In order to reduce the emission of greenhouse gases, much attention has been focused on energy utilization of biomass in recent years. The promotion of the utilization of domestic woody biomass contributes not only to the improvement of energy selfsufficiency, but also to the environmental protection of forests and undeveloped woodlands near populated areas or satoyamas in Japan. Typical woody biomass derived from Japanese forests and satoyamas are Japanese Cedar and Konara. When woody biomass is utilized as biomass fuel, it is important to examine the energy consumptions for pretreatments such as comminution and reforming. In this study, using Konara, Japanese Cedar, and Balsa, the effects of tree species, comminution methods, and semicarbonization of the woody biomass on comminution energy are investigated. The results obtained in this study are as follows. (1) In the case that water content is less than a fiber saturation point, the comminution energy for three species is expressed as a function of water content. In the case that water content exceeds a fiber saturation point, comminution energy for three species is expressed as a function of density. The comminution energy can be estimated by using the present empirical equations within ±50% accuracy. (2) Regarding the comminution property of semi-carbonized woody biomass, for the wood region, the empirical equations of work index depend on the comminution methods regardless of tree species and sieve of screen. For the semi-carbonized and carbonized regions, the empirical equation of work index is presented regardless of tree species, comminution methods, and sieve of screen. The comminution energy can be estimated by using the present empirical equations within ±60% accuracy.
Biomass is one of the sustainable energy sources and is the most suitable natural energy for storage and transport. Woody pellet is a typical biomass fuel and is accessible in most places around the world. Its transportation efficiency, however, is not so high, due to lack of energy density. In order to improve the efficiency of woody biomass energy transportation, the ‘semi-carbonization pelletizing’ method was adopted. Semi-carbonized pellet,‘ Biomass Carbonized Densified Fuel’ (BCDF), is not a fully carbonized woody biomass, but is an intermediate of desiccated woody biomass and charcoal. Although charcoal is a high energy density fuel in J/kg and is widely being used, about a half of the original energy is lost during the carbonization process. Semi-carbonization is a balanced method for energy density improvement and energy yield. The process parameters of semi-carbonization, however, are so many and are not examined yet. In the present study, the effect of water content in woody biomass on the energy density and energy yield of semi-carbonized pellet was examined. Results show that water content diminish the process temperature range for improvement of energy transport efficiency compared to an absolute dry condition.
The utilization of unused biomass such as logging residues and broadleaf trees has come to attract attention to protect forests and satoyamas (a Japanese term for undeveloped woodlands near populated areas) in Japan. In this study, the modification of bio-coke fuels as an alternative to coal coke is investigated by using bamboo and Japanese cedar, which are the typical domestic woody biomass in forests and satoyamas. To improve the compressive strength under high temperature environment and the heating value of bio-coke, carbonized Japanese cedar is mixed with bamboo. The effect of the carbide mixture on the forming characteristics of bio-coke such as density, compressive strength, and heating value are experimentally clarified. The results obtained in the present study are as follows: (1) the density of bio-coke increases with increase in forming temperature and forming pressure, but is reduced by the addition of carbide as the thermoplastic polymer is reduced (2) the increase in carbide reduces the compressive strength under normal temperature environment and improves the compressive strength under high temperature environment. When the carbide content was 30%, the compressive strength under high temperature environment was 3.26MPa. (3) The addition of carbide is an effective way to improve the compressive strength under high temperature environment and to enhance the heating value of bio-coke.
The development of new energy sources have been advancing due to global warming and exhaustion of fossil fuels. The biomass fuel is one of these energy sources and is expected from the viewpoint of carbon neutral agricultural and biomass waste recycling and thermal recovery. Bio-coke is an alternate fuel of coal coke and is made by heating organic waste while being compressed at high pressures. The ignitability of Bio-coke worsens by high density. This study was an attempt to produce Bio-coke added with waste glycerin that is generated from the manufacturing process of bio-diesel fuel. The gasification characteristic of the fuels was examined by thermogravimetric analysis, while the stress-strain characteristic was examined by a high-temperature compression testing machine. The ignition and combustion characteristics of the fuels were observed in a fall-type electric furnace. Results show that Bio-coke can be made with the addition of waste glycerin. The gasification of the resulting fuel was promoted with the increase in amount of added waste glycerin. Moreover, the combustibility of the fuel was also promoted and the ignition delay time and burnout time became shorter.
A new type of circulating fluidized bed gasifier, called “fluidized bed gasifier with triple-beds and dual circulation”, was proposed. The objectives of this work are to clarify the gasification characteristics of biomass by using a laboratory-scale hot model gasifier and to compare the characteristics of biomass and coal. The tested biomass is wood pellet. As a result, the cold gas efficiency of wood pellet is higher than that of coal. The wood pellet is easy to gasify because the volatile matter content in the pellet is considerably high. Additionally, the amount of H2 formed is higher than that of the CO formed in both conditions since the amount of H2 increases due to the partial cracking of absorbed tar in porous alumina particles. The proposed gasifier can make porous alumina particles absorb tar, which is formed by the pyrolysis reaction, efficiently.
Our previous studies have reported on the combustion characteristics of sewage sludge in a fluidized bed incinerator with a turbocharger which can achieve not only energy recovery but also a low environmental impact. The objective of this study is to elucidate the co-firing characteristics of the sewage sludge and biomass in a demonstration plant. The tested biomass is wood tip, bark, grass and pasture. As a result, the temperature of the sand bed in co-firing condition is considerably higher than that in the sludge only combustion because the residual char of biomass after pyrolysis burns stably in the sand bed for the co-firing. Additionally, N2O emission can be controlled by the freeboard temperature in all experimental conditions. Therefore, our results indicate that the combustor can reduce the environmental impact of N2O emission in co-firing conditions.
Conventional fuel cells such as PEFC, MCFC, and the like, have big issues such as on cost, on fuel procurement, expensive catalysts, etc. At a more cost-effective viewpoint, the use of bio-fuel cells is recently gaining popularity because of the utilization of catalysts from enzymes produced by microbes by using sugar and alcohol carbon sources as a fuel. These carbon sources are easier to obtain than fuels like hydrogen and the enzymes can be mass-produced from microbes by genetic recombination technology. However, performances issues regarding power density, stability, and durability, among others, are worse compared to other fuel cells. Therefore, new technologies such as enhancing enzymatic activity by protein engineering, increasing the surface area of electrodes, and developments on mechanical engineering studies such as on oxygen and fuel supply methods, decreasing internal resistance, membrane material selection and separating methods, and stack technology are necessary for the improvement enzymatic fuel cells and the practical use of Bio fuel cells. This study shows enhanced reactiveness of a cathode in an enzymatic fuel cell through mechanical improvement. The influences of the electrode structure, the mediator/enzyme concentrations, and the oxygen supply method on the cell performance were evaluated using a half-cell. The influence of the electrode structure on cell performance was evaluated by applying Ketjenblack to the carbon paper electrode. As a result, the increase of the electrode surface area and the fixation of the enzyme/mediator to the electrode greatly improved the cathode reactiveness. Regarding the influence of mediator concentration on the cell performance, the mediator did not inhibit the enzyme reaction even when the concentration of the mediator on the enzyme was too high. The results of the influence on the performance by an increase in the dissolved oxygen by aeration of the solution and an increase in the oxygen concentration in the supplied gas were that the increase of the oxygen concentration in the solution improved the cathode diffusion polarization more than the forced convection.
The world should sever the dependence of fossil fuel to solve serious global environmental issues. Recently, although the dissemination of the nuclear plant was promoted because of the low CO2 emission in the world, it will be controlled by the accident of the Fukushima nuclear plant due to the East Japan great earthquake. Therefore, renewable energies such as the sunshine, the wind forces and biomasses are paid to attention as an alternative energy of the fossil fuel and nuclear power, and the dissemination of the fuel cell such as Polymer Electrolyte Fuel Cells and Molten Carbonate Fuel Cells is greatly expected from the world, especially. However, these fuel cells are too expensive by use of the noble metal catalyst, a high manufacturing cost, a low lifetime and insufficient ensuring hydrogen. Therefore, as the development of a low-cost fuel cell is expected, microbial fuel cells (MFC) are paid to attention. The cost of MFCs can be reduced because microbes as a catalyst can be manufactured from the genetic operation at a low price, and organic waste such as sludge and food residue etc. become a fuel for MFC. Therefore, MFC are expected to apply to from large-scale sewage plant to a portable power source. However, the MFCs performances such as power density, stability, durability and so on are worse than that of other fuel cells and power source. Therefore, we aim to solve these issues by improving the mechanical factors. However, it is difficult to evaluate the performance of the MFCs accurately because the growth and extinction of a microbe greatly depend on the experimental condition such as temperature, power generation and fuel quantity etc. Wherein, we made two trial products of MFC that used the commercially available active dry yeast as an anode catalyst, evaluated its performance, and have extracted the problem of MFC. As a result, we obtained the max power of 0.85 - 1.0 mW/cm2 by two trial products of MFC. Moreover, the influence of the fuel diffusion polarization on the performance was larger than conventional fuel cells. It was clarified that the cell structure such as an interelectrode distance and a shape of fuel tank in each pole etc. influences the cell performance. Additionally, the fixation in electrode of microbe and the effective supply method to microbe of fuel should be further examined to improve the cell performance.
Microorganisms utilizing glycerol as a carbon source were isolated from various soils for glycerol/O2bio-fuel cell system. Among 19 locations at the campus of Osaka Prefecture University Collage of Technology and Uchiagegawa flood-control green space in Neyagawa city, the microorganisms isolated from three points (sample numbers 1-2, 1-3 and 1-8) were able to grow in the medium containing 15% glycerol at 37°C and ones from ten locations could proliferate in the same concentration of glycerol at 25°C. In the case of the microorganisms growing at 37°C, they were similar in appearance and seemed to form biofilm. Among ten isolation bacteria at 25°C, three samples (sample number 2-2, 2-3 and 2-5) showed good proliferation in the condition of 15% glycerol medium. The growth profiles of the microorganism which showed the most significant proliferation (sample number 2-5) were also investigated at various glycerol concentrations, resulting that maximum cell density was suppressed at higher glycerol concentration.