Biofuel Generation Technologies: A global perspective

126

Biofuel Generation Technologies: A global perspective Priyabrata Pradhan1, Amit Arora2 1,2

Centre for Technology Alternatives for Rural Areas, Indian Institute of Technology Bombay, Mumbai Email : [email protected], [email protected]

Abstract The rapid development in energy dependent countries and climate change regulations encourages utilization and promotion of renewable energy such as bioenergy or biofuel. Sustainable economic and industrial growth requires safe and sustainable resources of energy. For the future re-arrangement of a sustainable economy to biological raw materials, completely new approaches in research and development, production, and economy are necessary. This paper reviews the historical perspective, current status, and predictable future trend of biofuel. Different generations of biofuel technologies are widely discussed using Popperian scientific principle. Overall, the global development and utilization of biofuel will continue to increase, particularly in the biopower, lignocellulosic bioethanol, and algae fuel sectors. It is expected that by 2050 biofuel will provide 30% of the worlds demanded energy from 10% today. Index Terms— Biofuel, biofuel technologies, sustainable development, Popperian principle. .

I. INTRODUCTION Energy resources will play an important role for the fulfilment of global need. The energy sources can be categorized in to fossil fuel, renewable energy and nuclear energy. The world‘s energy markets mainly depend on fossil fuel based energy sources such as coal, petroleum crude oil and natural gas as sources of energy, fuel and chemicals. In the twentieth century the major research emphasis was given for the development of fossil fuel based refinery to exploit the cheaply available fossil feed stock. These feed stocks are used in industry to produce multiple products such as fuel, chemicals, detergents, fertilizers, plastics, lubricants, waxes, coke, etc. to meet the need of growing population [1], [2]. The twenty first century is looking for a shift from conventional industrial energy sources to alternate renewable industrial feed stock [3]. Currently, fossil fuel resources are being questioned from economy, ecology, environment and sustainability point of view. Therefore, the quest for sustainable and environment friendly sources of energy for our industrial economies and consumer societies become urgent in recent years. Different sources of renewable energy such as solar, wind, hydropower, and biomass provide substantial benefits to the society in terms of energy, economy and climate. Biomass resources are relatively, uniformly available compared to other renewable energy sources and it is the only renewable source of fixed carbon [4]. Hence, it has attracted considerable attention as alternate energy source in recent years. Consequently, the interest has grown in the production and use of fuel from plants or organic residues. These biological sources of energy are commonly called as biofuel. The biofuel produced from renewable resources could help to reduce world‘s dependence on fossil fuel and

carbon dioxide production. These biofuel can have the potential to cut carbon dioxide emission because the plants use carbon dioxide as they grow [5]. Additionally, the biofuel production and bio products can provide new income and employment opportunities in rural areas. In this paper an attempt has been made to review the advancement in biofuel generation technologies at global level. In this aspect, this paper aims to encapsulate the whole concept of biofuels through its transition at different generations. II. HISTORICAL PERSPECTIVE Prior to mid nineteen centuries, whale oil was commonly used as energy along with other oils derived from vegetables and animals. By the late 1830s, ethanol blend with turpentine (refined from pine trees) was used to replace the more expensive whale oil [6]. However, the reality is that ethanol was developed as an alternative fuel before the discovery of petroleum by Edwin Drake in 1859 [7]. Furthermore, Alexander Graham Bell was quoted in a 1917 National Geographic interview stating ―Alcohol can be manufactured from corn stalks, and any vegetable matter capable of fermentation. The waste products of our farms are available for this purpose and even the garbage of our cities.can be for the said purpose. We need never fear the exhaustion of our present fuel supplies so long as we can produce an annual crop of alcohol to any extent desired‖ [8]. In the beginning of 20th century, biofuel became prominent and was linked with the discovery of the automobile. Henry Ford envisioned automobiles that relied on ethanol as their fuel source [7]. The demand of biofuel again appeared during World War years of 1917-1919 and 1941-1945 due to rationing of raw materials and natural resources including gasoline. During the World War I years, ethanol production increased to 60 million gallons

Proceedings of International Conference on Renewable Energy and Sustainable Environment – RESE 15 Dr. Mahalingam College of Engineering and Technology, Pollachi-642003, India. August 10-13, 2015

