The world production of seaweeds was some 8 million tons in 2003 (McHugh 2003). Seaweeds are used in the production of food, feed, chemicals, cosmetics, and phar­maceutical products.

Most microalgae are strictly photosynthetic, i. e., they need light and carbon diox­ide as energy and carbon sources. This culture mode is usually called photoau­totrophic. Some algae species, however, are capable of growing in darkness and of using organic carbons (such as glucose or acetate) as energy and carbon sources. This culture mode is termed heterotrophic.

Microalgae cultivation using sunlight energy can be carried out in open or cov­ered ponds or closed photobioreactors, based on tubular, flat plate, or other designs. Closed systems are much more expensive than ponds, present significant operating challenges (overheating, fouling), and, due to, among other things, gas exchange limitations, cannot be scaled up much beyond approx. 100 m2 for an individual growth unit.

The concept of using microalgae as a source of fuel is older than most people realize. The idea of producing methane gas from algae was proposed in the early 1950s. Currently there are three types of industrial reactors used for algal culture: (1) photobioreactors, (2) open ponds, and (3) closed and hybrid systems.

Photobioreactors are different types of tanks or closed systems in which algae are cultivated. Open-pond systems are shallow ponds in which algae are cultivated. Nutrients can be provided through runoff water from nearby land areas or by chan­neling the water from sewage/water treatment plants. Technical and biological lim­itations of these open systems have given rise to the development of enclosed pho­toreactors. Microalgae cultivation using sunlight energy can be carried out in open or covered ponds or closed photobioreactors, based on tubular, flat plate, or other de­signs. A few open systems are presented for which particularly reliable results are available. Emphasis is then put on closed systems, which have been considered to be capital intensive and are justified only when a fine chemical is to be produced. Mi­croalgae production in closed photobioreactors is highly expensive. Closed systems are much more expensive than ponds. However, closed systems require much less light and agricultural land to grow algae. High oil species of microalgae cultured in growth-optimized conditions of photobioreactors have the potential to yield 19,000 to 57,000 L of microalgal oil per acre per year. The yield of oil from algae is over 200 times the yield from the best-performing plant/vegetable oils (Chisti 2007).

Large-scale production of microalgal biomass generally uses continuous culture during daylight. In this method of operation, fresh culture medium is fed at a con­stant rate and the same quantity of microalgal broth is withdrawn continuously (Molina Grima et al. 1999). Feeding ceases during the night, but the mixing of broth must continue to prevent settling of the biomass (Molina Grima et al. 1999). As much as 25% of the biomass produced during daylight may be lost during the night due to respiration. The extent of this loss depends on the light level under which the biomass was grown, the growth temperature, and the temperature at night (Chisti 2007).

Algal cultures consist of a single or several specific strains optimized for pro­ducing the desired product. Water, necessary nutrients, and CO2 are provided in a controlled way, while oxygen has to be removed (Carlsson et al. 2007). Algae receive sunlight either directly through the transparent container walls or via light fibers or tubes that channel it from sunlight collectors. A great amount of devel­opmental work to optimize different photobioreactor systems for algae cultivation has been carried out and is reviewed in Janssen et al. (2003), Choi et al. (2003), Carvalho et al. (2006), and Hankamer et al. (2007).

Bioreactors are the preferred method for scientific researchers, and recently for some newer, innovative production designs. These systems are more expensive to build and operate; however, they allow for a very controlled environment. This means that gas levels, temperature, pH, mixing, media concentration, and light can be optimized for maximum production (Chisti 2007). Unlike open ponds, bioreac­tors can ensure a single alga species is grown without interference or competition (Campbell 2008).

A bioreflnery is a facility that integrates biomass conversion processes and equip­ment to produce fuels, power, and value-added chemicals from biomass. The biore­flnery concept is analogous to today’s crude oil refinery, which produces multiple fuels and products from petroleum. Bioreflnery refers to the conversion of biomass feedstock into a host of valuable chemicals and energy with minimal waste and emissions. In a broad definition, biorefineries process all kinds of biomass (all or­ganic residues, energy crops, and aquatic biomass) into numerous products (fu­els, chemicals, power and heat, materials, and food and feed). Figure 7.2 shows a schematic diagram of a biorefinery.

A biorefinery is a conceptual model for future biofuel production where both fuels and high-value coproduct materials are produced. Biorefineries can simultane­ously produce biofuels as well as bio-based chemicals, heat, and power. Biorefiner-

ies present more cost-effective options where bio-based chemicals are coproducts of liquid fuel. Future bioreflneries would be able to mimic the energy efficiency of modern oil refining through extensive heat integration and coproduct development. Heat that is released from some processes within the biorefinery could be used to meet the heat requirements for other processes in the system (WI2007).

