It is reported in various publications and press articles that biofuels (incl. bioethanol and biodiesel) do actually contribute to global warming (Fargione et al., 2008; Reijnders and Huijbregts, 2008; Searchinger et al., 2008) under certain conditions. Other WtW studies, such as that of Beer and Grant (2007), found only marginal advantages for E10 blends (of the order of 4% reduction on GHG emissions). Looking at the results presented in this chapter so far, however, it does not seem to be the case for bioethanol from wheat produced in the Swiss context. This is not always true and is really the result of the default choices made in this chapter (which correspond to the most likely situation in the present European context). Let us assume A-2 as the allocation method (i. e., economy) and E-3 as the vehicle/fuel per­formance option (i. e., energy basis) and evaluate the net GHG emissions of bioethanol from wheat under various land-use change scenarios. This framework is among the most unfavor­able set of options and actually corresponds to that of EMPA (2007a). Economic allocation is the default method in the ecoinvent database and the method chosen by the Swiss authorities to evaluate the sustainability of fuels in the frame of the Ordinance on the ecological balance of fuels. Vehicle/fuel performance based on the energy content of fuels is undoubtedly the most frequent hypothesis in LCA studies of biofuels (e. g., CONCAWE-EUCAR-JRC, 2008; EMPA, 2007a; GM-LBST, 2002; IFEU, 2004; VIEWLS, 2005). The results are presented in Table 5 and illustrated in Figure 5.

Under these assumptions, the variation of life-cycle GHG emissions with respect to gaso­line ranges from —24% to +383%. Unless the land-use change leads to an improved annual carbon stock (i. e., LUC-5 LUC-8 and LUC-9 as shown in Table 4), the net GHG emissions of

wheat to ethanol are indeed larger than those of gasoline. In the worst scenario (LUC-6, i. e., forested land to cultivated land), the net GHG emissions of bioethanol can be as large as

3.8 times that of gasoline.

2 CONCLUSIONS

The default case in this chapter for fuel-bioethanol production from wheat in the Swiss context considers allocation based on energy content (A-1), the switch from set-aside land to cultivated land (LUC-1) and vehicle/fuel performance based on actual vehicle test with fuel-ethanol used as E5 (E5-1). With net GHG emissions of 0.066 kg CO2 eq./km (i. e., —72% with respect to gasoline) and a net energy use of 0.567 MJp/km (i. e., -84% with respect to gasoline), this default case may seem particularly advantageous compared to other simi­lar studies. This default case, however, is realistic and corresponds to the most likely situa­tion in the European context. Energy allocation is the methodology adopted by the European Union in its Directive on the promotion of the use of energy from renewable sources. Set-aside to long-term cultivated is a reasonable option when considering the pro­duction of biofuels from agricultural crops. Finally, fuel ethanol in the EU is mainly used as E5 at present. If the set of methodological choices as in EMPA (2007a) is applied to the same system, meaning economic allocation (A-2) and vehicle/fuel performance based on the energy content of fuels (E-3), the resulting net GHG emissions and net energy use are 0.273 kg CO2eq./km (i. e., +15% with respect to gasoline) and 1.944 MJp/km (i. e., —44% with respect to gasoline), respectively. These results are much more unfavorable and signifi­cantly different from those of the default case.

Various authors have demonstrated the significant effect of methodological choices on the GHG and energy balance of biofuels through review papers and other similar studies (Borjesson, 2009; Farrell and Sperling, 2007; Reijnders and Huijbregts, 2003). The present chapter quantifies these effects, based on a case study concerned with the production of fuel-ethanol from wheat in the Swiss context. In addition, it demonstrates and quantifies the effects of the fuel blend and the choices regarding vehicle/fuel performance.

