Ahindra Nag, Ph. D., is a Senior Assistant Professor in the Department of Chemistry at the Indian Institute of Technology, Kharagpur. He has 21 years of teaching experience and has published 60 research papers in major national and international journals. He is the author of three other books: Analytical Techniques in Agriculture, Biotechnology, and Environmental Engineering; Environmental Education and Solid Waste Management; and Foundry Natural Product Materials and Pollution.

Quite a few prototype experiments have been done, and a large number of postulations are yet to be worked out, based on the potential differ­ence maintained within and outside the living cell. Two well-known phenomena are the membrane potential and the injury potential.

If the inside and outside walls of a cell membrane are brought to elec­trical continuity, current will flow. Usually the inside is anodic, mainly due to the dominating fixed charges on the membrane protein. When injury is caused, the excess mobile cations from the outer surface infil­trate the inner layer and a local flow of current takes place. A healthy (uninjured) cell maintains an intact membrane, spends some metabolic energy to pump in nutrients and K+, and retains them within the cell against a concentration gradient. Likewise, some of the metabolic prod­ucts, including Na+ are pumped out (exceptions, namely, Halobacterium— are few).

Most of these functions are chemically mediated (by ATPase, ATP — Mg2+, etc.) and amount to mechanical work. Maintenance of the poten­tial difference on the membrane inside out is an indirect electrical mani­festation of the chemical activity. The membrane components, particularly protein, uphold its configuration with desired functional groups pro­jected within. Retention of selective ions with the cell, in addition to offering electrical neutrality, offers colloid osmotic steady state (through Donnan equilibrium).

Another interesting phenomenon associated with chemical activity of cells is the pH specificity of specialized cells. Normally, the mammalian body fluid behaves as an alkaline buffer, pH 7.4, with only about 0.1 M, contributed by metal ions, but has high osmolarity due to colloid osmotic components. In spite of the pH 7.4 of the circulating fluid, the stomach, part of the kidney, and the respiratory system maintain distinct acid pH. This mechanism of upholding higher H+ concentration is by metabolic expenses. In plants, the tissue fluid is usually acidic, say pH 6.5, and certain specialized tissues, namely fruits, exhibit strong acidity. In very rare cases (marine flora), plant tissue fluids show alkaline pH.

These examples are sufficient to indicate that if gastric mucosa is connected to the intravenous system, a potential difference or an EMF will be experienced. Likewise, if the root tissue and the fruit of a tree are short-circuited, current (however feeble) will be experienced. This information is not worth much at this present state of the art because the magnitude of instrumentation will appear prohibitive. But in space research, there was no alternative left but to develop solar cells, and sil­icon cells have found their place despite their cost. Because roughly 4 kcal of energy is available per gram of coal or hydrocarbon, this tech­nique is of limited value at present. However, with enhanced improve­ment, the renewable resources of flora and fauna may be sources of direct energy when we run out of oil and coal and will also appear inex­pensive under those circumstances.

Lignocellulosic materials predominantly contain a mixture of carbohy­drate polymers (cellulose and hemicellulose) and lignin. The carbohydrate polymers are tightly bound to lignin mainly through hydrogen bonding, but also through some covalent bonding. The contents of cellulose, hemi — cellulose, and lignin in common lignocellulosic materials are listed in Table 3.2. Different types of carbohydrates (glucan, xylan, galactan, arabinan, and mannan), lignin, extractive, and ash content of many lig — nocellulosic materials have been analyzed and are available in the lit­erature [2, 11-14] (see Table 3.2).

1.5.1 Cellulose

Cellulose is the main component of most lignocellulosic materials. Cellulose is a linear polymer of up to 27,000 glucosyl residues linked by ^-1,4 bonds. However, each glucose residue is rotated 180° relative to

its neighbors so that the basic repeating unit is in fact cellobiose, a dimer of a two-glucose unit. As glucose units are linked together into polymer chains, a molecule of water is lost, which makes the chemical formula C6H10O5 for each monomer unit of “glucan.” The parallel polyglucan chains form numerous intra — and intermolecular hydrogen bonds, which result in a highly ordered crystalline structure of native cellulose, interspersed with less-ordered amorphous regions [15, 16].