Reliable designs of equipment for the thermochemical stages of biomass conver­sion have yet to be widely demonstrated and shown capable of continuously produc­ing synthesis gas of the required quality. Synthesis gas has to be free of nitrogen; this requires the use of oxygen (expensive), a pyrolytic process optimized for gas, or a multistage process. The main nontechnical barriers to acceptance of liquid bio­fuels, especially in the transport sector, relate to the costs of production, available markets, taxation policies, and legislation, as well as blending and distribution. From an economic point of view the use of agricultural crops, without subsidy, is too ex­pensive to produce either bioethanol or biodiesel at a price competitive with untaxed petrol or diesel fuel, while processes for using lower cost lignocellulosic materials have not been perfected. There are a number of pilot-scale and demonstration plants operating, under development, or planned with fully commercial developments not expected for another decade or two (GBRP 2007).

Developed and developing countries clearly have different goals in the develop­ment of biomass energy. Biomass energy is promoted in developed countries as a re­placement for fossil fuels, particularly in the transportation sector, whereas its use serves basic livelihood purposes in developing countries. Combining higher-value products with higher-volume energy production and employing any combination of conversion technologies has the greatest potential for making fuels, chemicals, ma­terials, and power from biomass competitive. Obtaining modern biofuels, biopower, and bioproducts from biomass can be realized only in integrated biorefineries. This chapter reviews current biorenewable fuel valorization facilities as well as the future importance of biorefineries. The development of biorefinery technologies is impor­tant, and these technologies are also very promising.

Broadly speaking, the term biorefinery can be thought of as a concept of mul­tiple products from various biomass feedstocks. A biorefinery processes biomass into value-added product streams. In theory, anything that uses biomass and makes more than one product is a biorefinery. A biorefinery is analogous to a petroleum refinery processing a range of crude oils. This very simple definition captures a wide range of existing, emerging, and advanced process concepts. Examples of existing biorefineries include corn processors and pulp and paper mills.

The concept is analogous to a combined use of fluid catalytic cracking, ther­mal cracking, and hydrocracking technology to convert the higher-boiling-range fractions of crude oil into more useful lower-boiling-range products. Just as few petroleum refineries use all available conversion technologies, biorefineries too will use only those technology platforms that are most cost effective for converting a cer­tain type of biomass into a certain collection of desired end products. For crops and agricultural waste, it would be better to convert the biomass into bio-oil near the farm and transport the high-density bio-oil to a central facility for processing rather than transporting the low-density biomass.

The bioreflnery concept attempts to apply to biomass conversion the methods that have been applied to the refining of petroleum. The goal is to maximize the value of the products obtained from the biomass. The goal of the integrated biorefin­ery program area is to support the establishment of integrated biorefineries through partnerships with industry and academia.

In previous economic studies of biodiesel production, the main economic factors such as capital cost, plant capacity, process technology, raw material cost, and chem­ical costs were determined (Zhang et al. 2003). The major economic factor to con­sider for the input costs of biodiesel production is the feedstock, which is about 75 to 80% of the total operating cost. Other important costs are labor, methanol, and catalyst, which must be added to the feedstock (Demirbas 2003). Using an estimated process cost, exclusive of feedstock cost, of US$0.158/L for biodiesel production, and estimating a feedstock cost of US$ 0.539/L for refined soy oil, an overall cost of US$ 0.70/L for the production of soy-based biodiesel was estimated (Haas et al.

2006) . Palm oil is the main option that is traded internationally, and with potential for import in the short term (Dene and Hole 2006). Costs for production from palm oil have been estimated; the results are shown in Table 5.4 (Dene and Hole 2006).

The oil in vegetable seeds is converted into biodiesel through oil extraction, oil refining, and transesterification. The cost of biodiesel can be lowered by increasing feedstock yields, developing novel technologies, and increasing the economic re­turn on glycerol production by finding other uses for this byproduct, which, at the moment, due to oversupply is sold for little or no value. Alternatively, the use of cosolvents, such as tetrahydrofuran, can consolidate the alcohol-oil-ester-glycerol system into a single phase, thereby reducing the processing costs (Granda et al.

2007) . However, these improvements still would not make biodiesel economically competitive at the current stage.

Biofuel production costs can vary widely by feedstock, conversion process, scale of production, and region. On an energy basis, ethanol is currently more expensive to produce than gasoline in all regions considered. Only ethanol produced in Brazil comes close to competing with gasoline. Ethanol produced from corn in the US is considerably more expensive than from sugar cane in Brazil, and ethanol from grain and sugar beet in Europe is even more expensive. These differences reflect many factors, such as scale, process efficiency, feedstock costs, capital and labor costs, coproduct accounting, and the nature of the estimates.