The results presented in this chapter show a large variation of the net GHG emissions of wheat-based ethanol for transportation with a high sensitivity to the following factors: the method used to allocate the impacts between coproducts, the type of reference systems, the type of land-use change, and the type of fuel blend. Depending on the allocation method (energy content, economy, dry mass or carbon content), the net GHG emissions of ethanol may vary by a factor of up to 2.6 (with carbon content being the most favorable and economy the least favorable). When substitution is applied, the net GHG emissions of ethanol may even be negative when both straw and DDGS are used as fuels, thereby making the difference even more significant. Depending on the land-use change situation, the net GHG emissions of ethanol may vary by a factor of up to 6.4. Similarly, the hypotheses regarding actual fuel blends and vehicle/fuel performance may result in a variation of net GHG emissions by a factor of 2.2. Depending on the combinations of methodological choices and land-use change situations, the variation of life-cycle GHG emissions with respect to gasoline may range from —112% to +120% for the same ethanol production pathway.

In face of missing data and time stress, many studies use pragmatic approaches to evaluate the energy and GHG balance of biofuels. Thus, several studies are not transparent enough and methodological choices can turn a positive GHG balance into a negative one and vice versa. As policymakers will take decisions by using these results, it is important to establish the rationale of the evaluation methods. Some items need further research works, for exam­ple, rationale of allocation methods, indirect land-use change (Gnansounou et al., 2008b). Others are till now subject to low transparency and consistency requirements.

Especially concerning the boundaries of the system, the authors recommend to use a WtW approach. One should not mind if the implementation of the WtW should be simplified; uti­lization stage must be taken into account as long as comparison of different qualities of fuels is concerned, that is, fuels associate with different mechanical efficiencies. The functional unit must be appropriate, reflecting the fact that these fuels must be compared for the same service (e. g., the distance traveled). Finally, for transparency purpose, the reference system must be explicitly defined.

The fundamental principle of a BFB furnace is that the fuel is dropped down a chute from above into the combustion chamber where a bed, usually of silica sand, sits on top of a nozzle distributor plate, through which air is fed into the chamber with a velocity of between 1 and 2.5 m/s (http://www. esru. strath. ac. uk/EandE/Web_sites/06-07/Biomass/HTML/ combustion_technology. htm). The bed normally has a temperature of between 800 and 900 °C and the sand accounts for about 98% of the mixture, with the fuel then making up a small fraction of the fuel and bed material. BFBs have two main advantages in terms of fuel size and type over more traditional fixed-bed systems. First, they can cope with fuel of varying particle size and moisture content with little problem, and second, they can burn mixtures of different fuel types such as wood and straw. BFBs are only a practical option with larger plants with a nominal boiler capacity greater than 10 MWth.

The production of bioethanol from wheat grains gives rise to coproducts both at the agri­cultural stage (i. e., wheat straw) and at the industrial stage (i. e., wheat DDGS). Both coproducts may be used as animal feed or as fuel (Kaparaju et al., 2009). According to the most common practice in the European context, the reference use of the coproducts is consid­ered to be animal feed. It is here considered that the land where the animal feed (baseline) was initially produced (now displaced by straw and DDGS) is turned into set-aside land. Simi­larly, it is considered in this reference framework that wheat is grown on land that was initially set aside (incl. green cover with no farming inputs). The corresponding systems are shown in Figure 1. When allocation is applied, the "from" (reference) and "to" (studied) systems are illustrated as in Figure 2 (showing the effect of allocation). When substitution is applied, the "from" and "to" systems are illustrated as in Figure 3, where the substituted products and the associated land use are included in the system studied with a negative impact in order to keep the reference system identical in all cases (i. e., limited to the produc­tion and use of gasoline). The effect of different allocation/substitution choices is investigated in the case study section.

The WtT GHG net GHG emissions of unleaded gasoline in the Swiss context are taken from ecoinvent and are equal to 0.018 kg CO2 eq,/MJth (i. e., 0.782 kg CO2 eq./kg or 0.586 kg CO2 eq./l) at the service station.

