Mohammad J. Taherzadeh and Keikhosro Karimi

3.1 Introduction

Ethanol (C2H5OH) is a clear, colorless, flammable chemical. It has been produced and used as an alcoholic beverage for several thousand years. Ethanol also has several industrial applications (e. g., in detergents, toi­letries, coatings, and pharmaceuticals) and has been used as trans­portation fuel for more than a century. Nicholas Otto used ethanol in the internal combustion engine invented in 1897 [1]. However, ethanol did not have a major impact in the fuel market until the 1970s, when two oil crises occurred in 1973 and 1979. Since the 1980s, ethanol has been a major actor in the fuel market as an alternative fuel as well as an oxy­genated compound for gasoline. Ethanol can be produced synthetically from oil and natural gas, or biologically from sugar, starch, and ligno — cellulosic materials. The biologically produced ethanol is sometimes called fermentative ethanol or bioethanol. Application of bioethanol as fuel has no or very limited net emission of CO2 [2] and is able to fulfill the Kyoto Climate Change Protocol (1997) to decrease the net emission of CO2 [3]. In this chapter, the global market and the production of bioethanol are briefly reviewed.

In order to allow blending of alcohol with gasoline, the water content of ethanol must be reduced to less than 1% by volume, which is not pos­sible by distillation. Higher water levels can result in phase separation of an alcohol-water mixture from the gasoline phase, which may cause engine malfunction. Removal of water beyond the last 5% is called dehy­dration or drying of ethanol. Azeotropic distillation was previously employed to produce higher-purity ethanol by adding a third component, such as benzene, cyclohexane, or ether, to break the azeotrope and pro­duce dry ethanol [82]. To avoid illegal transfer of ethanol from the indus­trial market into the potable alcohol market, where it is highly regulated and taxed, dry alcohol usually requires the addition of denaturing agents that render it toxic for human consumption; the azeotropic reagents conveniently meet this requirement [82]. Except in the high-purity reagent-grade ethanol market, azeotropic drying has been supplanted by molecular sieve drying technology.

My sincere thanks to the following people and organizations for their generosity in letting me use their photos: Dr. Kazuo Yamasaki (Teikyo Heisei University, Japan), Abdulrahman Alsirhan (www. alsirhan. com), Eric Winder (Biological Sciences, Michigan Technological University), Jack Bacheler (Department of Entomology, North Carolina State University), Dr. Alvin R. Diamond (Department of Biological and Environmental Sciences, Troy University), Piet Van Wyk and EcoPort, Food and Agricultural Organization of the United Nations, Antoine van den Bos (Botanypictures), Forest and Kim Starr (USGS), Dr. Davison Shillingford (Dominica Academy of Arts and Sciences), Prof. Arne Anderberg (Swedish Museum of Natural History), Rolv Hjelmstad (Urtekilden), Peter Chen (College of DuPage), Josina Kimottho (ICRAF), Gernot Katzer (University of Graz), Prof. Gerald D. Carr (University of Hawaii, Botany Department), Barbara Simonsohn, Dr. Mike Kuhns (Utah State University), and Eugenio Arantes de Melo (Arvores do Brasil).

Methanol is more toxic as compared to petrol, which creates difficulty in its handling. The toxicity of methanol is reduced by adding chemical emetics.

The heterocyst, regularly spread among more numerous vegetative cells (ratio 1:15), receives carbon compounds fixed by the neighboring vege­tative cells in exchange of the nitrogenous compounds fixed by them. Nitrogenase, like hydrogenase, needs an anaerobic environment to func­tion and can produce hydrogen only under certain conditions (absence of molecular nitrogen). The ratio of evolution of hydrogen and oxygen roughly corresponds to the ratio of the heterocysts and vegetative cells and also with the ratio of nitrogen and carbon for nutritive requirements.