The cost of large-scale production of bio-based products is currently high in de­veloped countries. For example, the production cost of biofuels may be three times higher than that of petroleum fuels, without, however, considering the nonmarket benefits. Conversely, in developing countries, the costs of producing biofuels are much lower than in the OECD countries and very near to the world market price of petroleum fuel (UN 2006). Average international prices for common biocrude, fat, crops, and oils used as feedstock for biofuel production in 2007 are given in Table 5.5 (Demirbas 2008). The cost of feedstock is a major economic factor in the viability of biodiesel production. Nevertheless, the price of waste cooking oil is 2.5 to 3.5 times cheaper than virgin vegetable oils, and this can significantly re­duce the total manufacturing cost of biodiesel (Table 5.5). Biodiesel obtained from waste cooking vegetable oils is considered a promising option. Waste cooking oil

is available at relatively cheap prices for biodiesel production in comparison with fresh vegetable oil costs.

The economic advantages of a biofuel industry would include value added to feedstock, an increased number of rural manufacturing jobs, greater revenue from income taxes, investment in plant and equipment, reduced greenhouse gas emis­sions, reduction of a country’s reliance on crude oil imports, and support for agricul­ture by providing new labor and market opportunities for domestic crops. In recent years, the importance of nonfood crops has increased significantly. The opportu­nity to grow nonfood crops under the compulsory set-aside scheme is an option to increase biofuel production.

Renewable liquid fuels such as bioethanol, biodiesel, green diesel, and green gasoline are important because they replace petroleum fuels. It is generally consid­ered that renewable liquid fuels address many pressing concerns, including sustain­ability, reduction of greenhouse gas emissions, regional development, social struc­ture and agriculture, and security of supply.

The socioeconomic impacts on the local economy arising from providing power through renewable resources instead of conventionally generated technologies are very important. These impacts include direct and indirect differences in jobs, in­come, and gross output. There are significant socioeconomic impacts associated with the investment in a new power plant, including increases in employment, out­put, and income in the local and regional economy. Increases in these categories occur as labor is directly employed in the construction and operation of a power plant, as local goods and services are purchased and utilized.

The potential for reduced costs of renewable liquid fuels and conservation of scarce fuel resources results in significant reductions in fuel usage. In addition to these economic benefits, development of renewable resources will have environ­mental, health, safety, and other benefits.

Agricultural ethanol is at present more expensive than synthesis-ethanol from ethylene. The simultaneous production of biomethanol (from sugar juice) in parallel to the production of bioethanol, appears economically attractive in locations where hydroelectricity is available at very low cost (~US$ 0.01/kWh) (RFA 2007).

Currently there is no global market for ethanol. The crop types, agricultural prac­tices, land and labor costs, plant sizes, processing technologies, and government policies in different regions cause ethanol production costs and prices to vary con­siderably by region. The cost of producing bioethanol in a dry mill plant currently totals US$ 6.24/L. Corn accounts for 66% of operating costs while energy (electric­ity and natural gas) to fuel boilers and dry DDG represents nearly 20% of operating costs (Grassi 1999).

Ethanol from sugar cane, produced mainly in developing countries with warm climates, is generally much cheaper to produce than ethanol from grain or sugar beet in IEA countries. For this reason, in countries like Brazil and India, where sugar cane is produced in substantial volumes, sugar-cane-based ethanol is becoming an increasingly cost-effective alternative to petroleum fuels. Ethanol derived from cel — lulosic feedstock using enzymatic hydrolysis requires much greater processing than that derived from starch or sugar-based feedstock, but feedstock costs for grasses and trees are generally lower than for grain and sugar crops. If targeted reductions in conversion costs can be achieved, the total cost of producing cellulosic ethanol in OECD countries could fall below that of grain ethanol.

Estimates show that bioethanol in the EU becomes competitive when the oil price reaches US$ 70 a barrel while in the USA it becomes competitive at US$ 50 to $ 60 a barrel. For Brazil the threshold is much lower — between US$25 and US$30 a barrel. Other efficient sugar-producing countries such as Pakistan, Swaziland, and Zimbabwe have production costs similar to Brazil’s (Urbanchuk 2007). Anhydrous ethanol, blendable with gasoline, is still somewhat more expensive. Prices in India have declined and are approaching the price of gasoline.

The generally larger US conversion plants produce biofuels, particularly ethanol, at lower cost than plants in Europe. Production costs for ethanol are much lower in countries with a warm climate, with Brazil probably the lowest-cost producer in the world. Production costs in Brazil, using sugar cane as the feedstock, have recently been recorded at less than half the costs in Europe. Production of sugar cane ethanol in developing countries could provide a low-cost source for substantial displacement of oil worldwide over the next 20 years.

