After corn, wheat (Triticum spp.) is the most employed grain for fuel ethanol pro­duction, especially in Europe and North America, due to its high starch content (Table 3.8). Other than the sugar beet, wheat is the main feedstock for ethanol production in France (Poitrat, 1999). In fact, France was the fifth world producer of wheat in 2007 (33.21 million tons) after China (109.86 million tons), India (74.89 million tons), United States (53.60 million tons), and Russian Federation (49.38 million tons; FAO, 2007b). The wheat yield in France is 6.25 ton/ha, while in Ireland, it reaches up to 8.1 ton/ha (FAO, 2007a).

Sorghum (Sorghum bicolor) is another grain proposed for ethanol produc­tion. The United States is the world’s leading producer of sorghum with a volume of 12.82 million tons in 2007 (FAO, 2007a, 2007b). Sorghum is employed in many countries, such as Colombia, as a component of animal feed, though corn is replacing it. One of the features of sorghum as feedstock for ethanol produc­tion is the presence of significant amounts of tannins. These tannins provoke the decrease in the ethanol production rate during the fermentation process, although they do not affect either the ethanol yield or the enzymatic hydrolysis of starch contained in sorghum (Mullins and NeSmith, 1987).

One of the most promising crops for fuel ethanol production is sweet sorghum, which produces grains with high starch content, stalks with high sucrose content, and leaves and bagasse with high lignocellulosic content (Sanchez and Cardona, 2008a). In addition, this crop can be cultivated in both temperate and tropical coun­tries, it requires one third of the water needed for the sugar cane harvest and half of the water needed by corn, and it is tolerant to drought, flooding, and saline alkalin­ity (du Preez et al., 1985; Winner Network, 2002). Grassi (1999) reports that from some varieties of sweet sorghum the following productivities can be obtained: 5 ton/ha grains, 8 ton/ha sugar, and 17 ton dry matter/ha lignocellulosics.

3.2.2.1 Cassava

The cassava (Manihot esculenta) is a perennial bush achieving 2 m by height and is native to South America. The main feature of this plant is its edible roots, thus the plant is uprooted after one year of growth in order to obtain its better conditions for its consumption. The cassava root is cylindrical and oblong and can reach up to 100 cm in length and 10 cm of diameter. Its pulp is firm and presents high starch content. Cassava tubers are consumed in a cooked form and represent a crucial component in the food of more than 500 million people in America, Asia, and Africa. The cassava is not a very exigent crop, but it should be grown no higher than 1,500 m above sea level. For cassava cropping, the soils should be porous because the root requires sufficient oxygen levels to grow; it also requires good drainage. The cropping temperature should be in the range 25 to 30°C (Agronet, 2007). For this reason, cassava is one of the most important tropi­cal crops in the world. Once planted, cassava roots can be harvested after seven months and stay in the soil for three years (Alarcon and Dufour, 1998).

The world’s largest cassava producer is Nigeria, followed by Brazil, Indonesia, and Thailand (FAO, 2007b). As can be observed in Table 3.9, major cassava producers are located in Africa, Southeast Asia, and South America. The most

elevated cassava yields among the main producers are from Thailand (20.28 ton/ ha) and Brazil (13.63 ton/ha; FAO, 2007a). In general, more than 90% of cas­sava production is directed to human food, while the balance is used for produc­ing starches and snacks. The substitution of corn with cassava flour has been proposed for animal feed production taking into account its high energy content (Espinal et al., 2005a). The importance of cassava cropping from the viewpoint of its agro-industrial applications lies in its high potential for energy production in the form of starch (see Table 3.8). Espinal et al. (2005a) report that the use of improved seeds and fertilizers, and a suitable weed control allows production of 20 to 30 ton/ha of fresh roots and 10 to 12 ton/ha of dried cassava in zones where other starch-producing crops like corn, sorghum, or rice do not reach yields above 4 or 5 ton/ha.

