07 Altemative energy sources (bioconversion energy)

30 50 days, low gas product ion in winter, etc. Therefore, efforts are needed to remove its various l imitat ions so as to popular ize this technology in the rural areas. Researchers have tr ied different techniques to enhance gas production. This paper reviews the various techniques, which could be used to enhance the gas product ion rate from solid substrates.

05/02148 Evaluation of biomass gasification in supercritical water process for hydrogen production Calzavara, Y. et al. Energy Conversion and 3lanagement, 2005, 46, (4), 615 631. Conver t ing biomass into hydrogen can be accomplished in supercr i t ical water. State-of- the-ar t exper iments are thoroughly presented. Chars and tars format ion may be the most significant technological problem. However, catalysis should be the solut ion to obtain higher yields of hydrogen and to decrease the amounts of chars and tars. As conversion yield reaches 98% with a propor t ion of hydrogen higher than 50% in the gaseous phase, the next step to consider in a successful t ransfer to the industr ia l scale is to evaluate the energy cost of the process. The study made an evaluat ion of the energy efficiency of biomass gasification, basing the work on data of the l i terature. The results show that the energy efficiency from thermodynamic calculat ion reaches 60% when consider ing hydrogen, carbon monoxide and methane as valuable species in the ideal case. Inc luding energy recovery from the water at 280 bar and 740~'C, the overall energy yield reaches 90%. These calculat ions are overes t imated because no heat losses are taken into account. However, this s tudy shows that the key point of the process is energy recovery as the chemical react ion is endothermic and needs high t empera tu re and a ra ther large rat io of water /biomass.

05•02149 Extraction of oil from Jatropha curcas L. seed kernels by combination of ultrasonication and aqueous enzymatic oil extraction Shah, S. et al. Bioresource Technology, 2005, 96, (1), 121 123. Use of u l t rasonica t ion as a p re t r ea tmen t before aqueous oil extract ion and aqueous enzymatic oil extract ion was found to be useful in the case of extract ion of oil from the seeds of Jatropha curcas L. The use of u l t rasonica t ion for 10 min at pH 9.0 followed by aqueous oil extract ion gave a yield of 67%. However, the max imum yield of 74% was obta ined by ul t rasonicat ion for 5 min followed by aqueous enzymatic oil extract ion using an a lkal ine protease at pH 9.0. Use of ul trasonica- tion also resulted in reducing the process time from 18 to 6 h.

05•02150 In situ FT-IR spectroscopic investigations of species from biomass fuels in a laboratory-scale combustor: the release of nitrogenous species Weissinger , A. et al. Combustion andFlame, 2004, 137, (4), 403 417. In situ FT-IR absorpt ion spectroscopy was used with a laboratory-scale reactor and thermogravimet r ic analysis to describe the release of n i t rogen-conta in ing compounds from a fixed bed of f ibreboard residues. Such in situ detect ion of NH3 requires knowledge of the absorpt ion coefficients at high temperatures . These coefficients were obta ined from cal ibrat ions using a laboratory-scale reactor at tem- pera tures up to 800~'C, as well as from calculat ions using a database. On the basis of laboratory experiments , the rates of re lease of N species, of the major C species (CO, COe, and CH4), and of HeO have been derived. I t is concluded tha t the release of ni t rogen from the fuel can be model led if such parameters as the superficial velocity and the flow rate of oxygen are known. This method allows profiles of the n i t rogenous species to be genera ted and used as input data for CFD calculat ions based on thermodynamic combust ion models for a fixed bed on a grate.