For biofuels, the cost of crop feedstock is a major component of overall costs. In particular, the cost of producing oil-seed-derived biodiesel is dominated by the cost of the oil and by competition from high-value uses like cooking. The largest ethanol cost component is the plant feedstock. Operating costs, such as feedstock cost, co­product credit, chemicals, labor, maintenance, insurance, and taxes, represent about one third of total cost per liter, of which the energy needed to run the conversion facility is an important (and in some cases quite variable) component. Capital cost recovery represents about one sixth of the total cost per liter. It has been shown that plant size has a major effect on cost (Dufey 2006). The plant size can reduce op­erating costs by 15 to 20%, saving another $0.02 to $0.03/L. Thus, a large plant with production costs of $0.29/L may save $0.05 to $0.06/L over a smaller plant (Whims 2002).

Biodiesel from animal fat is currently the cheapest option ($ 0.4 to $ 0.5/L), while traditional transesteriflcation of vegetable oil is at present around $ 0.6 to $ 0.8/L (IEA 2007). Rough projections of the cost of biodiesel from vegetable oil and waste grease are, respectively, $ 0.54 to $ 0.62/L and $ 0.34 to $ 0.42/L. With pretax diesel priced at $0.18/L in the USA and $0.20 to 0.24/L in some European countries, biodiesel is thus currently not economically feasible, and more research and tech­nological development will be needed (Bender 1999).

Carbon credits are a tradable permit scheme under the United Nations Framework Convention for Climate Change (UNFCCC), which gives the owner the right to emit one metric ton of carbon dioxide equivalent. They provide an efficient mechanism to reduce greenhouse gas (GHG) emissions by monetizing the reduction in emissions.

Global warming is caused by the emission of GHGs that get trapped in the at­mosphere. Table 8.1 shows the global warming (GW) potential of gases. The potent GHGs are carbon dioxide, methane, nitrous oxide, hydroflourocarbons, perflouro — carbons, and sulfur hexafluoride (Humbad et al. 2009).

CERs awarded =

Tons of GHG reduced x GW potential of the gas (metric tons of C) (8.2)

GW is an imminent catastrophe with irreversible consequences. The Kyoto Proto­col was adopted in Kyoto, Japan on 11 December 1997 and entered into force on 16 February 2005. One hundred eighty countries have ratified the treaty to date. It aims to reduce GHG emissions by 5.2% against the 1990 levels over the 5-year period 2008-2012. Developed countries are categorized under Annex 1 countries and are legally bound by the protocol, while the developing nations, categorized as Non-Annex 1 countries, which ratify the protocol, are not legally bound by it. The

Kyoto Protocol has three mechanisms: joint implementation (JI), a clean develop­ment mechanism (CDM), and international emission trading (IET).

The CDM mechanism allows Annex 1 countries to meet their reduction targets by implementing emission reduction projects in Non-Annex 1 developing nations. A certified emission reduction (CER) is a certificate given by the CDM board to projects in developing countries to certify that they have reduced GHG emissions by one metric ton of carbon dioxide equivalent per year. These CERs are bought by the Annex 1 countries to meet their emission reduction targets.

Under JI, an Annex 1 party may implement an emission reduction project or a project that enhances removal by sinks in another Annex 1 country. It can use the resulting emission reduction units (ERUs) for meeting its target. Under the IET mechanism, countries can trade their surplus credits in the international carbon cred­its market to those countries with quantified emission limitation and reduction com­mitments under the Kyoto Protocol.

The very long-chain polyunsaturated fatty acids (vlcPUFAs) eicosapentaenoic (EPA), docosahexaenoic acid (DHA), and arachidonic acid (AA) are well known for their nutritional importance. As they confer flexibility, fluidity, and selective permeability properties to cellular membranes, they have been shown to be vital for brain development and beneficial for the cardiovascular system and for other im­portant nutraceutical and pharmaceutical targets in human and animal health (Funk 2001; de Urquiza 2000; Colquhoun 2001). For example, vlcPUFAs are found in many different product applications including formulas for infants, adult dietary supplements, animal feed, food additives, and pharmaceutical precursors. These ap­plications represent an extensive market for vlcPUFAs: the world wholesale market for infant formula alone is estimated to be about $ 10 billion per annum (Ward and Singh 2005).

Animals lack the capability to synthesize vlcPUFAs, and therefore these essen­tial fatty acids must be obtained from food/feed. Typically sources of PUFAs are oil-rich fish such as eel, mackerel, herring, salmon, and sardines (Ward and Singh 2005). Due to concerns over declining fish stocks and the potential for fish oils to be contaminated by a range of pollutants, the possibilities for obtaining these fatty acids from other sources have been investigated (Qi et al. 2004). Interestingly, the vlcPUFAs in oil-rich fish originate from marine microalgae that are eaten by the fish. Algal genes encoding relevant enzymes have been identified, and recently several groups have reported progress on using these genes to produce DHA and ARA in transgenic plants, including crops such as soybean, linseed, tobacco, and the model species Arabidopsis (Qi et al. 2004; Abbadi et al. 2004). By adding addi­tional genes to those that are needed to produce ARA and EPA, production of DHA has been established in soybean, Brassica juncea, and Arabidopsis (Robert et al. 2005; Wu etal. 2005).