If the algal culture is exposed to argon for about 24 hours, due to nitro­gen starvation, differentiation of the heterocysts increases from 6% up to 20%. In addition, a yellowish color appears due to the loss of the light­trapping pigment phytocyanin, resulting in less carbon dioxide fixation, i. e., oxygen evolution and an increase in light conversion efficiency by almost 0.5%. Induction of reversible hydrogenase in the heterocysts, as its theoretically higher turnover principle, is less affected by N2 and O2, and independent of ATP, it becomes more desirable and needs heterocysts to be genetically improved.

Native (indigenous) cellulose fractions of cellulosic materials are recal­citrant to enzymatic breakdown, so a pretreatment step is required to render them amenable to enzymatic hydrolysis to glucose. A number of pretreatment processes have been developed in laboratories, including:

■ Physical pretreatment—mechanical comminution, irradiation, and

pyrolysis

■ Physicochemical pretreatment—steam explosion or autohydrolysis, ammonia fiber explosion (AFEX), SO2 explosion, and CO2 explosion

■ Chemical pretreatment—ozonolysis, dilute-acid hydrolysis, alkaline hydrolysis, organosolvent process, and oxidative delignification

■ Biological pretreatment

However, not all of these methods may be technically or economically feasible for large-scale processes. In some cases, a method is used to increase the efficiency of another method. For instance, milling could be applied to achieve better steam explosion by reducing the chip size. Furthermore, it should be noticed that the selection of pretreatment method should be compatible with the selection of hydrolysis. For exam­ple, if acid hydrolysis is to be applied, a pretreatment with alkali may not be beneficial [18]. Pretreatment methods have been reviewed by Wyman [2] and Sun and Cheng [12].

Among the different types of pretreatment methods, dilute-acid, SO2, and steam explosion methods have been successfully developed for pre­treatment of lignocellulosic materials. The methods show promising results for industrial application. Dilute-sulfuric acid hydrolysis is a favorable method for either pretreatment before enzymatic hydrolysis or conversion of lignocellulose to sugars.

Crop description. Pongamiapinnata (L.) Pierre, P. glabra Vent., Cytisus pinnatus L., Derris indica (Lam.) Bennett, and Galedupa indica Lam.— commonly known as karanja, pongam, coqueluche, Vesi Ne Wai, vesivesi, hongay, and honge—belong to the Leguminaceae family and are widely distributed in tropical Asia (see Fig. 4.7). The tree is drought-resistant, tolerant to salinity, and is commonly found in East Indies, Philippines, and India. The karanja tree grows to a height of about 1 m and bears pods that contain one or two kernels. The kernel oil content varies from 27% to 39% and contains toxic flavonoids, including 1.25% karanjin and 0.85% pongamol [86-88]. The fatty acid composition consists of oleic acid (44.5-71.3%), linoleic acid (10.8-18.3%), palmitic acid (3.7-7.9%), stearic acid (2.4-8.9%), and lignoceric acid (1.1-3.5%) [86, 89].

Main uses. The oil is used mainly in agriculture, pharmacy (particularly in the treatment of skin diseases), and the manufacture of soaps. It has insecticidal, antiseptic, antiparasitic, and cleansing properties, like neem oil [86-88]. The cake after oil extraction may be used as manure.

Figure 4.7 Pongamiapinnata (L.) Pierre. (Photo courtesy of the Food and Agricultural Organization of the United Nations[www. fao. org].)

All parts of the plant have also been analyzed for its reported medical importance. Several scientists have investigated and guaranteed karanja oil as a potential source of biodiesel [78]. Most researchers have conducted the transesterification of P. pinnata oil by using methanol and potassium hydroxide catalysts [90-92]. Meher et al. [90] found that using a methanol-oil molar ratio of 12:1 produced maximum yield of biodiesel (97%), while Vivek and Gupta [91] stated the optimum ratio was 8-10:1. In both cases, the optimal temperature was around 65°C, with a reaction time of 180 min [90] and 30-40 min [91]. Vivek and Gupta used 1.5% w/w of catalyst (KOH), while Meher et al. used 2% w/w solid basic Li/CaO catalyst [93]. Due to the high FFA (free fatty acid) content, some researchers have proposed esterification with H2SO4 prior to trans­esterification with NaOH [94, 95]. In all cases, karanja oil has shown a feasibility to be used as a raw material to produce biodiesel, saving large quantities of edible vegetable oils. Diesel engine performance tests were carried out with karanja methyl ester (KME) and its blend with diesel fuel from 20% to 80% by volume [92]. Results have revealed a reduction in exhaust emissions together with an increase in torque, brake power, thermal efficiency, and reduction in brake-specific fuel consumption, while using the blends of karanja-esterified oil (20-40%), compared to straight diesel fuel.