Crop description. Ricinus communis L., commonly known as the castor — oil plant, belongs to the family Euphorbiaceae (see Fig. 4.3). This peren­nial tree or shrub can reach up to 12 m high in tropical or subtropical climates, but it remains 3 m tall in temperate places. Native to Central Africa, it is being cultivated in many hot climates. The oil contains up to 90% ricinoleic acid, which is not suitable for nutritional purposes due to its laxative effect [52]. This hydroxycarboxylic acid is responsi­ble for the extremely high viscosity of castor oil, amounting to almost a hundred times the value observed for other fatty materials [53].

Main uses. Castor bean is cultivated for its seeds, which yield a fast­drying oil used mainly in industry and medicine. Coating fabrics, high — grade lubricants, printing inks, and production of a polyamide nylon-type fiber are among its uses. Dehydrated oil is an excellent drying agent and is used in paints and varnishes. Hydrogenated oil is utilized in the man­ufacture of waxes, polishes, carbon paper, candles, and crayons. The pomace or residue after crushing is used as a nitrogen-rich fertilizer. Although it is highly toxic due to the ricin, a method of detoxicating the meal has been developed, so that it can safely be fed to livestock [54]. Several authors have found that castor-oil biodiesel can be considered as a promising alternative to diesel fuel. Transesterification reactions have been carried out mainly by using both ethanol and NaOH, and through enzymatic methanolysis [55-57]. Several authors have studied the influ­ence of the nature of the catalyst on the yields of biodiesel from castor oil. They found that the most efficient transesterification of castor oil could be achieved in the presence of methoxide and acid catalysts [58]. The influence of alcohol has also been studied. Comparing the use of ethanol versus methanol, Meneghetti et al. have found that similar yields of fatty acid esters may be obtained; however, the reaction with methanolysis is much more rapid [59]. Cvengros et al. produced both ethyl and methyl esters, using NaOH in the presence of ethanol and methanol, respectively. Despite the high viscosity and density values, they concluded that both methyl and ethyl esters can be successfully used as fuel. A positive solution to meet the standard values for both viscosity and density parameters can be a dilution with esters based
on oils/fats without an OH group, or a blending with conventional diesel fuel [60].

With the advent of low-sulfur petroleum-based DFs, the issue of DF lubric­ity is becoming increasingly important. Desulfurization of petrodiesel reduces or eliminates the inherent lubricity of this fuel, which is essen­tial for proper functioning of vital engine components such as fuel pumps and injectors. Several studies [10, 11, 67-82] on the lubricity of biodiesel or fatty compounds have shown a beneficial effect of these materials on the lubricity of petrodiesel, particularly low-sulfur petrodiesel fuel. Adding biodiesel at low levels (1-2%) restores the lubricity to low-sulfur petroleum-derived DFs. However, the lubricity-enhancing effect of biodiesel at low blend levels is mainly caused by minor components of biodiesel such as free fatty acids and monoacylglycerols [83], which have free COOH and OH groups. Other studies [84, 85] also point out the beneficial effect of minor components on biodiesel lubricity, but these studies do not fully agree on the responsible species [83-85]. Thus, biodiesel is required at 1-2% levels in low-lubricity petrodiesel, in order for the minor components to be effective lubricity enhancers [83]. At higher blend levels, such as 5%, the esters are sufficiently effective without the presence of minor components.

While the length of a fatty acid chain does not significantly affect lubricity, unsaturation enhances lubricity slightly; thus an ester such as methyl linoleate or methyl linolenate improves lubricity more than methyl stearate [80, 83]. In accordance with the above observation on the effect of free OH groups on lubricity, castor oil displayed better lubricity than other vegetable oil esters [75, 80, 81]. Ethyl esters have improved lubricity compared to methyl esters [75].