An alternative approach is to use directly the algae that are the most efficient primary producers of the vlcPUFAs. Algae groups that contain vlcPUFAs include diatoms, crysophytes, cryptophytes, and dinoflagellates (Cohen etal. 1995; Behrens and Kyle 1996). High amounts of DHA, for example, are produced in the algae Crypthecodinium cohnii, Thraustochytrium spp., Schizochytrium spp, Isochrysis galbana, and Crypthecodinium spp. (Ward and Singh 2005). The algae Porphyrid — ium cruentum and Parietochloris incise accumulate AA (Zhang et al. 2002; Guil — Guerrero et al. 2000) and several species have been suggested for the production of EPA including Nitzschia spp., Nannochloropsis spp., Navicula spp., Phaeodatylum spp., and Porphyridium spp. (Tan and Johns 1996; Sukenik 1991; Molina Grima et al. 2003; Cohen et al. 1995). For additional information about the content of vlcPUFAs in different microalgae see Barclay et al. (1994), Wen and Chen (2003), and Ward and Singh (2005). A slight inconvenience with using algal feedstocks di­rectly for the production of vlcPUFAs is that in many species the accumulation of these fatty acids involves their presence in lipids other than triacylglycerides such as galactolipids. This makes their isolation more complicated. For vlcPUFA produc­tion directly from microalgae it has been estimated that the cost of producing EPA from Phaeodactylum tricornutum cultured in photobioreactors is about $ 4602 kg-1 (Molina Grima et al. 2003).

Conventional processes used to harvest microalgae include concentration through centrifugation (Haesman et al. 2000), foam fractionation (Csordas and Wang 2004), flocculation (Poelman et al. 1997; Knuckey et al. 2006), membrane filtration (Ros — signol et al. 2000), and ultrasonic separation (Bosma et al. 2003). Harvesting costs may contribute 20 to 30% to the total cost of algal biomass (Molina Grima et al. 2003). Microalgae are typically small with a diameter of 3 to 30 pm, and the culture broths may be quite dilute at less than 0.5 g/L. Thus, large volumes must be handled. The harvesting method depends on the species, on the cell density, and often also on the culture conditions (Carlsson et al. 2007).

Algae pressing is very similar to the techniques used to press flowers and is used widely by scientists as a means of preserving algal specimens and observing their features.

Algae can be harvested by centrifugation, flocculation, or froth flotation. Alum and ferric chloride are chemical flocculants used to harvest algae. Water that is brackish or salty requires additional chemical flocculants to induce flocculation. Harvesting by chemical is a method that is often too expensive for large operations. However, interrupting the carbon dioxide supply to an algal system can cause algae to flocculate on its own, which is called “autoflocculation.” In froth flotation, the water and algae are aerated into froth and algae and then removed from the water.

The typical cell density achieved in the industrial application is between 0.3 and 0.5 g dry cell/L or 5 g dry cell/L at best, which makes harvest difficult and expensive (Wang et al. 2008). Two processes are involved in harvesting, bulk harvesting and thickening. Bulk harvesting is a large-scale operation separating biomass from bulk culture. It has a concentration factor of 100 to 800 times, depending on the culture and harvesting method. Bulk harvesting can be categorized into flocculation and floatation. Flocculation reduces/neutralizes the negative surface charge of microal­gal cells, allowing them to aggregate into larger lumps with an efficiency of >80. The thickening process consists of either centrifugation or filtration. Centrifugation, a semicontinuous or continuous process, utilizes centrifugal force generated by the spinning of a suspension to separate and harvest algal cells.

For mass cultivation of algae, optimization of algae harvesting and processing is needed. Algae properties such as algae size, cell wall sensitivity to shear force, ease of flocculation, and oil content need to be taken into consideration in the design process.

There are a lot of technical and nontechnical gaps and barriers related to the imple­mentation and commercialization of the biorefinery. Current technical barriers with the use of energy crops are associated with the cost of production and difficulties in harvesting and storing the material grown, especially for annual or other crops that have to be harvested within a narrow time period in the autumn. Transportation costs are of prime importance when calculating the overall cost of biomass; hence local or regional production of biomass is most favorable. Other technical problems associated with growing energy crops include provision of nutrients and control of pests and disease.

