| 21. |
- Natarajan, E., et al.
(författare)
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Overview of combustion and gasification of rice husk in fluidized bed reactors
- 1998
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Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 14, s. 533-546
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Tidskriftsartikel (refereegranskat)abstract
- Rice is cultivated in more than 75 countries in the world. The rice husk is the outer cover of the rice and on average it accounts for 20% of the paddy produced, on weight basis. The worldwide annual husk output is about 80 million tonnes with an annual energy potential of 1.2 x 10 9 GJ corresponding to a heating value of 15 MJ/kg. India alone generates about 22 million tonnes of rice husk per year. If an efficient method is available, the husk can be converted to a useful form of energy to meet the thermal and mechanical energy requirements of the rice mills themselves. This paper provides an overview of previous works on combustion and gasification of rice husk in atmospheric bubbling fluidized bed reactors and summarizes the state of the art knowledge. As the high ash content, low bulk density, poor flow characteristics and low ash melting point makes the other types of reactors like grate furnaces and downdraft gasifiers either inefficient or unsuitable for rice husk conversion to energy, the fluidized bed reactor seems to be the promising choice. The overview shows that the reported results are from only small bench or lab scale units. Although a combustion efficiency of about 800 can normally be attained; the reported values in the literature, which are more than 95%, seem to be in higher order. Combustion intensity of about 530 kg/h/m 2 is reported. It is also technically feasible to gasify rice husk in a fluidized bed reactor to yield combustible producer gas, even with sufficient heating value for application in internal combustion engines. A combustible gas with heating value of 4-6 MJ/Nm 3 at a rate of 2.8-4.6 MW(th)/m 2 seems to be possible. Only very little information is available on the pollutant emissions in combustion and tar emissions from gasification. The major conclusion is that the results reported in the literature are limited and vary widely, emphasizing the need for further research to establish suitable and optimum operating conditions for commercial implementations.The combustion and gasification of rice husks in atmospheric bubbling fluidized bed reactors are studied. The rice husks are gasified in the bed reactor to yield combustible producer gas, even with sufficient heating value for application in internal combustion engines. A combustible gas with heating value of 4-6 MJ/Nm 3 at a rate of 2.8-4.6 MW th/m 2 is possible.
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| 22. |
- Simell, P., et al.
(författare)
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Provisional protocol for the sampling and anlaysis of tar and particulates in the gas from large-scale biomass gasifiers. Version 1998
- 2000
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Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 18:1, s. 19-38
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents tar sampling protocols for pressurised and atmospheric large scale gasification processes. Methods for constructing sampling lines either to on-line analysers or into sampling systems are described. The tar sampling system consists of a heated probe, a particulate filter and a series of impinger bottles. Dichloromethane is used as the tar absorbing solvent. The solvent containing bottles are placed in a cold bath so that gradual cooling of the sampled gas from about 0 degrees C to the final temperature -79 degrees C takes place in them. Recommendations for suitable sampling gas flow rates and gas temperatures are given. Tar characterisation methods based on different garvimetric measurements and GC analysis are described.
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| 23. |
- Tarantili, P.A., et al.
(författare)
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Cross-synergism in enzymatic hydrolysis of lignocellulosics : Mathematical correlations according to a hyperbolic model
- 1996
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 10:4, s. 213-219
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Tidskriftsartikel (refereegranskat)abstract
- The effect of cross-synergism in enzymatic hydrolysis of ball-milled Avicell, alkali-treated straw cellulose (ATSC), cotton and filter paper was investigated using mixtures of Fusarium oxysporum and Neurospora crassa enzymes. The experimental data were fitted according to an empirical hyperbolic model which utilized two parameters, the maximum conversion (xmax) and the enzymatic hydrolysis time corresponding to 50% of xmax (). The model can predict conversion of polysaccharides as a function of hydrolysis time. Both model parameters were found to be strongly dependent on the crystallinity index as well as on the degree of delignification of the substrate. Up to 60% cellulose hydrolysis can be achieved when the crystallinity index of Avicell is reduced from 94.8% to 63.3%. The percentage increase of xmax due to delignification was higher than the corresponding increase of . The extent of cross-synergism depends strongly on crystallinity index and degree of delignification. This type of synergism has been found to be significant in the case of substrates which are resistant to hydrolysis, such as Avicell (with high crystallinity index) or cotton. Cross-synergistic phenomena caused by enzymatic mixtures can double cellulose hydrolysis yield with delignified straw as compared to the hydrolysis yields achieved by single-microorganism cellulases.
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| 24. |
- Wahlund, B., et al.
(författare)
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A total energy system of fuel upgrading by drying biomass feedstock for cogeneration : a case study of Skelleftea bioenergy combine
- 2002
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Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 23:4, s. 271-281
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Tidskriftsartikel (refereegranskat)abstract
- Emissions of greenhouse gases, such as CO2, need to be greatly reduced to avoid the risk of harmful climate changes, One way to mitigate emissions is switching fuels, from fossil fuels to renewable energy, e.g., biomass. In this paper we investigate a new approach for improving the performance of biomass-based cogeneration plants, a bioenergy combine. The system is a conventional biomass-based combined heat and power (CHP) plant with integrated pellet production, where part of the CHP plant's heat is used for drying biomass feedstock for producing pellets, This unique integration enables increased annual operational hours and an increased use of biomass because the upgraded pellets as an energy carrier can be economically and technically transported from regions with a surplus biofuel to regions with demand for biofuel. In the studied case of this paper, the produced pellets are transported to another CHP plant for substituting fossil fuels. The total energy system of the bioenergy combine and the linked CHP plant is analysed from a perspective Of CO2 reduction and energy efficiency. The results show that the system has great potential for reducing CO2 and increasing the efficiency. Furthermore, the non-technical factors influencing the realisation of the project has also been studied through interviews, showing that the main criterion behind the investment was the potential for profitability. In addition, an important factor that facilitated the realisation was the co-operative environment between the municipality and Skeileftei Kraft. Environmental issues appeared not to be influencing direct, but indirect through government subsidies.
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| 25. |
- Zanzi, Rolando, et al.
(författare)
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Rapid pyrolysis of agricultural residues at high temperature
- 2002
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Ingår i: Biomass and Bioenergy. - 0961-9534 .- 1873-2909. ; 23:5, s. 357-366
-
Tidskriftsartikel (refereegranskat)abstract
- This paper deals with rapid pyrolysis of agricultural residues such as olive waste and straw at high temperature (800 -1000degreesC) in a free-fall reactor at pilot scale. The conditions are of interest for gasification in fluidized beds where rapid pyrolysis plays an important role as first stage. The objective of the work is to study the effect of the process conditions such as heating rate, temperature and particle size on the product distribution, gas composition and char reactivity. A higher temperature and smaller particles increase the heating rate resulting in a decreased char yield. The cracking of the hydrocarbons with an increase in the hydrogen content is favoured by a higher temperature and by using smaller particles. Wood gives more volatiles and less char than straw and olive waste. The higher ash content in agricultural residues favours the charring reactions. The higher lignin content in olive waste results in a higher char yield in comparison with straw. Chars from olive waste and straw are more reactive in gasification than chars from birch because of the higher ash content.
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| 26. |
- Abedinifar, S., et al.
(författare)
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Ethanol production by Mucor indicus and Rhizopus oryzae from rice straw by separate hydrolysis and fermentation
- 2009
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 33:5, s. 828-833
-
Tidskriftsartikel (refereegranskat)abstract
- Rice straw was successfully converted to ethanol by separate enzymatic hydrolysis and fermentation by Mucor indicus, Rhizopus oryzae, and Saccharomyces cerevisiae. The hydrolysis temperature and pH of commercial cellulase and β-glucosidase enzymes were first investigated and their best performance obtained at 45 °C and pH 5.0. The pretreatment of the straw with dilute-acid hydrolysis resulted in 0.72 g g-1 sugar yield during 48 h enzymatic hydrolysis, which was higher than steam-pretreated (0.60 g g-1) and untreated straw (0.46 g g-1). Furthermore, increasing the concentration of the dilute-acid pretreated straw from 20 to 50 and 100 g L-1 resulted in 13% and 16% lower sugar yield, respectively. Anaerobic cultivation of the hydrolyzates with M. indicus resulted in 0.36-0.43 g g-1 ethanol, 0.11-0.17 g g-1 biomass, and 0.04-0.06 g g-1 glycerol, which is comparable with the corresponding yields by S. cerevisiae (0.37-0.45 g g-1 ethanol, 0.04-0.10 g g-1 biomass and 0.05-0.07 glycerol). These two fungi produced no other major metabolite from the straw and completed the cultivation in less than 25 h. However, R. oryzae produced lactic acid as the major by-product with yield of 0.05-0.09 g g-1. This fungus had ethanol, biomass and glycerol yields of 0.33-0.41, 0.06-0.12, and 0.03-0.04 g g-1, respectively.