Standards for testing DF lubricity use the scuffing load ball-on-cylinder lubricity evaluator (SLBOCLE) (ASTM D6078) or the high-frequency reciprocating rig (HFRR) (ASTM D6079; ISO 12156). Lubricity has not been included in biodiesel standards despite the definite advantage of biodiesel over petrodiesel with respect to this fuel property. However, the HFRR method has been included in the petrodiesel standards ASTM D975 and EN 590.

Thermal decomposition of vegetable oil was performed to prove the theory of the origin of mineral oil from organic matter [14] as early as 1888. Literature up to 1983 has been reviewed by Schwab et al. [15]. In many cases, inadequate characterization of products formed in pyrol­ysis of vegetable oils was found. Therefore, analytical data obtained by gas chromatography—mass spectrometry (GC-MS) from thermally decomposed soybean oil and high oleic safflower oil in the presence of air or nitrogen were reported [15].

The ASTM standard method for distillation of petroleum products D86-82 has been used for decomposition experiments. Catalytic systems were excluded in this destructive distillation. The actual temperature of the oil in the feeder flask was about 100oC higher than the vapor temper­ature throughout the distillation. Under these conditions, GC-MS analy­sis showed that approximately 75% of the products were made up of alkanes, alkenes, aromatics, and carboxylic acids with carbon numbers ranging from 4 to more than 20 (see Table 8.1).

A comparison of fuel properties is given in Table 8.2. The carbon — hydrogen ratio shows 79% C and 11.88% H for the pyrolyzate of soybean

oil. This indicates considerable amounts of oxygenated compounds in the distillate. Consequently, methylation of these oils has revealed 9.6-12.2% of carboxylic acids ranging from C-3 to over C-18. This is reflected in the higher viscosity compared to diesel.

Mass-spectral fingerprints of the entire pyrolysis product slate from tripalmitin, different vegetable oils, and extracted oils from microalgae confirm that the decomposition of ester bonds in the absence of external catalysts is extensive [16-18]. However, a great variability in primary pyrolysis/vaporization product slates was observed [18].

Thermodynamic calculation in the degradation process shows that the cleavage of C-O bond takes place at 288°C and fatty acids are the main product [19]. The actual pyrolysis temperature should be higher than 400°C to obtain maximum diesel yield [20]. The mechanism of pyrolysis of vegetable oil has been discussed by various authors [9, 15, 19]. Generally, thermal decomposition proceeds through either a free-radical or carbonium ion mechanism. The primary R-COO splits off carbon dioxide. The alkyl radicals (R), upon disproportionation and elimination of ethene, give rise to alkanes and alkenes. The formation of aromatics is facilitated by a Diels-Alder addition of ethene to a conjugated diene formed in the pyrol­ysis reactions. However, the product mix and product quality are influenced by many factors such as feed pretreatment, heating rate, and temperature. As vegetable oils may contain trace elements, catalytic effects cannot be completely excluded from any thermal degradation process [21].

8.1.1 Catalytic cracking (CC)

In 1979, a paper [22] from the petrochemical industry reported for the first time that high-molecular-weight triglycerides such as corn oil (C57H104O6) and castor oil (C57H104O9) were convertible to a high-grade gasoline when passed over H-ZSM-5, a catalyst. The latter is a synthetic, medium-pore, shape-selective acid catalyst. Lipids were fed with a piston displacement pump at a rate of 2 mL/h with flowing hydrogen (300 mL/h) over 2 mL of H-ZSM-5 catalyst (0.77 g, 14-30 mesh) contained in a ver­tical Pyrex reactor at atmospheric pressure and T = 400-450°C. Paraffins, olefins, aromatics, and nonaromatics could be detected in the product mixture. The distribution of hydrocarbons is similar to selective conversion of methanol into hydrocarbon units with up to 10 carbon atoms per molecule. In all cases, a high degree of BTX aromatics (ben­zene, toluene, and xylene) was achieved. The precondition for the catalytic conversion is that the molecule penetrate the cavities of microporous zeolite.