Biofuel Generation Technologies: A global perspective and this further increased during the World War II years to 600 million gallons [6]. This created an early interest in the United States of America (U.S.) to develop educational or training materials for ethanol plant operation. The 1974 Arab oil embargo also resurrected interest in ethanol production throughout the world. Darlington [9] reported that the ethanol production in the U.S. will increase to 15 billion gallons by 2015. Development of diesel engine by Rudolph Diesel to improve the efficiency of steam engines of the late 1800s opened the door to search for alternate fuel. In 1890s, he envisioned that vegetable oils could power diesel engines. First research conducted in the 1930s in Belgium for modern biodiesel, which is made by converting vegetable oils into esters compounds [6]. Surprisingly, not a single biodiesel industry could be established in Europe until the late 1980s. As of 2013, worldwide biodiesel production had reached 6.3 billion gallons, with most fuel being produced in the European countries, although biodiesel projects worldwide have been on the rise due to rising crude oil prices and concerns over global warming. Producing energy through gasification process is more than 200 years old technology. During 1800s, coal power plants were used to produce town gas for lighting and cooking and later this was replaced by natural gas and electricity. In 1940s, during world war years, the need of producer gas was resurrected due to the shortage of petroleum. Today, producer gas can be further processed to synthetic diesels and other chemical products. III. POPPERIAN THEORY FOR DEVELOPMENT OF BIOFUEL RESEARCH

Fig. 1. Popperian cycle for development of biofuel research

127 Biomass and bio-fuels have attracted growing interest as sustainable and renewable energy. In this section, the paradigm shift in the different stages of biofuel generation has been discussed in detail. The developments of biofuel research are shown in Fig. 1. A. THEORY A (FIRST GENERATION BIOFUELS: APPROACH FOR ALTERNATE SOURCE )

First generation biofuels are made from sugars and the vegetable oil, cultivated in arable land which can be easily extracted using conventional technology. In this case, crops such as wheat, sugar, corn and plant oils are the most widely used as feedstock for biofuel production. However, first generation biofuels have a number of associated problems. The most contentious issue with first generation biofuel is fuel versus food. As the majority of biofuels are produced directly from food crops, the increase in demand for biofuels has led to an increase in the volumes of crops being diverted away from the global food market. First generation biofuel processes are useful but limited to certain extent as there is a threshold above which they cannot produce enough biofuel without threatening food supplies and biodiversity. Many first generation biofuels depend on subsidies and are not cost competitive with existing fossil fuels. On the account of production, transport and life cycle assessment, the first generation biofuels frequently approach to those of traditional fossil fuels [10]. B. THEORY B (SECOND GENERATION BIOFUELS: FOCUS ON NON- FOOD CROP)

Second Generation biofuels have been developed to overcome the limitations of first generation biofuels. They are produced from non-food crops such as wood, organic waste, food crop residue and specific biomass crops, thus eliminating the main problem with first generation biofuels. Second Generation biofuels are also aimed at being more cost competitive in relation to existing fossil fuels [11]. Life cycle assessments of second-generation biofuels have also indicated that they will increase net energy gains coming over another main limitation of first generation biofuels. While first and second generation biofuels account for more than 99% of current global biofuel production and the US already appropriates 30% of its corn supply to displace about 6% of its gasoline consumption. A number of important technologies are on the brink of commercialization that produces drop-in fuels with the same chemical characteristics of petroleum. First and second generation biofuels like ethanol and plant oil have a number of inherent limitations that make them less than ideal as a long term replacement for petroleum. The primary feed stocks for first generation ethanol (corn and sugarcane) and oil from crops (rapeseed, soybeans, and palm) are all food-based crops that compete for scarce cropland, fresh water, and fertilizers. These fuels cannot be used in unmodified engines above small blends and are not


Biofuel Generation Technologies: A global perspective applicable to the jet fuel market. These technological hurdles have paved my for third generation biofuel. There are more than 2 billion people in China and India together and are currently undergoing their industrial revolutions, combined with global population increases of 80 million per year [12] and increases in standards of living for nonOECD (Organisation for Economic Cooperation and Development) populations which forecast increase in global petroleum consumption to more than the current level. This promotes further research towards alternate fuel to sustain the growth and economy. This adds one more reason for third generation biofuel.

128 IV. CURRENT STATUS Biofuels are used in solid, liquid or gaseous form for various applications. Different generations of biofuels have been classified in Fig. 2. The present form of biofuel utilization status is highlighted below.

