Showing papers in "Biomass & Bioenergy in 1993"

Diesel fuel from vegetable oils: Status and opportunities

Abstract: The technical and economic aspects of using vegetable oils as alternative sources for diesel fuels have been studied extensively during the past two decades. Although much of the recent research and development on the production and use of diesel fuel substitutes has been carried out in developed countries, the need for such substitutes and the potential for their production is much greater in developing countries. This report will review some of the results obtained from using vegetable oils and their derivatives as fuel in compression ignition engines and examine opportunities for their broader production and use. It will include some historic background, as well as current and potential yields of candidate crops, the technology and economics of vegetable oil conversion to diesel fuel, the performance of various oils, the potential inherent in diesel fuel coproduction, environmental considerations, and other research opportunities. Vegetable oils will not entirely displace petroleum as a source of diesel fuel. There are, however, technical, economic, and environmental considerations that can lead to their wider use in this application.

Wood ash composition as a function of furnace temperature

Abstract: The elemental and molecular composition of mineral matter in five wood types and two barks was investigated as a function of temperature using thermal gravimetric analysis, differential thermal analysis, inductively coupled plasma emission spectroscopy, and X-ray diffraction. Low temperature ash was prepared at 500°C, and samples were heated in a tube furnace at temperature increments to 1400°C. The dissociation of carbonates and the volatilization of potassium, sulfur, and trace amounts of copper and boron were investigated as a function of temperature. Overall mass loss of the mineral ash ranged from 23–48% depending on wood type. The mass of K, S, B, Na, and Cu decreased, whereas Mg, P, Mn, Al, Fe, and Si did not change with temperature relative to Ca which was assumed to be constant. Sintering of the ash occurred, but fusion of the ash did not occur. In the 600°C ash CaCO 3 and K 2 Ca(CO 3 ) 2 were identified, whereas in 1300°C ash CaO and MgO were the main compounds. The implications for ash deposition in furnaces is discussed.

Biochemical methane potential of biomass and waste feedstocks

Abstract: The biochemical methane potential (BMP)) assay was evaluated in terms of inoculum (rumen versus primary sludge digester), inoculum-to-feed ratio, and particle size for analysis of extent and rate of conversion of biomass and waste feedstocks to methane. The rumen and sludge inocula exhibited similar solubilization of particulate matter. An inoculum-to-feed ratio of 2:1 was shown to give maximum conversion rates. Particle size did not influence rate in the range of 1–8 mm. An extensive data base on the biochemical methane potential of several biomass and waste feedstocks is presented, including freshwater, marine, herbaceous, and woody feedstocks and municipal wastes; data for plant parts are also included. In addition, the influence of several parameters on the BMP of feedstocks are presented, including growth and harvest conditions, and ensiling.

Ash deposition during biomass and coal combustion: A mechanistic approach

Abstract: The variability in both inorganic and organic properties of biomass fuels is large. This paper discusses combustion-driven transformations and deposition of inorganic material found in solid fuels, with a focus on the formation of deposits and their properties. A small number of mechanisms is used to describe both the transformations and deposition. The discussion below outlines this mechanistic approach to describing the fate of inorganic material in solid fuels with a particular focus on the mechanisms of ash deposition. This mechanistic approach has the potential of embracing a large range of fuel variations, combustor types, and operating conditions without the need of developing extensive databases or testing procedures for each new situation. The approach has been successfully demonstrated for coal combustion, and examples from coal experiments will be used as illustrations. The same methodology and logic can be applied to biomass combustion. A comparison of coal and biomass is briefly presented, including the chemical structures and the modes of occurrence of inorganic material in the fuels. The major mechanisms of ash deposition during combustion of coal and biomass are related to the types of inorganic material in the fuel and the combustion conditions. The effects of fuel (biomass or coal) characteristics and combustor operating conditions on ash deposit properties such as tenacity, emissivity, thermal conductivity, morphology, strength, chemical composition, viscosity, and rate of growth are discussed. A mechanistic model describing ash deposition in solid-fuel combustors is presented and used to postulate characteristics of ash deposits formed in biomass combustors.

