant include chips from limbs and tops, by-products from sawmills and chips from willow energy plantations. The results show that residues from sawmills are very favourable in terms of the studied environmental parameters. Air emissions from limbs and tops is 5-8 times greater than that from sawmills. The use of a terminal for temporary storage means that additional transport and loading operations are necessary which result in a 30% increase in air emissions. The most important effects of the stricter emission regulations are that emissions of nitrous oxides (NOx) caused by the supply system will decrease by up to 70% within 10 years and that the unburned hydrocarbon (HC) emissions will decrease by 30-35%. © 2002 Elsevier Science Ltd. All rights reserved.
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| 6. |
- Boman, Christoffer, 1970-, et al.
(författare)
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Effects of increased small-scale biomass pellet combustion on ambient air quality in residential areas : A parametric dispersion modeling study
- 2003
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Ingår i: Biomass and Bioenergy. - : Elsevier. - 0961-9534 .- 1873-2909. ; 24:6, s. 465-474
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Tidskriftsartikel (refereegranskat)abstract
- Sweden's goals of contemporaneously reducing CO2 emissions and phasing out nuclear power will require a maximum utilization of biomass fuels. This would imply a significant shift from electricity and fuel oil to biomass generated heat, but must also be accomplished without a deterioration of the local air quality. The most suitable energy carrier seems to be pelletized biomass fuels with their associated low emissions and considerable residential conversion potential. Using an underlying statistical design, a parametric dispersion modeling study was performed to estimate and illustrate the combined effects of source-specific, meteorological and modeling variables on the ambient air quality in a typical residential area for different conversion scenarios. The work nicely illustrated the benefits of combining statistical designs with model calculations. It further showed that the concentration of combustion related ambient THC was strongly related to conditions affecting the source strength, but only weakly to the dispersion conditions and model variables. Time of year (summer or winter); specific emission performance; extent of conversion from electricity; conversion from wood log combustion; and specific efficiency of the pellet appliances showed significant effects in descending order. The effects of local settings and model variables were relatively small, making the results more generally applicable. To accomplish the desired conversion to renewable energy in an ecologically and sustainable way, the emissions would have to be reduced to a maximum advisable limit of (given as CH4). Further, the results showed the potential positive influence by conversion from wood log to low emission pellet combustion.
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| 7. |
- Brage, C., et al.
(författare)
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Tar evolution profiles obtained from gasification of biomass and coal
- 2000
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Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 18:1, s. 87-91
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Tidskriftsartikel (refereegranskat)abstract
- The tar content of the product gases from gasification of biomass is one of the major factors affecting the subsequent process stages. In this work, evolution profiles of the main tar constituents, i.e. benzene, toluene, indene, naphthalene and phenol were obtained during about 1 h gasification runs of biomass and coal in a pressurised fluidised-bed at 700 and 900 degrees C, 0.4 MPa. Sampling and analysis was achieved, using the solid-phase adsorption (SPA) method, previously developed in our laboratory. Our main objectives were: (1) to illustrate the usefulness of the SPA method; (2) to shed new light on the main factors governing tar evolution. It was found that temperature and the type of feedstock used mainly affected tar yields. For both biomass and coal the concentration of tar products decreased with increasing run time at a rate that was fastest initially. This behaviour, which was much more pronounced for coal, provides evidence that char catalytically affects tar evolution. Accordingly, char accumulates in the bed to a various extent depending on fuel and gradually approaching steady state. Biomass char, contrary to coal char, is readily oxidised during gasification, and thus only small steady-state amounts are available to catalyse tar cracking reactions.
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| 8. |
- Gabra, M., et al.
