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

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 quantitatively studied and their chemical characteristics were elucidated.


(2) Bioethanol

1) Ecoethanol Production by Acetic Acid Fermentation with Hydrogenolysis from Lignocellulosics
(Graduate School of Energy Science) Shiro Saka, Haruo Kawamoto, Hisashi Miyafuji

Compared to starch and molasses, lignocellulosics are difficult to convert to ethanol by yeast. Therefore, innovative technology for ethanol production is widely anticipated for lignocellulosics. A two-step hotcompressed water treatment process was, therefore, studied in this work to obtain a high yield of pentose, hexose, oligosaccharides, uronic acid and fragmented products etc. from lignocellulosics. The obtained saccharides and fragmented products etc. were studied to be fermented to acetic acid, which is further converted to ethanol by hydrogenolysis. Consequently, a highly-convertible eco-ethanol production system can be expected to be established with highly-effective CO2 reduction, compare with conventional concentrated sulfuric acid process. In a study with buna wood, hot-compressed water treatment resulted in 72wt% yield of sacchrides. Additionally, lignin was found to de decomposed to lower-molecular weight substances. In acetic acid fermentation, hot-compressed water-treated products can be effectively converted to acetic acid by the coculture of Clostridium. thermoaceticum and C. thermocellum. In hydrogenolysis, ethyl acetate was found to be converted to ethanol effectively. Based on these results, our proposed process would be better, compared with conventional method by yeast in bioethanol production.

2) Prospect of Nipa Palm for Bioethanol Production
(Graduate School of Energy Science) Shiro Saka

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 infl orescence 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 Effi cient Bioethanol Production Yeast Using Protein Engineering
(Institute of Advanced Energy) Tsutomu Kodaki

Xylose is one of the major fermentable sugars present in lignocellulosic biomass. The effi cient 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. Although S. cerevisiae transformed with native XR and XDH genes from P. stipitis can ferment xylose, its ethanol production was not suffi cient for application in the industrial bioprocess. One of the main reasons is the unfavorable excretion of xylitol caused by the different coenzyme specifi city between XR and XDH. In this study, we at fi rst developed the mutated XR and XDH by protein engineering and then the effects of mutation were examined by transforming the mutated enzymes into S. cerevisiae. The change of coenzyme specifi cities of XR and XDH by protein engineering has been shown to have the positive effects on the production of bioethanol from xylose.


(3) Biodiesel

1) High Quality Biodiesel as Prepared by Non-Catalytic Supercritical Methanol Method
(Graduate School of Energy Science) Shiro Saka

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 was subjected to supercritical methanol treatment during preparing biodiesel. It was found that lignin was decomposed to small molecular substances that have very good antioxidation effect. Thus, the study proved that lignin addition provides 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

The current commercial biodiesel production called the alkali-catalyzed method, transesterifi es 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; a non-catalytic transesterifi cation reaction between methyl acetate and triglycerides, evidently succeeded in producing high yield of fatty acid methyl esters and triacin. Since triacin has very similar fuel properties as biodiesel, a mixture of fatty acid methyl ester and triacin was demonstrated to be used efficiently as biodiesel. In addition, the supercritical dimethyl carbonate method has also demonstrated that, without any catalyst applied, converted triglycerides to fatty acid methyl esters with glycerol carbonate and citramalic acid as by-products. The byproducts from this process which are glycerol carbonate and citramalic acid are much higher in value than glycerol produced by the conventional process. 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

Among various alternative fuels available for the conventional diesel engine, biodiesel fuel (BDF) is the most attractive. This research aims to provide the fundamental data of ignition delay and combustion characteristics of BDF spray. 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 several kinds of BDF from the edible oil with different properties, together with the standard gas-oil for comparison. Although penetration lengths of both fuels are almost same, physical properties such as higher density and lower vaporization may retard the mixture formation of BDF at spray tip. Experimental results at ambient temperature lower than 800 K show that the fresh BDF has a longer ignition delay compared with the gas-oil, whereas the aged one has the almost same delay, and that a small amount of IPA may promote the ignition. Those results may contribute for consideration the optimal condition of 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

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 liquefi ed 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 clarifi ed.

2) Production of Biofuels and Biomaterials by Pyrolysis
(Graduate School of Energy Science) Haruo Kawamoto, Shiro Saka

In this study, pyrolysis and gasifi cation 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. Wood gasifi cation is a two-stage process which includes the primary pyrolysis to form volatile and carbonized products and their secondary reactions. Softwood and hardwood are expected to exhibit different reaction behaviors in this process, since chemical structures of hemicelluloses and lignins in these species are different. With sugi (Cryptomeria japonica) and buna (Fagus crenata) woods as a softwood and a hardwood, respectively, their different pyrolysis and gasifi cation behaviors were clarifi ed, which include the greater gasifi cation reactivity of buna primary char than sugi char, and different infl uences of deionization [ex: gasifi cation reactivity: sugi (increase), buna (not infl uenced)]. As for cellulose pyrolysis, the reducing end-groups were found to have higher reactivities than other parts and cause color formation and transglycosylation (depolymerization) of the glycosidic linkages even at such low pyrolysis temperatures as 200-240 °C. Furthermore, by using model dimers, radical chain-reactions were suggested to play an important role in pyrolysis of lignin in wood. Wood polysaccharides were also found to affect the chain-reactions very much and their infl uences were signifi cantly different depending on their chemical structures.

3) Biofuel and Biomaterial Production by Ionic Liquid Treatment
(Graduate School of Energy Science) Hisashi Miyafuji, Shiro Saka

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-methylimidazoriumchloride. Cellulose, hemicelluloses and lignin which are components of wood could be liquefied. It was also clarified that these components were depolymerized and monosaccharide could be produced from cellulose and hemicelluloses. From the study on the effect of reaction atmosphere on ionic liquid treatment of wood, oxygen was found to accelerate the liquefaction of wood. Ionic liquid is thought to work as a solvent for chemical conversion of wood with liquefaction and depolymerization.

4) Oil Palm (Elaeis guineensis) Chemical Characteristics for Its Effi cient Utilization
(Graduate School of Energy Science) Shiro Saka, Haruo Kawamoto

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. Effi cient 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 clarifi ed fi rst 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.


(5) Framework Design for Biomass Utilization

1) 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

This study aims to investigate the possible biomass-utilization system in a region, and to design the framework for realizing the desirable system in future. Concretely speaking, the microscopic information about energy and biomass utilization in a region is investigated by taking Kyoto City as a study area. And the information about biomass utilization technology is also surveyed with the collaboration of the research groups of GCOE project. The biomass utilization model is developed based on the information obtained through the investigation. The important characteristics about the modeling is to include the microscopic and macroscopic viewpoints about the energy and biomass utilization.ina region The robust framework design procedure will be applied to the framework design for biomass utilization system in Kyoto City. In 2008, the concept of modelbased analysis was developed for renewable energy use, and the basic survey of biomass use in Kyoto City was started.