2.1.3.2 OXYGEN-BLOWN GASIFICATION

It is an alternative route for the production of a nitrogen-free product gas. To prevent local hotspots in the reactor, the oxygen is normally diluted with steam or CO2. The methane content drops with increasing steam/O2 and CO2/O2 ratio. The decrease on dry gas basis is mainly caused by the dilution by CO2 or H2 that is produced from steam by the CO shift reaction.

A low steam or CO2/O2 ratio produces a product gas with the highest CH4 content, which is desired for synthetic natural gas (SNG) production. A low amount of CO2 or steam also increases the gasifier efficiency, because less "inert" gas needs to be heated to the process temperature. A certain amount of oxygen dilution is required to prevent possible agglomera­tion of biomass (http://www. biosng. com/experimental-line-up/o2-blown-gasification/).

Thallada Bhaskar*, Balagurumurthy Bhavya,

Rawel Singh, Desavath Viswanath Naik, Ajay Kumar,

Hari Bhagwan Goyal

Bio-Fuels division (BFD), Indian Institute of Petroleum (IIP),

Council of Scientific and Industrial Research (CSIR), Dehradun 248005, India
*Corresponding author: Thallada Bhaskar; E-mail: tbhaskar@iip. res. in; thalladab@yahoo. com

1 INTRODUCTION

The demand for energy sources to satiate human energy consumption continues to increase. Currently, the main energy source in the world is fossil fuels. Although it is not known how much fossil fuel is still available, it is generally accepted that it is being depleted and is nonrenewable. Prior to the use of fossil fuels, biomass was the primary source of energy for heat via combustion. With the introduction of fossil fuels in the forms of coal, petroleum, and natural gas, the world increasingly became dependent on these fossil fuel sources. Renewable energy is of growing importance in responding to concerns over the environment and the security of energy supplies. Given these circumstances, searching for other renewable forms of energy sources is reasonable. Other important consequences associated with fossil fuel uses include global warming. Also, fossil fuel resources are not distributed evenly around the globe, which makes many countries heavily dependent on imports.

Governments across the world are stimulating the utilization of renewable energies and resources such as solar, wind, hydroelectricity, and biomass. The three major forces that drive them are (i) secured access to energy; (ii) threat of climate change; (iii) develop/maintain agricultural activities (Lange, 2007). Agricultural economies could be supported by promot­ing the exploitation of local (bio) resources for food, energy, and material. Interestingly, each of these major drivers also represents one of the three dimensions of sustainability, namely, profitability (affordable energy), planet (climate change), and people (social stability).

Current use of fossil fuels is split, with about three-quarters for heat and power generation, about one-quarter for transportation fuel, and just a few percent for chemicals and materials (US Department of energy, 2006). The heat and power sector can be supplied with a variety of renewable sources, namely wind, solar, hydropower, and biomass. The transportation sector has a much more limited choice, however. At this time, biomass is the only resource that can provide renewable liquid fuels. Apart from the transportation sector, biomass is also a promising feedstock for the chemical industry due to the presence of a wide range of functionalities available with biomass, the natural polymer.

Biomass is unique in providing the only renewable source of fixed carbon, which is an essen­tial ingredient in meeting many of our fuel and consumer goods requirements. Wood and annual crops and agricultural and forestry residues are some of the main renewable energy resources available (Bridgewater, 2006). Biofuel production has been growing rapidly in recent years.

Biomass, a renewable energy source, via photosynthesis, has provided energy for life for the longest period of existence. Industrial processes that take in biomass can be integrated with the natural photosynthesis/respiration cycle of vegetation. If used in this manner, biomass is a renewable energy source and by its utilization, much less CO2 is added overall to the atmosphere compared with the fossil fuel counterpart processes. When combined with CO2 sequestration, biomass-based processes can actually lower the CO2 concentrated in the atmosphere (Van swaaij et al., 2004). Lignocellulosic biomass, which is not competing with the food chain, should be used for the production of fuels, chemicals, power, and heat. This competition can be avoided by first using the abundant residues from forests, agriculture, and subsequently energy crops. The potential of special energy crops is estimated to be in the range of 50-250 EJ/annum (Berndes et al., 2003).