This new catalytic approach has paved the way for a variety of appli­cations. A schematic diagram of experimental arrangements for pyrol­ysis and catalytic conversion is given in Fig. 8.1.

Conversion of different kinds of vegetable oils over medium-pore H- ZSM-5 have been investigated in detail [23-26]. Catalytic cracking of by-products from palm oil mills with a selectivity of 51wt.% toward aro­matic hydrocarbon formation has been reported [27]. To achieve higher yields, this type of work was extended to pyrolysis and zeolite conver­sion of both whole algae and their major components as well as whole seeds and selected vegetable oils [18, 28-31]. Hot vapors from solid organic material (microalgae, seeds, etc.) or vaporized vegetable oils were passed directly over the H-ZSM-5 catalyst. Products of different

algae, seeds, or vegetable oils emerging from the passage showed a uni­form, high-octane, aromatic gasoline product. Obviously, the molecular pattern of products is insensitive to the nature of lipids used. This is in contrast to pyrolysis without a catalyst [18].

Upgrading of crude tall oil to fuels and chemicals has been studied at atmospheric pressure and in the temperature range of 370—440oC, in a fixed-bed microreactor containing H-ZSM-5 [32]. The oil was co-fed with diluents such as tetralin, methanol, and steam. High oil conversions, in the range of 80-90 wt.%, were obtained using tetralin and methanol as diluents. Conversions under steam were reduced to 36-70 wt.%. The maximum concentration of gasoline-range aromatic hydrocarbons was 52-57 wt.% with tetralin and steam, but only 39% with methanol. The amount of gas product in most runs was 1-4 wt.% [32].

Gasification, an exothermic reaction, yields mostly producer gas, a mixture of carbon monoxide, hydrogen, and methane at temperatures

above 1000oC, mostly in the absence of air. The starting materials may be any kind of organic matter, preferably waste materials like cotton and jute sticks, corn cobs, bagasse, and many other plant and vegetation products. In India, annually 16 million tons of rice husk, 160 million tons of paddy straw, 2 million tons of jute sticks, and 2.2 million tons of groundnut shells are available as agricultural by-products.

The gas can be directly used as fuel or used to drive irrigation pump sets. Several designs are available.

Pyrolysis, a thermochemical conversion, also performed in absence of air at a temperature of 500-6000C, yields gaseous components, hydro­carbons, carbon monoxide, hydrogen, methane, butane, some liquids, tars, and a little coke, all of which have very high energy content. Starting materials are similar to those mentioned under gasification. The vegetable matter in the municipal refuse (as much as 50%) is also good feed for pyrolysis. Very optimistic economic analysis for the pyrolytic process has been put forward by investigators, and a properly designed plant, say capable of handling 250 tons of organic refuse per day, will be fully paid off at the end of 5 years. There are 20 domestic or family-size models suggested by organizations. As per the available information, large-scale use of either gasifier or pyrolyser has not been noticed so far. But for the municipalities, the responsibility of quick dis­posal of the refuse and the environmental issues will prompt installa­tion of such plants in the near future. One such flowchart of a model plant is given in Fig. 1.12.

A great number of bacteria are able to produce ethanol, although many of them generate multiple end products in addition to ethanol. Zymomonas mobilis is an unusual Gram-negative bacterium that has several appealing properties as a fermenting microorganism for ethanol production. It has a homoethanol fermentation pathway and tolerates up to 120 g/L ethanol. Its ethanol yield is comparable with S. cerevisiae, while it has much higher specific ethanol productivity (2.5 X) than the yeast. However, the tolerance of Z. mobilis to ethanol is lower than that of S. cerevisiae, since some strains of S. cerevisiae can produce ethanol to give concentrations as high as 18% of the fermentation broth. The tol­erance of Z. mobilis to inhibitors and low pH is also low. Similarly,

S. cerevisiae and Z. mobilis cannot utilize pentoses [14, 57]. Several genetic modifications have been performed for utilization of arabinose and xylose by Z. mobilis. However, S. cerevisiae has been more welcomed for industrial application, probably because of the industrial problems that may arise in working with bacteria. Separation of S. cerevisiae from fermentation media is much easier than separation of Z. mobilis, which is an important characteristic for reuse of the microorganisms in ethanol production processes.

Using genetically engineered bacteria for ethanol production is also applied in many studies. Ingram et al. [58] have reviewed metabolic engineering of bacteria for ethanol production. Recombinant Escherichia coli is a valuable bacterial resource for ethanol production. Construction of E. coli strains to selectively produce ethanol was one of the first suc­cessful applications of metabolic engineering. E. coli has several advan­tages as a biocatalyst for ethanol production, including the ability to ferment a wide spectrum of sugars, no requirements for complex growth factors, and prior industrial use (e. g., for production of recombinant protein). The major disadvantages associated with using E. coli cultures are a narrow and neutral pH growth range (6.0—8.0), less hardy cultures compared to yeast, and public perceptions regarding the danger of E. coli strains. Lack of data on the use of residual E. coli cell mass as an ingre­dient in animal feed is also an obstacle to its application [8].

Recently, the Japanese Research Institute of Innovative Technology for the Earth (RITE) developed a microorganism for ethanol production. The RITE strain is an engineered strain of Corynebacterium glutamicum that converts both pentose and hexose sugars into alcohol. The central metabolic pathway of C. glutamicum was engineered to produce ethanol. A recombinant strain that expressed the Z. mobilis gene coding for pyru­vate decarboxylase and alcohol dehydrogenase was constructed [59]. RITE and Honda jointly developed a technology for production of ethanol production from lignocellulosic materials using the strain. It is claimed that application of this strain by using engineering technology from Honda enables a significant increase in alcohol conversion efficiency, in comparison to conventional cellulosic—bioethanol production processes.

Besides nonedible oils, there are some edible oils from plants that yield a relatively lower-cost source to produce biodiesel compared to biodiesel from rapeseed oil or soybean oil.

4.3.1 Cardoon oil

Crop description. Cynara cardunculus L.—commonly known as car­doon, Spanish artichoke, artichoke thistle, cardone, dardoni, or cardo— belongs to the family Asteracea (see Fig. 4.14). Artichokes originated in the Mediterranean region and climates, becoming an important weed of the Pampas in Argentina, and in Australia, and California because of its adaptation to dry climate. Its fatty acid composition mainly includes palmitic acid (19.3%), stearic acid (6.1%), oleic acid (39%), and linoleic acid (30%) [123].

Main uses. The leaf stalks are eaten as a vegetable. The leaves contain cynarin, which improves gall bladder and liver functions, increases bile flow, and lowers cholesterol. The down from the seed heads is used as rennet.

Encinar et al. transesterified C. cardunculus oil using methanol and several catalysts (sodium hydroxide, potassium hydroxide, and sodium methoxide) to produce biodiesel. Best properties were achieved by using 15% methanol and 1% sodium methoxide as catalyst, at 60°C temperature [124].

The reaction can also be accomplished by using an ethanol-oil molar ratio of 12:1 and 1% sodium hydroxide, at 75°C [125]. C. cardunculus methyl esters also provide a significant reduction in particulate emis­sions, mainly due to reduced soot and sulfate formation [126].

Ethanol is the most appropriate fuel for India to replace petrol, and the utmost of efforts have been made to increase alcohol production in the country. India is in an extremely happy position in this regard as it is the world’s largest producer of sugarcane, a major source of alcohol. India topped the world in sugar production with 181 Mton (in 1978), followed by Brazil (130 Mton) and Cuba (67 Mton).

