Crop description. Taraktogenos kurzii, Hydnocarpus wightiana, Oncoba echinata (West Africa), and Carpotroche brasiliensis (Brazil)—commonly known as chaulmoogra, chaulmugra, maroti, hydnocarpus, and gorli seed—belong to the family Flacourtiaceae and grow in India, Sri Lanka, Burma, Bangladesh, Nigeria, and Uganda (see Fig. 4.21). The trees

Figure 4.21 Chaulmoogra leaves. (Photo courtesy of Prof. Gerald D. Carr [www. botany. hawaii. edu/ faculty/carr/flacourti. htm].)

grow to a height of 12-15 m. The kernels make up 60-70% of the seed weight and contain 63% of pale-yellow oil. The oil is unusual in that it is not made up of straight-chain fatty acids but acids with a cyclic group at the end of the chain [77].

Main uses. Chaulmoogra oil has been used for thousands of years in the treatment of leprosy. However, it has now been replaced by modern drugs. The expeller cake is a useful manure and is reported to ward off ants and other insect pests. It cannot be used for animal feed due to its toxicity. The oil has been highly active against fungal plant pathogens including Aspergillus niger and Rhizopus nigricans. There may be a wide scope of integrating the pharmaceutical industries based on chaul — moogra, with the fuel and energy industries dealing with production of petroleum hydrocarbons, such as biodiesel [180].

Methanol behaves much like petroleum, so it can be stored and shifted in the same manner. It is a more flexible fuel than hydrocarbon fuels, per­mitting wider variation from the ideal A:F ratio. It has relatively good lean combustion characteristics compared to hydrocarbon fuels. Its wider inflammability limits and higher flame speeds have shown higher ther­mal efficiency and less exhaust emissions, compared with petrol engines.

Methanol can be used directly or mixed with gasoline. Tests have shown improvements in fuel economy by 5—13%, decreases in CO emis­sion by 14-70%, and reductions in exhaust temperature by 1-9%, with varying methanol in petrol from 5 to 30%. Depending on the gasoline — methanol mixture, some changes in fuel supply are essential. Simple modifications to the carburetor or fuel injection can allow methanol to replace petrol easily. Some important features of methanol as fuel are listed below:

1. The specific fuel consumption with methanol as fuel is 50% less than a petrol engine.

2. Exhaust CO and HC are decreased continuously with blends con­taining higher percentage of methanol. But exhaust aldehyde con­centration shows the opposite trend.

3. Like ethanol, methanol can also be used as a supplementary fuel in heavy vehicles powered by CI engines with consequent savings in diesel oil and reduced exhaust pollution. No undue wear of engine components are encountered with methanol as a fuel, while engine peak power improves and smoke density and NOx concentration in exhaust is reduced.

Phase separation, vapor lock, and low-temperature starting difficulties are the problems associated with the use of methanol or its blends as

IC engine fuels. Availability from indigenous sources, ease of handling, low emission, and high thermal efficiency obtainable with its use make methanol a logical alternative fuel for vehicular engines.

Water management is critical for fuel cell operation. Water is a product of the fuel cell reaction, and it must be removed from the exhaust gas for use in various operations such as fuel reformation and humidifying reactant gases (to avoid drying out the fuel cell membrane). For auto­motive applications, water condensed from the exhaust steam is recy­cled for reforming and reactant humidification in a closed cycle to avoid periodical recharging with water.

In the electron transfer chain, the conversion takes place at lower poten­tials, i. e., NAD/NAD+ to NADH/NADH+ between ±0.6 V, favorable at a pH higher than 7.0. But the process develops other energy-rich compounds, and thus, very little free energy in the form of heat is directly available.

1.7.1 Photosynthetic path

Cytosolic to mitochondrial compartments, the interconversions of pyru­vate to aspartate and to glutamate; malate to a-ketoglutarate; the energy produced is utilized to synthesize higher carbon compounds, ultimately to glucose or even polysaccharide and polynucleotide (genetic material) (see Fig. 1.5). Artificial culture of thylakoid or chloroplast, (only remains a possibility for academic purposes at present); cannot be commercially achieved as yet.