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| 27. |
- Aguilar Cabezas, Francisco X
(författare)
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Assessment of residential wood energy consumption using German household-level data
- 2019
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 126, s. 117-129
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Tidskriftsartikel (refereegranskat)abstract
- The residential sector accounts for about half of annual wood energy consumption in Germany. We applied a left-censored Tobit model to a cross-sectional dataset to quantify factors affecting household-level German residential wood energy consumption in years 2005, 2010 and 2014. Explanatory variables distinguished between (1) heating technology, dwelling characteristics and alternative energies; (2) woody biomass accessibility and weather; as well as (3) households' socio demographic characteristics. Results show that wood energy consuming households with central heaters used an additional 0.83-1.82 m(3) year(-1) of wood. Households' wood energy consumption showed a positive correlation with residence area and elastic responses to year of building construction. Greater elasticities in wood energy consumption were found when alternative energy prices exceeded US$ 1,050-1,330 per ton of oil-equivalent net calorific value. Local accessibility of woody biomass measured through forest ownership and forest density was associated with greater wood for energy consumption by an average 0.27-0.52 m(3) year(-1) and 0.13-0.25 m(3) year(-1), respectively. In addition, wood energy consumption increased proportionally with increasing rurality. Elasticity of household wood energy consumption with respect to heating degree days was estimated at 0.83-1.15. Among demographic variables, households at lower and higher income levels exhibited greater amounts of wood energy consumption. Results provide evidence that greater adoption of central wood energy heaters, price competitiveness of wood energy over alternative energies, and improving access to wood energy sources can lead to greater residential wood energy consumption in Germany.
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| 28. |
- Aguilar Cabezas, Francisco X
(författare)
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Comparison of small area estimation methods applied to biopower feedstock supply in the Northern US region
- 2019
-
Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 121, s. 64-77
-
Tidskriftsartikel (refereegranskat)abstract
- Increasing interest in utilization of forest biomass for bioenergy has prompted extensive contemporary research regarding costs, supply and technology for efficiently producing electricity and other forms of renewable energy. One challenge facing both researchers and users is obtaining precise estimates of available forest biomass within plausible supply areas for individual power plants. Due to the wide distribution of power plants poised to co-fire with forest biomass, assessing its availability requires methods that can yield precise and low-bias estimates of aboveground forest biomass and other key attributes at varying spatial scales. Small area estimation (SAE) methods have high potential to accomplish this due to the availability of national forest inventory data, combined with satellite imagery and other forms of remotely-sensed auxiliary information. The study assessed several indirect, direct and composite estimators of four forest attributes: aboveground tree biomass, biomass of small-diameter trees, biomass of tops and limbs, and volume at the county-level and within the estimated supply areas around power plants across 20 states in the contiguous Northern U.S. Composite estimators using both k-nearest neighbors imputation and multiple linear regression provided superior estimates of indicators of forest biomass availability based on both precision and bias at the county-level at sampling intensities as low as 10-20%, compared to the other SAE methods examined. The composite estimator using k-nearest neighbors imputation was subsequently shown to produce precise estimates of forest biomass availability for selected power plant supply areas.
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| 29. |
- Ahlberg-Eliasson, Karin, et al.
(författare)
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Production efficiency of Swedish farm-scale biogas plants
- 2017
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Ingår i: Biomass and Bioenergy. - : Elsevier BV. - 0961-9534 .- 1873-2909. ; 97, s. 27-37
-
Tidskriftsartikel (refereegranskat)abstract
- Biogas from agricultural waste streams represents an important way to produce fossil-free energy, allow nutrient recycling and reduce greenhouse gas emissions. However, biogas production from agricultural substrates is currently far from reaching its full potential. In Sweden, the number of biogas plants and their output have increased in recent years, but they are still experiencing harsh economic conditions. A recent evaluation (2010–2015) of 31 farm-scale biogas production facilities in Sweden sought to identify parameters of importance for further positive development. In this paper, data on plant operation, gas yield and digestate quality for 27 of these plants are summarised and statistically analysed to investigate factors that could allow an increase in overall biogas production and in nutrient content in the digestate. The analysis showed that addition of co-substrates to manure results in higher gas production, expressed as both specific methane potential and volumetric gas production, than when manure is the sole substrate. Use of co-substrate was also found to be influential for the nutrient content of the digestate. These observed improvements caused by co-digestion should be considered when subsidy systems for manure-based biogas processes are being created, as they could also improve the economics of biogas production. However, to achieve higher efficiency in existing biogas plants and to improve the situation for future investments, a more detailed, long-term evaluation programme should also be considered.
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| 30. |
- Ahmed, Ali, 1977-, et al.
(författare)
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Biomass energy, technological progress and the environmental Kuznets curve: Evidence from selected European countries
- 2016
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Ingår i: Biomass and Bioenergy. - : Pergamon Press. - 0961-9534 .- 1873-2909. ; 90, s. 202-208
-
Tidskriftsartikel (refereegranskat)abstract
- We examine the causal relationship between economic growth and CO2 emissions in a panel of 24 European countries from 1980 to 2010. Using an analytical framework that considers pooled mean group estimations in a dynamic heterogeneous panel setting, we show that there is an inverted U-shaped relationship between CO2 emissions and economic growth in the long run and that there is no such relationship in the short run. In particular, we find that biomass energy is insignificantly linked to CO2 emission. However, technological innovation significantly facilitates reduction of CO2 emissions in the investigated countries. Altogether, our study implies that economic growth and environmental quality can be achieved simultaneously, which opens up new insights for policy-makers for sustainable economic development via implementation of renewable energy consumption through technological innovation.
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