There exist two main methods for industrial production of native cassava starch: the traditional method employed in India and some Latin American coun­tries, and the modern method of the type used by the company Alfa Laval for large-scale production. In the traditional process, fresh roots are washed and debarked before crushing in a rotary rasper. Starch is separated from the crushed pulp before passing through a series of reciprocating nylon screens of decreasing mesh size (50250 mesh). The resultant starch milk is settled over a period of four to eight hours using a shallow settling table or a series of inclined channels laid out in a zigzag pattern. Settled starch is sun-dried on large cement drying floors for approximately eight hours. During this period, the moisture content reduces from 45 to 50% down to 10 to 12%. To achieve efficient drying, sunny conditions are required with ambient temperatures of more than 30°C and relative humidity of 20 to 30%. Dried starch is ground to a fine powder and packaged for sale (FAO and IFAD, 2004). In the modern Alfa Laval-type process, roots are washed and debarked, sliced and then crushed in a rotary rasper. Starch pulp is passed through two conical rotary extractors to separate starch granules from fibrous materials, and then fed via a protective safety screen and hydro cyclone unit to a continuous centrifuge for washing and concentration. The concentrated starch milk is passed through a rotary vacuum filter to reduce water content to 40 to 45% and then flash dried. The flash drying reduces moisture content to 10 to 12% in a few seconds, so starch granules do not heat up and suffer thermal degradation.

By applying random genetic modification techniques, also called mutagenesis, mutations in the microbial DNA are induced through employing physical or chemical agents (mutagens). The mutations are produced randomly in the DNA chain and lead to the production of mutant microorganisms that can transfer these changes in the genome to the subsequent generations. Among the most used physical agents, ultraviolet radiation (usually with a wave length of 260 nm) is highlighted. This radiation is absorbed by the double bonds of pyrimidines composing the DNA chain. As a result, DNA photoproducts are obtained that provoke drastic changes in the nucleic acids. This process is not directed and leads to the death of most irradiated cells. However, a small number of cells survive and even acquire some desirable traits as a higher product yield. The best mutants are selected by screening procedures and are irradiated again in order to obtain mutants with better yields. Besides ultraviolet radiation, x-rays and ionizing radiations are also employed though these agents can cause the death of all the irradiated cell population. Among the most employed chemical mutagens are the nitrogenated base analogues (5-bromouracile, 2-aminopurine), deami — nating or hydroxylating agents (nitrous acid, hydroxyl amine), alkylating agents (mustard gas, ethyl-ethanesulfonate, ethyl-methanesulfonate, nitrosoguanidine), intercalant agents (acridine orange, ethidium bromide, proflavine), and pairing blocking agents (benzopyrene, aflatoxine B1; Crueger and Crueger, 1993). The selection programs of industrial microorganisms by mutagenesis are very pro­longed, tedious, and expensive, but can cause significant increases in the yield of the overall process.

In the case of fuel ethanol production, the development of mutant cells has been oriented, besides increasing ethanol yield, to the enhancement of tolerance to salts and impurities contained in the medium (e. g., for the case of yeasts culti­vated on molasses) or to the acquiring of flocculating properties. This latter trait allows the ready separation of yeast cells during schemes of continuous fermenta­tion or by repeated-batch regimes (see Chapter 7) because the cells agglomerate and settle (or float) allowing their rapid removal from the cultivation broth.

The intensification of fuel ethanol production processes has become a priority dur­ing the design of technological configurations with enhanced technical, economic, and environmental performance. Process integration achieves this intensification through the combination of several unit operations and processes in a same single unit or through the better utilization of the energy flows. In this chapter, main aspects of the intensification of ethanol production by different ways of process integration (reaction-reaction, reaction-separation, separation-separation, heat integration) are presented. Examples of the application of the integration prin­ciple to bioethanol production are provided emphasizing their efficiency from an energy point of view. The potential offered by the implementation of technologies with a high degree of integration, such as the simultaneous saccharification and co-fermentation and consolidated bioprocessing, are discussed highlighting their advantages and limitations as well as their possibilities for further development. In addition, some configurations involving the ethanol removal from culture broth are analyzed because one of the most important challenges in ethanol production is the reduction of end product inhibition on the growth rate of ethanol-producing microorganisms.