Goering et al. [24] have suggested that vegetable oils are too viscous for prolonged use in direct-injected diesel engines, which has led to poor fuel atomization and inefficient mixing with air, contributing to incomplete combustion. These chemical and physical properties caused vegetable oils to accumulate and remain as charred deposits when they contacted engine cylinder walls. The problem of charring and deposits of oils on the injector and cylinder wall can be overcome by better esterification of the oil to reduce the viscosity and remove glycerol.

Acid-catalyzed alcoholysis of triglycerides (TG) can be used to produce alkyl esters for a variety of traditional applications and for potentially large markets in the biodiesel fuel industry [26]. It can overcome some of the shortcomings of traditional base catalysis for producing alkyl esters. A significant disadvantage of base catalysts is their inability to esterify free fatty acids (FFA). These FFA are present at about 0.3 wt% in refined soybean oil and at significantly higher concentrations in waste greases, due to hydrolysis of the oil with water to produce FFA. The FFA react with soluble bases to form soaps through the saponification reaction mechanism. The soap forms emulsions and makes recovery of methyl esters (ME) difficult. Saponification consumes the base catalyst and reduces product yields. The use of alkaline catalysts requires that the oil reagent be dry and contain less than about 0.3 wt% FFA [27, 28].

Acid catalysts can handle large amounts of FFA and are commonly used to esterify FFA in fat or oil feedstock prior to base-catalyzed FFA alcoholysis to ME [29]. Though it solves FFA problems, it adds additional reaction and cleanup steps that increase batch times, catalyst cost, and waste generation.

Generally, acid-catalyzed methanolysis of TG is carried out at tem­peratures at or below that of methanol reflux (65°C). Using sulfuric acid catalysis under reflux conditions, Harrington and D’Arcy-Evans [30] first explored the feasibility of in situ transesterification, using homog­enized whole sunflower seeds as a substrate. Using reflux conditions, a 560-fold molar excess of methanol and a 12-fold molar excess of sulfu­ric acid relative to the number of moles of triacylglycerol (TAG) were used. They observed ester production, with yields up to 20% greater than in the transesterification of preextracted oil, and suggested that this was an effect of the water content of the seeds, an increased extractability of some seed lipids under acidic conditions, and also the transesterifica­tion of seed-hull lipids.

Stern et al. [31] have developed a process to prepare ethyl esters for use as a diesel fuel substitute from various vegetable oils using hydrated ethyl alcohol and crude vegetable oil, with sulfuric acid as a catalyst. Ethyl ester of 98% purity with a very low acidity has been reported.

Schwab et al. [32] have compared acid and base catalysts and con­firmed that, although base catalysts performed well at lower tempera­tures, acid catalysis requires higher temperatures. Liu [33] has compared the influence of acid and base catalysts on yield and purity of the product, and suggested that an acid catalyst is more effective for alcoholysis if the vegetable oil contains more than 1% FFA.

Goff et al. [34] have conducted acid-catalyzed alcoholysis of soybean oil using sulfuric, hydrochloric, formic, acetic, and nitric acids, which were evaluated at 0.1 and 1 wt% loadings at temperatures of 100°C and 120°C in sealed ampoules, and observed sulfuric acid was effective. Kinetic studies at 100°C with 0.5 wt% sulfuric acid catalyst and 9 times methanol stoichiometry provided more than 99 wt% conversion of TG in 8 h, and with less than 0.8 wt% FFA concentration in less than 4 h (see Fig. 6.12).