Biomass combines solar energy and carbon dioxide into chemical energy in the form of carbohydrates via photosynthesis. The use of biomass as a fuel is a carbon neutral process since the carbon dioxide captured during photosynthesis is released during its combustion. Biomass includes agricultural and forestry residues, wood, byproducts from processing of biological materials, and organic parts of municipal and sludge wastes. Photosynthesis by plants captures around 4000 EJ/year in the form of energy in biomass and food (Kumar et al., 2009a).

The most important factor is that all fossil fuels are taken out from under the earth’s surface, and its continuous excavation creates many geothermal disturbances. Biomass is grown and consumed only over the earth’s surface and hence does not create such problems.

The events of the last few years have brought into sharp focus the need to develop sustainable green technologies for many of our most basic manufacturing and energy needs. Since the beginning of the new millennium, we have witnessed an ever-increasing merger of technical, economic, and societal demands for sustainable technologies. As such, this seeks to develop a new "carbohydrate-lignin economy" that will initially supplement today’s petroleum economy and, as these nonrenewable resources are consumed, will become the primary resource for fuels, chemicals, and materials (Yunqiao et al., 2008).

With the increasing demand of energy world over and depleting reserves of con­ventional fossil fuel, there has been growing global interest in developing alternative sources of energy. Also, there has been con­cern in growing economies with energy secu­rity. Biofuels offer much promise on these frontiers. In addition to above, they also offer benefits on environmental impact in compar­ison to fossil fuels. The present book provides state-of-the-art information on the status of the biofuel production and related aspects and also identifies the future R&D directions and perspectives.

The book has five sections. Section I is gen­eral and presents four chapters which deal with the principles of biorefineries, life cycle assessment of biofuels, thermochemical con­version of biomass to biofuels, and biomass- derived syngas fermentation into biofuels. Section II deals with different aspects of the production of second-generation bioethanol from lignocellulosic feedstocks. The first chapter in this section is introductory, giving state-of-the-art information on the status and perspectives; this is followed by a chapter on techno-economic analysis of lignocellu — losic bioethanol. Subsequent chapters deal with the different aspects of bioconversion process such as the pretreatment of ligno — cellulosic biomass, production of cellulo­lytic and hemicellulolytic enzymes for the hydrolysis of lignocellulosic biomass, hydro­lysis oflignocellulosic biomass, production of bioethanol from agro-industrial residues as feedstocks, and removal of inhibitory compounds from lignocellulosic hydrolyzates for bioethanol production. Section IIIA presents state-of-the-art information on the production of second-generation biodiesel from oilseeds. In this, the first chapter is intro­ductory and presents current perspectives and future, followed by the biotechnological methods to produce biodiesel, biodiesel pro­duction in supercritical fluids, biodiesel pro­duction using palm oil, and biodiesel from waste oil. Section IIIB contains chapters deal­ing with the production of third-generation biofuels from algal sources. The first chapter in this section as usual presents the current perspectives and future, followed by life cycle assessment of algal biodiesel, and the cultiva­tion of algae in photobioreactors.

Section IV is devoted on the fourth — generation biofuels, that is, biohydrogen. The section has five chapters and the first one gives general information with current perspectives and future. The other chapters are on biohydrogen production from bio-oils and industrial effluents, thermophilic biohydrogen production, and biohydrogen production with high-rate bioreactors. Section V provides two articles on the produc­tion of biobutanol and production of green liq­uid hydrocarbon fuels.

We thank the authors of all the chapters for their cooperation and also for their prepared­ness in revising the manuscripts in a time­framed manner. We also acknowledge the help from the reviewers, who in spite of their busy professional activities helped us by evaluating the manuscripts and gave their critical inputs to refine and improve the chapters. We warmly thank Dr. Marinakis Kostas and Dr. Anita Koch and the team of Elsevier for their cooperation and efforts in producing this book.

