07 Alternative energy sources (bioconversion energy)

the use of poultry litter as a viable co-fuel in combustors and gasifiers. In particular, the benefits of using fluidized-bed combustion and gasification methods to process the poultry litter are discussed.

02/02061 Biomass for energy or materials? A Western European systems engineering perspective Gielen, D. J. et al. Energy Policy, 2001, 29, (4), 291-302. This paper discusses an assessment of the optimal use of biomass in Western Europe for the long term (2010-2030) for reducing green- house gas emissions. The assessment is based on a linear programming model for the Western European energy and materials system, called MARKAL MATTER 4.2. The goal of the study was the comparison of the cost-effectiveness and the interactions between bioenergy, bioma- terials and afforestation strategies in comparison to other greenhouse gas emission reduction strategics. The results suggest that the use of biomass for energy and materials applications will increase by up to 200 Mt (compared to the case with no permit price) if greenhouse gas policies are introduced. The main increase occurs in the production of transportation fuels and substitution of petrochemical feedstocks and electricity generation from waste and residues. Afforestation offers a cost-effective competing land-use strategy. The total contribution of biomass strategies is an emission reduction of up to 400 Mt CO2 equivalents (9% of 1990 emissions).

02/02062 Catalysed and uncatalysed steam gasification of eucalyptus char: influence of variables and kinetic study Encinar, J. M. et al. Fuel, 2001, 80, (14), 2025-2036. A study of the steam gasification of Eucalyptus chars has been carried out, using Li, Na and K chlorides as catalysts, in order to characterize the gas phase with a view to its energy use, analysing the influence of steam flow rates, initial mass of char, particle size and temperature. The main gases generated were HE, CO and CO2, with a higher heating value between 9 and 10 MJ/N mL The presence of alkaline metals as catalysts resulted in a high process rate. The catalyst concentration had a positive effect up to a given level (1% for LiCI and 3% for NaCI and KCI), above which there was saturation due to the blocking of the carbon pores. A kinetic model based on gas generation gave the activation energy and the reaction order with respect to each catalyst. These activation energies were in all cases lower than that of the uncatalysed process. This, together with a decrease in the Arrhenius pre-exponential factor, leads to isokinetic points, i.e. temperatures at which the catalysed and uncatalysed processes take place at the same rate. These isokinetic points were 903, 1356 and 998°C for Li, Na and K chlorides, respectively.

02/02063 Cattle feedlot manure quality for coal/biomass blend combustion Sweeten, J. M. et al. Proceedings - Annual International Pittsburgh Coal Conference, 2000, (17), 1192-1199. The energy potential of feedlot manure diminished with composting time and in storage. The main value of composting for combustion fuel would be to improve physical properties. Partial composting seems preferable to full composting cycle. The addition of 5% crop residues had little apparent effect on heating value. The pilot plant experiment at FETC was a very successful test of a 90%/10% coal/feedlot manure blend. The documentation will be outstanding when all results are in. Even though nitrogen content (N%) in the coal/manure blend was 16% higher than for coal, the emission of NO2 in Ib/MM BTU remained almost constant. Or was reduced.

02/02064 Co-firing of bark and sub-bituminous coal on stoker and fiuidized bed systems Clemens, A. H. et al. Proceedings - Annual International Pittsburgh Coal Conference, 2000, (17), 1858-1872. The addition of biomass (a low sulphur and carbon dioxide neutral fuel) to the fuel at coal-fired plant has a number of benefits including reduced SO2 emissions and eftectively reducing CO2 levels. However, before using biomass in existing coal-fired facilities, detailed assess- ment of the performance of biomass/coal mixtures is required to understand and minimize operational problems and to optimize the properties of the coal/biomass blend. This paper examines the cofiring of an 85:15 (by calorific value) mixture of coal to biomass (bark) mixture on a laboratory scale (nominal 50 kW) combustion rig using both stoker and fluidized bed combustion regimes. The biomass was radiata pine bark sourced from the debarking operations at an industrial saw mill. The coal was an alkaline sub-bituminous coal typical of those used for industrial purposes in New Zealand. Combustion performance of the coal biomass fuel was markedly different to that of the sub-bituminous coal alone. For both types of combustor the reduction in SO2 emissions was found to be greater than that expected solely on the grounds of reduced sulphur content in the mixed fuel. A reduction in fouling deposit formation was also observed for both combustion systems when the mixed fuel was used. For the stoker combustion system a higher degree of hard ash slag formation was observed than for either the coal or biomass burned alone. Most of

these changes were found to be strongly dependent on the complex ash chemical reactions occurring in the firebox during combustion. Some key ones are discussed along with their implications for cofiring.