C. THEORY C (THIRD GENERATION BIOFUELS: FOCUS ON MORE ENERGY FROM LESS AREA )

The Third Generation of biofuel is based on improvements been in the production of biomass. Here special energy crops such as algae have considered as its energy source [13]. The algae are cultured to act as a lowcost, high-energy and entirely renewable feedstock. It is predicted that algae will have the potential to produce more energy per acre than conventional crops. Algae can also be grown using land and water unsuitable for food production, therefore reducing the strain on already depleted water sources. A further benefit of algae based biofuels is that the fuel can be manufactured into a wide range of fuels such as diesel, petrol and jet fuel. On this model, research has just been started, so the challenges may come on large scale commercialization. D. THEORY D (FOURTH GENERATION BIOFUELS: FOCUS ON CARBON CAPTURING )

All the above biofuel types work as a substitute to fossil fuel and are carbon neutral. In the next generation i.e. in fourth, happens major emphasis is to reduce the emission so that a transition from carbon neutral to carbon negative. Fourth generation biofuels are aimed at not only producing sustainable energy but also a way of capturing and storing carbon dioxide. Biomass materials, which have absorbed while growing, are converted into fuel using the same processes as second generation biofuels. This process differs from second and third generation production as at all stages of production the carbon dioxide is captured using processes such as oxy-fuel combustion [14] i.e. burning of fuel by pure oxygen instead of air as the primary oxidant. The carbon dioxide can then be geo sequestered by storing it in old oil and gas fields or saline aquifers. This carbon capture makes fourth generation biofuel production carbon negative rather than simply carbon neutral; as it locks away more carbon than it produces. This system not only captures and stores carbon dioxide from the atmosphere but it also reduces carbon dioxide emissions by replacing fossil fuels.

Fig. 2. Different generation of biofuels

A. STATUS OF FIRST GENERATION BIOFUELS 1) Grain Ethanol (from edible starchy crops) Commercial alcohol is that currently being produced from starch or sugar based crops such as corn, barley, wheat, sugar cane, sweet sorghum through biochemical process is called grain alcohol. Dry and wet mill processes are the two categories of grain ethanol production process. Dry grinding process (Fig. 3) is specially designed for production of ethanol and animal feed whereas, wet mill ethanol process produces variety of valuable coproducts such as nutraceuticals, pharmaceuticals, organic acids and solvent [15]. Theoretically, referring to (1) the maximum conversion efficiency of sugar to ethanol is 51% on the weight basis.

Fig. 3. Grain ethanol production through dry grind process


Biofuel Generation Technologies: A global perspective Yeast C6H12O6   2CH3CH2OH + 2CO2 (1)

constituent Sugar ethanol Avg. mol.wt. 180 2×46 percentage 100.00 51.11 The global commercial ethanol production was 4.0 billion gallons (15.1 billion liters) in 1990. It increased slightly to 4.5 billion gallons (17 billion liters) in 2000 but rapidly to 23.3 billion gallons (88.2 billion liters) in 2010 [16]. In 2014, the figure was 24.5 billion gallons (92.7 billion liters), with 58.2% of the production in the U.S. followed by 25.2% in Brazil. Together, the U.S. and Brazil produce 83% of the world's ethanol. In fact, the U.S. invested 42% of its harvested corn grains (114 million tons/yr) in bioethanol production, attempting to replace 10% of its gasoline demand with ethanol [17]. Sugar cane is the predominant feedstock for bioethanol in Brazil. The European countries use primarily wheat and sugar beet to produce ethanol. In China, the principal ethanol feedstocks are corn, wheat, and cassava, while in Canada, feedstocks are corn and wheat. In India, production of grain ethanol is prohibited as per National Biofuel Policy of 2009 to reduce stress on food crops. India currently produces 155 million gallons (0.6 billion liters) only from non-edible feedstocks such as molasses [16]. India has also mandated 20% ethanol blending with gasoline by 2017. 2) Biodiesel (from edible oil seeds) Biodiesel is mono-alkyl esters of fatty acids derived from vegetable oil or animal fats through transesterification in the presence of alcohol and alkaline catalyst. Common oil seed plants include camelina, canola, castor bean, coconut, palm, peanut, rapeseed, soybean, sunflower etcetera, can all 1) be used as feedstock to produce biodiesel (Fig. 4). Oil crop

Vegetable oil

Transesterification

Biodiesel

Transportation fuel

+

Glycerol

Value added chemicals

Fig. 4. Biodiesel production process from edible oil crops Typically, 98% ester yields achieved at complete conversion of triglyceride and methanol by transesterification with glycerol as by product. (2) Catalyst C 3 H 5 (COOCH3 ) 3 + 3CH 3 OH   3CH 3 COOCH3 + C 3 H 5 (OH)3