The most important achievement is the photolysis of water (see Fig. 1.6), i. e., production of proton to hydrogen, reduction of carbon dioxide, reduc­tion of nitrogenous material, and increase in nitrogenous and carbona­ceous biomass. Attempts have been made to utilize the energy-trapping process of the photosynthetic pigments of the plastoquinones at two stages: (1) Pigment II utilizes 680-700 nm, converts water to a more

Chloroplast

Heterocysts

H20— ►ATP, (NADPH), CO2

——— Carbohydrate

Biomass

Figure 1.5 Electron flow in biophotolysis.

hv o2

_______ _______________

Chloroplast ІУІУІУІУІУІУІУІУІУІУІУ/ІУ;

Figure 1.6 Separated photolytic chamber design.

energetic intermediate, and undergoes a change of +0.8 to —1.1 V. (2) Pigment I utilizes 700-730 nm, undergoing +0.5 to almost —1.4 V, production of hydrogen, oxidation of coenzyme, making electrons available.

Models can be created where direct tapping from the thylakoid mem­brane may be made possible. Electrochemical cells have been designed where living thylakoids are used and exposed to sunlight from which, through proper instrumentation, the energy can be tapped.

Enzymatic hydrolysis has several advantages compared to acid hydroly­sis. First, the specificity of enzymes allows the production of sugar syrups with well-defined physical and chemical properties. Second, milder enzymatic hydrolysis results in few side reactions and less “browning” [8]. Different types of enzymes involved in the enzymatic hydrolysis of starch are a-amylase, ^-amylase, glucoamylase, pullua — nases, and isoamylases. The mechanism of action of these enzymes is presented schematically in Fig. 3.4.

There are two popular industrial processes from starch materials, dry milling and wet milling. In the dry-milling process, grain is first ground into flour and then processed without separation of the starch from germ and fiber components. In this method, the mixture of starch and other components is processed. Starch is converted to sugar in two stages: liquefaction and saccharification, by adding water, enzymes, and heat (enzymatic hydrolysis). Dry-milling processes produce a coprod­uct, distillers’ dried grains with solubles (DDGS), which is used as an animal-feed supplement. Without the revenues from that coproduct, ethanol from dry-milled corn processing would not be economically favorable [2]. A dry-milling process for alcohol production processes the whole grain, or components derived from the whole grain. Sacchari­fication and fermentation of dry-milled corn result in ethanol and dis­tillers’ dried grains (DDG). When DDG are combined with fermentation liquids and dried, they result in DDGS as the major feed by-product [10].

In the wet-milling process, grain is steeped and separated into starch, germ, and fiber components. Wet milling is capital intensive, but it gen­erates numerous coproducts that help to improve the overall production economics [2]. Wet mills produce corn gluten feed, corn gluten meal, corn germ, and other related coproducts. In this method, after the grain is cleaned, it is steeped and then ground to remove the germ. Further grind­ing, washing, and filtering steps separate the fiber and gluten. The starch that remains after these separation steps is then broken down into fer­mentable sugars by the addition of enzymes in the liquefaction and sac­charification stages. The fermentable sugars produced are then subjected to fermentation for ethanol production, like the other fermentable sugars.

Crop description. Salvadora oleoides Decne, S. persica L., and S. indica— commonly known as bahapilu, chootapilu, jhal, jaal, pilu, kabbar, khakan, and mitijar—belong to the family Salvadoraceae and are found in arid regions of western India and Pakistan (see Figs. 4.1 and 4.2). The crop is typical of the tropical thorn forest. It is highly salt tolerant and grows in coastal regions and on inland saline soils [48, 49]. S. oleoides is a shrub or small tree up to 9 m in height. Seeds contain 40-50% of a greenish-yellow fat containing large amounts of lauric and myristic acids [50].

Main uses. The fruits are sweet and edible. The seed cake contains 12% protein and is suitable for livestock fodder. The wood is used for building purposes. It is also an important source of fuelwood. The fat in seeds can be used for making soap and candles. The leaves and fruits are used in medicine to relieve cough, rheumatism, and fever. The tree contributes to erosion control in fragile areas [50]. Some authors have carried out systematic studies on the lubrication properties of biodiesel from S. oleoides and its blends. Biodiesel was prepared by base-catalyzed transesterification using methanol. Results indicate that addition of biodiesel improves the lubricity and reduces wear scar diameter even at a 5% blend [51].

