that the proper anaerobic consortium in each separate compartment was developed according to the substrate(s) availability and the specific environmental conditions. The ABR has the potential to provide a higher efficiency at higher loading rates and be applicable for extreme environmental conditions and inhibitory compounds. 05/01623 Performance optimization of solar collector equipped with different arrangements of square-celled honeycomb Ghoneim, A. A. International Journal of Thermal Sciences, 2005, 44, (1), 95-105. Honeycomb materials are inserted between the glass cover and the absorber of flat plate solar collector to suppress natural convection. This paper presents the results of an experimental investigation of the thermal performance of solar collector equipped with different arrangements of square-celled honeycomb material. The collector test facility installed at the College of Technological Studies, Kuwait is used to carry out this study. The adapted honeycomb unit is structured from polycarbonate sheet of 10 mm cell size. The effect of air gap thickness above and below the honeycomb material is examined using different arrangements of honeycomb panels with different lenghs. The bottom and top air gap thicknesses are varied from 0 to 12 ram. Experimentally obtained Nusselt number-Rayleigh number plots are presented for free convective heat transfer across honeycomb panels for a wide range of Rayleigh number. Linear regression analysis is implemented to determine the thermal and optical parameters of the solar collector with different honeycomb configurations. A solar collector with air gaps below and above the honeycomb is found to be superior in convection suppression. It is found that the bottom gap thickness is crucial with respect to the heat loss coefficient. The arrangement of honeycomb material with bottom gap thickness of 3 mm is the optimum as it offers the highest efficiency between all arrangements and the lowest heat loss coefficient among other honeycomb configurations. Generally, the results of the present study reveals that compound honeycomb solar collector with proper air gap thickness above and below the honeycomb material attains substantial suppression of free convection. 05/01624 Perspectives for the use of biomass as fuel in combined cycle power plants Franco, A. and Giannini, N. International Journal of Thermal Sciences, 2005, 44, (2), 163-177. The paper analyses the perspectives of biomass and biomass derived fuels utilization for energetic use. After a brief review about the current technologies for biomass conversion to energy and biomass based power plants, an exergy loss based economic analysis of biomass utilization is proposed. This analysis shows the opportunity of using biomass in plants with a thermodynamic efficiency higher than a minimum value. Thus the attention is focused on the use of thermal energy from biomass as integrative source together with natural gas in combined cycle power plants, considering methods for upgrading biomass energy conversion to power. The paper provides a thermo- dynamic analysis of combined plants using biomass to obtain exhaust gas aftertreatment with atmospheric postcombustion (reheat). Two different technical solutions are proposed. A general optimization of the two soiutions shows the possibility of obtaining plant efficiency up to 60% in perspective and of 57% by using currently available gas turbine models. 05101625 Phosphorus sorption, desorption and resorption by soils of the Brazilian Cerrado supporting eucaiypt Barros, N. F. et al. Biomass and Bioenergy, 2005, 28, (2), 229-236. Oxisols of the Brazilian Cerrado are highly weathered phosphorus deficient soils, on which eucaiypt is increasingly being grown as a source of carbon and energy for steel manufacturing. Phosphorus fertilization is a necessary practice to assure adequate eucalypt production; therefore, an understanding of cycling by inorganic soil phosphorus should lead to efficient phosphorus management and more accurate modeling of phosphorus bioavailability. Since sorption and desorption reactions control inorganic phosphorus bioavailability, the purpose of this study was to contrast phosphorus sorption, desorption and subsequent resorption for a range of Cerrado soils. Its specific objectives were to determine: (i) if desorption and resorption show the same hysteresis shown by sorption and desorption, (ii) if Kd values of resorption and desorption for Cerrado soils are dependent on the soil's clay content and (iii) if resorption and desorption Kd values are a function of the amount of labile phosphorus on the soil surface. Three levels of phosphorus were sorbed onto four Cerrado soils with clay contents between 13% and 81%. Phosphorus desorption was measured using anion-exchange membranes. Sorption was a function of soil clay content, and a pedotransfer function for the soil partition coefficient was calculated with an rZ=0.99. Desorption and resorption were dependent on both the clay content of the soil (r 2 = 0.59-0.99) and the amount of sorbed labile phosphorus. Pedotransfer functions for each of these processes depend on accurate measurement of the inorganic 07 Altemative energy sources (bioconversion energy) phosphorus that responds to disequilibria exchange. Desorption and resorption were not hysteretic; yet desorption was hysteretic with the original sorption isotherm. This suggests the question: how useful are commonly produced sorption isotherms? 