05•02151 Methane emission from fixed dome biogas plants in hilly and plain regions of northern India Khoiyangbam, R. S. et al. Bioresource Technology, 2004, 95, (1), 35 39. Methane emissions from the slurry d isp lacement chambers of different fixed dome type biogas plants (Capaci ty 2 m 3) instal led in hilly and plain regions of nor thern Ind ia were quant i ta t ively est imated. The slurry t empera tu re in the biogas plants in the hilly areas of Himacha l Pradesh at an a l t i tude of 1300 m above mean sea level remains below the lower mesophi l ic range (16 25c'C) dur ing most par t of the year. Difference in the ambien t t empera tu re under the two climatic condi t ions of Hills and plain regions affects the CH4 flux. Methane

1 fluxes from the plants ranged between 7 and 120 g m 2 d . In nor thern plain, t empera tu re remains warm (21 33~'C) th roughout the year except dur ing winter (December to January) when there is a s teep fall. Seasonal emiss ion of CH4 ranged between 10 and 178 g m 2 d *. The annua l average methane emission from the biogas plants in plain areas

1 1 was 83.1 g m 2 d as compared to 43.1 g m - d in the hilly areas. Annua l contr ibut ion per p lant to the global methane budge t from a fixed dome biogas plant (Cap 2 m 3) in plain region of nor thern India was 53.2 kg as compared 22.3 kg in hilly area.

05•02152 New process of maize stalk amination treatment by steam explosion Chen, H. et al. Biomass and Bioenergy, 2005, 28, (4), 411 417. Amina t ion t rea tment of s traw proceeds slowly at the low envi ronmenta l tempera tures . Al though the aqueous ammonia has a relat ively good effect, it has high volat i l i ty and an i r r i tant odour. Steam explosion has the advantage of short react ion time, but it cannot improve the ni t rogen content of the straw for an imal feed. A new process combined with the two methods for maize stalk p re t r ea tmen t was s tudied to improve its nutri t ive value. The results showed tha t ni t rogen sources coupled with s team explosion modif ied the t rea ted materials . Except for urea, other ni t rogen sources p romoted the degrada t ion of hemicel lulose and the increase of the soluble sugars content. Decrease of hemicel lu lose t rea ted with 5% (NH4)eSO3 was highest (58.0%), but no significant changes were detected in cellulose and l ignin content using chemical methods after ni t rogen source addit ion. Compared with s team explosion pre t rea tment , amina t ion by s team explosion increased the ni t rogen content of maize stalk. The highest total n i t rogen content (2.30%) was obta ined by adding urea. The t r ea tment of 5% (NH4)eSO3 led to the highest re tent ion of added ni t rogen (84.0%) and 15% NH4OH led to the lowest percentage of re ten t ion (18.1%). Amina t ion by s team explosion effectively increased the poten t ia l digestibi l i ty of DM, and the maximum digestibi l i ty value (71.2%) was obta ined when 5% (NH4)eSO3 was added. Amina t ion by s team explosion shor tened the aminat ion t ime and was a rapid and effective method of improving the nutri t ive value of straw.

05/02153 On the storage batteries used in solar electric power systems and development of an algorithm for determining their ampere-hour capacity Mahmoud, M. M. Electric Power Systems Research, 2004, 71, (1), 85 89. Storage bat ter ies are indispensable in all s tand-alone solar electric systems (PV power systems). Their efficiencies and life t imes affect significantly the overal l PV system performance and economics. Bat ter ies specified especial ly for use in PV systems have to be dis t inguished with s tanding of very deep discharge rate and high cycling stability. Ord inary bat ter ies being marke ted world wide for use in automobi le , are mostly not appropr ia te for PV power systems. The most impor tan t characteris t ics of lead acid bat ter ies are p resen ted and discussed in this paper. Moreover, the paper i l lustrates an exper imenta l procedure for developing an a lgor i thm for de te rmin ing the ampere hour capacity of bat ter ies opera t ing in PV systems. This a lgor i thm enables de te rmin ing the s tate-of-charge of a bat tery by measur ing voltage and electrolyte-specific gravity at defini te t empera tu re and is appl icable also for large bat tery storage systems.