Methane fermentation of energy crops: maximum conversion kinetics and in situ biogas purification.

Abstract: A seven-year study addressed both the limitations on the rate and efficiency of biomass conversion, and the enrichment of biogas methane content. Energy crops examined included sorghum ( Sorghum bicolor ), napiergrass ( Pennisetum purpureum ), corn ( Zea mays ), and a sorghum/α-cellulose mix. High solids digestion work (25–30% effluent total solids (TS)) showed the need to address ammonia toxicity and trace nutrient limitations. Trace nutrient supplementation and control of the feedstock C/N ratio enabled stable operation of digesters at volatile solids (VS) loading rates up to 24 grams per kilogram reactor wet mass per day (gVS kg −1 day −1 ), with mean methane production rates of 7.5 L kg −1 day −1 . Acid-extractable metal concentrations were used as an indicator of bioavailable metals. Initial work with low solids digestion (8–10% TS) resulted in efficient VS conversion but low methane production rates. Subsequent work using trace nutrient supplementation enabled stable operation of intermittently-fed (three times per week) digesters at loading rates up to 12 gVS kg −1 day −1 , resulting in methane production rates up to 3.3 L kg −1 day −1 . Continuous feeding of corn at rates up to 18 gVS kg −1 day t-1 resulted in a mean methane production rate of 5.4 L kg−1 day-' with a 67% VS conversion efficiency. The maximum methane production rates for both the high solids and low solids systems are among the highest observed for biomass conversion. An in situ technique to enrich digester offgas was developed to take advantage of the differing solubilities of C0 2 and CH 4 , in which dissolved C0 2 was removed from the reactor in a recycled leachate stream and gas-stripped in an external stripper. Such a system easily enriched the remaining digester offgas to over 90% methane, and contents in excess of 98% were achieved. Quantitative evaluation of system variables defined the effects of leachate recycle rates, leachate alkalinity, and pH on the resulting offgas methane contents.

Soil carbon sequestration beneath hybrid poplar plantations in the North Central United States

Abstract: Hybrid poplar plantations grown on tilled agricultural lands previously in prairie, sequester significant quantities of soil carbon. Comparisons are made between hybrid poplar plantations and adjacent row crops or mowed grass. Establishing and tending plantations often results in early soil carbon loss, but soil carbon is significantly related (positive) to tree age. Increasing tree age eventually results in a net addition of soil carbon from plantations older than about 6 to 12 years of age. Soil carbon loss under trees occurred most frequently from the surface 30 cm early in the plantation history—evidence that the loss was due to mineralization. Soil carbon gain was most significant in the 30–50 cm layer and was attributed to tree root growth. Soil carbon accretion rate beneath 12- to 18-year-old poplar plantations exceeded that of adjacent agricultural crops by l.63 ± 0.16 Mg ha−1 yr−1. There was a significant crop × soil depth interaction for bulk density with bulk density lower beneath trees in the 0–30 cm layer and higher in the 30–50 cm layer. There was little evidence of carbon trapping of wind-blown organic detritus by tree plantations in the prairie environment.

Willow coppice systems in short rotation forestry: Effects of plant spacing, rotation length and clonal composition on biomass production

Abstract: Above ground biomass production was determined for ten Salix clones grown in pure and mixed stands at a square spacing of 1 m and seven rotation periods (1 to 6 and 8 years), and of one clone grown at four square spacings (0.5, 0.6, 0.7 and 1 m), with rotation cycles of 1 to 5 years. Most clones reached a maximum mean annual increment (8 to 14 tons dry matter ha −1 yr −1 ) under a rotation period of 4 to 5 years. Densely spaced stands exhibited a higher production than wider spacings during the first harvests under the shortest rotation periods. Neither in later harvests of short cycles (1 to 3 years) nor in any harvests of longer cycles (> 3 years) did spacing affect biomass production. Some clones suffered from leaf rust and grazing by roe deer. Clone mixtures showed a higher biomass production in the later stages due to the compensatory effect of the successful clones which, when growing in mixtures, could fill out the gaps left by individuals that suffered from impacts other than competition. We conclude that extremely short rotations (1 to 2 years) are unsuitable for Swedish conditions, and that 4- to 6-year rotations perform best. In such longer rotations, biomass production of stands with 2 × 10 4 plants per hectare equals the production of denser stands.