05101626 Photoproduction of hydrogen from acetate by a chemoheterotrophic bacterium Rhodopseudomonas palustris P4 Oh, Y.-K. et al. International Journal of Hydrogen Energy, 2004, 29, (11), 1115-1121. Rhodopseudomonas palustris P4 can produce H2 either from CO by water-gas shift reaction or from various sugars by anaerobic fermentation. Fermentative H2 production by P4 is fast, but its yield is relatively low due to the formation of various organic acids. In order to increase H2 production yield from glucose, P4 was investigated for the photo-fermentation of acetate which is a major by-product of fermentative H2 production. Experiments were performed in batch modes using both light-grown and dark-grown cells. When the dark- grown P4 was challenged with light and acetate, H2 was produced with the consumption of acetate after a lag period of 25 h. Ha production was inhibited when a nitrogen source, especially ammonium, is present. When the dark-fermentation broth containing acetate was adopted for photo-fermentation with light-grown cells, Hz production and con- comitant acetate consumption occurred without a lag period. The Ha yield was estimated as 2.4-2.8 tool H2/mol acetate and the specific H2 production rate was as 9.8 ml H2/g cell h. The fact that a single strain can perform both dark- and light-fermentation gives a great advantage in process development. Compared to a one-step dark-fermentation, the combined dark- and light-fermentation can increase the H2 production yield on glucose by two-fold. 05/01627 Prospects of biodiesel production from vegetable oils in India Barnwal, B. K. and Sharma, M. P. Renewable and Sustainable Energy Reviews, 2005, 9, (4), 363-378. The world is confronted with the twin crises of fossil fuel depletion and environmental degradation. The indiscriminate extraction and con- sumption of fossil fuels have led to a reduction in petroleum reserves. Alternative fuels, energy conservation and management, energy efficiency and environmental protection have become important in recent years. The increasing import bill has necessitated the search for liquid fuels as an alternative to diesel, which is being used in large quantities in transport, agriculture, industrial, commercial and dom- estic sectors. Biodiesel obtained from vegetable oils has been considered a promising option. In this paper, an attempt has been made to review the work done on biodiesel production and utilization, resources available, process(es) developed/being developed, perform- ance in existing engines, environmental considerations, the economic aspect, and advantages in and barriers to the use of biodiesel. 05/01628 Screening of poplar biomass for bio-active compounds: a simple method to assess antioxidant activity Warnant, P. et al. Bioresource Technology, 2004, 93, (1), 43-48. Poplar bud resinoids are a potential source of natural antioxidants. As poplar culture today involves many hybrids, a simple screening test to assess antioxidant properties was proposed. This method used the second derivative of the UV spectra at 233 nm of the iron-induced peroxidienes resulting from linoleic acid peroxidation. Kinetic data showed a lag period followed by a quadratic increase in peroxidienes. These two phases were more clearly separated using the square root of the data. An acceptable linear fitting of the length of the lag phase with antioxidant concentration was observed, Calibrating the experimental test with BHA therefore allowed an antioxidant assessment as 'BHA equivalent'. First results clustered well with taxonomic data, with typically 0.5, 0.15 and 0.08 'BHA equivalent' for P. nigra, P. X euramericana and P. X interamericana, respectively. 05101629 Simulation of vegetable oil extraction in counter- current crossed flows using the artificial neural network Thomas, G. C. et al. Chemical Engineering and Processing, 2005, 44, (5), 579-590. A new mathematical model of processes in a 'Rotocell' extractor was developed. The model considers: a two-dimensional approach of counter-current crossed flows (CCC) with oii diffusion for miscela; mass transfer between the bulk, pore and solid phases; the effect of the existing processes in the drainage and loading sections; oil losses; and variation in the miscela viscosity and density. The model leads to a system of coupled partial and ordinary differential equations, where- upon is transformed in the neural network. The solution is compared with experimental data and with the method of ideal stages. The numerical simulations reveal the extraction field properties in the transient regimes. Fuel and Energy Abstracts July 2005 241