05•02154 Preliminary evaluation of fungicidal and termiticidal activities of filtrates from biomass slurry fuel production Kartal, S. N. et al. Bioresource Technology, 2004, 95, (1), 41 47. Biomass slurry fuel (BSF) product ion has recently been developed as a na tura l energy for the conversion of solid b iomass into fuel. In addi t ion to using fuel, fi l trates from BSF product ion may also serve a chemical source with several organic compounds. There is an increasing in teres t in the research and appl icat ion of biomass-based filtrates. In this study, fungicidal and termit ic idal proper t ies of fil trates from BSF product ion using sugi (Cryptomeria japonica) and acacia (Acacia mangium) wood were evaluated in labora tory decay and termite resistance tests. Wood blocks treated with the fil trates showed increased resistance agains t brown-rot fungus, Fomitopsis palustris. However the fil trates f rom sugi wood processed at 270c'C which contained less phenolic compounds than the other fil trates were effective against white-rot fungus, Trametes versicolor. Phenolic compounds of f i l trates seemed to play a role in the decay resistance tests however the fil trates did not increase the durabi l i ty of the wood blocks against subter ranean termites Coptotermes formosanus. Despi te high acetic and lactic acid content of the filtrates, vanil l in content of the fil trates may have served as an addi t iona l food source and p romoted termite at tack. It can be concluded that fil trates with phenol ic compounds from lignin degra- dat ion dur ing BSF produc t ion can be considered for targeted inhibi t ion of brown-rot .

05/02155 Soil carbon under switchgrass stands and cultivated cropland Liebig, M. A. et al. Biomass and Bioenergy, 2005, 28, (4), 347 354. Switchgrass (Panicum virgatum L.) is considered to be a valuable bioenergy crop with significant po ten t ia l to sequester soil organic carbon (SOC). A study was conducted to evaluate soil carbon stocks within establ ished switchgrass s tands and nearby cul t ivated cropland on farms th roughout the nor thern Great Plains and nor thern Cornbel t . Soil f rom 42 paired swi tchgrass /cropland sites th roughout MN, ND, and SD was sampled to a depth of 120 cm and analysed for soil carbon in depth increments of 0 5 , 5 10, 10 20, 20 30, 30 60, 60 90, and 90 120 cm. SOC was greater ( P < 0.1) in switchgrass s tands than cul t ivated

316 Fuel and Energy Abstracts September 2005

cropland at 0 5, 30 60, and 60 90 cm. Differences in SOC between switchgrass s tands and cul t ivated cropland were especially p ronounced at deeper soil depths, where t reatment differences were 7.74 and 4.35 Mg ha 1 for the 30 60 and 60 90 cm depths, respectively. Greater root b iomass below 30 cm in switchgrass likely contr ibuted to trends in SOC between switchgrass s tands and cul t ivated cropland. Switchgrass appears to be effective at s tor ing SOC not just near the soil surface, but also at depths below 30 cm where carbon is less susceptible to minera l iza t ion and loss.

05•02156 UK biomass energy since 1990: the mismatch between project types and policy objectives van der Horst, D. Energy Policy, 2005, 33, (5), 705 716. Biomass energy is expected to play an impor tan t role in achieving the U K government ' s ambit ious targets to boost renewables. Since 1990, the main UK suppor t mechanism for renewables has been the non- fossil fuel obl igat ion (NFFO). With only seven of 22 N F F O contracts for fibrous biomass energy projects now operat ional , the level of real progress has been disappoint ing. The government ' s renewables policy has changed over the years and is now based on five objectives. The paper a ims to assess wha t types of b iomass energy systems would be most sui table to achieve those objectives. The assessment shows that the nature of the suppor ted developments was inconsis tent with most individual objectives. To an impor tan t extent this was due to inheren t opera t iona l contradic t ions between these objectives. I t is argued that the ra t ionale for suppor t ing renewables should pr imari ly lie in reducing greenhouse gas emissions or in energy diversity and security. Suppor t for the rura l economy, the deve lopment of export technologies and increased compet i t iveness of renewables, should be seen as desirable longer- te rm outcomes from the deve lopment of a b iomass energy sector. By t rea t ing these as equals (and even as superiors) to the objectives of cl imate change and energy diversity, the U K government has actually cr ippled the deve lopment of the biomass energy sector.