Gaseous emissions from circulating fluidized bed combustion of wood

Abstract: The emissions of NO, N2O, CO and SO2 were investigated during combustion of wood in a circulating fluidized bed boiler as a function of various parameters, including bed temperature, air supply and load. Emissions from mixtures of wood and coal were also investigated. The results show that the nitrogen oxide emission is directly related to the nitrogen content of the wood. The small amount of char in the bed during combustion of wood results in a much smaller reduction in the NO formed in the case of wood compared to that during combustion of coal and reduces the impact of bed temperature and air supply on the NO emissions during combustion of wood as compared to coal. Emission of N2O during combustion of wood was negligible.

Agglomeration of silica sand in a fluidized bed gasifier operating on wheat straw

Abstract: The effects of straw feed rate and ash composition on the agglomeration characteristics of the bed material (silica sand) in a fluidized bed gasification system were investigated. By changing the air flow rate and/or straw feed rate, the effects of four equivalence ratios (0.26, 0.38, 0.57 and 0.76) on agglomeration were investigated. The effect of straw ash content (0.0, 3.3, 27.8 and 43.5%) on the agglomeration of the bed material was also investigated at various temperatures (620, 740 and 850°C) using a high temperature furnace. It was found that a fluidized bed of silica sand agglomerated at around 800°C in the presence of straw ash, resulting in serious channelling and defluidization. A very hard and brittle structure was formed at 850°C. Changes in air velocity and/or fuel rate did not improve agglomeration characteristics. K2O, which is present at a high weight percentage in the straw ash and has a relatively low melting temperature, was the major contributor to the agglomeration process.

Extraction and characterization of chitin from crustaceans

Abstract: Chitin was isolated from various natural sources including Cuban lobsters, Sanlucar prawns, Norway lobsters, Squills, Spanish crayfish, American crayfish and Fusarium oxysporum with a yield of 14–25% on a dry basis. The physico-chemical properties of chitin from the different sources were studied by IR spectroscopy and scanning electron microscopy, and its degree of acetylation was determined. The chitin thus obtained is suitable for biotechnological applications (e.g. as supporting material for immobilizing enzymes).

Control of in-bed agglomeration by fuel blending in a pilot scale straw and wood fueled AFBC

Abstract: Bed agglomeration in a pilot scale atmospheric fluidized bed combustor was controlled by blending wood into rice straw in concentrations of 50% wood or more and stoichiometrically holding reaction temperature at or below 800°C. At higher straw concentrations, agglomeration of the bed occurred over run times inversely proportional to the straw concentration in the blend. Bed agglomeration was preceded by a characteristic decline in bed pressure drop most likely related to combustion air channeling through the bed. Blend ash composition was not substantially affected until straw concentration decreased to 50% or below because of the four-fold higher ash concentration in the straw compared to wood. Blend ash base-to-acid ratio also was not substantially affected above 50% straw concentration, remaining essentially constant at 0.3, compared to the wood ash base-to-acid ratio of 1.1. Initial deformation temperature, as measured by standard cone test of the blend ash, increased from a minimum of 880°C for a 75% straw blend to 1120°C for a 10% straw concentration in the blend.

