• Critical temperature : -82.7 °C

• Critical pressure : 45.96 bar

43.1.4. Gaseous phase

• Gas density (1.013 bar at boiling point) : 1.819 kg/m3

• Gas density (1.013 bar and 15 °C (59 °F)) : 0.68 kg/m3

• Compressibility Factor (Z) (1.013 bar and 15 °C (59 °F)) : 0.998

• Specific gravity (air = 1) (1.013 bar and 21 °C (70 °F)) : 0.55

• Specific volume (1.013 bar and 21 °C (70 °F)) : 1.48 m3/kg

• Heat capacity at constant pressure (Cp) (1 bar and 25 °C (77 °F)) : 0.035 kJ/(mol. K)

• Heat capacity at constant volume (Cv) (1 bar and 25 °C (77 °F)) : 0.027 kJ/(mol. K)

• Ratio of specific heats (Gamma:Cp/Cv) (1 bar and 25 °C (77 °F)) : 1.305454

• Viscosity (1.013 bar and 0 °C (32 °F)) : 0.0001027 Poise

• Thermal conductivity (1.013 bar and 0 °C (32 °F)) : 32.81 mW/(m. K)

4.3.2. Miscellaneous

• Solubility in water (1.013 bar and 2 °C (35.6 °F)) : 0.054 vol/vol

• Autoignition temperature : 595 °C

Polyurethanes are made of diisocyanate and polyol precursors, which have been used for the highly diversified applications. Traditionally, they were made from petroleum-based synthetic polyols and nowadays soy-based polyols are also widely used as the renewable feedstock. Nakamura and his co-researchers [189] investigated the lignin-based polyurethane (PU) films using polyethylene glycol (PEG) and diphenylmethane diisocyanate (MDI). They reported the thermal behavior of new polyurethane system, which indicates that the addition of lignin to PEG enhances their Tg proportionally. The combination of lignin and PEG for the formation of polyurethane resulted in various types of microstructure such as soft and flexible and hard. Their mechanical properties were highly dependent on their distribution as well as cross­linking ability between lignin-PEG-MDI segments [190]. Sarkar et al. [191] reported the synthesis of lignin-hydroxyl terminated polybutadiene (HTPB) co-polyurethanes using toluene diisocyanate as initiator. Their characterizations showed the better properties up to 3% lignin incorporation and further increment of lignin caused the reduction in their properties [191]. Saraf et al. [192—194] made an extensive research on various aspects of lignin-based polyurethane and suggested their suitable formulations for the enhanced performance. In addition to that, various types of lignin also investigated for the fabrication of polyurethane systems [195—196]. Thring et al. [195] reported the fabrication of polyurethanes from Alcell®.

They found that the increasing lignin content decreases the degree of swelling and cross-

linking and causes the formation of brittle and hard structures. Yoshida et al. [196] utilized the kraft lignin for the fabrication of polyurethanes. They reported that the increasing lignin content increases the cross-link density and generally causes a hard and brittle nature. They also fabricated the polyurethane from various kraft lignins with different molecular weight and found that the cross-link density has increased with increasing molecular weight [197]. These studies conclude that the higher loadings of lignin in polyurethane caused the formation of rigid structure due to higher cross-link density and resulted in poor mechanical properties. This can be overcome by employing suitable chemistry in controlling the order of cross­linking.

