Today,ethanol and biodiesel are predominantly produced from corn kernels, sugar cane or soybean oil. However another biofuel feedstock, lignocelluloses—the most abundant biological material on earth is being explored. Lignocellulosesis everywhere—wheat straw, corn husks, prairie grass, discarded rice hulls or trees. The race is on to optimize the technology that can produce biofuels from lignocelluloses sources more efficiently—and biotech companies are in the running. There is campaign, which advocates that 25% of US energy come from arable land by 2025. The EU had called for a threefold increase in biofuel use by 2010, to 5.75% of transportation fuel.
Use of biomass for energy and industry allows a significant quantity of hydrocarbons to be consumed without increasing the CO2 content of the atmosphere and thus makes a positive contribution to the Greehouse effect and to the problems of "global change" as occurs in both industrialized and developing countries (Kumar,2008, Kumar 2011) Climate change is any long-term significant change in average temperature, precipitation and wind patterns. It takes place due to emissions of greenhouse gases. Carbon dioxide (CO2)is the most important greenhouse gas and increasing the use of biomass for energy is an important option for reducing CO2 emissions. Carbon dioxide emission is projected to grow from 5.8 billion tonnes carbon equivalent in 1990 to 7.8 billion tonnes in 2010 and 9.8 billion tonnes by 2020 (Fig.1) (Kumar, 2001) .
The Kyoto conference agreement indicates the role clean energy sources will play in future. Biomass is renewable, non pollutant and available world wide as agricultural residues, short rotation forests and crops. Thermochemical conversion using low temperature processes are among the suitable technologies to promote a sustainable and environmentally friendly development. Biomass can play a dual role in greenhouse gas mitigation related to the objectives of the United Nations Framework Convention on Climate Change (UNFCC) i.e. as an energy source to substitute for fossil fuels and as a carbon store. The fact that nearly 90 percent of the worlds population will reside in developing countries by 2050 probably implies that local solutions for energy needs will have to be found to cope up with the local energy needs on one hand and environment protection on the other hand (Table 2).Biomass should be used instead of fossil energy carriers in order to reduce (i) CO2 emissions(ii) the anticipated resource scarcity of fossil fuels and (iii) need to import fuels from abroad(Kumar, 2001).
1.1 Global land availability and biomass production:
Global land availability estimates for energy crop production vary widely between 350 and 950 million hectares (Alexandratos, 1995). Biomass resources are potentially the worlds largest and sustainable energy source a renewable resource comprising 220 billion oven dry tones (about 4500 EJ) of annual primary production. The annual bio-energy potential is about 2900 EJ though only270 EJ could be considered available on a sustainable basis and at competitive prices. Current commercial and non-commercial biomass use for energy is estimated at between 20 and 60 EJ/are presenting about 6 to 17 % of the world primary energy. Most of the biomass is used in developing countries where it is likely to account for roughly one third of primary energy. As a comparison, the share of primary energy provided by biomass in industrialized countries is small and is estimated at about 3 % or less (Fig 3).Agriculture and allied sectors contribute nearly 22 percent of Gross Domestic Product (GDP of India), while about 65-70 percent of the population is dependent on agriculture for their livelihood. The agricultural output,however, depends on monsoon as nearly 60 percent of area sown is dependent on rainfall. Most of the population dependent on agriculture in India uses biomass for fuel in open chulhas ( firestoves) with poor fuel efficiency and lot of smoke generation causing serious asthmatic problems in rural women and children.
1.2 Advantages of using biofuels:
There are several advantages of using biofuels: biodiesel burns up to 75% cleaner than petroleum diesel fuel. Biodiesel reduces unburned hydrocarbons (93% less), carbon monoxide (50% less) and particulate matter (30% less) in exhaust fumes, as well as cancer-causing PAH (80% less) and nitrited PAH compounds (90% less) (US Environmental Protection Agency), and Sulphurdioxide emissions are eliminated (biodiesel contains no sulphur). Biodiesel is plant-based and using it adds noextra CO2 greenhouse gas to the atmosphere. Nitrogen oxide (NOx) emissions may increase or decrease with biodiesel but can be reduced to well below petro-diesel fuel levels. Biodiesel exhaust is not offensive and doesn't cause eye irritation.
Biodiesel can be used in any diesel engine withou tmodification. Biodiesel can be mixed with petro-diesel in any proportion, with no need for a mixing additive. Biodiesel has a higher cetane number than petroleum diesel because of its oxygen content. The higher the cetane number,the more efficient the fuel -- the engine starts more easily, runs better and burns cleaner. With slight variations depending on the vehicle, performance and fuel economy with biodiesel is the same as with petro-diesel. Biodiesel is a much better lubricant than petro-dieseland extends engine life -- even a small amount of biodiesel means cleaner emissions and better engine lubrication: 1% biodiesel added to petro-diesel will increase lubricity by 65%. The ozone-forming (smog) potential of biodies elemissions is nearly 50% less than petro-diesel emissions.
1.3 EU mandate:
Worldwide production of biodiesel increased by 60% in 2005, and ethanol by 19% over theprevious year’s production, as per World watch Institute, USA. The EU mandated that three times more than the current level of 2% of the total energy contentof petrol and diesel needs to come from renewable fuels. Countries like Thailand are aiming for a 10% renewable mix in the next five years; India 20%by 2020. Sweden has stated that it aims to become 100% energy independent by 2020; most of this independence will come through its own nuclear power, but renewable fuels will likely make up the balance..
1.4 Objectives of Biofuel production:
• First generation biofuel: salt and drought resistance for growing in wastelands.
• Second and third generation biofuels:altering host material and /or developing new enzyme systems.
• Metabolic engineering for entire product
• Industrial application of biofuel inclusive of related bio products of commercial value from fourth generation products.
Next generation bio-fuels shall involve technical components (1) Biological sciences: Plant biotechnology, Cellular andmolecular biology, microbial /industrial biotechnology. (2) Chemical technologysciences: catalysis, reaction engineering and separations
Present status and future prospects:
• 1. Wood, wood chips agriculture waste to Briquetting, Gasifier, Vacuumpyrolysis or Bio-gas, heat and electricity generation.
• 2. Oil to trans-esterification to obtain Fatty acid methyl ester (FAME)e.g. Rape seed methyl ester ( RME)
• 3. Liquid hydrocarbons to hydro-cracking – cracking of tri-terpenoid chain and adding of hydrogenusing zeolite catalyst in bio-refinery.
• Technically, Mono-alkyl esters of long chain fatty acids derivedfrom renewable lipid feedstock such as vegetable oils and animal fats foruse in Compression Ignition engines”.
• The definition eliminates pure vegetable oils
Dependingon the feed stock it may be referred as
– Soybean methyl ester - SME or SOME
– Rape methyl ester - RME
– Fatty acid methyl ester - FAME (a collective term including both of theabove)
– Vegetable oil methyl ester - VOME yielding plants provide bio-diesel.
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