Alcohol is derived not directly from sugarcane but molasses-sugar­cane by-products. All starch-rich plants like maize, tapioca, and potato can be used to produce alcohol; cellulosic waste materials can also be used. Production of ethanol from biomass involves fermentation and distillation of crops. India has a vast potential to produce ethanol, and only 2.5% of the country’s irrigated land is used to produce sugarcane. This can be raised to a much higher level without adversely affecting the production of food-bearing crops.

At present, Brazil is the only country that produces fuel alcohol on a large scale from agricultural products (mainly sugarcane). Other coun­tries, especially those with an substantial agricultural surpluses, such as the United States and Canada, are also bound to enter into this field of so-called energy forming. The area of land required is substantial. A medium-sized car with an annual run of 15,000 km needs 2000 L of ethanol. To produce this amount, the crop areas required are given in Table 7.2. To provide enough sugar beet alcohol to fuel 20 million cars in Germany requires half the area of the entire country.

Sugarcane. The present method adopted to obtain alcohol for energy purposes requires three stages: (1) extracting the juice from sugarcane, (2) fermentation of the juice, and (3) distillation into 90-95% alcohol.

Molasses. The black residue remaining after the sugar is extracted from sugarcane is called molasses. It contains mostly invert sugars and some sucrose. This sucrose also undergoes hydrolysis to produce invert sugar by a catalytic action of acids in molasses.

C12H22O11 + H2O ^ C6H12O11 (D-Glucose) + C6H12O6 (D-Fructose)

This mixture product is not crystallizable. Yeast organisms in the pres­ence of oxygen oxidize sugars into CO2 and H2O and convert sucrose mostly into ethyl alcohol.

C6H12O6 ^ 2C2H5OH + 2CO2

Process adopted. Molasses is mixed with water so that the concentra­tion of sugar in it is 10-18% (optimum is 12%). If the concentration is high, more alcohol may be produced and may kill the yeast. Then, a selected strain of yeast is added (it should not contain any wild yeast). For some nutrient substances like ammonium and phosphates, the pH value is kept between 4 and 5, which favors the growth of yeast organ­isms. H2SO4 is used for lowering pH. The temperature of the mixture is kept at 15-25°C. The fermentation takes place as follows:

1. First, the yeast cells multiply at an optimum temperature (30°C).

2. Rapid fermentation takes place at the boiling temperature, and oxygen is given off. The optimum temperature (50°C) is maintained, and the process is continued for 20-30 h.

3. The fermentation rate is reduced, and alcohol is produced slowly. Total time for fermentation is 36-48 h, depending upon the temper­ature and sugar content. Last, the formed ethanol is distilled.

Starch. In this process, starchy materials are first converted into fer­mentable sugars. This is done by enzymatic conversion (by means of malt process) or by acid hydrolysis.

Starch ^ C12H22O11 (Maltose) + C6H12O6 (Dextrose)

Malt process. Malt is prepared by germination of barley grains to pro­duce required enzymes. The grain is ground and steam cooked at 100-150oC to break the cell wall of starch. For every 25 kg of grain, 100 L of water is added. Then the formed mass is cooled to 60-700C and taken to large vessels where malt is added within 2 h and 60-70% of the stock is converted into maltose. Converted mash is cooled to a fermenting temperature of 20-250C. pH is adjusted and fermentation is affected, producing ethanol.

Acid hydrolysis. This process involves treatment with concentrated sulfuric or hydrochloric acid at pH 2-3 and 10-20 kg pressure in an auto­clave to make sugar and then conversion of sugar to alcohol by yeast.

Cellulose material.

Wood. Cellulose from wood is hydrolyzed into simple sugars by using diluted acid at a high temperature or concentrated acid at a low tem­perature. Similarly, cellulosic agricultural waste and straws can be used in place of wood.

