Bioethanol is a bio-based alcohol (C₂H₅OH) produced through the biological fermentation of carbohydrates derived from renewable agricultural feedstocks. It serves as a low-carbon substitute for fossil-based gasoline and as a versatile industrial alcohol. Because it contains oxygen within its molecular structure, bioethanol enhances combustion efficiency and reduces harmful exhaust emissions.
Feedstocks & Raw Materials
Bioethanol production depends on region-specific agricultural resources:Sugar-Based Feedstocks
Sugarcane (India, Brazil)
Sugar beet
Molasses (by-product of sugar refining)
Starch-Based Feedstocks
Corn (Maize)
Wheat
Cassava
Sorghum
Cellulosic / Advanced Feedstocks (2G Ethanol)
Agricultural residues (rice straw, wheat straw)
Bagasse
Corn cobs
Forestry waste
Energy crops (switchgrass, miscanthus)
Note: Cellulosic bioethanol significantly improves sustainability by avoiding food-vs-fuel conflicts.
Manufacturing Process
1. Feedstock Preparation
Crushing (sugar crops)
Milling and liquefaction (starch crops)
Pre-treatment and hydrolysis (cellulosic biomass)
2. Fermentation
Yeast (Saccharomyces cerevisiae) converts sugars into ethanol and CO₂
Typical fermentation temperature: 30–35°C
Duration: 24–72 hours
3. Distillation
Ethanol separated from fermented mash
Produces ~95% hydrous ethanol
4. Dehydration
Water removed using:
Molecular sieves
Vacuum distillation
Azeotropic distillation
Final purity: 99.5–99.9% anhydrous ethanol
Grades & Specifications
Fuel Grade Bioethanol
Purity: ≥ 99.5%
Water content: ≤ 0.5%
Used for blending with petrol
Industrial Grade Bioethanol
Purity: 95–99.9%
Used in chemicals, coatings, inks, and pharmaceuticals
Extra Neutral Alcohol (ENA)
Highly purified ethanol
Used in beverages and pharma applications
Physical & Chemical Properties
| Property | Value |
|---|---|
| Chemical Formula | C₂H₅OH |
| Molecular Weight | 46.07 g/mol |
| Density | ~0.789 g/cm³ (20°C) |
| Boiling Point | ~78.37°C |
| Flash Point | ~13°C |
| Solubility | Completely miscible with water |
| Energy Content | ~21–23 MJ/L (lower than gasoline) |
| Octane Number | 108–110 (RON) |
Performance Characteristics
Combustion Behavior
Oxygenated fuel → cleaner and more complete combustion
Reduces engine knocking due to high octane rating
Improves throttle response in high-compression engines
Fuel Economy
Lower energy density than petrol
Requires higher volume for same mileage
Offset by improved combustion efficiency
Environmental & Sustainability Benefits
Emission Reductions:
Up to 60–90% lower lifecycle CO₂ emissions
Significant reduction in:
Carbon monoxide (CO)
Unburned hydrocarbons (HC)
Particulate matter (PM)
Carbon Neutral Cycle
CO₂ released during combustion is re-absorbed by crops during growth
Minimal net greenhouse gas contribution
Biodegradability:
Rapid environmental breakdown
Lower risk of long-term soil and water contamination
Blending Standards & Applications
| Blend | Ethanol Content | Application |
|---|---|---|
| E5 | 5% | Standard petrol |
| E10 | 10% | Widely used globally |
| E20 | 20% | India’s ethanol blending program |
| E85 | 70–85% | Flex-fuel vehicles |
| E100 | 100% | Modified engines |
Industrial & Commercial Applications
Fuel Sector: Automotive gasoline blending Flex-fuel vehicles Small engines and generatorsChemical Industry: Solvent for paints, coatings, inks Intermediate for ethyl acetate, acetic acid, ethylene
Pharmaceuticals & Healthcare: Antiseptics and disinfectants Drug formulation solvent
Personal Care & FMCG: Perfumes Cosmetics Sanitizers
Storage & Handling
Storage Conditions
Stainless steel or carbon steel tanks
Moisture-free environment to prevent water absorption
Proper grounding to avoid static discharge
Safety Measures
Highly flammable liquid
Requires flame-proof storage
Classified under Class 3 flammable liquids
Regulatory & Policy Landscape (India Focus)
National Bio-Energy Mission
Ethanol Blended Petrol (EBP) Programme
Target: 20% blending (E20) nationwide
Supports farmers, reduces crude oil imports, and boosts energy security
Advantages vs Limitations
Advantages
Renewable and domestically produced
Reduces fuel import dependency
Cleaner combustion
High octane enhancer
Limitations
Lower calorific value than petrol
Hygroscopic nature (absorbs moisture)
Requires compatible engine materials at higher blends