The viscosity measurement and dynamic rheology were performed on Rheometer (ATS Rheosystems, Rheologica Instruments Inc, NJ) using cup and bob assembly. Approximately 15 mL of sample was filled in cup and shear rate was applied through the bob. The viscosity of bio-oils was tested in rheometer at 20°C with shear rate up to 1 to 200/s. The stress and viscosity was calculated for the shear rate applied using the software. In order to identify the linear viscoelastic region, stress sweep was performed at a constant frequency. For frequency
sweep (1 to 100 Hz), stress was selected from the linear region identified in the stress sweep test. Temperature sweep (20-100°C) was then performed by employing constant stress and frequency identified in the previous steps. The viscoelastic modulii (G’ — storage modulus and G" — loss modulus) were measured as a function of frequency for all the samples. A graph was plotted on logarithmic scales to identify the linear viscoelastic region.

Recently, in depth catalytic hydrotreatment experiments with the Ru/C catalyst in a continuous packed bed set-up were reported (Venderbosch et al., 2010). The results of this study will be provided in detail in the following as it provides detailed insights in the effect of process conditions on product yields, product properties and the various reactions taking place on a molecular level. Some experiments were carried out in the absence of catalysts to probe thermal reactions.

The catalytic hydrotreatment reactions were carried out in a set-up consisting of 4 packed bed reactors in series. The temperature in each reactor may be varied independently, allowing experiments at different temperature profiles over the length of the reactor. Typical pressures were between 150 and 300 bar, temperatures between 150 and 400 °C and WHSV’s between 2-10 kg/kg. cat. h. In the following, the thermal reactions will be discussed, followed by catalytic hydrotreatment reactions at different temperature levels.

1.1.1.1 Thermal reactions

To study the thermal, non-catalytic reaction in detail, pyrolysis oil was pumped through the reactor (without catalyst) at pressures of up to 300 bar and temperatures of maximum 350 oC for residence times in the order of tenths of second — minutes. Typically under these conditions, a single-phase pyrolysis oil is converted into a viscous organic liquid, an aqueous phase and a gas phase. The carbon content of the viscous phase is about 60 wt.% (starting with 40 wt.% in the original oil), and the oxygen content about 32 wt.%. Additional water is produced, up to 30 % compared to the water initially present in the pyrolysis oil. The water is distributed over the two layers, but most of it ends up in the aqueous phase. Energetically, 80% of the thermal energy in the pyrolysis oil is transferred to the viscous product, less than 20% and 1 % is retained by the water phase and gas phase, respectively. The gas phase in such experiments consists of CO and CO2 in a ratios varying from 1:10 to
1:3 (depending on temperature, pressure, residence time), and in yields of almost 4 wt.% of the pyrolysis feed.

Although it is unknown at a molecular level which reactions actually take place, at least two parallel pathways can be distinguished, viz. a reaction causing the formation of gas (here referred to as decarboxylation / decarbonylation, yielding CO and/or CO2), and the other causing dehydration (likely by condensation (polymerisation) reactions). Possible sources of these gases are the organic acids in the oil. For all aqueous (and organic) samples produced the pH, however, is almost similar to the pyrolysis oil feed. This indicates that either the acids are not converted or the acids are converted and simultaneously produced as well. A detailed acid analysis of the products is not available, and the precise events taking place and mechanism however remain unclear. It seems that dilution of the pyrolysis oils with ‘inert’ solvents suppresses the re-polymerisation. Additionally, the gas yield becomes independent of the temperature and the residence time after a certain threshold in the residence time, while the amount of water produced is increasing. This indicates that the reaction mechanism for the formation of gas is different than the polymerisation reactions. Phase separation of the oil at these conditions may have a number of causes, e. g. an overall increase in the water content due to the formation of water by condensation reactions. It is known (but not fully explained yet) that above a certain water content pyrolysis oils phase separate into an aqueous phase and a rather nonpolar phase. Repolymerisation of some molecules / fractions in the oil is also a plausible reason, as it renders the products less soluble in water, for example caused by transformation of the polar sugar constituents behaving as bridging agents in the dissolution of hydrophilic lignin material (Diebold 2002).

Densification or compaction of agricultural biomass grinds into pellets is an essential process towards production of biofuels. Ground biomass particles behave differently under different applied pressures (Adapa et al., 2002 and 2009a). Therefore, it is important to investigate the change in compact density and volume with pressures. One of the main purposes of fitting experimental data to an equation is usually to develop linear plots in order to make comparisons easier between different sets of data (Comoglu, 2007). A majority of compression models applied to biomass materials have been discussed and reviewed in detail by Adapa et al. (2002 and 2009a), Denny (2002) and Mani et al. (2003). Adapa et al. (2009a) reported that Kawakita and Ludde (1971), Cooper and Eaton (1962) and Jones (1960) models provided the best compression and deformation characteristics of agricultural biomass.