Sulfite waste liquor from paper manufacture. Waste liquor contains 2-3.5% of sugar, out of which 65% is fermentable into alcohol. Before fermen­tation, all acids in the liquor are removed by adding calcium. Then fer­mentation is carried out by special yeasts. Generally, 1% of liquor is converted into alcohol.

Hydrocarbon gases.

Hydration of ethylene. Conversion of ethylene to ethyl alcohol can be carried out with high yield by first treating ethylene with H2SO4, forming ethyl hydrogen sulphate and diethyl sulfate, as given by the following reactions:

C2H5HSO4 — (C2H5)2SO4 2C2H4 + H2SO4 — (C2H5)2SO4

These products, ethyl sulfuric acid and diethyl sulfate, when treated with water give ethanol as per the following reactions:

C2H5HSO4 + H2O — C2H5OH + H2SO4
(C2H5)2SO4 + 2H2O — 2C2H5OH + H2SO4

Direct hydration. Ethanol is also formed as per the following chemical reaction:

C2H4 + H2O — C2H5OH

This type of conversion is very small as the reaction is exothermic; it is not a suitable method for mass production. The corn is first ground, then mixed with water and enzymes, and cooked at 150oC to convert starch to sugar. The mixture is then cooled and sent to fermentation tanks, where yeast is added and the sugar is allowed to ferment into ethanol. After 60 h in the tanks, the mixture is sent to distillation columns, where ethanol is evaporated out, condensed, and mixed with unleaded gaso­line to form gasohol, which contains 90% gasoline and 10% ethanol.

Tapioca materials. Tapioca is available in plenty in Asia, the United States, central Europe, and Africa. Its production can be increased through modern cultivation techniques. The process consists of con­verting the tapioca flour into fermentation sugars with enzymes prior to fermentation with yeast. Modern technology uses a-amyl glycosidase, one of two enzymes required in the process, and then saccharification of the material into alcohol by using yeast.

Anhydrous alcohol from vegetable wastes. The Philippines has embarked on an “alcogas program” to produce its own anhydrous alcohol from local vegetable wastes for blending with petrol. The program is cur­rently based on sugarcane juice and molasses, but it plans to diversify by using other raw materials. In the basic process, cellulose conversion begins with the pretreatment of the raw materials, which may include coffee hulls, rice straw, grass—even sawmill wastes. Enzymes then take over by converting the feedstock into a sugary liquid that is fermented and finally distilled into anhydrous alcohol. After distillation, waste residues can be evaporated into syrup to feed animals, while uncon­verted cellulose is used as the primary fuel for the plant. If the Philippines could engineer a breakthrough in this area, its agricultural and forestry wastes could supply energy equivalent to 9720 mL of oil annually. In the years to come, this new energy source could make a sig­nificant economic impact on a country that depends on imports of crude oil for 95% of its energy.

Manioc. As oil prices continue to rise, more and more work is being done on alternatives. Manioc is one such staple crop in many tropical lands. Brazil has planned to use manioc in its ethanol production plants, aiming to make 35,000 bbl a day from 400 X 103 ha of manioc plantation. Conversion of manioc to ethanol is somewhat more complex than is the case with sugarcane. The raw material has to be turned into sugar by fer­mentation. This first step requires the use of enzymes. Danish Co. has developed the necessary heat-resistant enzymes in a pilot plant in Brazil.

Manioc does not grow in higher temperature zones; so scientists have turned to other plants, and there is work being done in Sweden that is in an advanced stage. They have developed fast-growing poplars and wil­lows. Their yield is 30 ton/ha, which is equal to 12 tons of fuel oil.

It is estimated that 1000 X 103 ha planted with such trees can pro­vide 10% of Sweden’s electricity. Also in Sweden, work has been carried out on the common reed, and the estimated yield is 10 ton/(yr • ha), which is equal to 4.5 tons of oil. Sweden has plans to have 100 X 103 ha of reeds. Brazil’s program of ethanol from sugarcane and manioc may employ 200 X 103 people and save $1600 million each year in foreign exchange.