07 Alternative energy sources (bioconversion energy)

from plants is seldom possible. This article reviews the options, covering both established commercial activities (such as starch, vegetable oil, paper- pulp and natural fibres), as well as the extensive research and development activities that should lead to new crops, new products and new markets.

99103227 Dual-bed counterflow and fixed-bed reactor system for gasification of wood and wood waste Schmidt, K. G. et al. Ger. Offen. DE 19,718,184 (Cl. ClOJ3/02), 5 Nov 1998, Appl. 19,718,184, 30 Apr 1997, 6 pp. (In German) For the purpose of this study, gasification of biofuels, especially wood and wood waste, was carried out in a dual-bed gasification reactor unit. The process consisted of initial gasification of the fuel in an upper counterflow reactor and a lower fixed-bed reactor for gasification of solids and unreacted material. To ensure only one-way flow of gas and solids a double-gate mechanism is located between the two reactors. Each reactor is equipped with its own separate inlet for gasification agents (e.g. air, steam and oxygen), which can be independently regulated for control of the reaction temperature, the amount of tar formed and the calorific value of the desired fuel gas.

99103228 Environmental effects of energy crop cultivation in Sweden - I: Identification and quantification Borgesson, P. Biomass & Bioenergy, 1999, 16, (2) 137-154. This paper presents an analysis of how energy crop cultivations in Sweden, consisting of short-rotation forest (Salir) and energy grass (reed canary grass), can be located and managed to maximize environmental benefits. The overall conclusion is that substantial environmental benefits, ranging from global to site-specific, could be achieved when traditional annual food crops produced with current agriculture practices are replaced by dedicated perennial energy crops. The emission of greenhouse gases could be reduced by reduced carbon dioxide emissions from organic soils, by reduced nitrous oxide emissions caused by the use of fertilizers and through accumulation of soil carbon in mineral soils, which also leads to increased soil fertility. Nutrient leaching could be reduced by using energy crop cultivations as buffer strips along open streams and wind erosion could be reduced by using Salti plantations as shelter belts. Cultivation of Salix and energy grass can also be used to purify municipal waste, such as waste water, landfill leachate and sewage sludge. Furthermore, the content of heavy metals in the soil can be reduced through Saliz cultivation. The biodiversity is estimated to be almost unchanged, or slightly increased in open farmland. These environmental benefits, which could be achieved on up to 60% of current Swedish arable land and last for 25 years or more, will increase the value of the energy crops. The economic value of these benefits is calculated in Part II of the analysis, which is presented in a second paper.

99103229 Sweden -

Environmental effects of energy crop cultivation in II: Economic valuation

Borgesson, P. Biomass & Bioenergy, 1999, 16, (2), 155-170. In this paper, environmental benefits of the cultivation of perennial energy crops in Sweden, which have been identified and quantified in an earlier paper, are evaluated economically. Several different benefits, ranging from global to site-specific, could be achieved by replacing annual food crops with perennial energy crops. The economic value of these environmental benefits, including reductions in costs to farmers (direct costs) and to society as a whole (external costs), has been estimated to be from US$O.l up to US$S/GJ biomass. For comparison, the production costs (excluding transport) of Sal& and reed canary grass are about US$4.4/GJ and US$5.0/ GJ, respectively. Purification of waste water in energy crop cultivation has the highest economic value, followed by reduced nutrient leaching through riparian buffer strips, recirculation of sewage sludge and reduced wind erosion through shelter belts consisting of Salir. The value of other environmental benefits is estimated to be less than USSO.7/GJ. If 200,000 ha of Sweden’s totally available arable land of 2.8 Mha were available for energy crop cultivation, around 45 PJ biomass could theoretically be produced per year, at an average cost of about US%O.7/GJ, including the value of environmental benefits. It is assumed that priority is given to cultivations with the highest total value, as several different environmental effects could be achieved on the same cultivation site. If 800,000 ha were to be available, the corresponding cost of some 150 GJ biomass per year would be around US$2.8/GJ.

99103230 An equilibrium model for biomass gasification processes Ruggiero, M. and Manfrida, G. Renewable Energy, 1999 (Pub. 1998), 16, (l-4), 1106-1109. Due to their contribution to the limitation of global COz emissions, energy conversion systems based on biomass utilization are particularly interesting. Within the possible methods for energy-based biomass utilization, thermal gasification seems the most mature technology. In the initial design stage, the designer of these systems or the user looking for performance predictions under different operating conditions, has advantages of running thermochemical simulations allowing a prediction of the syngas composi- tion and calorific value. The equilibrium model described in this paper is very simple, but it considers chemical species typically encountered by biomass gasifiers and was tested against published experimental data.