1.4 Thermogram analysis

The TG and DTG curves for cellulose, lignin, EFB and PS at different heating rates are shown in Figures 1-4. The effect of different heating rate can be described by a lateral shift appeared at high heating rates. These lateral shifts are due to the thermal lag effect between surrounding and biomass particles (Yang et al., 2004; Luangkiattikhun et al., 2007). As a result, conversions are delayed at high heating rates. Thermal lag effect is due to the small heat conductive property of biomass particles (Zhang et al., 2006).

In the DTG curves (Fig. 1-4, b) for all samples, high decomposition rate was observed at 50 °С/min, which shows the increase of thermal decomposition rate of biomass at high heating rates.

The investigated EFB exhibited the decomposition rate corresponds to -41 wt%/min which is higher than -33 wt%/min of PS at 50 °С/min (see Fig. 5). The high decomposition rate for EFB and PS appeared at 342 and 382 °С, respectively. It is important to consider that 60 wt% of EFB and PS is decomposed at 400 and 429 °С for 50 °С/min. These results depict relatively easy and fast decomposition for EFB as compared to PS. This fast decomposition of EFB may be attributed to the comparatively high volatiles matter and low lignin content present in EFB as compared to PS. ^nyeme^, pure cellulose and lignin decomposition rate is the highest and lowest among all species which is -124 and -19 wt% / min at 50 °С/min, respectively. Furthermore, the highest decomposition rate for cellulose and lignin is observed at 386 and 418 °C.

(a)

The TG and DTG curves for EFB and PS are given in Figures 3-4. In these figures, the first peak represents the decomposition of hemicellulose. The second peak, which is sharper, gives the highest rate corresponds to the cellulose decomposition. The decomposition range of hemicellulose and cellulose of EFB is between 240-300 °C and 300-340 °C, respectively, at heating rate of 10 °C/min. Decomposition rate of hemicellulose in PS falls almost in the same temperature region as for EFB but higher decomposition range for cellulose (340-370 °C). It is important to consider that the cellulose decomposition rate in PS is in the same temperature region as pure cellulose (340-370 °C at 10 °C/min). The tail at high temperature shows lignin decomposition as found by Yang et al. (2004) and Luangkiattikhun et al. (2008). In the present study, at 10 °C/min, no lignin decomposition was observed for EFB and PS. Similar observation is reported by Yang et al. (2004) for heating rate of 10 °C/min at

temperature >340 °C. At higher heating rates, there is some small lignin decomposition observed for EFB and PS which is in the range of 450-530 °C and 680-750 °C, respectively. Different region for lignin decomposition in EFB and PS may be due to different lignin structure and composition in both species.

Among all species, lignin decomposition produced highest residual fraction of ~40% followed by ~27% of EFB and PS and <7% for cellulose, respectively. High residual fraction for lignin shows its high resistance to thermal decomposition which can be seen by its lowest decomposition rate.

In the pre-processing process, there are sub-processes of chipping, transportation, and drying of biomass materials. In particular, within the sub-processes of transportation and drying, we have to consider uncertainties. To date, there are few studies considering these uncertainties. CO2 emissions and energy intensities in the biomass LCA would be affected by the moisture content of biomass materials, and the transportation distance from the
cultivation site, or the site of accumulating waste materials, to the energy plant. Table 6 shows heating values, and that of CO2 emissions, for each fuel with biomass materials, respectively. Also, CO2 emissions and energy intensities were estimated using the Monte Carlo simulation in order to consider these uncertainties (Dowaki and Genchi, 2009).

The greenhouse gases (GHGs) are gases occurring in the Earth’s atmosphere that absorb in the infrared field (carbon dioxide, ozone, methane, nitrogen oxides, carbon monoxide and so on). This feature enables them to trap the heat of the sun reflected back from the Earth’s surface.

The GHG that occurs in the largest quantities is carbon dioxide, and that is why it attracts so much attention. In fact, the carbon cycle is a delicate balance between carbon accumulation, release and recycling that enables vegetable and animal species to survive. Problems linked to CO2 began to emerge at the start of the industrial era: the ever-increasing use of fossil fuels as a source of energy meant that the carbon dioxide trapped for centuries in the fossils was being put back into the atmosphere, with no correspondingly reinforced recycling mechanism, which relies on chlorophyllic photosynthesis).

