Bio-ethanol is a form of ethanol (ethyl alcohol) produced from the fermentation of sugars found in crops like corn, sugarcane, or cellulosic materials like wood. Fermentation is a biological process in which microorganisms (like yeast) break down sugars (usually glucose) into simpler compounds. In the case of bioethanol, fermentation produces ethanol and carbon dioxide as by-products.

Reaction for Ethanol Production

C ₆H ₁₂O ₆ → 3CH ₂H ₅OH+ 3CO ₂

(Glucose → Ethanol + Carbon Dioxide)

This reaction shows that glucose (a sugar from crops like corn or sugarcane) is fermented by yeast, producing ethanol and releasing carbon dioxide. The ethanol can then be distilled and used as a biofuel.

Use in Green Energy:

• Transportation Fuel: Bioethanol is commonly blended with gasoline to create ethanol blends (E10, E85) for use in vehicles. This helps reduce the carbon footprint compared to traditional fossil fuels.
• Cleaner Combustion: Cutting-edge technologies that keep you ahead of industry trends and regulatory changes.
• Green Chemistry: Bioethanol is also used as a solvent in industrial applications, providing a renewable alternative to petrochemical-based solvents.

Conversion of CO2 to Ethanol

Biogas conditioning is the process of transforming raw biogas into high-quality fuels like CBG (Compressed Biogas) and CNG (Compressed Natural Gas).

The conversion of CO₂ to ethanol involves a process called carbon capture and utilization (CCU). In this process, CO₂ is first captured from the atmosphere or industrial emissions and then converted into ethanol through biological or electrochemical methods. In biological conversion, microorganisms like yeast or bacteria are used to fix CO₂ and convert it into ethanol through fermentation. In electrochemical conversion, CO₂ is reduced using electrical energy, typically from renewable sources, to produce ethanol and other chemicals. This process helps reduce CO₂ emissions while producing valuable biofuels, contributing to a circular carbon economy.

Biological Conversion (Fermentation)

In the biological pathway, CO₂ is first converted into glucose (or other sugars), which is then fermented by microorganisms (like yeast or bacteria) to produce ethanol. This process typically involves photosynthesis as the first step (in plants or algae), followed by fermentation.

Fermentation reaction (simplified)

C ₆H ₁₂O ₆ → 2C ₂H ₅OH+ 2CO ₂

Here, glucose (C₆H₁₂O₆) is converted into ethanol (C₂H₅OH) and carbon dioxide (CO₂). The CO₂ used to form glucose comes from the atmosphere or from captured industrial emissions.

Electrochemical Reduction of CO₂

In the electrochemical pathway, CO₂ is directly reduced to ethanol through an electrochemical reaction, usually using renewable electricity.

Key Components of the Electrochemical System

• Electrolyte: Provides ionic conductivity. Commonly aqueous or non-aqueous electrolytes containing ions like bicarbonate (HCO ₃ ^-) or carbonate (CO ₃ ^2-).
• Electrode Materials:
  • Cathode: A catalyst (e.g., copper) facilitates CO ₂ reduction.
  • Anode: Facilitates the oxygen evolution reaction (OER).
• CO ₂ Source: Gaseous CO ₂ dissolved in the electrolyte.
• Electricity: Provides energy to drive the reaction, ideally from renewable sources.

Reactions at the Electrodes

At the Cathode (Reduction of CO₂):

The reduction of CO₂ to ethanol occurs in a multi-step process involving various intermediates.

• Electrolyte: Provides ionic conductivity. Commonly aqueous or non-aqueous electrolytes containing ions like bicarbonate (HCO ₃ ^-) or carbonate (CO ₃ ^2-).
• Electrode Materials:
  • Cathode: A catalyst (e.g., copper) facilitates CO ₂ reduction.
  • Anode: Facilitates the oxygen evolution reaction (OER).
• CO ₂ Source: Gaseous CO ₂ dissolved in the electrolyte.
• Electricity: Provides energy to drive the reaction, ideally from renewable sources.
• Reaction Steps:
  • Initial Electron Transfer: CO ₂ + e ^- → CO ₂ ^•-. The CO ₂ molecule is activated by accepting an electron, forming a CO ₂ radical anion.
  • Formation of Carbon Monoxide (CO): CO ₂ ^•- + e ^- + H ⁺ → CO + OH ^-. CO is a critical intermediate in forming multi-carbon products.
  • C–C Bond Formation (Key Step): Two CO molecules or a CO and CHO group combine to form a carbon-carbon bond.
  • Hydrogenation to Ethanol: Sequential proton (H ⁺) and electron additions reduce the intermediates to ethanol:
    • CO + H ⁺ + e ^- → CHO (formyl group)
    • CHO + H ⁺ + e ^- → CH ₃CH ₂OH (ethanol)
  • Overall Cathodic Reaction (Simplified):

    2CO ₂ + 12H ⁺ + 12e ^- → C ₂H ₆O + 3H ₂O

At the Anode (Oxygen Evolution Reaction)

Water is oxidized to produce oxygen gas, balancing the overall reaction

2H ₂O → 4H ⁺ + 4

Overall Reaction

3CO ₂ + 12H ⁺+12e ^-→ C ₂H ₅OH + 3H ₂O

Both methods contribute to reducing CO₂ emissions while producing ethanol, offering pathways for sustainable fuel production.

Biomass (Rice Straw to Ethanol)

The conversion of rice husk to ethanol involves breaking down its lignocellulosic structure to extract fermentable sugars. The husk is first pretreated using chemical or enzymatic methods to release cellulose, followed by enzymatic hydrolysis to convert cellulose into simple sugars. These sugars are fermented by microorganisms like yeast to produce ethanol and carbon dioxide. The ethanol is then purified through distillation and dehydration to achieve fuel-grade quality, providing a sustainable use for agricultural waste

he conversion of rice husk to ethanol involves a series of biochemical reactions, primarily focusing on the hydrolysis of cellulose and fermentation of glucose. Here's a simplified breakdown of the key reactions:

• Hydrolysis of Cellulose (using enzymes): Cellulose + H ₂O Cellulase → Glucose
• Fermentation of Glucose (by yeast or other microorganisms): C ₆H ₁₂O ₆ ^Yeast → 2C ₂H ₅OH + 2CO ₂
• C₆H₁₂O₆ (glucose) is converted into C₂H₅OH (ethanol) and CO₂ (carbon dioxide).

• These reactions enable the transformation of the complex sugars in rice husk into ethanol, a renewable fuel.