Aquatic biomass resources and carbon dioxide trapping

Abstract: Intensively managed microalgal production facilities are capable of fixing several-fold more carbon dioxide per unit area than trees or crops. Although CO2 is still released when fuels derived from algal biomass are burned, integration of microalgal farms for flue gas capture approximately doubles the amount of energy produced per unit of CO2 released. Materials derived from microalgal biomass also can be used for other long-term uses, serving to sequester CO2. Flue gas has the potential to provide sufficient quantities of CO2 for such large-scale microalgae farms. Viewing microalgae farms as a means to reduce the effects of a greenhouse gas (carbon dioxide, CO2) changes the view of the economics of the process. Instead of requiring that microalgae-derived fuel be cost competitive with fossil fuels, the process economics must be compared with those of other technologies proposed to deal with the problem of CO2 pollution. However, development of alternative, environmentally safer energy production technologies will benefit society whether or not global climate change actually occurs. Microalgal biomass production has great potential to contribute to world energy supplies, and to control CO2 emissions as the demand for energy increases. This technology makes productive use of arid and semi-arid lands and highly saline water, resources that are not suitable for agriculture and other biomass technologies.

Leaf allometry in young poplar stands: reliability of leaf area index estimation, site and clone effects

Abstract: Different allometric relationships were established at the leaf, branch, stem and whole-tree levels for young poplar (Populus) trees during their first and second year of growth. Five poplar clones were grown under an intensively cultured regime at two different locations, Afsnee (near Gent, Belgium) and Orsay (near Paris, France). Leaf area was related linearly or non-linearly (power or logarithmic functions) to parameters that can be measured easily and non-destructively, such as leaf length or width, stem or branch diameter, stem or tree height, and volume index. Only small differences in the basic allometric relationships were noticed between the two sites and the five clones. A very good agreement was observed between leaf area index (LAI) values estimated from allometric relations and from indirect measurements using a plant canopy analyzer. These observations suggest that simple and general relations can be used to estimate LAI in young, high density poplar stands or leaf area at different organizational levels in trees.

Future biomass-based electricity supply in Northeast Brazil

Abstract: Hydroelectric resources in the semi-arid Northeast of Brazil will be exhausted about the year 2000. Unless viable alternatives can be found, relatively high-cost hydroelectric resources in the environmentally-sensitive North (Amazon) region will be tapped after 2000 to meet electricity demands in the Northeast. The Hydroelectric Company of Sao Francisco (CHESF), the federally-owned utility responsible for generation and transmission of bulk electricity in the Northeast, initiated studies in 1982 to quantify the potential for establishing a widespread biomass-based electricity generating system in its service territory as an alternative to hydro expansion. The analysis here builds on these studies, and includes the possibility of converting biomass into electricity using advanced gas-turbine technologies that are now the focus of commercial demonstration projects in Brazil and elsewhere. Existing sugarcane residues and future potential production of wood on dedicated plantations in the Northeast could be used to generate annually up to 41 TWh and 1400 TWh of electricity, respectively, compared to CHESF's present total annual generation of about 30 TWh. The cost of most of the biomass-derived electricity would be under 4.5 cents kWh−1, which compares favorably with marginal costs projected for hydroelectric projects in the Amazon region and would involve lower capital investment. Expansion of the CHESF system based on biomass rather than hydropower would also bring social benefits, including greater job creation.

Ecology and microbiology of biogasification

Abstract: The biodegradation of organic matter to form methane and carbon dioxide requires the interactions of diverse populations of bacteria. The roles of each of these organisms in the process and how they interact with each other is understood only in a rudimentary way. This paper describes the investigation of the microbial ecology of the anaerobic degradation of biomass feedstocks.

Hybrid poplar spacing/productivity relations in short rotation intensive culture plantations

Abstract: It is often argued that in short rotation intensive culture plantations, biomass productivity increases with narrower tree spacings. Biomass productivity and tree spacing relations were studied for up to 16 years in northern Wisconsin hybrid poplar plantations. Maximum mean annual biomass increment was 12.8 Mg ha −1 yr −1 for Populus clone NE-41 planted at a l m 2 spacing. Productivity differences related to spacing were found to be minor. Productivity was influenced mainly by clone, irrigation and disease. A hypothesis is proposed that time to canopy closure is linearly related to time to maximum mean annual biomass productivity. Wide spacing and wide-crown trees that permit wider tree spacing allow longer rotations, which can lower costs and increase flexibility in management.