The assessment of the environmental impacts generated during the fuel ethanol production process is a key criterion to select different conversion technologies during early stages of the design of such process. If different feedstocks are evalu­ated, the analysis of the environmental performance for the proposed technological configurations is even more important. In a previous work (Cardona et al., 2005a), the environmental performance of several process alternatives for fuel ethanol production from two types of feedstock was determined. The types of feedstock corresponded to lignocellulosic materials (herbaceous biomass, wood chips, sug­arcane bagasse, and waste paper) and starchy materials (corn, wheat, and cassava). Using the commercial process simulator Aspen Plus, different configurations were analyzed considering two options for ethanol dehydration step: adsorption using molecular sieves and azeotropic distillation.

The results obtained for the environmental performance of these processes (in terms of PEI per mass of product) are shown in Figure 10.5 for the three most rep­resentative process alternatives: (1) ethanol production from corn by dry-milling technology using molecular sieves for the dehydration step, (2) ethanol produc­tion from lignocellulosic biomass (wood chips) using azeotropic distillation for the dehydration step, and (3) ethanol production from lignocellulosic biomass (wood chips) using molecular sieves for the dehydration step. It is evident that the produc­tion of ethanol from starch has a lower impact on the environment than the bio­mass ethanol process. Because processes using biomass involve a pretreatment step where inorganic acids are used, which tends to increase the PEI. In comparing two

FIGURE 10.5 Potential environmental impact (PEI) per mass of product streams for different ethanol production flowsheets according to the eight impact categories addressed by the WAR algorithm: HTPI = human toxicity potential by ingestion, HTPE = human toxicity potential by either inhalation or dermal exposure, TTP = terrestrial toxicity poten­tial, ATP = aquatic toxicity potential, GWP = global warming potential, ODP = ozone depletion potential, PCOP = photochemical oxidation or smog formation potential, AP = acidification or acid-rain potential. Dehydration technologies: AD = azeotropic distilla­tion, MS = molecular sieves.

kinds of separation technologies for the same feedstock (wood biomass), the utili­zation of molecular sieves for recovery of the product has slightly lower PEI than the process involving azeotropic distillation due to the release of relatively small amounts of the entrainer (in this case, the toxic benzene) into the output streams. In this sense, the adsorption with molecular sieves is a cleaner separation technology and it is currently being used in the bioethanol industry.

In the framework of the conflict-based approach, process synthesis is defined as the process of decision making for identifying and handling the design conflicts in order to satisfy multiobjective requirements (Li, 2004). Under this concept, a design problem is decomposed into subproblems instead of applying a hierarchical design. This allows for overcoming the drawback related to the interactions among several hierarchical levels of analysis. The design problem is represented by the conflicts among the interrelated design objectives or by the features of the techno­logical scheme (Li and Kraslawski, 2004). Undoubtedly, this approach represents a change of paradigm in process design, although some aspects should be developed, such as the quantification of the conflicts and heuristic rules in function of their contribution to the conflicts as well as the development of the solving algorithms.

Lignocellulosic materials can be comminuted by a combination of chipping, grinding, and milling to reduce cellulose crystallinity. This reduction allows the cellulases to access the biomass surface in an easier way increasing the conversion of cellulose into glucose. The energy requirements of mechanical comminution of agricultural materials depend on the final particle size and waste biomass charac­teristics (Sanchez and Cardona, 2008). In some specific cases, it has been demon­strated that wet or dry crushing used as a sole pretreatment method provokes the conversion of biomass into glucose in the following process steps of 56 to 60% for rice straw. For cane bagasse, a 25% conversion using wet crushing and 49.2% conversion for dry crushing have been observed (Rivers and Emert, 1988). In these cases, particle size plays a crucial role in the efficiency of the method. An important amount of data has been presented on the yields during the hydrolysis of timothy grass and alfalfa for different fractions of milled material with dif­ferent particle sizes (Alvo and Belkacemi, 1997). Thus, 56.4% yield for timothy grass (53 to 106 pm) and 62.5% for alfalfa (53 to 106 pm) during 24 h of pretreat­ment using roller mills have been achieved. In contrast, the hydrolysis yields for nonmilled materials were 51.4% for timothy grass and 38% for alfalfa.