02/02065 Determination of the optimal quantity of crop residues for energy in sugarcane crop management using linear programming in variety selection and planting strategy Sartori, M. M. P. et al. Energy, 2001, 26, (11), 1031 1040. The aim of this work was to present organizational models for optimizing the reduction of crop residue generated by the sugarcane culture. The first model consisted of the selection of varieties of sugarcane to be planted meeting the mill requirements and, at the same time, to minimize the quantity of residue produced. The second model discussed the use of residue to produce energy. This is related to the selection of variety and quantity to be planted, in order to meet the requirements of the mill, to reduce the quantity of residue, and to maximize as much as possible the energy production. The use of linear programming was proposed. The two models presented similar results in this study, and both may be used to define the varieties and areas to be cultivated.

02/02066 Farm animal manure is an important sustainable renewable energy resource Sheffield, J. Proceedings - Annual Internat ional Pi t tsburgh Coal Conference, 2000, (17), 1646-1655. A review with references. Farms for raising cattle, poultry, and swine are very important to feeding this country and other parts of the world. However, they ca n suffer from severe environmental problems. In the United States alone at least a billion tons of manure, wet weight, are generated annually. Run-off and emissions from these farms and the fields that provide feed for them - fertilizers, pesticides, pathogens, antibiotics, and hormones - can pollute the water and air. The manure contributes significantly to greenhouse gas emissions. Methane emis- sions for the US alone (about 10% of the manure) are estimated to be 2.76 million tonnes for 1996. Fortunately, technological solutions, cleverly applied, can offer additional benefits to the farmers to offset the costs of pollution control. In fact, given the wealth of technology opportunities to do better it might be possible to become more profitable. The manure is commonly used a fertilizer, but it also represents a large, generally untapped, source of energy and can be utilized as a feedstock for both energy and other products. It is estimated that the world's farm livestock and poultry includes about 1 billion cattle, 0.8 billion pigs, 0.9 billion sheep and goats and, on average, 8 billion chickens (broilers and layers). A rough estimate of total dry weight for the world's farm animal manure in 1997 is 1.7 billion tonnes. The energy content of dry manure is in the range 12 to 18 GJ per tonne, about half that of coal. If half of this amount of manure were collected it would have an energy content of about 12 E J/ year (300 million tonnes of oil equivalent per year), or about 10% of present world oil use. The use of anaerobic digestion in a contained system has the additional advantages of a significant reduction in pathogen levels in the remaining manure; important to its safe application as a fertilizer. The best solutions to the problems will require an understanding of the integrated picture. The areas involved include agriculture, biomass energy, biol. & medicine, biotechnology, separations, sciences, chemical engineering, economics, energy end-use and production technologies, computer modelling, environmental sciences, hydrology, sensors (standard and special) integrated with data collection and analysis capabilities, and the capability of integrating all the knowledge into the design of more effective systems. In this paper, visions of systems of the future are discussed, highlighting the opportunities to benefit from advances and contribute to sustainable energy and reduced greenhouse gas emissions.

02•02067 Fuel supply strategies for large-scale bio-energy projects in developing countries. Electricity generation from agricultural and forest residues in Northeastern Thailand Junginger, M. et al. Biomass and Bioenergy, 2001, 21, (4), 259-275. Agricultural and forest residues represent a major fuel source for potential bio-energy projects in many developing countries. However, a number of risks can threaten a secure fuel supply. This paper presents a methodology to set up fuel supply strategies for large-scale biomass conversion units (between 10 and 40 MWc), and to determine the connected risks and to minimize them. The methodology focuses (amongst others) on variations in residue quantities.produced, limited accessibility of residues, utilization by other compet,tors and logistical risks. For each risk, possible ranges are determined and incorporated in different fuel supply scenarios which indicate how biomass quantities and prices may vary under different circumstances. The methodology was demonstrated in Northeastern Thailand. It is shown that process- based residues are already highly utilized, while more expensive field- based residues represent the largest net available biomass potential. Both residue quantities and prices (US$0.59-2.58/GJ) can vary strongly, mainly depending on fluctuating harvests, increased utiliz-

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