Feedstock storage, handling and processing

Abstract: This paper is a review of the technology and research covering components of a methane from biomass system between the field and the digester. It deals primarily with sorghum as a feedstock and focuses on research conducted by the Texas Agricultural Experiment Station. Subjects included in this paper are harvesting, hay storage, ensiling, materials handling, pumping and hydraulic characteristics, hydraulic conductivity, pressure/density relationship, and biological pretreatment. This paper is not a comprehensive design manual; however, design equations and coefficients for sorghum are presented, where available, along with references describing the development and application of design models.

Kinetic and performance study of a batch two-phase anaerobic digestion of fruit and vegetable wastes

Abstract: Anaerobic digestion of a simulated organic fraction of the waste of a central market selling fruit and vegetables was carried out in two-phase digesters in the mesophilic range of temperatures. Batch digestion was prolonged until no biogas was produced (33 days). With digested pig manure as inoculum, maximum biogas production was obtained around day 10, and within 3 weeks the digestion was almost complete. A kinetic analysis was carried out using first-order, Monod and Chen-Hashimoto models. The Chen-Hashimoto model represents the best fit, whereas a first-order model was not consistent with the experimental results.

The pyrolysis kinetics of bagasse at low heating rates

Abstract: Thermogravimetric Analysis (TGA) was used to study the thermal degradation of wet and dry bagasse at low heating rates (5 to 50°C min −1 under a nitrogen atmosphere. For engineering purposes, it was found that a single first-order reaction gave the simplest and best fit to the rapid pyrolysis zone between 195 and 395°C, with an activation energy of 93.2 kJ mol −1 and pre-exponential factor of 4.33 x 10° s −1 These values have no chemical significance, but have been derived for use in modelling studies of the ignition and combustion of bagasse. Sample moisture content up to 18% by weight had no effect on the degradation, because moisture evaporation was complete before pyrolysis commenced at these low heating rates. The choice of the final mass from the TGA curve significantly affected the deduced kinetic parameters. The final sample mass at the end of the rapid pyrolysis zone was 26.2% of the dry sample mass. Some earlier workers neglected the subsequent slow pyrolysis zone and took the final sample mass to be the ash content. If this were done for the experiments reported here, then lower activation energies in the range 58.6 to 71.2 kJ mol −1 would be obtained, illustrating the importance of using the correct final sample mass.

Effect of alkali delignification on wheat straw saccharification by fusarium oxysporum cellulases

Abstract: The effect of alkaline delignification of wheat straw on the chemical composition and the subsequent enzymic hydrolysis of the pretreated straw are reported. Both hot (120°°C) and cold (20–36°°C) delignification were investigated, using either aqueous or organic alkaline solutions. The treated lignocellulosic materials were hydrolyzed by the cellulases of Fusarium oxysporum strain F3. Both delignification and saccharification yield showed linear relationships with the level of alkali used. Under the chosen experimental conditions 70–100% hydrolysis was achieved either by hot or cold delignification. Delignification to at least 50% appeared crucial for total polysaccharide conversion.

Biomass gasification: Environmentally sound technology for decentralized power generation, a case study from India

Abstract: This study aims at understanding the need for decentralized power generation systems and to explore the potential, feasibility and environmental implications of biomass gasifier-based electricity generation systems for village electrification. Electricity needs of villages are in the range of 5–20 kW depending on the size of the village. Decentralized power generation systems are desirable for low load village situations as the cost of power transmission lines is reduced and transmission and distribution losses are minimised. A biomass gasifier-based electricity generation system is one of the feasible options; the technology is readily available and has already been field tested. To meet the lighting and stationary power needs of 500,000 villages in India the land required is only 16 Mha compared to over 100 Mha of degraded land available for tree planting. In fact all the 95 Mt of woody biomass required for gasification could be obtained through biomass conservation programmes such as biogas and improved cook stoves. Thus dedication of land for energy plantations may not be required. A shift to a biomass gasifier-based power generation system leads to local benefits such as village self reliance, local employment and skill generation and promotion of in situ plant diversity plus global benefits like no net CO2 emission (as sustainable biomass harvests are possible) and a reduction in CO2 emissions (when used to substitute thermal power and diesel in irrigation pump sets).