In addition to reducing carbon dioxide emissions, bioethanol can be seen as a no-impact fuel because the amount of CO2 released into the atmosphere is compensated by the amount of CO2 converted into oxygen by the plants grown to produce the bioethanol (Ferrel & Glassner, 1997).

In the high-calorie gasification method, finely crushed biomass of 1-3 mm in diameter is subjected to the gasification reaction together with steam in an atmosphere of 800-1000°C within the reaction tube. At this time, the reaction tube is heated using high-temperature combustion gas that is separately combusted using additional biomass. The introduced biomass raw materials leave only ash, and all organic content is gasified, resulting in a clean, high-calorie gas (ca. 12MJ/Nm3) composed of H2, CO, CH, etc. The basic principle of the technology is illustrated in Fig. 10.

Fig. 10. Suspension/external heating type high-calorie gasification.

The gas composition varies with gasification reaction conditions such as reaction temperature, residence time (reaction time), and the [steam]/[biomass carbon] mode ratio, but an example is represented by the following reaction formula.

(Endothermic reaction)

C1.3H2O0.9 + 0.4 H2O ^ 0.8H2 + 0.7CO + 0.3CH4 + 0.3CO2 + 165.9kJ/mol (Biomass) (Steam) (Resulting gas fuel) (Absorbed heat)

In this process, the total biomass material reacts with steam and is converted to an [H2, CO, CH4, CO2] gas mixture. The application of external heat is required due to the fact that the gasification reaction is endothermic. However, the potential heat stored in the gas mixture generated in the reaction is greater than that contained in the raw biomass material, such that the cold gas efficiency surpasses 100%. In the formula shown above, a figure of ca. 115% is obtained by solving for cold gas efficiency (Ec). On the other hand, the externally supplied heat used in the reaction, is not considered in the calculation of Ec, and the total gasification efficiency is ca. 85% when this external heat is taken into account.

While the previous biomass gasification technology of "Norin Green No. 1" test plant mentioned above uses the partial oxidation technology, this high-calorie gasification technology enables the production of a high-calorie gas fuel that was not possible with the conventional method due to the formation of an exhaust gas. The principle is illustrated in Fig. 11.

oxidation technology.

The primary criterion for biodiesel quality is adherence to the appropriate standard. The technical specifications for biodiesel depend on the country or the region where the fuel was produced. Biodiesel has a number of standards for its quality including European standard EN 14214 (Table 2), ASTM D6751 (Table 3), and others.

The European standard for Fatty Acid Methyl Esters (FAME) used as automotive fuel was set in 2003 by the Comite Europeen de Normalisation (CEN) and is known under the standard number EN 14214. This standard sets limits and measurement methods for FAME, known as biodiesel that may be used either as a stand alone fuel or as a blending component in diesel fuel. The CEN standard for diesel fuel, EN 590, requires that all biodiesel blended in the fuel must conform to the standard EN 14214. At present, the European diesel fuel allows biodiesel to be blended at up to and including 5% by volume. Some national standards in EU countries allow biodiesel to be distributed as a stand-alone fuel, notably in Germany, for specially adapted vehicles. The CEN is presently studying a revised EN 590 specification for diesel fuel that will permit up to and including 7% of biodiesel blend. Simultaneously CEN is studying a revision of the biodiesel standard EN 14214 with a view to widening the range of feedstock oils that may be used, without compromising the security of vehicles using this product either in blends or as a stand-alone fuel. At the same time the European Commission has mandated CEN to revise the EN 590 specification for diesel fuel up to 10% of biodiesel blend.

The United States of America has chosen to use the specifications developed by ASTM International for both conventional diesel fuel and biodiesel. Specification efforts for biodiesel in the United States of America began in 1993 in Committee D02 on 24 Petroleum

Products and Lubricants. While the initial proposal for the biodiesel specifications at ASTM was for B100 (pure biodiesel) as a stand alone fuel, experience of the fuel in-use with blends above B20 (20% biodiesel with 80% conventional diesel) was insufficient to provide the technical data needed to secure approval from the ASTM members. Based on this, after 1994 biodiesel efforts within ASTM were focused on defining the properties for pure biodiesel which would provide a ‘fit for purpose’ fuel for use in existing diesel engines at the B20 level or lower. A provisional specification for B100 as a blend stock was approved by ASTM in 1999, and the first full specification was approved in 2001 and released for use in 2002 as "ASTM D6751 Standard Specification for Biodiesel Fuel Blend Stock (B100) for Middle Distillate Fuels".