05•02157 Wood ash effects on plant and soil in a willow bioenergy plantation Park, B. B. et al. Biomass and Bioenergy, 2005, 28, (4), 355 365. Intensive managemen t for b iomass product ion results in high rates of nu t r ien t removal by harvesting. The study tes ted whether wood ash genera ted when burning wood for energy could be used to amel iora te negative soil effects of shor t - rota t ion harvest ing practices. The t empora l and spat ial dynamics of soil nu t r ien t proper t ies after wood ash appl icat ions were measured in a wil low planta t ion in centra l New York State and de te rmined the influence of wood ash appl icat ion on wil low growth. Wood ash was appl ied annual ly for 3 years at the rates of 10 and 20 Mg ha 1 to coppiced willow, Salix purpurea, clone SP3. Wood ash appl ica t ion significantly increased soil pH in the 0 10 cm soil layer f rom 6.1 in the control to 6.9 and 7.1 in the 10 and 20 Mg ha 1 treated plots. Wood ash appl ica t ion significantly increased soil extractable phosphorus , potass ium, calcium, and magnes ium concen- trations. Potass ium was the element most affected by wood ash t reatment at al l soil depths. Wood ash had no significant effect on nut r ient concentra t ions of foliar, litter, and stem tissue. Wood ash did not affect either individual p lant growth or plot b iomass product ion, which declined over the course of the study; it did increase the size of stems, but this effect was balanced by a decrease in the number of stems. Apply ing ni t rogen as well as wood ash might be required to main ta in the product iv i ty of this SRIC system.

Geothermal energy

05•02158 An automated well-test analysis system (AWTAS) O'Sull ivan, M. J. et al. Fuel, 2005, 84, (2 3), 3 25. Tradi t ional methods of well- test analysis are of l imited applicabi l i ty to well- tests carr ied out in geo thermal reservoirs. An automat ic well- test analysis system (AWTAS) has been constructed that is based on fast numer ica l models, ra ther than the analytical (or semi-analyt ical) models used in t radi t ional analysis. This approach makes it possible to s imulate complex non- iso thermal si tuations, including phase changes. I t also allows the use of a broader range of model types. Examples are given which demons t ra te the abili ty of the software to analyse geo thermal well tests.

05•02159 Geothermal reservoir characterization via thermal injection backflow and interwell tracer testing Kocabas, I. Geothermics, 2005, 34, (1), 27 46. The jo in t appl icat ion of a thermal injection backflow test and an interwel l t racer test for an in-situ de te rmina t ion of geo thermal reservoir flow and heat t ranspor t parameters is proposed. The procedure is un ique in several aspects. First, it uses two tracers with totally different t ranspor t characterist ics, i.e. heat and a chemical /

07 Altemative energy sources (geothermal energy)

radioact ive tracer, in a single field tes t operat ion. Dur ing field appl icat ion of the proposed test, a low-tempera ture t racer carrying fluid is injected into the reservoir unt i l an adequa te amoun t of the chemical / radioact ive tracer is recovered at the observat ion well(s). The tracer re turn profi les are in te rpre ted to de te rmine connectivity and flow velocity between the injector and producer wells. As the thermal front does not t ravel far from the injection well, the t empera tu re t ransients dur ing backflow are used to de te rmine the heat t ranspor t parameters . The most impor tan t pa ramete r s control l ing the rmal b reak th rough dur ing long- term injection are, therefore, inferred in situ in a single field test. New analytical models are presented for in terpre t ing the t empera tu re and concentra t ion profiles dur ing the backflow period, providing a valuable insight into the collective roles of the parameters control l ing heat t ranspor t in a single f racture/matr ix system.