Birch production and utilization for energy

Abstract: Natural birch stands represent a significant biomass resource since birches are one of the most common deciduous genera in cool temperate regions, even in places ranging up to the forest line Many characteristics of birch make it highly suited for short rotation forestry However, growing birch in very short rotations (less than 10 years) in northern climates is not worthwhile on the basis of biomass production and economics Rotations of 15 to 20 years may give good results everywhere The intensive culture of birch plantations has largely remained untested, but it is very likely that the yield levels can be increased significantly by using cloned material as well as improved silvicultural treatments, fertilization and pest control Birch feedstock, compared to material of many other tree species, is of even quality Moisture content is low and basic density high Branches and bark are also suitable for energy use Birch plays an important part in the energy budget of entire nations, particularly of Finland and Sweden

Effect of H2-pressure on the structures of bio-oils from the mild hydropyrolysis of biomass

Abstract: Low intensity hydropyrolysis of biomass has been investigated as a likely process route for upgrading agricultural and municipal waste, aiming to produce less highly oxygenated bio-oils with more stable storage characteristics than atmospheric pressure pyrolysis oils. A high-pressure wire-mesh pyrolysis reactor, recently re-designed to allow continuous sweeping of volatile products away from the reaction zone, was used during these experiments. This reactor configuration allows the determination of bio-oil yields and the recovery of condensible products for analytical characterisation in the relative absence of extra-particle secondary reactions. Samples of Swedish pine-wood and pine-wood lignin have been pyrolysed at temperatures between 300–700°C, at hydrogen pressures up to 70 bar. Product bio-oils have been characterised by size exclusion chromatography (SEC), UV-fluorescence spectroscopy (UV-F) and gas chromatography-mass spectrometry (GC-MS). Bio-oil yields from both pine-wood and lignin decreased by relatively small amounts over the pressure range, but significant changes in liquid product structures were observed: product bio-oils with progressively smaller molecular masses and lower polarity have been obtained with increasing pressure. Nevertheless, product bio-oils were characterised by a preponderance of oxygenates, including syringol and guaiacol derivatives and carboxylic acids, rather than alcohols, ketones, terpenoid and polynuclear aromatic hydrocarbons. Considerable differences have been observed between hydropyrolysis yields from pinewood and lignin: bio-oil and total volatile yields from the parent wood were greater than those observed for the lignin sample by about 30%. Comparison by GC-MS and UV-F suggests that the lignin derived bio-oils contain considerably more aromatic and less polar structures than the wood derived oils. At 70 bars, traces of di- and tri-bromodibenzodioxins have been detected in pinewood bio-oils from experiments at 400 and 700°C, apparently liberated from the wood during hydropyrolysis; it is presumed that the precursor fungicide molecules had previously been incorporated into the wood structure.

The fractionation of almond shells by thermo-mechanical aqueous-phase (TM-AV) pretreatment

Abstract: The fractionation of almond (Prunes amygdalus) shells using an aqueous phase thermo-mechanical pretreatment is the main goal in the present work. Almond shells are an abundant agricultural waste in the Mediterranean regions with an estimated world production of 550,000 Tm yr−1. The solubilization profile, the pretreated fiber composition and the yield of the xylan recovered in the aqueous phase have been studied as a function of the pretreatment severity. Two different models have been used to describe the xylan solubilization kinetics: a pseudo-kinetic model and a model based on the generalized severity factor. The results of xylan solubilization and recovery are in concordance with those reported for hardwood. It has also been found that under certain operational conditions and reactor configurations, the reaction rate may not be under kinetic control due to poor stirring of the lignocellulosic-aqueous slurry.

