One of the great merits of bioethanol consists in the enormous variety of raw materials, and not only plants, from which it can be produced. The production methods vary depending on whether or not the raw material is rich in fiber.

The basic materials for producing biofuels must have certain features, including high carbon and hydrogen concentrations and low concentrations of oxygen, nitrogen and other organic components. The following is a brief description of some of the most important raw materials suitable for use in bioethanol production.

1.2 Alfalfa (medicago sativa)

This is a lucerne of the Fabaceae family that grows in cool subtropical and warm temperate regions. It demands no nitrogen-based fertilizers and its leaves are a precious source of protein in animal fodder. In a recent paper (Dien et al., 2006) it was observed that this plant has a low glucose yield due to a low-efficiency cellulose hydrolysis. The stems contain high concentrations of crude proteins and organic acids.

The surface area of biofuel cells determines its amperage, meaning that cell power is directly proportional to the electrode surface area. A conventional 2D power system is typically a parallel arrangement of a planar cathode and an anode separated by a solid or liquid electrolyte. More recently, carbon-microelectromechanical (C-MEMS) fabrication technology has offered the flexibility to fabricate complex carbon-based EBFCs, with 3D dense microelectrode arrays. C-MEMS, describes a manufacturing technique in which carbon microstructures are fabricated by baking UV sensitive polymers at high temperatures in an inert environment. It has been demonstrated that 3D high-aspect-ratio carbon structures can be made from carbonizing (pyrolysis) patterned NANO™ SU-8 negative photoresist (Wang et al., 2005). The four steps involved in converting organic polymer to pyrolytic carbon is shown as schematic in Fig. 1. Positive photoresist (AZ4620, AZ1518) as well as negative photoresist (SU-8) can be converted to carbon by pyrolysis depending on the application. Electrodes based on 3D microstructures are expected to offer higher surface area and significant advantages in comparison to thin-film devices for powering MEMS and miniaturized electronic devices.

2.1 C-MEMS microelectrodes

Fig. 2. shows the various carbon architectures possible using C-MEMS technique. The versatility in the technique gives us the opportunity to integrate nanofeatures such as suspended carbon nanowires, carbon nanofibers with microelectrodes (Wang et al., 2005; Malladi et al., 2006).

Besides, in order to increase the surface area, we reported a modified C-MEMS process using a block copolymer F127 as porogen capable of producing porous carbon microelectrodes (Penmatsa et, al., 2010). These results indicated that porous carbon thin film electrodes derived from 10% F127 mixed in SU-8 had an Aeff 185% compared to the conventional photoresist derived carbon electrode. This fabrication approach can be employed to produce reproducible high aspect ratio carbon microelectrodes with different shapes for various electrochemical devices.

Although the 3D structures compared to 2D planar electrodes or thin films have advantages, such as an increase in the surface area and power density for same foot print area, there are yet certain important issues which need to be addressed in order to use these structures effectively. Anandan and Godino have studied the mass transport phenomenon in micro and nano-electrodes by finite element analysis approach. They suggest that in order to accommodate the specific analyte species in terms of reaction kinetics and mass transport, it is necessary to optimize the geometry of nanopillars (their diameter, spacing and height), to reap the true benefit of using micro-nanostructured electrodes for enhancing the performance of biosensors. They reveal that the glucose immediately react with the top portions of the nanopillars due to higher reaction rate of enzymes and hence the bottom portion of the pillars lack the diffusion of glucose, which may not be favorable to improve the performance of EBFC. Jeffrey suggests that in contrast to the 2D electrodes, in which uniform current density is naturally obtained over the surface of the cathodes and anodes, the current density in the 3D
microelectrode array suffer from a non-uniform primary current distribution. These non­uniform currents result in utilization of the electrode materials and are thus associated with lower cell efficiencies, reduced electrodes stability due to non-uniform stresses, and non­uniform heat dissipation. Therefore, it is essential to optimize the geometries of electrodes to homogenize the current density distribution around microelectrodes surfaces.

In the later section, we introduced finite element method based simulative approach to understand the effect of 3D design rule and spatial distributions of the microelectrodes in the arrays with respect to the mass transport of glucose, enzymatic reaction rate and open circuit output potential.

