The second generation biofuel technology for the production of ethanol is cellulosic ethanol technology. Cellulose plants are the main source for the production of cel — lulosic biofuels. They have categorized it as “energy crops” rather than the crops for food production. Some of the examples are perennial grasses and trees, like switch grass and Miscanthus. Another source of cellulosic biomass is residues (crop) such as stems and leaves.

Generally it has been observed that the lignocellulosic biomass is the main feed stock for ethanol and includes various materials like agricultural residues such as corn stover, husks, bagasse, woody crops, waste paper and municipal and industrial wastes. Environmental issues can be resolved by using or disposal of agricultural waste residues and other wastes for the production of bioethanol. There is no inter­ference of the lignocellulosic feedstocks with food security and are important in terms of energy security in all areas, environmentally and also agricultural develop­ment and employability.

Two different processing methods can be used for the production of ethanol from lignocellulosic biomass. These are as follows:

• Biochemical Method—In this method before fermentation, enzymes and other micro-organisms are used for the conversion of cellulose and hemicellulose part of the feedstocks into sugars for the production of ethanol.

• Thermo chemical Method—In this method pyrolysis/gasification technologies are used to produce a synthesis gas (CO+H2) from which a range of long carbon chain biofuels, such as synthetic diesel, can be reformed.

The main compositions of the lignocellulosic biomass are lignin, polysaccha­rides cellulose, and hemicellulose. It is generally seen that the use of lignocellulosic biomass becomes difficult because of the stability of the polysaccharides and it became difficult to ferment the pentose sugars by Saccharomyces cerevisiae. Hydrolysis of the polysaccharides must be undertaken for the conversion of ligno­cellulosic biomass to biofuels, or broken into simple sugars by using acid or enzymes. To overcome these problems several biotechnology-based approaches are being used which include development of strains of Saccharomyces cerevisiae, which is used to ferment pentose sugars. Generally the biochemical routes are used to produce ethanol from lignocellulosic biomass. The three main steps involved for the production of ethanol are pretreatment, hydrolysis of enzymes, and fermenta­tion. In detail, first the pretreatment of Biomass is undertaken to enhance the advancement of enzymes. After pretreatment hydrolysis of biomass can be under­taken to change polysaccharides into monomer sugars, like glucose and xylose.

Simultaneous saccharification and cofermentation (SSCF) process can be used to convert pretreated biomass into ethanol. Generally it is assumed that the pretreat­ment is an important step used to improve the enzymatic hydrolysis of biomass. The basic step involved in this process is that it modifies the physical and chemical properties of biomass and ultimately enhances the enzyme access and efficacy l eading to modification in crystallinity and degree of polymerization (cellulose). This process also increases the internal surface area and pore volume of pretreated biomass leading to facilitate substantial improvement in enzymes accessibility. Enzymatic hydrolysis step also enhances the rate and yield of monomeric sugars.