3.2.2. Lignin in adhesives

Phenolic structure of lignin offers possible substitution with phenol-formaldehyde (PF) resin, which exhibits a wide range of applications as adhesives. Lignin substitute in phenol-formal­dehyde (PF) formulation can vary from 30 to 50%, which exhibits similar or better performance compared to virgin PF resin. Haars et al. [198] reported the fabrication of room-temperature curing adhesives using lignin and phenoloxidases as precursor chemicals. They reported the possible use of this new bioadhesive as thermosetting glue. They also indentified the increment of water resistance during the usage in particleboard production. Mansouri et al. [199] demonstrated the fabrication of lignin adhesives without formaldehyde for wood panel. Their synthesized lignin adhesives showed better internal bond strength, which also passed required international standard specifications. They found that the newly bioadhesive from lignin exhibits many properties comparable to formaldehyde-based commercial adhesives. Schneid­er et al. [200] patented the new technology for the fabrication of new kind of adhesives using furfuryl alcohol and lignin employing zinc chloride-based catalyst. Lignin isolated from bagasse was also experimented for the fabrication of biobased cost effective adhesives [201—202]. The obtained adhesives were used for the purpose of particleboard and wood adhesives.

1.1. The global biofuel industry status

The biofuel industry has been growing rapidly during recent years and continues to expand for the next decade. Such expansion is basically driven by renewable energy goals and different policy supports as for example use mandates, tax relief, fuel quality specifications and investment capacities in leading producing countries [18]. Based on the projection reported by

the OECD (organization for economic co-operation and development) — FAO (food and agriculture organization of the united nations) Agricultural Outlook for the 2011-2020 period, the global bioethanol industry will be growing almost 68% from an average of 92 billion liter in the 2008-2010 period to 155 billion liter in 2020 (Figure 2) [19]. In this regard, coarse grains and sugarcane are going to remain the major precursors in bioethanol production and in 2020 they are expected to account for 78% of bioethanol feedstock (Figure 3) although this value was 81% on average during the 2008-2010 period [20]. The large scale production of cellulosic ethanol is still not achieved and under research and development. Therefore, it is expected to expand in the latter projected years reaching up to more than 4 billion liter in 2020. This is far less than the respective value for the first generation ethanol. The rest feedstocks include wheat (3.9%), molasse (3.2%), non-agricultural feedstock (2.6%), sugar beet (2%) and other (5.8%) [20].

Similar trend has been presented for biodiesel as illustrated in Figure 2 [21]. The growth in this industry in 2020 is projected to be almost 138% compared to 2008-2010 period on average; an increase from 17.6 to 41.9 billion liter. Vegetable oils will contribute more than 78% as the main feedstocks for biodiesel production. The application of non-food oils such as jatropha in biodiesel production still remains very less as compared with the contribution of vegetable oils such as soybean and palm oil. Feedstocks other than edible oils in biodiesel production include non-agriculture feeds (12.3%), biomass-based (6%) and jatropha oil (3.2%) (Figure 3)

[22]. The huge impact of such expansion in biofuel industry on the respective coproducts is incontestable. Based on the feedstock share in the biofuel production by 2020, the major coproducts of different sectors of the biofuel industry can be listed as dried distillers’ grains with solubles (DDGS) from dry mill corn ethanol, corn gluten meal and corn gluten feed from wet mill corn ethanol, bagasse from sugarcane ethanol, lignin from second generation lignocellulosic ethanol, and soy meal and crude glycerol from biodiesel. More focus on these coproducts will be dedicated in the following sections.

(b) Biodiesel

Beverage sample solution (1~5 mL) was steam distillated to obtain alcoholic eluate (> 50 mL), and then oxidized with acidified dichromate. The excessive potassium dichromate was then titrated with ferric oxide. The ethanol content in beverage sample could be obtained by calculating the volume difference of potassium dichromate consumption between sample solution and control solution (Anonymous. 1992; Collins et al., 1997).

3.2.4.2. Distillation-hydrometric method

Alcoholic volatile compounds in beverage samples were separated by distillation, and the gravity of the distillate was measured by hydrometer. The ethanol content was then convert­ed (Anonymous. 1992; Collins et al., 1997).

Polyolefins such as polypropylene (PP) and polyethylene (PE) were the first polymers compounded with DDGS up to 30 wt% [118]. The mentioned work included a comparison of four types of biofiller such as big blue stem (BBS) grass, soybean hull, pinewood and DDGS in terms of the mechanical performance of the their biocomposites with PP and PE. The composite processing was performed in a twin screw extruder and mechanical properties tests were conducted. Generally, the studied biofillers increased the flexural and tensile moduli. However, DDGS increased the modulus not significantly in comparison with neat PE and PP. Moreover, the tensile and flexural strengths decreased drastically as a result of compounding with DDGS. In general, the authors of [118] came to a conclusion that DDGS is not a suitable biofiller because of the decreased mechanical properties of the studied DDGS/polyolefin composites. In another work, the composite of high density PE with DDGS has been produced via extrusion and injection molding technique with DDGS content of 25 wt% [119]. The effect of maleated polyethylene (MAPE) as the compatibilizer was studied. Moreover, DDGS was solvent-treated to remove its oil and polar extractables. It has been reported that the application of the MAPP with solvent-treated DDGS resulted in better tensile and flexural properties of the composite compared to the respective properties of the neat HDPE.

It is important that when you are purchasing fuel you make sure it is high quality by meet­ing all ASTM specifications. Fuel that is off specification on just one of the ASTM standards can not only cause serious engine problems, but it can void engine warranties if it is deter­mined that the fuel caused damage. This can cause unnecessary costly repairs for vehicles/ equipment. To review specifications for diesel fuel, biodiesel and biodiesel blends, see the specifications in the Appendix. In an effort ensure that producers and marketers operate in a manner consistent with proper specifications, the National Biodiesel Accreditation Commis­sion created the BQ-9000 program in 2005. This voluntary program establishes quality sys­tems for producers and marketers of biodiesel in the areas of storage, sampling, testing, blending, shipping, distribution and fuel management practices. If purchasing B100 or a bio­diesel blend, ask if the biodiesel is from a BQ-9000 biodiesel producer/marketer. If you are unable to get fuel from a BQ-9000 producer/marketer, the next best thing is to verify with your supplier that the fuel meets all ASTM specifications.

In most cases the blending process takes place right at the terminal rack by a process called in-line blending. This is the preferred method because it ensures complete blending. In-line blending occurs when warm biodiesel is added to a stream of diesel fuel as it travels through a pipe or hose in such a way that the biodiesel and diesel fuel become thoroughly mixed by the turbulent movement. This product is sold directly to customers, petroleum jobbers or a distribution company for sale to customers.

The blend level (percentage of biodiesel in the biodieseldiesel mixture) determines many im­portant characteristics of the blended fuel. A higher-than-specified level of biodiesel may ex­ceed the engine manufacturer’s recommended limitation, compromising the engine performance. A lower blend level of biodiesel may reduce the expected benefits, such asfuel lubricity and tail pipe emission. In addition, cloud point and pour point of biodiesel are usu­ally higher than that of diesel fuel, and a higher blend level makes the fuel unsuitable or dif­ficult to use in cold weather conditions. Engine injection timing can be adjusted based on the blend level in order to improve the engine emission and performance (Tat and Van Gerpen, 2003).

It has been reported that the actual biodiesel content of blended biodiesel fuel sold at gas stations can be significantly different from the nominal blend level. A 2% nominal blend has been found to actually contain anywhere from 0% to 8% biodiesel (Ritz and Croudace, 2005). There are several reasons why the actual blend level may differ from the specified level. For instance, if biodiesel is blended at a temperature less than 10°F above its cloud point, it will not mix well with diesel, causing a rich mixture in one portion of the tank and a lean mix­ture in another portion (NBB, 2005). Other reasons for the discrepancy may include profit — driven fraud and involuntary mixing of diesel into the blend to lower the overall blend level of biodiesel. Biodiesel is usually sold at a higher price than diesel fuel; therefore, the price of the fuel is dependent on the blend level. Knothe (2001) has shown that near-infrared (NIR) spectroscopy and nuclear magnetic resonance (NMR) can be used to detect biodiesel blend levels. However, the NMR method depends on the biodiesel fatty acid profile; hence, knowledge of the biodiesel feedstock is required before this method can be used. In addi­tion, using NMR only to detect blend level may not be cost effective. For NIR spectroscopy, Knothe suggested using wavelengths around 1665 nm or 2083 to 2174_nm. Since aromatic compounds produce strong and sharp infrared bands due to their relatively rigid molecular structure and diesel fuels have varying amounts of aromatics between 20% and 35% (Song et al., 2000), the absorbance of a blend may not directly correlate to the percentage of biodie­sel. The absorbance is defined as the logarithm of the radiation intensities ratio, that is, be­fore and after being absorbed by a sample.

Diesel fuel is distilled from crude petroleum, which is composed primarily of hydrocarbons of the paraffinic, naphthenic, and aromatic classes. Each class contains a very broad range of molecular weights. One of the features of diesel fuel is the presence of 20% to 35% aromatic compounds by weight. Aromatics are a class of hydrocarbons that are characterized by a stable chemical ring structure. They are determined primarily by the composition of the crude oil feed, which is usually selected based on considerations of availability and cost (Chevron, 2006). On the other hand, biodiesel is a mixture of fatty acid esters. Fatty acids with 16 to 22 carbon chain lengths are predominant in oils and fats. The resulting mixture of fatty acid esters depends on the kind of feedstock used. Neat biodiesel contains essentially no aromatic compounds.

The presence of aromatics in diesel and their absence in biodiesel creates the possibility of distinguishing these two fuels using ultraviolet spectroscopy. Benzene, the simplest aromat­ic compound, has maximum absorption at 278 nm (Zawadzki et al., 2007). Biodiesel, which is esters of long-chain fatty acids when adequately diluted in и-heptane, has negligible ab­sorbance compared to the aromatics at the same frequency. Hence, differences in biodiesel feedstocks will have a minimal impact on absorbance at this wavelength. The ultraviolet (UV) range between 200 and 380 nm is also referred to as near-UV. In general, light sources, filters, and detectors are less expensive for this vicinity of the spectrum than for IR at 8621 nm, as used by the CETANE 2000. Hence, near-UV spectroscopy may present a low-cost al­ternative method for biodiesel blend level sensing (Figure 12 and 13).

Recently, carbonaceous nanomaterials that include carbon nanotubes, carbon nanofibres, graphene/graphite nanosheets and also particulate carbon nanostructures have received an extensive importance due to their possible commercial values in diversified areas like poly­meric composites, sensors, energy storage/ conversion, catalysis, filters and biology [203—208]. Traditionally, carbonaceous materials were prepared from petroleum-based precursors (liquid/gaseous hydrocarbons and carbon rich polymers such as polyacrylonitrile-PAN). As the global demand for carbon materials (nano/micro) grows continually and also the conven­tional sources are finite there is a need to investigate for the alternate carbon source. Thus, renewable resource-based biomaterials such as seed, oil, dried fibres as well as stem have been explored for the development of various carbon materials [209—212]. The challenge in using plant-based materials as carbon feedstock is to control the carbonizing process as well as the usage of suitable catalysis in order to achieve nanostructured materials. In addition to the larger availability of biobased feedstocks for the carbonaceous materials, it also provides eco­friendliness with the reduced carbon footprint. The biofeedstock exhibits a diversified morphology with the various combination of chemical structures, which can result in the formation of varieties of carbon nanostructures. Lignin has been widely used for the fabrication of activated carbon, however synthesizing carbon nanostructures such as particles/fibres are very new, thus next section summaries the effective uses of lignin as precursor for the fabrication of carbon nanostructures and their emerging applications [213—214].

1.1.1. Corn bioethanol

Starch-based ethanol can be obtained from corn, wheat, barley, sorghum or any other starchy grain by fermentation. However, due to highly fermentable starch content, corn is the main feedstock for ethanol production by fermentation and accounts for 98% of all starch-based ethanol feedstocks [1]. Bioethanol from corn is produced in both dry mill and wet mill plants each of which producing specific coproducts as described below.

