Cleaner Energy Sources

Cleaner fuels are those fuels which:

• Emit relatively lower pollutants and greenhouse gases
• Act as a bridge between fossil fuels and a future renewable / hydrogen economy

They are especially relevant for:

• Urban transport
• Reducing oil import dependence
• Improving air quality

Alcohol-based Cleaner Fuels: Methanol & Ethanol

Methanol and Ethanol: Basic Understanding

Both methanol and ethanol are alcohols and are increasingly discussed as alternative transport fuels.

🔸 How are they produced?

• From coal, petroleum, natural gas, and biomass waste
• Currently, methanol is mainly produced by:
  • Breaking natural gas (methane) at high pressure and temperature into:
    • Hydrogen (H₂)
    • Carbon Monoxide (CO)
  • These are then recombined to form methanol
    👉 This process is expensive

🔸 A crucial future pathway

• CO₂ can be converted into methanol or methane by reacting it with hydrogen
• This allows:
  • Productive use of CO₂
  • Utilisation of India’s vast coal reserves without directly burning coal

Methanol vs Ethanol (Conceptual Comparison)

Methanol

• Chemical name: Methyl Alcohol (CH₃OH)
• Highly toxic, not fit for consumption
• Used mainly as:
  • Industrial solvent
  • Raw material for chemicals like acetic acid and formaldehyde
• Burns with a bright white flame
• Mostly produced from coal and natural gas

Ethanol

• Chemical name: Ethyl Alcohol (CH₃–CH₂–OH)
• Used in:
  • Alcoholic beverages
  • Food additives
  • Antibacterial wipes and hand gels
• Has antiseptic properties
• Burns with a bright blue flame
• Mostly produced by fermentation of biowaste and food crops

👉 Common point:

• Both are clean fuels, solvents, and can be blended with petrol.

Why is Methanol a Promising Transport Fuel?

✅ Advantages of Methanol as Fuel

• Much cleaner than petrol and diesel
• Lower unit cost of energy compared to petrol, diesel, LPG
• Lighter than petrol and diesel → better combustion
• Produces:
  • No particulate matter (PM)
  • No soot
  • Almost nil SOx and NOx emissions
• M15 blend (15% methanol in petrol):
  • Reduces pollution by 33%
• Replacing diesel with methanol:
  • Pollution reduction of more than 80%
• Requires minimal infrastructure modification compared to CNG or LPG

👉 This makes methanol extremely attractive for developing countries.

Methanol Economy: The Bigger Vision

• The Methanol Economy is seen as a bridge to a Hydrogen-based energy system
• China already uses 10% methanol blending in transport fuels
• In India:
  • NITI Aayog plans to replace 20% of crude oil imports with methanol
  • Government aims to reach 20% fuel blending (methanol, ethanol, biodiesel) by 2030

👉 From UPSC’s perspective, this directly links:

• Energy security
• Climate goals
• Import substitution

LPG, LNG and CNG

Liquefied Petroleum Gas (LPG)

🔹 Composition

• Mainly propane and butane
• Produced as a by-product of natural gas processing and petroleum refining

🔹 Safety Aspect

• LPG is heavier than air
  • In case of leakage, it accumulates near the ground → dangerous in poorly ventilated areas
• