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Biomass Energy Research

(1)Characterization of Biomass Resources for Biofuel Production

1)Characterization and Potential Evaluation of Various Biomass Resources for Biofuel Production

(Graduate School of Energy Science)Shiro Saka

Plan and Achievement in FY 2009

Although various biomass resources are available for biofuels production, their characteristics affect the properties of produced biofuels. Therefore in this study, basic characteristics of biomass resources were investigated and their potentials were planned to be evaluated. In this year, chemical constituents of various biomass resources such as cellulose, hemicelluloses, lignin, extractives and inorganic constituents were continued to be studied quantitatively, and their chemical characteristics were elucidated. In addition, the standardized methodology applicable for any biomass species was proposed for quantification of their chemical compositions.


1)Ecoethanol Production by Acetic Acid Fermentation with Hydrogenolysis from Lignocellulosics

(Graduate School of Energy Science)Shiro Saka, Haruo Kawamoto, Hisashi Miyafuji

Plan and Achievement in FY 2009

Compared to starch and molasses, lignocellulosics are difficult to convert to ethanol by yeast. Therefore, innovative technology for ethanol production is highly anticipated for lignocellulosics. A two-step hot-compressed water treatment process coupled with acetic acid fermentation of the obtained products was thus proposed in this work to produce bioethanol. The obtained products of monosaccharides, oligosaccharides, their decomposed products, lignin-derived products and organic acids were then found to be used as substrates for acetic acid fermentation in the co-culturing system of Clostridium thermoaceticum and C. thermocellum. Consequently, with buna (Fagus crenata) and sugi (Cryptomeria Japonica) woods, hot-compressed water treatment resulted in 82 and 65wt% substrate yields on wood basis. Additionally, lignin was found to de decomposed to a lower-molecular weight substances and their pathway was becoming elucidated. In acetic acid fermentation, hot-compressed water-treated products were found to be effectively converted to acetic acid by its co-culturing. In hydrogenolysis, ethyl acetate was found to be converted to ethanol effectively with hydrogen produced in acetic acid fermentation. Based on these results, our proposed process would be a good candidate for 2nd generation bioethanol production from cellulosic biomass.

2)Prospect of Nipa Palm for Bioethanol Production

(Graduate School of Energy Science)Shiro Saka

Plan and Achievement in FY 2009

The global bioethanol supply is produced mainly from sugar and starch feedstock. Sugarcane in the form of molasses and starchy materials in corn and cassava contain high levels of glucose, fructose and sucrose, are the easiest to convert to ethanol. Similarly, nipa (Nypa fruticans) is a non-threatened and underutilized sugar yielding palm which produces rich sugar sap from its inflorescence continuously for up to 50 years. We are currently focusing on comparative study of nipa sap produced in Thailand and Philippines with sugarcane sap mainly on chemical compositions and bioethanol production. Nipa sap was found to have higher total recoverable dry mass (17wt%) compared to sugarcane sap (15wt%). Ash analysis showed a group of different dominating salts such as Na+ and K+ for nipa and K+, Mg2+ and Ca2+ for sugarcane. Fermentation trend of nipa sap was similar to sugarcane sap with high yields of bioethanol (above 90% conversion). However, the presence of inorganic elements in nipa sap is now being studied for its role in the fermentation to bioethanol.

3)Development of Highly Efficient Bioethanol Production Yeast Using Protein Engineering

(Institute of Advanced Energy)Tsutomu Kodaki

Plan and Achievement in FY 2009

Xylose is one of the major fermentable sugars present in lignocellulosic biomass. The efficient fermentation of xylose is required to develop economically viable processes for producing bioethanol. Although a few xylose fermenting yeasts are found in nature, Saccharomyces cerevisiae is used universally for industrial ethanol production because of its ability to produce high concentrations of ethanol and high inherent ethanol tolerance. However, native S. cerevisiae cannot ferment xylose, so engineering S. cerevisiae for xylose utilization has focused on adapting the xylose metabolic pathway from the xylose-utilizing yeast such as Pichia stipitis. We have already developed the mutated XDH by protein engineering and the change of coenzyme specificities of XDH has been shown to have the positive effects on the production of bioethanol from xylose. In this study, construction of the first strictly NADPH dependent xylose reductase from Pichia stipitis was succeeded by site directed mutagenesis, where two double mutants with almost the same activity of wild-type were generated. More efficient xylose fermentation could be expected by introducing the strictly NADPH dependent PsXR with the strictly NADP+ dependent PsXDH due to the full recycling of coenzymes between the mutated XR and XDH.


1)High Quality Biodiesel as Prepared by Non-Catalytic Supercritical Methanol Method

(Graduate School of Energy Science)Shiro Saka

Plan and Achievement in FY 2009

Properties of biodiesel as prepared by supercritical methanol method were determined. It was found that most of the fuel properties can meet the standard specifications except for oxidation stability of biodiesel from oil/fat resources with high unsaturated fatty acid content. To evaluate oxidation stability of biodiesel, biodiesel produced by alkali-catalyzed method was exposed to supercritical methanol. As a result, it was found that after supercritical methanol treatment, hydroperoxides were greatly reduced for biodiesel with initially high in peroxide value, while the natural antioxidant slightly decreased in its content. Therefore, supercritical methanol method can produce biodiesel with better oxidation stability especially waste oils/fats. In order to improve the oxidation stability of biodiesel, lignin prepared with 72% concentrated sulfuric acid was subjected to supercritical methanol treatment during preparing biodiesel. It was, consequently, found that lignin was decomposed to small molecular substances that have very good antioxidation effect. Therefore, lignin-derived products produced by hot-compressed water treatment in the project of B) Bioethanol were added to the reaction system and found that the similar effect can be obtained. The study proved that both lignin additions provide an inexpensive and technically acceptable way to improve the oxidation stability of biodiesel as prepared by supercritical methanol method with satisfactory fuel properties.

2)New Biodiesel Production Process from Oils/Fats by Supercritical Carboxylate Esters and Neutral Esters

(Graduate School of Energy Science)Shiro Saka

Plan and Achievement in FY 2009

The current commercial biodiesel production called the alkali-catalyzed method, transesterifies triglycerides in the presence of alkaline catalyst with methanol to produce fatty acid methyl esters (FAME) and glycerol as by-product. As biodiesel production becomes rapid in years to come, the overproduction of glycerol lower its economical value and available applications are not likely to be align with its abrupt increase. Thus, new production methods of biodiesel without the production of glycerol are therefore worth to be explored. In this line of study, an additional new supercritical process utilizing other potential reactants such as carboxylate esters and neutral esters have been explored. The supercritical methyl acetate method as one of the carboxylate ester methods; a non-catalytic transesterification reaction between methyl acetate and triglycerides, evidently succeeded in producing high yield of fatty acid methyl esters and triacetin as one of triacins. Since triacetin has very similar fuel properties as biodiesel, a mixture of fatty acid methyl ester and triacetin was demonstrated to be used efficiently as biodiesel. In addition, in this year, systematic research was made on biodiesel production by various carboxylate alkyl esters. The supercritical dimethyl carbonate method as one of the neutral ester methods has also demonstrated that, without any catalyst applied, converted triglycerides to fatty acid methyl esters with glycerol carbonate and citramalic acid as by-products. These by-products are much higher in value than glycerol produced by the conventional process. Furthermore, to establish the mild reaction condition for practical application, the two-step supercritical dimethyl carbonate process has been proposed. Without doubt, these studies could charter the path towards exploration of novel and alternative biodiesel production processes for the future.

3)Ignition and Combustion Characteristics in Various Kinds of Biodiesel Fuels

(Graduate School of Energy Science)Masahiro Shioji

Plan and Achievement in FY 2009

Biodiesel has been regarded as the most attractive alternative fuel with carbon neutral, exhibiting the favorable feasibility for conventional diesel engines. This research aims to provide the fundamental data of ignition delay and combustion characteristics of BDF sprays. Experiments were carried out in a constant-volume vessel under diesel-engine conditions to investigate the spray developments, ignition delays and heat-release rates using four kinds of FAME from the Jatropha, Coconut, Soybean, Palm oils with different properties, together with the standard gas-oil for comparison. Among tested fuels, coconut spray with lowest 10% distillation temperature and kinetic viscosity promotes the atomization, evaporation and fuel-air mixing, exhibiting the shortest ignition-delay period in spite of lowest cetane index. Experimental results at ambient temperature lower than 800 K show that FAME sprays have a shorter ignition delay compared with the gas-oil, and that a diffusive combustion followed by the premixed one. Those results may provide the valuable data for optimal design and operation in diesel engines fuelled by BDF.

(4)Biomass Conversion to Liquid Biofuels and Useful Biomaterials

1)Biomass Conversion to Liquid Biofuels and Useful Biomaterials by Supercritical Fluid Technologies

(Graduate School of Energy Science)Shiro Saka

Plan and Achievement in FY 2009

In this study, liquefaction of wood is being studied to produce liquid biofuels by supercritical (or subcritical) alcohol technology. In liquefaction of woody biomass by supercritical alcohol, there exist characteristics such as
i) the obtained liquefied products can be directly utilized together with alcohol which is itself a kind of fuels, and
ii) various alcohols such as methanol, ethanol,1-butanol and 1-octanol can be produced from biomass resources.
Therefore, by liquefying biomass with these alcohols, 100% biomass-based liquid biofuels can be achieved. In this study, therefore, phenol species as a solvent were also used to liquefy the biomass resources and its optimum treatment conditions were studied and clarified.

2)Production of Biofuels and Biomaterials by Pyrolysis

(Graduate School of Energy Science)Haruo Kawamoto, Shiro Saka

Plan and Achievement in FY 2009

In this study, pyrolysis and gasification mechanisms of woody biomass are studied at the molecular level, aiming at the development of effective conversion methods to liquid biofuels and useful biomaterials. The following results are obtained in this year. As for gasification, pyrolysis and secondary reactions behaviors of lignin were found to be different for softwood and hardwood samples. Studies with the lignin fractions isolated from the wood samples and simple model compounds, such difference was suggested to arise from their different pyrolytic reactivities of guaiacyl (G)- and syringyl (S)-types of aromatic unclei (softwood: G-type, hardwood: G- + S-types ). As for the cellulose pyrolysis at relatively low temperature <280oC, pyrolytic reaction occurring at the reducing end-group was found to be a key reaction for coloring and weight-loss of cellulose. Such pyrolytic reactions were effectively inhibited in presence of alcohols by stabilizing the reducing end-groups through formation of glycosidic bonds with alcohols.

3)Biofuel and Biomaterial Production by Ionic Liquid Treatment

(Graduate School of Energy Science)Hisashi Miyafuji, Shiro Saka

Plan and Achievement in FY 2009

For production of biofuel and biomaterial, the treatment of wood with ionic liquid was studied. Wood was found to be liquefied around 100°C by the 1-ethyl-3-methylimidazorium chloride or 1-ethyl-3-methylimidazorium acetate. Cellulose, hemicelluloses and lignin which are components of wood could be liquefied. It was also clarified that these components were depolymerized. After the liquefaction of wood with the ionic liquid, wood components in the ionic liquid were recovered as precipitates by the addition of water. Enzymatic hydrolysis with cellulase was carried out for the obtained precipitates. The yield of glucose from the precipitates is found to be higher than that from untreated wood.

4)Oil Palm (Elaeis guineensis) Chemical Characteristics for Its Efficient Utilization

(Graduate School of Energy Science)Shiro Saka, Haruo Kawamoto

Plan and Achievement in FY 2009

Oil palm plantation is rapidly growing especially in south-east Asian countries such as Malaysia and Indonesia to produce palm oil. With this trend, huge amount of oil palm wastes are produced, which include trunk and frond from the plantation site and mesocarp, shell, kernel cake and empty fruit bunch (EFB) from the palm oil production. Efficient utilization of these various kinds of oil palm wastes is expected. In this study, chemical compositions of cellulose, hemicelluloses, lignin and other minor inorganic cell wall components were clarified first for these oil palm wastes. Furthermore, the products obtained by supercritical water treatment of these materials were characterized chemically as compared with those from wood samples. As a result, from a viewpoint of chemical composition, oil palm is more likely to be hardwood, compared with softwood. However, decomposition behaviors are more excessive than hardwood as treated in supercritical water.

(5)Framework Design for Biomass Utilization

Modeling of Biomass Utilization in a Region and Framework Design of Autonomous Decentralized Energy Supply-demand System with Biomass Use

(Graduate School of Energy Science) Tetsuo Tezuka

Plan and Achievement in FY 2009

  • Economic viability of the thinned-wood utilization system in Kyoto Prefecture is investigated by estimating the cost structure about the thinned-wood. In this study analyzed are the costs for thinning, that is, the costs of forest-road construction, cutting down, carrying out, and transportation, respectively. The maximum price payable to the thinned wood is also inquired of lumber workers by using questionnaire. The tax rate necessary for promoting the utilization of thinned wood as fuel for boilers is estimated based on the estimated cost structure.
  • The biodiesel production from used-cooking oil is analyzed from the viewpoints of energy and economy. And the economic viability of pyrolysis system for the combinatorial use with other waste oil is also analyzed.
  • Forecast of availability of energy-related technologies and its uncertainty play an important role in evaluating future energy systems. In this study a discrete-event model for representing the causality among energy-related technologies and the uncertainty in the technological development is proposed. It can be utilized for evaluating the future energy supply-demand system in combination with the conventional optimization-type energy system model. This model can be used for identifying the technologies indispensable for realizing zero-emission society.