Characterization of rockrose wood, char and activated carbon

Abstract: The starting rockrose ( Cistus ladaniferus L.), as well as charred and activated products prepared by heat treatment conducted under different conditions, were characterized in terms of composition, calorific value, texture and surface chemistry. Techniques used were thermogravimetric analysis, gas adsorption, mercury porosimetry, density measurements, scanning electron microscopy and FT-IR. The rockrose composition and calorific value were similar to other woods. Rockrose chars were prepared by heat treatment of the material over the temperature range 200–1000°C. The production of charcoal occurred at 400°C. Above 600dgC the microporous structure of the chars became partially closed. Activated carbons were prepared by gasification (burnoff = 40%) of a carbonized product (carbonization temperature = 600°C) in air at 600°C and in CO 2 and steam at 750°C. Significant differences in properties of the activated carbons were noted depending on the activating agent. Activated carbon produced in steam possessed better textural characteristics, in particular the development of mesoporosity was observed. The presence of surface oxygen groups containing CO bonds, which may be formed from C=C bonds, was greater with air and steam than with CO 2 .

Use of biomass in electric power generation: the california experience

Abstract: This paper considers the performance and operating characteristics of the 46 power plants in central and northern California presently generating electric power using wood wastes and/or agricultural residues to fire steam turbines. The paper is a synopsis of an assessment of the more than 750 MW of biomass-fueled capacity providing power to the PG&E grid which came on line during the past decade, following the passage of the federal Public Utility Regulatory Policies Act. The plants are fueled by sawdust or pulp process wastes, hog fuel, in-forest thinnings, clean landfilled wood, orchard and vineyard wastes, and other agricultural residues. The challenges associated with combustion of agricultural residues have proved to be much greater than had been anticipated. The smallest plant provides less than 3 MW of power to the utility grid and the largest nearly 50 MW. Overall they consume more than 7 million bone dry tons (BDT) of fuel each year, using about 1 BDT to generate 1 MWh, an overall efficiency of about 20%. Lack of a fuels supply infrastructure resulted in a very tight fuels market and resultant high spot market prices during 1989 and 1990. Nevertheless, most of the plants have had a capacity factor of greater than 80%, though there have been problems associated with design, management and fuels procurement at some others. Some of the plants were constructed from rehabilitated boilers and turbines and have minimal environmental controls; others reflect the best of fluidized bed combustion technologies, with non-catalytic deNOx and “zero-discharge” water treatment capability. Future research should include work on harvesting and collection technologies, better characterization of the fuel resources and integrated programs to produce and use biomass to fuel advanced generation technologies, such as gas turbines and fuel cells.

Napiergrass genotypes and plant parts for biomass energy.

Abstract: Twenty Pennisetum genotypes were evaluated at Gainesville, FL, USA, in 1987 for biomass as an alternative energy source via bioconversion to methane. The genetic lines included napiergrass and interspecific hybrids (triploid and hexaploid) between pearl millet and napiergrass. Studies included determinations for ultimate methane yield [l g−1 volatile solids (VS)], methane production rate (day−1), biomass yield, in vitro organic matter digestibility (IVOMD), crude protein (CP), neutral detergent fiber (NDF), plant height and leaf/stem ratio. Biomass yields ranged from 8.3 to 24.8 Mg ha−1 yr−1 among the genotypes. At the time of harvest, leaves of six genotypes were separated from stem material to calculate leaf percentage. This trait varied from 27.4% leaves in cv. Kinggrass (PI 300086) to 57.1 % in cv. Mott, a dwarf. Internode length also varied widely among the lines and ranged from 2.5 to 15.5 cm. Highest ultimate methane yields of leaves (0.31-0.331 g−1 VS) were recorded for three triploids (41S, 44S, 23AX) and were higher (P < 0.10) than the yield (0.2781 g−1 obtained from leaves of the tall tetraploid (PI 300086). For the estimated ultimate methane yield, overall means for leaves and stems were 0.31 and 0.291 g−1 VS, respectively. The tall tetraploid (Kinggrass) was lower in IVOMD and CP, but significantly higher in NDF than the other genotypes tested. Positive correlations were obtained between CP, IVOMD, and ultimate methane yields indicating that it is possible to predict methane production. In an additional experiment, performed in 1990, the tall tetraploid (Kinggrass) again was low in IVOMD and CP, whereas cv. Mott and line 551 were high in concentrations of IVOMD and CP and low in NDF. This supportive evidence indicates that breeding for improved quality components is a possibility in this genus.