(2)

Triglyceride Methanol Esters Glycerol 218 96 222 92 The100.00 world production steadily 44.03of biodiesel 101.83 has increased 42.20 from 0.213 billion gallons (0.8 billion liters) in 2000 to 6.3 billion gallons (23.8 billion liters) in 2013 [18]. The top five biodiesel production countries are (the European Union, Brazil, Argentina, the U.S., and China) using oils from soybean, rapeseed, canola seed, sunflower seed, castor bean, animal fats, and yellow grease. Currently, more than 95% of the world biodiesel is produced from edible oils

129 which are easily available on large scale from the agricultural industry [19].The U.S. produced 1.34 billion gallons (5.1 billion liters) of biodiesel in 2013, solely from soybean oil [20] and production rate slightly decreased to 1.27 billion gallons (4.8 billion liters) in 2014 [18]. With the world‘s growing demand for biofuels, global production and consumption of biodiesel will be high. In India, the National Biofuel Policy (NBP) of 2009 aimed to meet 20% of diesel demand with biodiesel from non-edible oil seeds. B. STATUS OF SECOND GENERATION BIOFUELS Second generation biofuels can be further classified into solid, liquid and gaseous biofuels based on production and utilization (Table.1). In short, solid biofuels are abundant and most effective in conversion technology and energy recovery, but products are inconvenient to handle, and low in energy density. Liquid biofuels are energy dense, convenient to handle and better energy substitute, however, these involve complicated conversion technology with high production cost. Gaseous biofuels can be produced from solid biofuels or organic wastes and can also be converted to liquid biofuels, yet there are fuel upgrading and byproduct utilization challenges. Table 1 Classification of second generation biofuels Solid biofuels

Second generation biofuels Liquid biofuels Gaseous biofuels Cellulosic ethanol Biogas Biodiesel Syngas

Firewood Densified biomass Biomass charcoal

Bio-CNG

1) Firewood Biomass combines solar energy, CO2 (carbon dioxide) and H2O (water) into chemical energy in the form of carbohydrates via photosynthesis (3). The use of biomass as a fuel is a carbon neutral process since CO2 captured during photosynthesis is released during its combustion. The energy content of C6H10O5 (cellulose in wood)is the releases in form of heat and light on complete combustion (in presence of O2 (oxygen)) that produces H2O and CO2 as pollutants (4). This combustion produce significant smokes (a mixture of water vapour, volatile organic compounds, and carbon black particulates) and creosote (smoke condensate) that are hazardous to human health as well as to the environment [20]. energy 6CO 2  6H 2 O solar   C6 H12O6 (glucose)  6O 2 (3) C6 H10O5 (cellulose) + 6O 2  6CO 2  5H 2 O + energy (4)

Firewood is one of the most predominant fuel for cooking and heating of the whole world and especially in developing and underdeveloped countries. Nearly 40 % (2.6 billion) of the world population in rural area of developing countries in Asia and sub-Sahara Africa relies on firewood for household energy requirement [22]. In India, biomass accounts for 33% of household energy consumption, while


Biofuel Generation Technologies: A global perspective in China, the share is nearly 37% [23]. Households don‘t substitute firewood over another fuel as the income increases, but instead reduce the consumption with technological advancement and improved cook stove [24]. 2) Densified biomass Densification is the process where the biomass is converted into a compressed and densified material, which can be used as an excellent fuel in the rural area. Pellets are cylindrical sticks, relatively smaller in size (6 – 12 mm typical) utilized in home pellet stove, boilers or in power plants to replace coal. Pelletizing is closely related to briquetting except that it uses smaller dies to produce pellets. Pellets are made by crushing biomass (bagasse, sawdust, garden waste, agricultural residues, dry leafs etcetera). Compared to wood, biomass pellets are more processed biofuel product. Pelletization is a process of applying a mechanical force to compact low bulk density biomass into uniformly sized, solid, high density substance (Fig. 5). The high pressure raises the temperature of biomass and thereby the inherent lignin (about 30%) glues the pellet when it cools. This is usually done to improve the fuel handling, transportation, conversion and also for storage for off season utilization. High quality pellets have low moisture content (5% to 10%), high packing density (around 650 kg/m3), mechanically durable (less than 2.5% broken into finer particles after each handling) and less ash content (below 0.7%) [25]. Due to its high price compared to firewood, it has a very limited use in residential heating or cooking purpose. However, biomass pellets are used for bio-power generation and also for energy efficient stoves. Organic binders