The major nontechnical barriers are restrictions or prior claims on use of land (food, energy, amenity use, housing, commerce, industry, leisure, or designated ar­eas of natural beauty, special scientific interest, etc.), as well as the environmental and ecological effects of large areas of monoculture. For example, vegetable oils are a renewable and potentially inexhaustible source of energy with an energy content close to that of diesel fuel. On the other hand, extensive use of vegetable oils may cause other significant problems such as starvation in developing countries. Veg­etable oil fuels are not acceptable because they were more expensive than petroleum fuels.

In addition to the technical challenges of commercializing advanced biorefiner­ies, there are also large infrastructure barriers. These barriers are associated with the development of new agricultural infrastructure for the collection and storage of crop wastes. An integrated feedstock supply system must be developed that can supply the feedstock needs in a sustainable fashion at a reasonable cost. Infrastruc­ture issues could be as significant as the technical issues when considering overall production costs.

A number of studies with comparisons of diesel, natural gas, and diesel/biodiesel blend bus emissions have been published (Janulis 2004; Tzirakis et al. 2007; Krahl et al. 2009; Soltic et al. 2009; Coronado et al. 2009). Biodiesel has a good energy return because of the simplicity of its manufacturing process, has significant benefits in emissions as well, and could also play an important role in the energy economy if higher crop productivities are attained (Granda et al. 2007).

Table 5.6 shows the emissions of biodiesel (B20 and B100) for same model compression-ignition (diesel) vehicles (Demirbas 2009a). Emissions of NOx in­crease with increasing biodiesel amounts in blends. The properties of biodiesel and diesel fuels, in general, show many similarities, and therefore biodiesel is rated as a realistic fuel as an alternative to diesel. There are several ways to control NOx in a biodiesel engine. One could run the engine very lean, which lowers the tem­perature, or very rich, which reduces the oxygen supplies, decrease the burn time. Emissions of NOx increase with the combustion temperature, the length of the high — temperature combustion period, and the availability of biodiesel, up to a point.

Alcohols have been used as a fuel for engines since the 19th century. Among the various alcohols, ethanol is known as the most suited renewable, bio-based, and eco-friendly fuel for spark-ignition (SI) engines. The most attractive properties of ethanol as an SI engine fuel are that it can be produced from renewable energy

sources such as sugar, cane, cassava, many types of waste biomass materials, corn, and barley. In addition, ethanol has a higher evaporation heat, octane number, and flammability temperature; therefore it has a positive influence on engine perfor­mance and reduces exhaust emissions. The results of an engine test showed that ethanol addition to unleaded gasoline increases engine torque, power, and fuel con­sumption and reduces carbon monoxide (CO) and hydrocarbon emissions (Demir — bas 2009a).

The biodiesel impacts on exhaust emissions vary depending on the type of biodiesel and on the type of conventional diesel. Blends of up to 20% biodiesel mixed with petroleum diesel fuels can be used in nearly all diesel equipment and are compatible with most storage and distribution equipment. Using biodiesel in a conventional diesel engine substantially reduces emissions of unburned hydrocar­bons, carbon monoxide, sulfates, polycyclic aromatic hydrocarbons, nitrated poly­cyclic aromatic hydrocarbons, and particulate matter. These reductions increase as the amount of biodiesel blended into diesel fuel increases. In general, biodiesel in­creases NOx emissions when used as fuel in a diesel engine. The fact that NOx emissions increase with increasing biodiesel concentration could be a detriment in areas that where ozone forms. The pollutant emissions of ethanol-gasoline blends of 0, 5, 10, 15, and 20% were experimentally analyzed in a four-stroke (SI) engine. The concentration of CO and HC emissions in the exhaust pipe were measured and found to decrease when ethanol blends were introduced. This was due to the high oxygen percentage in the ethanol. In contrast, the concentration of CO2 and NOx was found to increase when ethanol was introduced (Najafl et al. 2009).

Oxygenated diesel fuel blends have the potential to reduce the emission of par­ticulate matter and to be an alternative to diesel fuel. Results obtained showed that the addition of bioethanol to the diesel fuel may be necessary to decrease diesel par­ticulate matter generation during combustion (Corro and Ayala 2008; Yu and Tao 2009). The total number and total mass of the particulate matter of ethanol-diesel blend fuels were decreased by about 11.7 to 26.9% (Kim and Choi 2008).

An experimental investigation was conducted to evaluate the effects of using blends of ethanol with conventional diesel fuel, with 5 and 10% (by vol.) ethanol, on the performance and exhaust emissions of a fully instrumented, six-cylinder, tur­bocharged and after-cooled, heavy-duty, direct-injection, Mercedes-Benz engine. Fuel consumption, exhaust smokiness, and exhaust-regulated gas emissions such as nitrogen oxides, carbon monoxide, and total unburned hydrocarbons were mea­sured. The differences in the measured performance and exhaust emissions of the two ethanol-diesel fuel blends from the baseline operation of the engine, i. e., when working with neat diesel fuel, were determined and compared (Rakopoulos et al.

