V. K. Joshi, Abhishek Walia and Neerja S. Rana

9.1 Introduction

Ethanol, a solvent, extractant, and antifreeze, is used for synthesis of many sol­vents in the preparation of dyes, pharmaceuticals, lubricants, adhesives, detergents, pesticides, explosives, and resins for the manufacture of synthetic fibers and liquid fuel [163]. Ethanol is a major solvent in industries and ranks second only to water [152].

It is also employed as a solvent for resins, cosmetics and household cleaning products. The ethanol obtained from biomass-based waste materials or renewable sources is called as bioethanol and can be used as a fuel, chemical feedstock, and a solvent in various industries. Besides ethanol, biofuels containing butanol, pro­panol, 2-methyl 1-butanol, isobutanol, isopropanol, etc. are also employed. Bio­ethanol produced by fermentation is rapidly gaining popularity all over the world. The US, Brazil, Japan, France, U. K., Italy, Belgium, and The Netherlands are among the few countries widely using bioethanol for various uses [98]. It has certain advantages as petroleum substitutes, viz., alcohol can be produced from a number of renewable resources, alcohol as fuel burns cleaner than petroleum which is environmentally more acceptable. It is biodegradable and thus, checks pollution. It is far less toxic than fossil fuels. It can easily be integrated to the

V. K. Joshi (H)

Department of Food Science and Technology,

Dr. Y. S. Parmar University of Horticulture and Forestry, Nauni, Solan, Himachal Pradesh, India e-mail: vkjoshipht@rediffmail. com

A. Walia • N. S. Rana Department of Basic Sciences,

Dr. Y. S. Parmar University of Horticulture and Forestry, Nauni, Solan, Himachal Pradesh, India e-mail: sunny_0999walia@yahoo. co. in

C. Baskar et al. (eds.), Biomass Conversion,

DOI: 10.1007/978-3-642-28418-2_9, © Springer-Verlag Berlin Heidelberg 2012 existing transport fuel system, i. e., up to 5% bioethanol can be blended with conventional fuel without the need for modification.

Gasohol (mixture of gasoline and alcohol) is widely used to run vehicles in developed countries. The use of alcohol as fuels is gaining vast popularity day-by­day and gasohol program is encouraged throughout the world. By encouraging bioethanol use, the rural economy could also receive a boost by growing the necessary crops. New technologies are being developed that are economically and strategically superior.

The interest in bioethanol as a fuel in response to petroleum price increase is the most significant factor influencing the world ethanol market. Recent oil shortage and escalating oil prices have led scientists to develop alternative energy sources to substitute petroleum. Global warming alerts and threats are on the rise due to the over utilization of fossil fuels. Alternative fuel sources like bioethanol and biodiesel are being produced to combat these threats. Bioethanol production from plant biomass has received considerable attention recently in order to mitigate global warming and demands for petroleum not from a finite resource and is a greenhouse gas emission. The road transport network accounts for 22% of all greenhouse gas emissions, and through the use of bioethanol as some of these emissions will be reduced as the fuel crops absorb CO2. Also, blending bioethanol with petrol will help extend the life of diminishing oil supplies and ensure greater fuel security, avoiding heavy dependence on oil producing nations.

Biofuel obtained from renewable sources can be classified on the basis of their production techniques as given below:

• First-generation fuels refer to biofuels made from plants rich in oil and sugar.

• Second-generation biofuels (Biomass to liquid) are made from organic materi­als, such as straw, wood residues, agricultural residues, reclaimed wood, saw­dust, and low value timber.

• Biofuels of third generation are produced from algae by using modern gene and nanotechnologies.

• Fourth-generation biofuels are produced from vegetable oil by using hydrolytic conversion/deoxygenating.

Tables 9.1 and 9.2 show biofuels of the four generations, their substrates and technological processes of their production.

It is apparent that different types of substrates can be employed to produce bioethanol. Accordingly, modification in its production technology has been made. The replacement of ethanol by ethylene is reversed in less industrialized nations. In Brazil and India, ethylene and its chemical derivates are produced by catalytic dehydration of fermentative ethanol [5].

The USA and Brazil are currently the primary producers of fuel ethanol, pro­ducing 49.6 and 38.3% of the 2007 global production, respectively. US bioethanol production is almost entirely from maize (corn) starch, which is converted into fermentable glucose by the addition of amylase and glucoamylase enzymes. In 2007, 24.6 billion L of ethanol was produced in the USA, that comprised of only 3.2% of gasoline consumption on an energy-equivalent basis [188].

Source [172]

The production costs of various chemicals from ethanol and petroleum feed­stocks are compared in Table 9.3. Clearly, the production of bioethanol from first generation is economically unreasonable because of discarding cellulose and hemicellulose which constitute the majority of carbon resources of plants. Fur­thermore, the biofuels of this generation also compete with food products intended for human consumption. Thus, second-generation bioethanol production is important as it allows improved CO2 balance and make use of cheap, waste source which does not compete with human food products.

In brief, the use of ethanol as a biofuel is gaining increasing popularity. Although it is produced from several sources but the technologies using the waste material for its production is most attractive as it does not interfere with food particular substrates needed for the ever increasing world population. Different types of waste materials, their composition, biochemistry, microbiology, and the technology involved in bioethanol production have been reviewed in this chapter. New strategies and future thrust has also been briefly highlighted.