Thermochemical liquidization of dewatered sewage sludge

Abstract: Dewatered sewage sludge (approximately 80% moisture content) was liquidized by a heating process in order to be transported through a pipeline, and the pressure loss of liquidized sludge measured. The dewatered sludge could be liquidized at temperatures above 150–175°C, and the viscosity of the liquidized sludge could be reduced to that of concentrated sludge (approximately 98% moisture content). The liquidized sludge showed pseudoplasticity. Liquidized sludge, which has a high solid concentration, could be transported by pumping through a pipe with the same pressure loss as that of concentrated sludge. The pressure loss could be calculated using Fanning's equation.

Genetics and management of physiologic systems of sorghum for biomass production

Abstract: Sorghum ( Sorghum bicolor (L.) Moench) is one of the five most important cereal crops in the world. A wide range of types has been developed in studying grain, sweet, high energy, and biomass. The purpose of this paper was to describe the variability of traits and systems affecting biomass quantity and quality. Different maturities and heights between cultivars existed among test materials. Maximum dry biomass yield was to 35.1 Mg ha−1. Two harvest sequences of 120-60 or 90-90 days per season (original seeded crop plus a ratoon) were superior to other sequences. Total carbohydrate content of the biomass (less the panicle) ranged from 73 to 84%. Cultivars produced a range of 22.2 to 46.9% non-structural carbohydrates and 38.1 to 64.6% structural carbohydrates. Structural components varied for cellulose (35.0 to 19.8%), hemicellulose (28.9 to 19.9%), and lignin (6.9 to 3.3%). Two types of hemicellulose were identified in the cultivars tested. Results showed the highest percent of structural carbohydrates was localized in the culm rind. Stems and leaf blades were similar in levels of structural carbohydrates but stems were significantly higher in non-structural carbohydrates. An inverse relationship between non-structural carbohydrates and total structural components is present in biomass. Total volatile solid content of all types exceeded 92%, but genetic differences exist among cultivars. Percentage reduction of the volatile solids appeared different between cultivars. Amount of methane produced and biomass yield (quantity and quality) can be increased/decreased by management practices and genotypic selection.

A biomass energy flow chart for Kenya.

Abstract: Terrestrial (above ground) biomass production and its utilization in Kenya was analyzed for the 1980s. Total biomass energy production was estimated at 2574 × 106 GJ per year, most of which (86.7%) is produced on land classified as agricultural. Of the total production, agriculture and forestry operations resulted in the harvesting of 1138 × 106 GJ (44.2% of total production), half of which (602 × 106 GJ) was harvested for use as fuel. Only 80 × 1006 GJ was harvested for food and 63 × 106 GJ for industrial (agricultural and forestry) plus other miscellaneous purposes. About 85% of Kenya's energy is from biomass, with a per capita consumption of 18.6 GJ (0.44 toe, tonne oil equivalent) compared to less than 0.1 toe of commercial energy. Use of the biomass resource was found to be extensive involving bulk harvesting but with low utilization efficiencies; as a result the overall losses were quite high. Only 534 × 106 GJ (46.9% of harvested biomass) was “useful energy”. 480 × 106 GJ was left unused, as residues and dung, all which was either burnt or left to decompose in the fields. 124 × 106 GJ was lost during charcoal manufacture. Intensified use of the harvested biomass at higher efficiencies in order to minimize wastes would decrease the stress on the biomass resource base.