(författare)
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Alkali retention/separation during bagasse gasification : A comparison between a fluidised bed and a cyclone gasifier
- 2001
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Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 21:6, s. 461-476
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Tidskriftsartikel (refereegranskat)abstract
- Biomass fuelled integrated gasification/gas turbines (BIG/GTs) have been found to be one of the most promising technologies to maximise electricity output in the sugar industry. However, biomass fuels contain alkali metals (Na and K) which may be released during the gasification processes and cause deleterious effects on the downstream hardware (e.g. the blades of gas turbines). Much research has therefore been focused on different kinds of gas cleaning. Most of these projects are using a fluidised bed gasifier and includes extensive gas cleaning which leads to a high capital investment. Increasing alkali retention/separation during the gasification may lead to improved producer gas quality and reduced costs for gas cleaning. However, very little quantitative information is available about the actual potential of this effect. In the present work, comparative bench-scale tests of bagasse gasification were therefore run in an isothermal fluidised bed gasifier and in a cyclone gasifier to evaluate which gasification process is most attractive as regards alkali retention/separation, and to try to elucidate the mechanisms responsible for the retention. The alkali retention in the fluidised bed gasifier was found to be in the range of 12-4% whereas in the cyclone gasifier the alkali separation was found to be about 70%. No significant coating of the fluidised bed's bed material particles could be observed. The SEM/EDS and the elemental maps of the bed material show that a non-sticky ash matrix consisting of mainly Si, Al and K were distributed in a solid form separated from the particles of bed material. This indicates the formation of a high temperature melting potassium containing silicate phase, which is continuously scavenged and lost from the bed through elutriation. © 2001 Elsevier Science Ltd. All rights reserved.
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| 9. |
- Gabra, Mohamed, et al.
(författare)
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Development of a sugar cane residue feeding system for a cyclone gasifier
- 1998
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Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 15:2, s. 143-153
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Tidskriftsartikel (refereegranskat)abstract
- For the smooth and continuous operation of a cyclone gasifier, the fuel must be fed continuously and without interruption or large fluctuations. A feeding system for bagasse/cane trash powder was therefore designed, built and tested. It consisted of a feeding bin with four feeder screws in the bottom which deliver the fuel to two downcomers from which the fuel is injected by steam into the gasifier. During the first tests, the low bulk density and cohesive characteristics of a crushed bagasse/cane trash powder were found to cause an accumulation of the fuel in the feeding system, creating difficulties for the flow into the gasifier. In addition, once the flow of the crushed bagasse/cane trash powder is interrupted by a build-up in the downcomer channels, the crushed bagasse/cane trash powder becomes progressively compacted into a dense structure, resulting in blockage of the discharge. It was found possible to eliminate this problem by changing the shape of the slivers of the crushed bagasse/cane trash powder to render them more homogeneous. This was achieved by pelletizing the crushed bagasse or cane trash before grinding it to powder.
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| 10. |
- Gabra, M., et al.
(författare)
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Evaluation of cyclone gasifier performance for gasification of sugar cane residue : Part 1: Gasification of bagasse
- 2001
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Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 21:5, s. 351-369
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Tidskriftsartikel (refereegranskat)abstract
- A method for avoiding excessive amount of alkali compounds and carryover particles in producer gas from gasification of sugar cane residue has been studied and evaluated. The cane sugar residue is gasified in a two-stage combustor at atmospheric pressure, where the first stage is a cyclone gasifier. The cyclone works as particle separator as well. This paper covers the results obtained for gasification of bagasse. Bagasse powder was injected into the cyclone with air and steam as transport medium. The gasification tests were made with two feeding rates, 39 and 52 kg/h. Seven experiments were conducted with the equivalence ratio being varied. The heating values of the producer gas are sufficient for stable gas turbine combustion. About 60-70% of the alkali input with fuel was separated from the producer gas in the cyclone. However the total alkali contents of the producer gas was found to be higher than in ABB Stal PFBC gas turbines and at least an order of magnitude higher than what is required by most gas turbine manufacturers for operation of a gas turbine. The carryover particles concentrations in the producer gas were found to be in the range of that for PFBC gas turbines, but higher than what is required by most gas turbine manufacturers for operation of a gas turbine. Samples studied with scanning electronic microscope give indication that most of the carryover particles are below 10 μm in size. Fly ash-melting tests have not shown any major ash melting up to 1200°C, but it was found that some of the particles entrained with producer gas were partially melted. Integrated experiments with a gas turbine need to be done for accurate evaluation of the possibilities to use the producer gas from the gasification of bagasse to run a gas turbine without problems of hard deposits and corrosion on the turbine blades. In part 2 of this two-part paper the results from cane trash gasification tests are reported. © 2001 Published by Elsevier Science Ltd.
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