We sincerely hope that the current dis­course on biofuels R&D would go a long way in bringing out the exciting technological possibilities and ushering the readers toward the frontiers of knowledge in the area of biofuels.

The text in all the chapters is supported by numerous clear, informative diagrams and tables. The book would be of great interest to the postgraduate students and researchers of applied biology, biotechnology, microbiol­ogy, biochemical, and chemical engineers working on biofuels.

Ashok Pandey Christian Larroche Steven Ricke Claude-Gilles Dussap Edgard Gnansounou Editors

Starting from biomass, butadiene potentially can be produced from ethanol: ethanol is firstly dehydrogenated to acetaldehyde, which is then followed by aldol condensation and dehydration over a catalyst to form butadiene, with an overall yield of 70% (Weissermel and Arpe, 2003). Butadiene can subsequently be converted to butane by reduction.

Francesco Cherubini, Anders H. Str0mman

Department of Energy and Process Engineering, Norwegian University of Science and Technology

(NTNU), NO-7491 Trondheim, Norway
*Corresponding author: E-mail: francesco. cherubini@ntnu. no

1 INTRODUCTION

1.1 Background

Driven by the increase in industrialization and population, the global demand for energy and material products is steadily growing. Since the world primary sources for energy and chemicals are fossil fuels, this growth raises important issues at environmental, economic, and social levels. Petroleum is exploited at a much faster rate than its natural regeneration through the planet C cycle, and the larger part of petroleum and natural gas reserves is located within a small group of countries. This production and consumption pattern is unsus­tainable because of equity and environmental issues that have far-reaching implications. In addition, there is a common increasing perception that the end of the cheap fossil era is around the corner, and prices for crude oil, transportation fuels, and petroleum-derived chemicals are likely to steadily increase in the years to come (Bentley et al., 2007; Greene,

2004) . Climate experts widely agree that emissions of greenhouse gases (GHG), such as car­bon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), arising from fossil fuel combus­tion and land-use change as a result of human activities, are perturbing the Earth’s climate (Forster et al., 2007). Global warming and other issues can be mitigated by shifting from fossil sources to renewable energy resources, which are more evenly distributed than fossil resources and cause less environmental and social concerns.

Among the other energy sources, biomass resources are extremely promising since they are widespread and cheaply available in most of the countries. Today, biomass constitutes about 10% of the global primary energy demand, and it is mainly used in inefficient and tra­ditional applications in developing countries (GBEP, 2007; IEO, 2009). Modern uses of bio­mass are restricted to developed countries to produce space heating, power, transportation biofuels (mainly bioethanol and biodiesel), and few chemical products. Given the variety of applications for biomass sources, it is extremely important to select the most promising options under environmental, economic and resource perspectives. Electricity and heat can be provided by several renewable alternatives (wind, sun, water, biomass, and so on), while bio­mass is very likely to be the only viable alternative to fossil resources for production of transportation fuels and chemicals. Today, more than 90% of the fossil carbon is used only for its energy content (Marquardt et al., 2010). This pattern is not likely to be followed in the future for biomass because of the lower efficiency in converting biomass into energy and the lower energy density of biomass than fossils. Stemming from these considerations, some authors convincingly argued that electricity should be produced by an increasing share of rene­wable sources, and the use of biomass be restricted to the production of transportation biofuels and carbon-based chemical products (Agrawal and Singh, 2010; Marquardt et al., 2010).

If the conversion of carbohydrates to oxygen-containing chemicals has been largely investigated, the replacement of bulk aromatic petrochemical compounds has received so far relatively little attention and limited success. Fermentation of glucose to a number of aro­matic structures has been described in the patent literature. However, these aromatic structures themselves were neither bulk products nor the desired end product of the fermen­tation process (adipic acid; Haveren et al., 2008).

Utilization of specific terpenes could offer potential for the production of aromatic compounds such as, for example, substituted phenols or terephthalic acid and fine and