Oleaginous microorganisms are microbes with an oil content that exceeds 20%. Biodiesel production from microbial lipids (known as single-cell oil or microdiesel) has attracted great attention worldwide. Although microorganisms that store oils are found among various microbes (such as microalgae, bacillus, fungi and yeast), not all microbes are suitable for biodiesel production (Demirbas, 2010).

Most bacteria are generally not good oil producers. Some exceptions are actinomycetes, which are capable of synthesizing remarkably high amounts of fatty acids (up to ~70% of their dry weight) from simple carbon sources such as glucose under growth-restricted conditions and which accumulate these fatty acids intracellularly as triglycerides (Alvarez & Steinbuchel, 2002).

The most efficient oleaginous yeast, Cryptococcus curvatus, can accumulate >60% lipids when grown under nitrogen-limiting conditions. These lipids are generally stored as triglycerides with approximately 44% percent saturated fatty acids, which is similar to many plant seed oils. Rhodotorula glutinis has been used for the wastewater treatment in monosodium-glutamate manufacturing. Monosodium-glutamate wastewater is as a cheap fermentation broth for the production of biodiesel using lipids from R. glutinis. To be efficient, the fermentation process needs a complementary source of glucose to obtain the proper C:N:P ratio (1:2.4:0.005). This process leads to a lipid production corresponding to 20% of the biomass after 72 h of culture and to an oil transesterification rate of 92% (Xue et al., 2008). In addition, R. glutinis can use various carbon sources including dextrose, xylose, glycerol, dextrose and xylose, xylose and glycerol, or dextrose and glycerol and can accumulate 16, 12, 25, 10, 21, and 34% triglycerides, respectively. The rate of unsaturated fatty acid accumulation was found to depend on the carbon source, with 25% and 53% accumulation when R. glutinis was grown on xylose and glycerol, respectively (Easterling et al., 2008). These results indicate that the use of R. glutinis can add value to several by-products, including glycerol. However, the resulting high levels of unsaturated fatty acids may require some additional saturation step to meet biodiesel standards.

Cyanobacteria are gram-negative photoautotrophic prokaryotes that can be cultivated under aqueous conditions ranging from freshwater to extreme salinity. They are able to produce a wide range of fats, oils, sugars and functional bioactive compounds such that their inclusion to wastewater treatment processes has been proposed (Markou & Georgakakis, 2011). Their duplication time is 3.5 h in the log phase of cell multiplication (Chisti, 2007). Using light energy, they are able to convert carbon substrates into oil (with a fatty acid composition that is similar to that of plants) at a rate of 20-40% of dry biomass (Meng et al., 2008).

Although microalgae are high-lipid-storing microbes, they require larger areas and longer fermentation times than do bacteria. The microalgae market produces approximately 5,000 t of dry biomass/year and generates approximately US$ 1.25 bn/yr (Pulz & Gross, 2004).

Eukaryotic diatoms, green algae and brown algae isolated from oceans and lakes typically reach dry-mass levels of 20%-50% lipids (Brennan & Owende, 2010). The quantities of lipids found in microalgae can be extraordinarily high. In Botryococcus, for instance, the concentration of hydrocarbons may exceed 80% of the dry matter. In comparison, dry — biomass plant oil levels are generally around 15-40% lipids (Spolaore et al., 2006).

There are approximately 300 strains of algae, among which diatoms (including genera Amphora, Cymbella, and Nitzschia) and green algae (particularly genera Chlorella) that are the most suitable for biodiesel production. The oil is accumulated in almost all microalgaes as triglycerides (>80%) that are rich in C16 and C18 (Meng et al., 2008). Lipid accumulation in oleaginous microorganisms begins with nitrogen exhaust or when carbon is in excess (Ratledge 2002).

Chlorella protothecoides can accumulate lipids at a rate of 55% by heterotrophic growth under CO2 filtration. Large quantities of microalgal oil have been efficiently recovered from these heterotrophic cells by n-hexane extraction. The microdiesel from heterotrophic microalgal oil obtained by acidic transesterification is comparable to fossil diesel and should be a competitive alternative to conventional biodiesel because of higher photosynthetic efficiency, larger quantities of biomass, and faster growth rates of microalgae as compared to those of plants (Song et al., 2008).