The philosophy used to approve D6751 was the same as that used for the No. 1 and No. 2 grades of fuels within the conventional specification, ASTM D975: If the parent fuels meet their respective specifications then the two can be blended in any percentage and used in conventional diesel engines. No separate set of properties was needed for the finished blends of No. 1 and No. 2, if the parent fuels met their respective specifications. These same conditions hold true for biodiesel; if biodiesel meets D6751 and conventional diesel meets D975 the two can be blended and used in conventional engines with the restriction of the upper limit of 20% biodiesel content in the finished fuel.

While this mode of operation has served the US market well, there has been substantial effort since 2003 to develop and formally approve specifications for the finished blend of biodiesel and conventional diesel fuel. In addition, several improvements and changes to D6751 were also undertaken, some as a result of changes needed to secure approval of the finished blended biodiesel specifications. At the time of this report ballots to allow the formal acceptance of up to 5% biodiesel (B5) into the conventional diesel specifications for on/off road diesel fuel (ASTM D975) and fuel oil burning equipment (ASTM D396) and a new stand alone specification covering biodiesel blends between 6% and 20% have been approved through the Subcommittee level of Committee D02. In addition, a ballot to implement a new parameter in D6751 to control the potential for filter clogging above the cloud point in B20 blends and lower has also passed the subcommittee and is on track for a June 2008 vote. Efforts to approve B100 and B99 as stand alone fuels have been discussed at ASTM, but have been put on hold in order to focus on the B5 and B6 to B20 blended fuel specification efforts.

This section describes the parameters of the specifications normally used in the biodiesel standards:

Ethanol, by nature, has a lower energy density than other liquid fuels and is not entirely compatible with the current distribution infrastructure because it is hygroscopic and can contribute to rust formation. In the United States, ethanol produced in the Midwest also requires costly transportation to sites of consumption, primarily the East and West Coasts. In other parts of the world, particularly Brazil, where ethanol production may be more economically produced from sugar cane, there are still limitations including the high energy input for distillation from the dilute solutions produced biologically.

Biofuels made from food crops may impose stresses on the existing world economy. The most serious of these are the possible effect on food prices due to subsidized farming, substantial input of fossil fuels for production, degradation of agricultural land resources, and potential alterations in ecosystems from expanded land use. Even emissions of non-CO2 greenhouse gases may increase with first-generation biofuel production. The use of nitrogen fertilizer on biofuel crops also has the potential to increase the release of nitrous oxide, a greenhouse gas more potent than carbon dioxide, as well as the consumption of natural gas for fertilizer production. While first-generation ethanol has initiated the biofuel revolution, advanced biofuels are clearly needed.

To adopt self-heat recuperative processes, it is necessary to generate power in substitution for heat energy. According to the energy balance shown in Figs. 1 and 2, much residue with insufficient heat value for utilization due to its high moisture content is produced during bioethanol production. By integrating the self-heat recuperative drying process with power generation, this wet biomass can be utilized for energy. In this section, an integrated system for self-heat recuperative bioethanol production with biomass gasification is introduced.

2.1 Biomass gasification and its impact on the system

One of the easiest ways to generate power from biomass is direct combustion of biomass in a boiler, wherein thermal energy is produced and power is generated from this thermal energy by using a steam turbine (boiler and turbine generator). However, energy conversion efficiency under this procedure is not good enough. To increase the conversion efficiency of energy from biomass to power, biomass gasification reaction is used. Gasification reactions can be divided into two mechanisms; pyrolysis and gasification by chemical reaction (partial oxidation, etc.) Biomass gasification normally passes through both of these. After passing through a series of gasification procedures, the gases are fed into a gas turbine, and then the power is generated. Gasification reactions are normally endothermic reactions, and must be provided with heat during reactions. However, the overall energy conversion efficiency will be increased compared with the boiler and turbine generator. In addition, a further increase in energy conversion efficiency, through a biomass-based integrated gasification combined cycle (IGCC) technology has been investigated (Bridgwater 1995).

It is currently assumed that the energy conversion efficiency of biomass through power generation and biomass gasification is 25%. The energy amount of the wet residue is 50 in Figs. 1 and 2. It assumed that half of the energy amount of this wet residue can be utilized for drying the biomass. According to the analysis of self-heat recuperative drying above, 1/8 of the amount of energy for water evaporation is required for power to dry this wet residue using self-heat recuperative drying. This means that power (8) can be generated and a part of this power (3) is used for drying, leading to 4% of the initial wet biomass being converted to power as net energy (5) from the wet residue as shown in Fig. 7.