2008) . Diesel emissions were measured from an automotive engine using anhy­drous bioethanol blended with conventional diesel, with 10% ethanol in volume and no additives. The resulting emissions were compared with those from pure diesel (Lapuerta et al. 2008)

The results of the statistical analysis suggest that the use of E10 results in sta­tistically significant decreases in CO emissions (—16%); statistically significant increases in emissions of acetaldehyde (108%), 1,3-butadiene (16%), and ben­zene (15%); and no statistically significant changes in NOx, CO2, CH4, N2O, or formaldehyde emissions. The statistical analysis suggests that the use of E85 results in statistically significant decreases in emissions of NOx (—45%), 1,3-butadiene (—77%), and benzene (—76%); statistically significant increases in emissions of formaldehyde (73%) and acetaldehyde (2,540%), and no statistically significant change in CO and CO2 emissions (Graham et al. 2008).

Biofuels are important because they replace petroleum fuels. There are many benefits for the environment, economy, and consumers in using biofuels. The ad­vantages of biofuels such as biodiesel, vegetable oil, bioethanol, biomethanol, biomass pyrolysis oil as engine fuel are liquid nature-portability, ready availabil­ity, renewability, higher combustion efficiency, lower sulfur and aromatic content and biodegradability. The biggest difference between biofuels and petroleum feed­stocks is oxygen content. Biofuels have oxygen levels of 10 to 45%, while petroleum has essentially none, making the chemical properties of biofuels very different from those of petroleum. Oxygenates are just preused hydrocarbons having a structure that provides a reasonable antiknock value. Also, as they contain oxygen, fuel com­bustion is more efficient, reducing hydrocarbons in exhaust gases. The only disad­vantage is that oxygenated fuel has less energy content.

Combustion is the chemical reaction of a particular substance with oxygen. It is a chemical reaction during which from certain matters other simple matters are produced. This is a combination of inflammable matter with oxygen from the air ac­companied by heat release. The quantity of heat involved when one mole of a hydro­carbon is burned to produce carbon dioxide and water is called the heat of combus­tion. Combustion to produce carbon dioxide and water is characteristic of organic compounds; under special conditions it is used to determine their carbon and hy­drogen content. During combustion the combustible part of fuel is subdivided into volatile parts and solid residue. During heating it evaporates together with some carbon in the form of hydrocarbons, combustible gases, and carbon monoxide re­lease by thermal degradation of the fuel. Carbon monoxide is mainly formed by the following reactions: first from a reduction in CO2 with unreacted C,

CO2 C C! 2CO (5.2)

and, second, from the degradation of carbonyl fragments (-CO) in fuel molecules at temperatures of 600 to 750 K.

The combustion process is started by heating the fuel above its ignition temper­ature in the presence of oxygen or air. Under the influence of heat, the chemical bonds of the fuel are cleaved. If complete combustion occurs, the combustible ele­ments (C, H, and S) react with the oxygen content of the air to form CO2, H2O, and, mainly, SO2.

If insufficient oxygen is present or the fuel and air mixture is insufficient, then the burning gases are partially cooled below the ignition temperature and the com­bustion process stays incomplete. The flue gases then still contain combustible com­ponents, mainly carbon monoxide (CO), unburned carbon (C), and various hydro­carbons (CxHy).

The standard measure of the energy content of a fuel is its heating value (HV), sometimes called the calorific value or heat of combustion. In fact, there are multiple values for the HV, depending on whether it measures the enthalpy of combustion (AH) or the internal energy of combustion (AU), and whether for a fuel containing hydrogen product water is accounted for in the vapor phase or the condensed (liquid) phase. With water in the vapor phase, the lower heating value (LHV) at constant pressure measures the enthalpy change due to combustion (Jenkins et al. 1998). The HV is obtained by the complete combustion of a unit quantity of solid fuel in an oxygen-bomb colorimeter under carefully defined conditions. The gross heat of combustion or higher heating value (GHC or HHV) is obtained by the oxygen — bomb colorimeter method as the latent heat of moisture in the combustion products is recovered.

Energy is an essential input for social development and economic growth. The role of energy as an essential catalyst to economic growth and an enhanced standard of living is a reality that policymakers should factor into their decisions and when evaluating environmental, economic, and social goals. The International Energy Agency estimates that world energy demand will increase by half again between now and 2030, with more than two thirds of this increase coming from developing and emerging countries. The population of developing countries is estimated to dou­ble by 2055, while the population of the industrial countries will increase by only 15% over the same period. New conventional fuel explorations, energy wars, and political maneuvers will not prevent the production of nonconventional fuels and the continuing evolution of a truly global energy market.