The energy requirements of the mechanical comminution of agricultural mate­rials depend on the final particle size and biomass properties (Sun and Cheng,

2002) and are usually very elevated. Cadoche and Lopez (1989) reported that power supply for mechanical comminution in a plant processing different ligno — cellulosic residues should be maintained below 30 kW/ton wastes by ensuring a final particle size in the range of 3 to 6 mm. On the other hand, it was demon­strated that milling and sieving of such residues as wheat straw could lead to an increased efficiency of the pretreatment using dilute acid due to the removal of noncarbohydrate biomass components before the physical-chemical pretreatment (Papatheofanous et al., 1998). Milling with vibratory balls is an effective method of transferring the energy input into size reduction and altering the crystalline cellulose structure. Although mechanical pretreatment methods increase cellu­lose reactivity toward enzymatic hydrolysis, they are unattractive due to their high energy and capital costs (Ghosh and Ghose, 2003).

Besides comminution, pyrolysis has been tested as a physical method for pre­treatment of lignocellulosic biomass since cellulose rapidly decomposes when treated at high temperature. In particular, it has been reported that this method can be improved in the presence of oxygen. When zinc chloride or calcium car­bonate is added as a catalyst, the decomposition of pure cellulose can occur at a lower temperature (Sun and Cheng, 2002). For instance, the pyrolysis of 100 g of waste cotton produces 80 g of a highly viscous pyrolyzate with a high content of levoglucosan (43% by weight), an intramolecular glucoside whose hydrolysis using dilute acid forms significant concentrations of glucose (Yu and Zhang,

2003) . Main physical methods employed for pretreatment of lignocellulosic mate­rials are presented in Table 4.2.

7.1.3.1 Conversion of Saccharified Corn Starch into Ethanol

Yeasts are not able to metabolize the starch, so this polymer should be hydrolyzed before fermentation, as was discussed in Chapter 5. Most cereal ethanol is pro­duced from corn.

To start the fermentation, the corn mash is cooled until reaching the cultivation temperature, usually 30° to 32°C, and then the cells of the process microorgan­ism (generally S. cerevisiae) are inoculated. The corn mash is obtained by dry­milling technology and contains, besides the starch, all the other components of the grain (proteins, oil, fiber, etc.) that remain unmodified during the fermentation process. As in the case of molasses, the culture medium is also supplemented with urea or even with ammonium sulfate. Recently, some proteases are being added to the mash to provide an additional nitrogen source to the yeast resulting from the hydrolysis of corn proteins (Bothast and Schlicher, 2005). In most corn dry­milling plants producing ethanol, fermentation is accomplished in batch regime though milling, liquefaction, and saccharification as well as the subsequent distil­lation and dehydration, which are performed in a continuous regime. To ensure a continuous flow of materials, three or more fermenters are used in such a way that at any given moment one apparatus is an filling-up with the mash, the starch is fermented in another, and a third one is being unloaded and prepared for the next batch. Fermentation time is about 48 h. At the end of fermentation, the culture broth (fermented mash or beer) is sent to a storage tank from which the constant supply of beer to the distillation step is guaranteed.

In the case of ethanol production plants employing the corn wet milling, the fermentation is mostly carried out in a continuous regime. The technology is called cascade fermentation and is applied in large-scale facilities. Thus, a con­tinuous cascade saccharification process is also employed. The effluent of this system feeds not only the bioreactors for yeast propagation, but also the prefer­mentation and fermentation trains. The fermentation train consists of a cascade of four continuous fermenters. The major infection source is concentrated in the saccharification step. To avoid the development of contaminating bacteria, the cultivation of yeasts is carried out at a pH of 3.5, which requires the construction of stainless steel bioreactors (Madson and Monceaux, 1995). The temperature is maintained below 34°C by recirculating the culture medium through an external heat exchanger. Airlift bioreactors are utilized in these technological configura­tions. The total residence time of the fermenters system is about 48 h and obtains an ethanol concentration in the effluent of the last tank of about 9% by weight (12% by volume; McAloon et al., 2000). Some ethanol-producing plants using the dry-milling technology also employ cascade fermentation; in those cases, higher yields are obtained by simultaneous saccharification and fermentation of corn mash.