05•02160 Interpretation of a well interference test at the Chingshui geothermal field, Taiwan Fan, K. C. et al. Geothermics, 2005, 34, (1), 99 118. Product ion in the l iquid-dominated Chingshui geo thermal field is largely from a fractured zone in the Jentse Member of the Miocene Lushan Format ion. The geological data strongly indicate a possibil i ty of l inear-f low geometry on a field-wide scale. This was confirmed by re- analysing the results of a mult iple-wel l in ter ference test per formed in 1979. Radia l and l inear-flow models were used in this process. An evaluat ion of computed reservoir t ransmissivi t ies and well capaci t ies indicated that a l inear model f i t ted the in terference test da ta significantly bet ter than a radia l model. The l inear-f low model tha t was developed for the Chingshui reservoir was also ins t rumenta l in obta ining an improved es t imat ion of the geo thermal fluid reserves (i.e. f luid-in-place ).

05•02161 The effect of moisture content on retention of fluorocarbon tracers on sand Maxfield, B. T. et al. Geothermics, 2005, 34, (1), 47 60. Several f luorocarbon compounds have been evaluated as geo thermal t racers in sand co lumn tests using damp, dry, and un t rea ted 'washed sea sand'. F luorocarbons evaluated in these tests included two hydrof luorocarbon freons: t r i f luoromethane (R23) and 1,1,1,2- t e t ra f luoroe thane (R134a), and five perf luorocarbons: perf luoro- dimethylcyclobutane, perf luoromethylcyclopentane, perf luoromethyl- cyclohexane, perf luorodimethylcyclohexane and perf luorotr imethyl- cyclohexane. Transpor t of the f luorocarbon compounds was explored in flowing he l ium at 23 and 60c'C. This work found that f luorocarbon re tent ion is strongly affected by sand mois ture content . The fluoro- carbon compounds flowed with the bulk fluid when the sand was damp, but were significantly re ta ined by the solid phase when the sand was thoroughly dried. The data suggest tha t the f luorocarbons may be conservative tracers in geo thermal condi t ions up to mild superhea t but they may not be conservative at geo thermal condit ions with a high degree of superheat .

05•02162 Variation in corn stover composition and energy content with crop maturity Pordesimo, L. O. et al. Biomass and Bioenergy, 2005, 28, (4), 366 374. How to harvest and process corn stover to maximize its quali ty as a fuel or industr ia l feedstock and minimize mater ia l losses are compel l ing issues in the industr ia l ut i l izat ion of corn stover. The objectives of this invest igat ion were to evaluate the var ia t ion in the chemical compo- si t ion and energy content of aboveground components of the corn p lant over t ime and to evaluate how composi t ion changes after grain physiological matur i ty is reached and the plants are wea the red while undergoing further field drying. Above ground biomass dis t r ibut ion and composi t ion of two a lmost ident ical corn cultivars (Pioneer 32K61 and 32K64 Bt) were s tudied from an es t imated 2 weeks before corn kerne l physiological matur i ty unt i l 4 weeks after the grain had already reached a mois ture content sui table for combine harvesting. Compo- si t ional analysis of corn stover fractions ga thered over the course of maturat ion, senescence, and wea ther ing using N I R spectroscopy showed (1) a rapid drop in soluble glucan, (2) increase in lignin, and (3) increase in xylan. By day 151 after planting, about when grain from sur rounding non- tes t plots was harvested at about 15.5% moisture, composi t ion of the different fractions remained fairly constant. Since product yield in fe rmenta t ion-based biomass conversion processes is propor t iona l to the s t ructural carbohydrate content of the feedstock, t iming of stover collect ion and the propor t ion of ana tomica l fractions collected affect the quali ty of corn stover as fe rmenta t ion feedstock. Since the energy content of corn stover ana tomica l fractions is shown to remain fairly constant over t ime and from one plant to ano ther

1 (16.7 20.9 kJ g ), insofar as combust ion processes are concerned, it apparent ly makes little difference which par t of the plant is used, or at what t ime the mater ia l is harvested.

Fuel and Energy Abstracts September 2005 317