Biomass

Siz e reduction

Pellets

Solid fuels

Fig. 5. Biomass pellets production process

The global production of wood pellets was 22 million tons in 2013 and projected to increase as 45.2 million tons in 2020 [26]. Europe and Northern America account for almost all global production (62% and 34% respectively) and consumption (81% and 15% respectively) [27]. Germany is currently the Europe‘s largest pellet producer with 2 million tons whereas United Kingdom is the Europe‘s largest consumer of pellets with 4.54 million tons. The U.S. and Canada are the main supplier of wood pellets to Europe. Asia and Africa soon become pellet exporters to Europe, Japan and Korea [28]. 3) Biomass charcoal Heating densified biomass materials (say wood) in a kiln or furnace at around 400 °C in the absence of oxygen until no volatiles are left yields high quality charcoal [29] (5). Good quality charcoal has an energy content of 28-33 MJ kg-1 and burns quickly with little smoke and with a temperature of around 2700 °C [29]. During World War II,

130 in Europe when gasoline was insufficient, many vehicles were driven by wood gas generated by partial combustion of charcoal in a gasifier [30]. Even today charcoal is still a useful product for cooking, heating, air and water purification, and steel making. C6H10O5  3.75CH 0.60O0.13(charcoal )  2.88H 2O (5)  0.5CO2  0.25CO + C1.5H1.25O0.38( tar)

About 51 million tons of wood charcoal was produced in 2013, with an increase of 9% from the year 2009. In 2013, Africa accounted for 61% of global charcoal production. In 2012, Brazil, India, China, U.S., and Russia produced 7.6, 2.9, 1.7, 0.85, and 0.053 million tons of charcoal, respectively [28]. Charcoal production trend is mostly unchanged in U.S., Europe and Asia. In Africa, charcoal is mainly used in urban households for cooking and in Latin America and Caribbean, the steel industry is the biggest consumer [28]. 4) Bioethanol (Cellulosic ethanol) Lignocellulosic biomass is currently the only renewable feedstock material to produce liquid fuel. Lignocellulose comprises carbohydrate polymers such as cellulose and hemicellulose which are tightly bound to lignin. Now, the current technology is to produce alcohol by fermenting plant biomass-derived simple sugars (6). (C6H10O5 )n + nH2O  nC6H12O6  2nCH3CH 2OH + 2nCO2

(6) cellulose n162 100.00

glucose n180 111.11

ethanol n92 56.79

Ethanol can be used as a gasoline substitute to power petrol engines. Commercial production of bioethanol from lignocellulosic materials (Fig. 6) has not been able to start spontaneously due to the low profitability with the current conversion technology and cost effective feedstock supply system. Theoretically, referring to (3) the maximum conversion efficiency of cellulose to ethanol is approximately 56% on the weight basis. In practice, between 40 and 48% of glucose is actually converted to ethanol with 46% fermentation efficiency, i.e. 1000 kg of fermentable sugar would produce about 583 liter of pure ethanol (specific gravity at 20 °C = 0.789) [31]. Lignin Lignocellulosic biomass

Hydrolysis

Pre-treatment

Glucose

Xylose

Fermentation

Distillation Bioethanol


CO2

Biofuel Generation Technologies: A global perspective Fig. 6. Bioethanol production process from lignocellulosic biomass

Worldwide, the first commercial scale cellulosic ethanol plant (The Crescentino Bio-refinery, Crescentino, Vercelli, Italy) entered into full operation on October 9, 2013 [22]. The Energy Independence and Security Act (EISA) of 2007 regulates that the U.S. reduces its gasoline consumption by 20% within 10 years and increases biofuel addition to gasoline from 4.7 billion gallons in 2007 to 36 billion gallons in 2022, with 21 billion gallons of biofuels (bioethanol 18.15 billion gallons) from non-corn products. It is clear that commercial production of cellulosic ethanol will speedily expand in the near future, boosting the global production and utilization of bioethanol as a gasoline alternative. South Asia‘s first demonstration plant for cellulosic bioethanol production process has initiated by Praj Industries Limited [32]. 5) Biodiesel (from non-edible oil seeds) Production of biodiesel from non-edible oil seeds come under second generation biofuels (Fig. 7). Non-edible oil crops