The logical culmination of reaction-reaction integration for the transformation of biomass into ethanol is the consolidated bioprocessing (CBP), known also as direct microbial conversion (DMC). The key difference between CBP and the other strategies of biomass processing is that only one microbial commu­nity is employed for both the production of cellulases and fermentation, i. e., cellulase production, cellulose hydrolysis, and fermentation are carried out in a single step (see Figure 9.2). This configuration implies that no capital or operation expenditures are required for enzyme production within the process. Similarly, part of the substrate is not deviated for the production of cellulases, as shown in Figure 9.7 (compare to the more complex configurations depicted in Figure 7.6 for the SHF process with the addition of commercial cellulases, and Figure 9.4 for SSF of biomass with in situ production of cellulases). Moreover,

TABLE 9.4

Integration of Reaction-Reaction Processes by Simultaneous Saccharification and Co-Fermentation (SSCF) for Fuel Ethanol Production from Different feedstocks

Source: Modified from Cardona, C. A., and O. J. Sanchez. 2007. Bioresource Technology 98:2415-2457. Elsevier Ltd. Note: SHCF = separate hydrolysis and co-fermentation.

FIGURE 9.7 Simplified diagram of the integrated process for fuel ethanol production from lignocellulosic biomass by consolidated bioprocessing (CBP).

the enzymatic and fermentation systems are entirely compatible (Cardona and Sanchez, 2007).

The extended concept of CBP involves four biologically mediated transforma­tions: (1) the production of saccharolytic enzymes (cellulases and hemicellulases); (2) the hydrolysis of carbohydrate components present in pretreated biomass to form sugars; (3) the fermentation of hexose sugars (glucose, mannose, and galac­tose); and (4) the fermentation of pentose sugars (xylose and arabinose). These four transformations occur in a single step. In this case, a dedicated process for production of cellulases is not required to make CBP a highly integrated configu­ration (Cardona and Sanchez, 2007; Lynd et al., 2005). This process is conceptu­ally depicted in Chapter 6, Figure 6.5 for the case of ethanol production from lignocellulosic biomass.

Process integration through CBP represents a considerable improvement of technologies for conversion of lignocellulosic biomass into ethanol. The enhance­ment of the conversion technology contributes by far the most reduction of etha­nol production costs (Cardona and Sanchez, 2007). According to projections of Lynd (1996), the reduction of production costs due to an advanced configuration involving the CBP is three times greater than the reduction related to the scale economy of the process and 10 times greater than the reduction associated with a lower cost of the feedstock. This diminish would be accomplished thanks to the reduction of more than eight times in the costs of biological conversion (Lynd et al., 1996). Lynd et al. (2005) reported the comparative simulation of SSCF and CBP processes assuming aggressive performance parameters intended to be rep­resentative of mature technology. Their results indicate that production costs of

ethanol for SSCF reach US4.99 cents/L including the costs of dedicated cellulase production, whereas CBP gives total costs of only US1.11 cents/L demonstrating the potential effectiveness of this process configuration.

Most studies on CBP of biomass contemplate the use of the thermophilic bacterium Clostridium thermocellum, which is employed for cellulase produc­tion, cellulose hydrolysis, and glucose fermentation. In addition, the bacterium Thermoanaerobacter thermosaccharolyticum can be co-cultured along with C. thermocellum to allow the simultaneous conversion of pentoses obtained from hemicellulose hydrolysis into ethanol (Cardona and Sanchez, 2007; Wyman, 1994). In particular, the CBP using C. thermocellum showed a substrate conversion 31% higher than a system using T. reesei and S. cerevisiae. South et al. (1993) tested the continuous CBP of cellulose into ethanol using C. thermocellum and showed, under very specific conditions with a residence time of 0.5 d, higher con­versions than a continuous SSF process. Some filamentous fungi such as Monilia sp., Neurospora crassa, and Paecilomyces sp. are also able to transform cellulose into ethanol (Szczodrak and Fiedurek, 1996). Nevertheless, this technique faces the problem of the low tolerance of clostridia to ethanol and the reduction in the ethanol yield due to the formation of acetic acid and salts of other organic acids like lactates (Baskaran et al., 1995; Cardona and Sanchez, 2007; McMillan, 1997; Wyman, 1994). This means that the final ethanol concentration is low in compari­son with the traditionally used yeasts (0.8 to 60 g/L) with very large cultivation times of 3 to 12 d (Szczodrak and Fiedurek, 1996).