Base catalysts are generally preferred to acid catalysts because they lead to faster reactions [35]. Base catalysts generally used in transes­terification reactions are NaOH, KOH, and their alkoxides. KOH is pre­ferred to other bases because the end reaction mixture can be neutralized with phosphoric acid, which produces potassium phosphate, a well-known fertilizer [36].

Darnoko et al. [37] explained transesterification of palm oil with methanol and KOH as a catalyst by the following three-step reaction sequence:

Knothe et al. [38] have reported optimal conditions of a 1 wt% KOH catalyst at 69°C and 7:1 alcohol—vegetable oil molar ratio gave 97.7% conversions in 18 min, when KOH was used with high-purity feedstocks.

Freedman et al. [39] have studied transesterification of sunflower oil and soybean oil with the reaction variables (a) molar ratio of alcohol to vegetable oil, (b) type of alcohol (methanol, ethanol, and t-butanol), (c) type of catalyst (acidic and alkali), and (d) reaction temperature (60°C, 45°C, and 32°C). They have suggested that esterification was 90-98% com­pleted at the respective molar ratio of methanol to sunflower oil 4:1 and 6:1. All three alcohols produced high yields of esters. Alkaline catalysts were
generally much more effective than acid catalysts. The reaction was performed successfully at both 45°C and 60°C in 4 h, with the production of 97% of ME.

Kruclen et al. [40] have presented a process for conversion of a high — melting point palm oil fraction into ethyl esters, which could be used as a diesel fuel substitute. The amount of catalyst used (KOH) was 0.1-1%, and the reaction was completed rapidly at 80°C with yields of 80-94%, depend­ing on the concentration of catalysts. The specific gravity of ethyl ester varied from 0.847 to 0.864 with kinematic viscosity of 4.4-4.6 cSt at 40°C.

Gelbard et al. [41] have determined the yield of transesterification of rapeseed oil with methanol and base by 1H-NMR (nuclear magnetic resonance) spectroscopy. The relevant signals chosen for integration are those of methoxy groups in ME at 3.7 ppm (parts per million) (sin­glet) and of the a-carbonyl methylene groups present in all fatty ester derivatives at 2.3 ppm. The latter appears as a triplet, so accurate meas­urements require good separation of this multiple at 2.1 ppm, which is related to allylic protons.

Chadha et al. [42] have studied base-catalyzed transesterification of monoglycerides from pongamia oil. They separated monoglyceride frac­tions (MG) by column chromatography and then characterized the frac­tions by 1H-NMR spectroscopy in deuterated chloroform (CDCl3) and tetramethylsilane (TMS) (see Fig. 6.13). They explain that 1- or 2-MG are positional isomers. Consequently, in 1-MG, the methylene protons at

C-1 and C-3 are magnetically nonequivalent, due to four double doublets, which are observed in the spectra. But 2-MG, on the other hand, are symmetrical, and C-1 and C-3 methylene protons are magnetically equiva­lent and appear as a multiplate.

In 1993, the influence of 3-30% rapeseed oil in vacuum distillate FCC feed on product slate and quality both at laboratory and at a continu­ously operated bench-scale apparatus was reported for the first time [41]. On the one hand, results showed decreasing yields of liquid hydro­carbons with increasing rapeseed oil concentrations. On the other hand,

the gasoline portion in the liquid product increased. Considering propenes, butanes, and i-butenes as gasoline potentials, low rapeseed oil portions in the FCC feed seem to result in an optimum yield of gaso­line plus gasoline potentials. Most interestingly, the gasoline fraction recovered from a 500-h bench scale run using a feed with 30% rapeseed oil proved suitable for standardized gasoline blending. Calcium con­centration c(Ca) > 2 ppm gradually decreases FCC catalyst activity. Oxygen contained in the vegetable oil was mainly converted to water. Moreover, traces of phenols and carboxylic acid were detected in the liquid reaction product.

MAT with animal fat. In a laboratory scale, mixtures of vacuum gas oil and up to 15% of animal fat were converted in a Micro-Activity Test (MAT) unit [37]. Results are given in Figs. 8.16 and 8.17. Two aspects are of special interest. First, yields of propene and butene increase with animal fat as a co-substrate. This is an advantageous finding as C-3 and C-4 are gasoline potentials. C-3 and C-4 liquefied petroleum gas can be used for the manufacture of isoparaffins for motor gasoline through alkylation and polymerization processes.

Second, a higher yield of gasoline fraction is observed. This is a con­sequence of the high hydrogen:carbon ratio of about 2 and the low het­eroatom content. For this reason, biomaterials with a hydrocarbon-like structure are particularly interesting candidates for conversion to low — molecular-weight fuels or chemical raw materials. Problems to be inves­tigated are possible calcium and phosphate deposits on the catalyst particles which may impair catalyst activity and process stability of the riser. Therefore, the process must include a regeneration step. The market will decide whether or not animal fat can substitute a bit of non­renewable resources in petroleum refining.

Animal fat (%) in VGO

Ahindra Nag and P. Manchikanti

2.1 Introduction

Renewable energy is an energy resource naturally regenerated over a short time scale derived from the sun (such as thermal, photochemical, and photoelectric) or from other natural environment effects (geothermal and tidal energy). It is forecasted that approximately half of the total resources in the world will be exhausted by 2025. This survey has also revealed that global warming and climate change are serious issues that need immediate action. The use of fossil fuels (coal, oil, gas, etc.) con­tributes significantly to global warming and climate change [1]. Worldwide there is strong support for renewable energy, as proven by a number of surveys [1, 2]. In 2003, a European Commission survey across the 15 European Union (EU) countries showed that 69% of the citizens supported more renewable energy-related research, compared to 13% for gas, 10% for nuclear fission, 6% for oil, and 5% for coal. Understandably, due to the inherent recycling nature as well as environmental benefits involved, renewable sources of energy are the solution for energy man­agement. There is an increased investment globally in such technologies for not only enhancing the preservation of biological resources but also for increasing energy efficiency and pollution control [1].

Biomass is one such renewable source of energy. Out of the 1.1 X 1020 kW heat generated every second by the sun, only 47% (~7 X 1017 kWh) reaches the earth’s surface. Solar energy is utilized by conversion to dif­ferent energy forms such as biomass, wind, or hydropower. Green plants are only able to effectively use visible light of wavelength falling between [7]

400 and 700 nm. This photosynthetically active radiation constitutes about 43% of the total incident solar radiation to produce biomass. Biomass energy generally involves the utilization of energy contents of such items as agricultural residues (pulp derived from sugarcane, corn fiber, rice straw and hulls, and paper trash) and energy crops. So, bio­mass is a comprehensive term that includes essential forms of matter derived from photosynthesis or ultimately available as animal waste [2]. The production of energy from plants is not a new idea; wood burning has been in common use since ancient times. About one-seventh of the energy used around the world is derived from firewood. Biomass sup­plies 14% of the world’s primary energy consumption and is considered to be one of the important renewable resources of the future. With the increase in population and the demand for resources, demand for bio­mass is expected to increase rapidly. On average, 38% of the primary energy resources in developing countries is biomass. In the United States alone, biomass sources provide about 3% of all the energy con­sumed. In terms of energy efficiency measures and stabilization of energy consumption between 2010 and 2020, the European Renewable Energy Council (EREC) survey estimates that among the various types of renewable energy resources, biomass-derived energy will be a sig­nificant portion of energy used [1]. The survey also reveales that biomass and biofuels are the top two in terms of employment that they gener­ate. Burning new biomass does not contribute to new CO2 into the atmosphere as replanting harvested biomass ensures that CO2 is absorbed and returned for a cycle of new growth [2].