99103231 Fate of alkali and trace metals in biomass gasification Salo, K. and Mojtahedi, W. Biomass Bioenergy, 1998, 15, (3) 263-267. Over the past decade, the fate of alkali metals (sodium, potassium) and 11 toxic trace elements (mercury, cadmium, beryllium, selenium, antimony, arsenic, lead, zinc, chromium, cobalt, nickel) in biomass gasification have been extensively investigated in Finland. The former is due to the gas turbine requirements and the latter to comply with environmental regulations. The results of several experimental studies to measure sodium and potassium in the vapour phase after the gas cooler of a simplified (air- blown) integrated gasification combined cycle (IGCC) system are reported. Trace element emissions from an IGCC plant, using alfalfa as the feedstock, are also discussed and the concentrations of a few toxic trace metals in the vapour phase in the gasifier product gas are reported.

99103232 Formation of dioxins and other semi-volatile organic compounds in biomass combustion Chagger, H. K. et al. Appl. Energy, 1998, 60, (2), 101-114. The advantages of using biofuels and biomass mixed with coal in combustion are highlighted. The availability of biomass with regard to land use is reviewed, followed by a brief account of the combustion process and the concomitant formation of semi-volatile organic compounds (SVOCS). Chemical compositions of selected biofuels and coal are presented. Routes of formation for polychlorinated dibenzodioxins/furans (dioxins and furans) are illustrated with subsequent reference to associated emissions. Graphs show coal and biofuel propensities for forming dioxin and furan isomers followed by methods for predicting emission levels and isomer distributions within combustion systems. Finally, the paper summarizes recent equili- brium concentration studies and discusses the on-going combustion experiments being conducted in the University of Leeds’ Department of Fuel and Energy. Preliminary results are presented and discussed, finishing with three main experimentally drawn conclusions.

99103233 Harvesting of COttOn residue for energy production Gemtos, T. A. and Tsiricoglou, Th. Biomass & Bioenergy, 1999, 16, (1) 51-59. The possibility of collecting cotton stalks in Greece and using them for energy production was investigated. The production and properties of cotton stalks were studied and a system for collection of the aerial part is proposed as a feasible solution to avoid wet conditions under the local climate. A successful method for collection and packaging of the residue was applied, using conventional, but highly advantageous equipment, offering reduced investment cost and use of existing machinery. The energy required to harvest cotton stalks was measured by an instrumented tractor. The tractor was able to measure the developed forces between tractor and implement, the power absorbed through the PTO, as well as tractor velocity and fuel consumption. The energy consumed for the operation was calculated and when compared to the energy of the biomass collected gave a positive balance. The work proved the feasibility of harvesting cotton stalks using conventional machinery giving the possibility to collect energy material with a total energy content of 500,000 tons of oil equivalent at national level.

99103234 Hydrogen production from biomass by catalytic gasification in hot compressed water Minowa, T. and Inoue, S. 1114-1117.

Renewable Energy, 1999 (Pub. 1998) 16, (l-4),

Using a reduced nickel catalyst in hot-compressed water of around 350°C and 15 MPa, cellulose, a major component of woody biomass, was gasified to hydrogen-rich gas. During the gasification, steam reforming and methanation can occur and the methanation was prevented at subcritical condition. The reaction model and the catalyst are described.

99JO3235 Studnicki, M.

Manufacture of C1_12 aliphatic electrolytic bioreactor Chenzik, 1998, 51, (7-8), 199-202. (In Polish)

This article describes the physico-chemical principles of the title process, using a DC current feeder to supply the bioreactor. The influence of electric field on biochemical changes is well-known and usually results in ten-fold growth of a biomass, in this case it applies to aliphatic alcohols. Attempts were undertaken to elucidate the mechanism of microbiological transition steps carried out during anodic oxidation of organic matter, supported by microbiological oxidation processes. Practical applications of the process to produce intermediates for organic syntheses and fuels are discussed.

99103236 Method and device for degasification and gasification or burning Kiefer, C. Ger. Offen. DE 19,720,331 (Cl. ClOJ3/58), 19 Nov 1998, Appl. 19,720,331, 15 May 1997, 6 pp. (In German) Presented here is a two-stage apparatus and method for gasification or combustion of biomass. Incorporated is a pyrolysis zone of a reactor in communication with a combined gasification-combustion zone, in which the biomass pyrolyses to produce a combustible gas and coke. The coke passes through a second gasification region in the apparatus and then through a size-reduction unit into the combustion reactor portion, where it is contacted with the initial pyrolysis gas and burned under injection of insufficient air, to produce a CO-H2 low-BTU fuel gas. The initial pyrolysis gas undergoes a steam conversion to also produce a CO-Hz-rich fuel gas. Coke from the bottom gasification-combustion region passes through a

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