To date, there is no microorganism known that can exhibit the whole com­bination of features required for the development of a CBP, as the one shown in Figure 6.5 (Chapter 6). However, there are realistic expectations about the possibility of overcoming the limitations of current CBP organisms. In Section 6.3.2.2, the main strategies for developing engineered microorganisms that can be used in technological configurations involving CBP were disclosed. In this way, the huge possibilities of CBP are based on the development of genetically modified microorganisms allowing such a high degree of reaction-reaction inte­gration that can make possible the direct conversion of pretreated lignocellu — losic biomass into ethanol at elevated yields under industrial conditions. Some examples of CBP, not only of lignocellulosic materials but also of starch, are presented in Table 9.5.

Cassava represents an important alternative source of starch not only for etha­nol production, but also for production of glucose syrups. In fact, cassava is the tuber that has gained the most interest due to its availability in tropical coun­tries, being one of the top 10 more important tropical crops. Ethanol production from cassava can be accomplished using either the whole cassava tuber or the starch extracted from it (Sanchez and Cardona, 2008). Starch extraction can be carried out through a high-yield, large-volume industrialized process as the Alfa Laval extraction method (FAO and IFAD, 2004), or by a traditional process for small- and midscale plants (see Chapter 3, Section 3.2.2.3). This process can be considered as the equivalent of the wet-milling process for ethanol produc­tion from corn. The production of cassava with high starch content (85 to 90% dry matter) and less protein and minerals content is relatively simple. Cassava starch has a lower gelatinization temperature and offers a higher solubility for amylases in comparison to corn starch. The hydrolysis of cassava flour has been proposed for glucose production in an enzymatic hollow-fiber reactor with 97.3%
conversion (Lopez-Ulibarri and Hall, 1997), considering that cassava flour pro­duction is simpler and more economic than cassava starch production. However, it is considered that cassava ethanol would have better economic indicators if the whole tuber were used as feedstock, especially when small producers are involved (Sanchez and Cardona, 2008). Fuel ethanol production from whole cas­sava is equivalent to ethanol production from corn by dry-milling technology. For this, cassava should be transported as soon as possible from cropping areas because of its rapid deterioration due to its high moisture content (about 70%). Hence, this feedstock should be processed within three to four days after its har­vest. One of the solutions to this problem consists in the use of sun-dried cassava chips (Sriroth et al., 2007). The farmers send the cassava roots to small chipping factories where they are peeled and chopped into small pieces. The chips are sun-dried for two to three days. The final moisture content is about 14% and the starch content reaches 65%.

The first step of the process in the distillery is the grinding of the dried cas­sava chips or fresh roots (if a permanent supply is ensured; Sanchez and Cardona, 2008). Milled cassava is mixed with water and undergoes cooking followed by the liquefaction process (Nguyen et al., 2008). Liquefied slurry is saccharified to obtain the glucose, which will be assimilated by the yeast during the next fer­mentation step. The process can be intensified through the SSF as in the case of corn (Figure 11.10). If fresh roots are employed, a fibrous material is obtained in the stillage after distillation. This material can be used as an animal feed similar to the DDGS produced in the corn-based process. The wastewater can be treated by anaerobic digestion to produce biogas, which can be used to produce steam and power for the process. Nevertheless, the amount of steam generated is not enough to cover the needs of the process. Hence, natural gas or other fossil fuel is required (Dai et al., 2006).

( Milling

FIGURE 11.10 Simplified diagram for fuelethanol production from cassava.