There are several reasons why biofuels are considered relevant technologies by both developing and industrialized countries. They include energy security reasons, environmental concerns, foreign exchange savings, and socioeconomic issues re­lated to the rural sectors of all countries in the world. Biofuels could be peaceful energy carriers for all countries.

Bioenergy offers opportunities for additional value to be derived from products already in the economy. The dispersed nature of most biomass resources lends it­self to smaller-scale operations of up to 50 MW. These are within the capability of communities to feed and operate, creating and retaining wealth within the local economy.

New employment opportunities arise in growing and harvesting biomass, trans­port and handling, and plant operation. They also extend to equipment manufactur­ers and maintenance crews. Farmers may improve returns as marginal crops become viable, giving an additional source of income from energy byproducts. Degraded forests may be rejuvenated and waste streams diverted to produce energy.

Bioenergy can also contribute to local and national energy security, which may be required to establish new industries. Bioenergy contributes to all important ele­ments of national/regional development: economic growth through business earn­ings and employment, import substitution with direct and indirect effects on GDP and trade balance, and security and diversification of energy supply. Other bene­fits include support of traditional industries, rural diversification, and the economic development of rural societies. These are all important elements of sustainable de­velopment.

At the same time, global population and affluence growth have caused upward pressure on food prices, which has led to food insecurity in the developing world. Conversion of corn into ethanol, or the use of arable land and fresh water for biofuel crops like corn, sugar cane, or jatropha, has exacerbated this situation and linked food and energy in a dangerous way.

To satisfy energy needs and avoid putting pressure on foodstocks, an alternative biofuel is needed. Water algae’s superior yields, combined with its ability to grow without arable land or fresh water, mean that algae is a far better biofuel candidate to replace oil than any land crop. An algaecentric energy-independence strategy would provide greater energy security while promoting poor-country development and without threatening food security.

6.1 Introduction

Continued use of petroleum sourced fuels is now widely recognized as unsustainable because of depleting supplies and the contribution of these fuels to the accumulation of carbon dioxide in the environment. Renewable, carbon-neutral transport fuels are necessary for environmental and economic sustainability (Chisti 2007). Biodiesel can be carbon neutral and produced intensively on relatively small areas of marginal land. The quality of the fuel product is comparable to petroleum diesel and can be incorporated with minimal change into the existing fuel infrastructure. Innovative techniques, including the use of industrial and domestic waste as fertilizer, could be applied to further increase biodiesel productivity (Campbell 2008).

Algae, like corn, soybeans, sugar cane, wood, and other plants, use photosynthe­sis to convert solar energy into chemical energy. They store this energy in the form of oils, carbohydrates, and proteins. The plant oil can be converted into biodiesel; hence biodiesel is a form of solar energy. The more efficient a particular plant is at converting that solar energy into chemical energy, the better it is from a biodiesel perspective, and algae are among the most photosynthetically efficient plants on earth.

Algae can be a replacement for oil-based fuels, one that is more effective and has no disadvantages. Algae are among the fastest growing plants in the world, and about 50% of their weight is oil. This lipid oil can be used to make biodiesel for cars, trucks, and airplanes. Microalgae have much faster growth rates than terres­trial crops. The per-unit area yield of oil from algae is estimated to be between 20,000 and 80,000L/acre/year; this is 7 to 31 times greater than the next best crop, palm oil. The lipid and fatty acid contents of microalgae vary in accordance with culture conditions. Most current research on oil extraction is focused on microal­gae to produce biodiesel from algal-oil. Algal-oil can be processed into biodiesel as easily as oil derived from land-based crops.

The production of microalgal biodiesel requires large quantities of algal biomass. Macro — and microalgae are currently mainly used for food, in animal feed, in feed

A. Demirbas, M. Fatih Demirbas, Algae Energy DOI 10.1007/978-1-84996-050-2, © Springer 2010

for aquaculture, and as biofertilizer. A 1-ha algae farm on wasteland can produce over 10 to 100 times as much oil compared to any other known source of oil crops. While a crop cycle may take from 3 months to 3 years for production, algae can start producing oil within 3 to 5 d, and thereafter oil can be harvested on a daily basis (just like milk). Algae can be grown using sea water and nonpotable water on wastelands where nothing else grows. Algae farming for biofuels is expected to provide a conclusive solution to the food vs. fuel debate.

The production of biodiesel has recently received much attention worldwide. In order to resolve the worldwide energy crisis, seeking for lipid-rich biological materi­als to produce biodiesel effectively has attracted much renewed interest. Algae have emerged as one of the most promising sources for biodiesel production. It can be inferred that algae grown in CO2-enriched air can be converted into oily substances. Such an approach can contribute to solving the major problems of air pollution re­sulting from CO2 emissions and future crises due to a shortage of energy sources (Sharif Hossain et al. 2008).