Non-edible oils

Transesterification

131 wastes like manure, plant residues are gradually decomposed in an anaerobic environment to CH4 (methane) and CO2 (7). digestion C6H12O6 Anaerobic    3CO2  3CH4 (7) Raw biogas consists of 60-65% of CH4, 30-35% of CO2, and small quantity of water vapour, H2 (hydrogen) and H2S (hydrogen sulphide) [36]. A typical biogas plant would yield 120 m3 of biogas from one ton dry bio-waste that can generate roughly 200 kW h of electricity [37]. Methane from biogas is stored at high pressure, commonly known as compressed natural gas (Bio CNG) which can be used as a 1)transportation fuel substitute. Cooking fuel Organic wastes / manures

Digestion

Biogas

Engine

Methane

Generator

compressed

Electricity

Bio-CNG

Fig. 8. Biogas production and utilization pathways

Biodiesel

Transportation fuel

+

Glycerol

Value added chemicals

Fig. 7. Biodiesel production process from non-edible oil crops

The process is same as in case of biodiesel production from edible oil seeds (2). Since more than 95% of the biodiesel is synthesized from edible oil, it is believed that this may bring global imbalance to the food supply and demand market. To overcome this issue, many researcher have tested non-edible vegetable oils such as Madhuca indica, Jatropha curcas and Pongamia pinnata and found it to be suitable for biodiesel production under the experimental conditions with 97-98% yield [33]. The U.S. is the biggest biodiesel producer (4.8 billion liters) followed by German (3.1 billion liters) and Brazil (2.9 billion liters) in year 2013 [34]. The world biodiesel production from non-edible sources is below 5% of the total biodiesel production. In U.S., solely soybean oil comprises 90% of total feedstock (in terms of oil equivalent) used to produce biodiesel while the rest of feed stocks include rapeseed oil, corn oil and animal fats. The European Union (E.U.) at the moment is producing only 2% of biofuel from second generation feed stocks. The principal feedstock for biodiesel in the E.U. is rapeseed oil i.e. 68% of total feedstock in terms of oil equivalent [35]. In India, NBP of 2009 targets 20% of biodiesel (only from non-edible source) blending with diesel by 2017.

China already have nearly 42 million household digesters in the rural areas which is expected to double by 2020 [38]. India has more than 4.5 million small-scale anaerobic digesters to produce biogas from manures [22]. This sector has been developed slowly due to various challenges such as initial capital layout, digester maintenance, availability of raw material, economic viability etcetera. Globally, there are 17.7 million natural gas vehicles in 2013, led by Iran with 3.3 million, Pakistan (2.79 million), Argentina (2.24 million), Brazil (1.74 million), Capital china (1.57 million) and India (1.5 million) [39]. It is estimated that Bio CNG can replace 2/3rd of India‘s natural gas import which is currently pegged at 12.15 billion cubic meter [40]. 7) Syngas Gasification is commercially practiced to produce syngas (Fig. 9). Syngas is a gaseous biofuel produced from gasification or pyrolysis of plant materials. Chemically syngas consists of 30-60% CO, 25-30% H2, 5-15% CO2, 05% CH4, and lesser portions of H2O, H2S, NH3, and others, depending on the feedstock. The typical gasification of wood to syngas has a carbon conversion rate of 92% (wood to CO, CO2, CH4), a hydrogen conversion rate of 71% (wood to H2, CH4), and an energy conversion rate of 62% (wood bioenergy to syngas energy). The syngas yield is around 1.2 N m3 kg-1 wood (2.3 N m3 kg-1 if with 48% N2) [41].

6) Biogas (Bio-methane) Biogas is a renewable gaseous biofuel, generated by anaerobic digestion of organic wastes (Fig. 8). Organic Proceedings of International Conference on Renewable Energy and Sustainable Environment – RESE 15 Dr. Mahalingam College of Engineering and Technology, Pollachi-642003, India. August 10-13, 2015