As stated above, microalgal oils differ from most plant oils in being quite rich in polyunsaturated fatty acids with four or more double bonds (Belarbi et al., 2000). This makes them susceptible to oxidation during storage and reduces their suitability for commercial biodiesel (Chisti, 2007). However, fatty acids with more than four double bonds can be easily reduced by partial catalytic hydrogenation (Dijkstra, 2006).

Changes in the degree of fatty acid unsaturation and the decrease or increase of fatty acid length are major challenges in modifying the lipid composition of microalgal oils. These features are regulated by enzymes that are mostly bounded to the cell membrane, which complicates their investigation (Certik & Shimizu, 1999). Currently, most of the genetic manipulations that have aimed to optimize metabolic pathways have been carried out on oleaginous microorganisms. This is mainly because of their abilities to accumulate high amounts of intracellular lipids, their relatively fast growth rates and their similarities of oil composition with plants (Kalscheuer et al., 2006a, 2006b).

Microalgae are often used for the sequestration and recycling of CO2 by "CO2 filtration" (Haag, 2007) and can reduce CO2 exhaust by 82% on sunny days and by 50% on cloudy days (Vunjak-Novakovic et al., 2005). This process is much more elegant than carbon storage (CCS) in depleted oil fields or in aquifers because the carbon can be recycled via microdiesel. The storage capacity of CCS is estimated to range between 2,000-11,000 Gt CO2; however, such aquifers are not evenly distributed around the world (Schiermeier et al., 2008). In addition, CCS does not result in any profit from the CO2 that is stored and is actually an additional cost in the whole process. In contrast, algae convert CO2 into oil. This means that the energy contained in the CO2 can be re-injected into the power plant after being filtered by the algae and transformed into microdiesel.

The stimulation of fish production by increasing phytoplankton biomass through CO2 injection into specific ocean localities has also been proposed (Markels & Barber, 2001). However, ocean fertilization has been severely challenged because it would eventually destroy the local ecosystem (Bertram, 2010; Glibert et al., 2008).

The organic matter in landfills tend to undergo anaerobic fermentation yielding methane and CO2 [14], which if naturally vented into the atmosphere would add to the greenhouse emissions that warm the climate. And the climate change impact of methane is 25 times larger than that of carbon dioxide for a time horizon of 100 years [15]. Thus, there is a need to sequester the carbon present in landfill methane. Nano-catalysts can crack methane into elemental carbon and hydrogen. The carbon can be produced in high-purity nano-graphite for use in aerospace, automobile, batteries, etc. This approach to handling methane can considerably improve the economics of landfills as well as of anaerobic digester plants that generate electricity from biogas fueled electricity.

Shuangning Xiu, Bo Zhang and Abolghasem Shahbazi

Biological Engineering Program School of Agriculture, NC A&T State University

U. S.A

1. Introduction

The development of products derived from biomass is emerging as an important force component for economic development in the world. Rising oil prices and uncertainty over the security of existing fossil reserves, combined with concerns over global climate change, have created the need for new transportation fuels and for the manufacture of bioproducts to substitute for fossil-based materials.

The United States currently consumes more than 140 billion gallons of transportation fuels annually. Conversion of cellulosic biomass to biofuels offers major economic, environmental, and strategic benefits. DOE and USDA predict that the U. S. biomass resources could provide approximately 1.3 billion dry tons of feedstock for biofuels, which would meet about 40% of the annual U. S. fuel demand for transportation (Perlack et al., 2005). More recently, in January 2010, U. S. President Barack Obama delivered a request during his State of the Union speech for Congress to continue to invest in biofuels and renewable energy technology. Against this backdrop, biofuels have emerged as one of the most strategically important sustainable fuels given their potential to increase the security of supply, reduce vehicle emissions and provide a steady income for farmers.

Several biorefinery processes have been developed to produce biofuels and chemicals from the initial biomass feedstock. Of all the various forms energy can take, liquid fuels are among the most convenient in terms of storage and transportation and are conducive to the existing fuel distribution infrastructure. This chapter comprehensively reviews the state of the art, the use and drawbacks of biorefinery processes that are used to produce liquid fuels, specifically bioethanol and bio-oil. It also points out challenges to success with biofuels in the future.

