Biochemical Conversion Technology

• Stages of Lignocellulosic Bioethanol Production:
• The biochemical platform for ethanol synthesis from lignocellulose follows four sequential operations:

• Pretreatment: Physical/chemical breakdown of crystalline cellulose and removal of hemicellulose and lignin sheath.
• Enzymatic Hydrolysis (Saccharification): Cellulase enzymes depolymerize cellulose into fermentable hexose sugars (glucose).
• Fermentation: Microbial conversion of hexoses/pentoses into ethanol using yeast (Saccharomyces cerevisiae).
• Distillation & Dehydration: Rectification and molecular sieve adsorption to concentrate hydrous ethanol to anhydrous grade ($\gt 99.5\%$).
  • Pyrolysis: A thermochemical process converting dry biomass into bio-oil, syngas, and biochar, which is not part of the biochemical bioethanol route.

• Conclusion: Pyrolysis (Option 4).

• Objectives and Characteristics of Liquid Biofuels:
• Liquid biofuels (bioethanol, biodiesel) are intended to:
• Provide a sustainable, renewable domestic alternative to fossil hydrocarbons.
• Substantially reduce life-cycle greenhouse gas emissions and environmental pollution.
• Deliver a favorable Net Energy Ratio (NER $\gt 1.0$), ensuring that the usable energy output exceeds the fossil energy input invested during cultivation and processing.
• Biofuels are definitely not intended to provide low energy output per unit input.
• Conclusion: Provide low energy output per unit input (Option 4).

Correct option: (4) Provide low energy output per unit input

Matching the items of List I with List II for India scenario in biofuel - potential – options for transport fuel – impacts studies:

The correct combination is Option 2: (A) - (II), (B) - (III), (C) - (1), (D) - (IV).

Correct option: (2) (A) - (II), (B) - (III), (C) - (1), (D) - (IV)