Methane fermentation is a versatile biotechnology capable of converting almost all types of polymeric materials to methane and carbon dioxide under anaerobic conditions. This is ach­ieved as a result of the consecutive biochemical breakdown of polymers to methane and car­bon dioxide in an environment in which varieties of microorganisms which include fermentative microbes (acidogens); hydrogen-producing, acetate-forming microbes (aceto — gens); and methane-producing microbes (methanogens) harmoniously grow and produce reduced end-products (Fig. 10—11). Anaerobes play important roles in establishing a stable environment at various stages of methane fermentation.

Methane fermentation offers an effective means of pollution reduction, superior to that ach­ieved via conventional aerobic processes. Although practiced for decades, interest in anaero­bic fermentation has only recently focused on its use in the economic recovery of fuel gas from industrial and agricultural surpluses.

The biochemistry and microbiology of the anaerobic breakdown of polymeric materials to methane and the roles of the various microorganisms involved are discussed here. Recent progress in the molecular biology of methanogens is reviewed, new digesters are described and improvements in the operation of various types of bioreactors are also discussed.

Methane fermentation is the consequence of a series of metabolic interactions among vari­ous groups of microorganisms. A description of microorganisms involved in methane fer­mentation, based on an analysis of bacteria isolated from sewage sludge digesters and from the rumen of some animals,. The first group of microorganisms secretes enzymes which hy­drolyze polymeric materials to monomers such as glucose and amino acids, which are sub­sequently converted to higher volatile fatty acids, H2 and acetic acid (Fig. 10). In the second stage, hydrogen-producing acetogenic bacteria convert the higher volatile fatty acids e. g., propionic and butyric acids, produced, to H2, CO2 and acetic acid. Finally, the third group, methanogenic bacteria convert H2 CO2 and acetate, to CH4 and CO2 (Nagai et al., 1986).

4% 24% ^ ► H2 ^ 28% COMPLEX 76% r HIGHER ORGANIC % 1 CH4 ORGANICS ACIDS TP f ACETIC 20% ACID TZvo METHANO- HYDROLYSIS ACETQGENESIS GENESIS AND AND ACIDOGENESIS DEHYDROGENATION STAGE 1 STAGE 2 STAGE3 Figure 10. The main steps for production of methane gas
Methane fermentation plant
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This is another attempt of biomaterial application of DDGS. The overall idea of such work was to utilize a tough binder between rigid particles of DDGS to create an acceptable flexible material. Thus, polyurethane prepolymer (PUP) from castor oil was used as a binder with different compositions of DDGS and the biocomposites were prepared in a two-step process;

PUP and DDGS were premixed in a micro-extruder and then compression molded to the shape of sheet. The mechanical and dynamic mechanical properties characterizations showed that the produced PUP/DDGS sheet was more flexible compared to the brittle DDGS material, thus polyurethane enhanced the properties of DDGS [120].

3.11.3. DDGS-phenolic resin biocomposites

Tatara et al. [121—122] bonded DDGS particles, from 0 to 90 wt%, with phenolic resin via compression molding process. Mechanical properties of the blends showed a reduction in modulus, tensile strength and elongation at yield by increasing the DDGS amount. However, the researchers believed that the cost saving resulted from the addition of low-cost DDGS filler in a reasonable quantity may offset the reduction in property performance; i. e. a cost-per­formance balance is achieved. In this context, inclusion of 25 and 50 wt% of DDGS maintained the mechanical strength to an acceptable value. In another work, the effect of DDGS particle size and content (25 and 50%) was studied when phenolic resin-based glue and wood glue were used to produce DDGS composites [123]. Overall, the DDGS composite with resin glue showed better mechanical properties and curing uniformity compared to wood glue/DDGS composites. Also, DDGS enhanced the flexural properties such as modulus and maximum stress. Also, composites of DDGS with smaller particle size (0.7 mm) had higher mechanical properties compared to those with higher particle size (0.34 mm).