Modern production of industrial composts is based on an idea that the compost is a substrate for plants with nutrient content. This is the reason why attention is mainly paid to the mechanical treatment of organic material — grinding, crushing and homogenisation. A homogenised blend, enriched with nutrients, applied water and/or compost additives, is subjected to fast fermentation. It is turned at the same time and homogenised again. The turning ensures a new supply of oxygen and if the compost has a sufficient amount of easily degradable organic matter, the temperature during composting increases up to 50 — 60°C, which allows a desirable breakdown of particles of the original organic material. The product acquires a dark colour, it is loose, often has a pleasant earthy smell while the odour of the original organic material is not perceptible any more. Farm sludge is often added to the compost formula as a nitrogen source or the improper C to N ratio is adjusted by the addition of mineral nitrogenous fertilisers. Slurry and liquid manure are used as an N and water source and sometimes limestone is added to prevent acidification. The aeration of the fermented pile of materials is provided by the addition of inert coarse-grained materials, mainly of wood chips, crushed straw, rubble, undecomposable organic waste and other materials available from local sources, whereas the use of horizontal and vertical ventilation systems is less frequent. It is often the type of "aeration" additive which explicitly shows that the compost producer prefers waste processing to the interest of future users of their products, farmers and productivity of their soils. The ion-exchange capacity of these composts is about 40 — 80 mmol chem. eq. 1000 g-1 and it is very low. It characterises a light, little fertile sandy soil.

How is the real "genuine" compost produced? The following principles should be observed:

1. Organic material of the compost formula should have a high degree of lability. If the compost producer does not have a sufficient amount of such very easily degradable organic material, its lability should be enhanced by saccharidic waste.

2. The C : N ratio should be adjusted to the value 10 — 15 : 1, not to total C and total N, but to the value of Chws and Nhws (hot water extractable carbon and nitrogen). Obviously, it is not worth adding to the compost a nitrogen source e. g. in waste polyamide because this nitrogen is not accessible. It is a flagrant example but we have detected many times that the C : N ratios are completely different from those the compost producers suppose them to be.

3. The compost formula should have a high proportion of buffering agent. It should always be ground limestone or dolomite, it should never be burnt or slaked lime. Do not economize on this additive very much. It will be utilised excellently after the application of this compost to soils.

4. Stabilisation of organic matter should be ensured by a sufficient amount of the clay mineral fraction. It must not be applied in lumps, but in the form of clay slurry, clay water suspension, used also for the watering of the blend of compost materials. Concrete mixers are ideal equipment for the preparation of clay slurry.

5. The compost blend should be inoculated by healthy fertile topsoil. Soil microorganisms are adapted in a different way than the microorganisms of the intestinal tract of animals. Therefore slurry and liquid manure are sources of water and nitrogen but they are not a suitable inoculant even though they are often recommended in literature for this purpose.

6. The basic requirement is to reach a high temperature (55 — 60°C) during composting and to maintain the second phase of temperature (40 — 50°C) for a sufficiently long time. This process will be successful only at a sufficiently high amount of highly labile organic matter in the compost formula, at a correct C : N ratio, at a correct water to air ratio in the pile (the moisture during fermentation should be maintained in the range of 50 — 60% of water-retention capacity) and at a reduction in heat losses. Heat losses of the compost into the atmosphere through the pile surface are relatively small. The highest quantity of heat is lost by conducting the heat through the concrete or the frozen ground of the compost pile, and mainly by an aerating system if it is installed.

7. Humification processes, formation of humus acids and humins or their precursors at least, occur rather in later stages of fermentation and so we should accept that the good compost cannot be produced by short-term fermentation. Old gardeners fermented composts for 10 — 12 years, but their composts reached the ion-exchange capacity of 300 — 400 mmol chem. eq. 1000 g-1.

Aleksander Ryzhkov, Vadim Silin, Tatyana Bogatova, Aleksander Popov and Galina Usova

Ural Federal University named after the first President of Russia B. N.Yeltsin

Russia

1. Introduction

In Russia exploitation of local low-grade fuels assumes the usage of bio fuels for a variety of purposes. The development of advanced combustion and gas-generating facilities operating on low-grade fuel requires the knowledge of burning and gasification processes in moderate low-temperature combustion modes.