Biofuel Generation Technologies: A global perspective

Cooking fuel

Biomass

Gasification

Producer gas

Tar cracking +cleaning

CO + H2

Synthetic diesel

Fig. 9. Biomass gasification process

European counties mainly Sweden, Portugal, Finland and Germany are producing power, liquid fuels (Synthetic diesel) and gaseous fuel (Synthetic Natural Gas) from biomass since 1983 [42]. In Asia, Japan and China are the leading producers of liquid fuels through biomass gasification. In India, biomass gasifier have been set up mainly for off grid power supply for rural areas and captive power generation application in industries [43]. C. Status of third generation biofuels 1) Algal biodiesel Algal biodiesel, a derived transport fuel from algae is today considered as a third generation biofuel (Fig. 10). There is no competition with food crops as algal can grow practically anywhere, simultaneously they have potential to absorb huge amounts of CO2. In addition, algae can provide value-added co-products, including nutraceuticals, animal feed, cosmetics and other bio-based products, while producing sustainable fuels. Algal biomass

Residual algal biomass

Extraction

Algal oil

Pigments and carotenoids

Algal biodiesel

Transportation fuel

Pharmaceutical products

Fig. 10. Biodiesel production process from Algal biomass

In year 2015, Algenol, a global industrial biotechnology company will establish its first commercial facility in the U.S. In Indian context, algae farming in less than 2-3% of country's total land can make the country self-sufficient in liquid fuel. In India, the Sundarbans delta, spread over 4,260 km2 on the Bay of Bengal, can be used for algal cultivation and extraction of biodiesel without interfering on crop lands [44]. V. FUTURE TREND Grain alcohol competes with animal feed and human food for the source materials. To minimize the adverse impacts, manufacturing second-generation bioethanol from non-food lignocellulosic plant materials has been explored. Development of cellulosic ethanol has been much slower because the technologies are not well developed and feed stocks are more expensive than previously hoped. But, EISA of 2007 which limits the conventional ethanol

132 (mainly corn ethanol) to 15 billion gallons (56.78 billion liters) could promote the cellulosic ethanol production at faster rate. Briquettes are mostly produced as well as consumed in the developing countries like India and China. There has been a move to the use of briquettes in the developed countries, where they are used to heat industrial boilers in order to produce electricity as solid fuel substitution. The use of biomass briquettes is strongly encouraged by issuing carbon credits. India has already started to replace charcoal with biomass briquettes for industrial boilers. Second generation biofuels will gain momentum at least in developing countries in near future. In Asian countries, Azadirachta indica, Calophyllum inophyllum, Jatropha curcas and Pongamia pinnata are the potential oil crops for use as biodiesel and they meet the major specification of biodiesel for use in diesel engine. Moreover, they contain 30% or more oil in their seed, fruit or nut whereas soybeans contain approximately 18% oil. The future of biodiesel lies in the world‘s ability to produce new renewable feedstocks in a sustainable manner to keep the cost of biodiesel competitive with petroleum, without compromising on land necessary for food production, or natural ecosystems. Proponents of algal biofuels make ambitious claims of the potential for contribution to the world‗s future fuel needs. Christi [45] claims that 50% of the U.S. transportation fuel needs could be produced on 4.5 million ha of land if the algal biomass was 30% oil by mass, and by comparison the same production would require 45 million ha of oil palm. Even today, less than 3% of the total fossil fuel will be able to replace by biofuels from first and second generation energy sources. This implies, algae have potential to replace much more percentage of conventional transportation fuel. Unfortunately, the current interest in algal oil is based on assumption of annual average productivity (approximately 22 g m-2d-1) and extractable triglyceride content (varies between 30%-50%) or moderate amount of R&D work at selected region for small duration (~ 5years). Next, fuel production coupled with carbon capture and storage will be the fourth generation biofuel technology. This novel bioconversion process will not only focus on alternate and efficient renewable solution but also fight against climate change. VI. CONCLUSION There is no doubt that good progress in research and development has been made during the past decade following increasing public and private investments. A lot of research has to be done for successful outcome through evaluation of innovative conversion technologies with improved performance and efficiencies. There is also a better understanding by the industry of the overall feedstock supply chain, whether it could ben from crop and forest residues or from purpose grown crops, necessary to provide consistent quality feedstock delivered all year-round to the


Biofuel Generation Technologies: A global perspective conversion plant gate. Overall, there is a need for technical breakthrough in different generations of biofuel discussed above which can significantly lower the production costs and accelerate investment and deployment. Unless it is expected that successful commercialization of biofuel will take another decade or so. ACKNOWLEDGMENT The authors sincerely thank Prof S.K. Jha, SJMSOM of IIT Bombay for his valuable comments. The authors would also like to acknowledge Centre for Technology Alternatives for Rural Areas, IIT Bombay for all kinds of support. REFERENCES [1]

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