Carlos A. Cardona is associate professor in the Chemical Engineering Department at the National University of Colombia at Manizales since 1995. He received M. Sc. and Ph. D. degrees in chemical engineering from the Moscow State Academy of Fine Chemical Technology M. V. Lomonosov (Russian Federation). In addition, he has attended the especialization program in rheology at Moscow State University (Russian Federation) in 1994. From 1996 to 1997, he worked at the University of Caldas supporting a new program in food engineering. He has been twice awarded the research merit recognition by the National University of Colombia.

Dr. Cardona’s research focuses on process system engineering for biotechno­logical processes, process integration, separation technologies, thermodynamics, biofuels production, fermentation technology, and agro-industry. In particular, he has worked on different research projects concerning the chemical and biochemi­cal process design, biofuels research and development, economic and sustainable utilization of agro-industrial residues by biotechnological methods, and separation technologies development. He has authored or co-authored over 50 research papers as well as 5 research books and 14 book chapters. Additionally, he has edited two research books. He has presented over 100 works at scientific events. Dr. Cardona has been a visiting professor at several universities and research institutes abroad. Currently, he leads the research group in Chemical and Biochemical Processes Design at National University of Colombia at Manizales and coordinates the research area of biotechnology at the protechnology and agroindustry pilot plants at this university. In addition, he is a Food and Agriculture Organization (FAO) consultant in the field of technologies for sustainable bioenergy production.

Oscar J. Sanchez is associate professor of food engineering at the University of Caldas, Colombia. He received a chemical engineer­ing degree and M. Sc. degree in Biotechnology with the highest honors from the Moscow State Academy of Fine Chemical Technology M. V. Lomonosov (Russian Federation), and a Ph. D. degree with honors in engineering from the National University of Colombia at Manizales. From 1996 to 1997, he worked in the bever­age ethanol industry. He joined the faculty of engineering at the University of Caldas in 1997 where he coordinates the biotechnology course for food engineering students. In addition, he has taught biochemical engineering to chemical engineering students at the National University of Colombia at Manizales.

His research focuses on process systems engineering for biotechnological pro­cesses, biofuels production, industrial microbiology and fermentation technol­ogy, and enzyme technology. In particular, he has completed different research projects concerning the economic and sustainable utilization of agro-industrial residues by biotechnological methods. Dr. Sanchez has authored or co-authored over 15 research papers as well as 2 research books and 9 book chapters. He has presented over 20 works at scientific events. In 2005, Dr. Sanchez was awarded the Elizabeth Grose prize in the field of microbiology applied to the industry in the framework of the VII Latin American Congress of Food Microbiology. He was Honorary Research Fellow in the Department of Chemical Engineering of University College London in 2006. Currently, he co-leads the research group in foods and agro-industry at the University of Caldas and coordinates the research area of food biotechnology at the Institute of Agricultural Biotechnology of this university. In addition, he has been an FAO consultant in the field of technologies for sustainable production of fuel ethanol.

Luis F. Gutierrez received a chemical engi­neering degree from the National University of Colombia at Manizales, an M. Sc. degree in chemical engineering from the University of Valle (Colombia), and a Ph. D. degree with honors in engineering from the National University of Colombia at Manizales. From 2002 to 2003, he worked in the precious metal processing indus­try. His research focused on chemical thermo­dynamics, process integration, precious metals refining, alloy production, and computer-aided process design. In particular, he has worked on different research projects for the application of the thermodynamics to chemical processes, and analysis of biodiesel production technologies as well as equipment design for chemical and biochemical processes.

He has authored or co-authored over 6 research papers as well as 3 research books and 4 book chapters. He has given over 12 presentations in scientific events.

Dr. Gutierrez has held traineeships at Queen’s University (Canada) and the National Autonomous University of Mexico. He has been a research director of ITEMSA SA, a firm manufacturing chemical equipment. Currently, he is profes­sor in the Department of Engineering at the University of Caldas. In addition, he has been an FAO consultant in the field of technologies for sustainable production of biodiesel.

1 Biofuels

This chapter deals with the generalities of biofuels in the context of the current situation in the fossil fuels market. The importance of using alternative renew­able energy sources is highlighted and the main advantages of liquid biofuels are presented. The state of the global ethanol market is analyzed and the advantages and disadvantages of fuel ethanol are described.