As is known, the amount and quality of fuel particle surface open for reaction with oxidizing agent is most important for the rate of thermochemical conversion. Under comparable conditions the fuel having the largest reaction surface will have the highest rate of burn out. In qualitative terms, the properties of internal surface that formed long before it entered the furnace (reactor) and those that are forming directly in the furnace may differ. Gasification of the above fuels in autothermal mode produces gas with high content of complete combustion products (СО2 and Н2О) and hydrocarbons and low chemical efficiency. To rise the efficiency it is necessary to implement allothermal conditions, to improve heat recirculation. To study marginal allothermal conditions ("ideal gasification") and the ways of their control a number of experiments and calculation-based estimates were made.

In a PSA unit for biogas upgrading, an adsorbent material is subjected to pressure changes to selectively adsorb and desorb CO2. Adsorption is an exothermic spontaneous process and the loading of CO2 in the adsorbent depends specifically on the properties of the material employed (surface area and composition, pore size, etc). Once the material is specified, then its regeneration should be realized. Note that since the material is continuously used and regenerated, there comes a point where the process achieves a "cyclic steady state" (CSS). The largest part of engineering a PSA process rely in designing a regeneration protocol for the adsorbent able to spent small amount of energy (reduce energetic penalty) and do it in the fastest way possible (increase productivity).

The operational principle of the PSA process can be observed in Figure 1 where two generic CO2 isotherms (representing two different materials) are shown. In both materials, the adsorbent may take CO2 up to the loading established by its partial pressure in the feed step (Pfeed) which is qfeed/i and qfeed,2 for adsorbents 1 and 2, respectively. After the adsorbent is saturated, it is regenerated to a lower pressure, Preg, where the loading of CO2 decreases to qreg/1 and qreg,2. The material 1 has a higher CO2 capacity than material 2 for the entire pressure range. However, the difference in loading between qfeed and qreg (Aq) is higher for material 2, indicating that the "cyclic capacity" will be better for this material. In fact, the conclusion from this image is that it is important to know the shape of the isotherm in order to design the PSA process. Also, ideally for PSA applications, linear or mild non-linear isotherms are better than very steep isotherms with high loading. Furthermore, when the isotherms are steep, it is more difficult to regenerate the adsorbent since the energy required to desorb CO2 is higher. From Figure 1, it is possible to see that the selection of the regeneration pressure has also an important effect in the cyclic operation of the PSA process. For this reason, in the next sections, the properties of the adsorbents and the cycles used for adsorbent regeneration in PSA for biogas upgrading will be discussed.

Theoretically, biofuel implantation in transport and industry should solve, or at least improve, the ecological and economic problems derived from the unsustainability of the fossil fuel-based energy model.

However, recent field experiences indicate a much more complex scenario. The market economy and unbalanced relations between different sectors of the economy and national markets generate unpredictable dynamics of fuels’ raw material prices. In this context, the development of subsequent new commercial and industrial opportunities has altered the already unstable behaviour of the agricultural international markets. The sudden peak in demand for grain, owing to its usage as a raw material for the production of ethanol, has abruptly increased the prices of corn (Fischer et al., 2009). The demand pressure has operated similarly in the palm oil market, generating a palm oil tree and soy culture surface expansion in several regions, with spectacular dimensions in South-East Asia (Abdullah et al., 2009; Jaruwat et al., 2010), where the biofuels fever threatens biodiversity and has a deep social impact because of the proliferation of unregulated, intensive, agricultural practices and the switching of oil usage for traditional human nutrition, housekeeping and livestock feed (Fortman et al., 2008; Guerrero-Compean, 2008; Demirba§, 2009; UNCTAD, 2010; Yee et al., 2009).

Bioethanol is only one of the products that may be extracted from lignocellulosic feedstocks. Other forms of energy and a full range of value-added bioproducts may be produced from biomass by thermochemical means. Thermochemical conversion processes include pyrolysis, hydrothermal conversion and gasification. The major product of pyrolysis and hydrothermal conversion, known as "bio-oil" or "biocrude", can be used as a boiler fuel or as fuel in combustion engines. Alternatively, the bio-oil can serve as a raw material for the production of chemicals and biomaterials. One of the major technical obstacles to large scale thermochemical conversion of biomass into bio-oil is its poor oil quality and low biofuel production rate. This section intensively reviewed current technologies used to produce bio-oil and technologies development towards improving the bio-oil yield and quality.