Viscosity affects the atomization of a fuel upon injection into the com­bustion chamber and, thereby, ultimately the formation of engine deposits. The higher the viscosity, the greater the tendency of the fuel to cause such problems. The viscosity of a transesterified oil, i. e., biodiesel, is about an order of magnitude lower than that of the parent oil [1, 2]. High viscosity is the major fuel property why neat vegetable oils have been largely abandoned as alternative DF. Kinematic viscosity has been included in most biodiesel standards. It can be determined by standards such as ASTM D445 or ISO 3104. The difference in viscosity between the parent oil and the alkyl ester derivatives can be used in monitoring biodiesel production [67]. The effect on viscosity of blending biodiesel and petrodiesel has also been investigated [68], and an equation has been derived, which allows calculating the viscosity of such blends.

The prediction of viscosity of fatty materials has received considerable attention in the literature. Viscosity values of biodiesel/mixtures of fatty esters have been predicted from the viscosities of the individual components by a logarithmic equation for dynamic viscosity [10]. Viscosity increases with chain length (number of carbon atoms) and with increasing degree of saturation. This holds also for the alcohol moiety as the viscosity of ethyl esters is slightly higher than that of methyl esters [11]. Factors such as double bond configuration influence viscosity (cis double bond con­figuration giving a lower viscosity than the trans configuration), while the double bond position affects viscosity less [11]. Thus, a feedstock such as used frying oils, which is more saturated and contains some amounts of trans fatty acid chains, has a higher viscosity than its parent oil. Branching in the ester moiety, however, has little or no influence on viscosity, again showing that this is a technically promising approach for improving low-temperature properties without significantly affecting other fuel properties. Values for dynamic viscosity and kinematic viscosity of neat fatty acid alkyl esters are included in Table 5.1.

Ernst A. Stadlbauer and Sebastian Bojanowski

8.1 Introduction

Lipids [1] in the form of fat and edible oils are important energy sources for humans due to the high calorific value of triacylglycerols (~37 kJ/g, or ~9 kcal/g) and the nutritional benefits of both essential fatty acids and phosphate. In addition, energy stored in lipids may be technically realized by either direct use in combustion or by upgrading into a more versatile fuel. In this respect, lipids play an important role for providing lighting and warmth.

Historically, whale oil lamps and tallow candles were gradually dis­placed by kerosene lamps and electric bulbs [2]. Nowadays, lipids are attracting interest as a renewable source of fuels and chemical feedstock. Therefore, segmentation in the marketplace for lipids is noticeable [3]. In emerging economies of eastern Asia, there is a demand for cheap, edible commodity oils, such as soybean or palm oils. In developed economies, a nutritionally led demand for niche oils, such as low-trans­fat oils, high-omega-3 oils, and enhanced lipophilic vitamins (especially A and E), prevails. More recently, nonedible uses of lipids arise from the proliferating demand for alternative fuels [4] to substitute liquid hydro­carbons derived from mineral oil [5]. Such strategies fall into four broad categories. One is aimed at fueling diesel engines with pure vegetable oils [6] or vegetable oil-fossil fuel blends [7]. The other focuses on biodiesel (alkyl esters of fatty acids), which is mainly sourced from rapeseed and palm oils [8-10]. Problems [11] associated with the more polar charac­teristics of vegetable oil and biodiesel in comparison to conventional

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diesel has given rise to studies for cracking of lipids (vegetable oils/animal fat) into nonpolar hydrocarbons [12] to be used as a base for fuels or chemical commodities. Decomposition studies with and without catalysts (metallic salts, metal oxides) have been performed. Finally, lipids (and proteins) in dead cellular matter such as sewage sludge or meat and bonemeal may be converted by natural catalysts present in the substrate to oil having properties similar to diesel fuel [13].

In the following sections, basic processes of converting lipids into non­polar hydrocarbons with alkanes, alkenes, and arenes as main con­stituents are discussed. Details of pure vegetable oils or biodiesel are outlined elsewhere (see Chaps. 4, 5, 6).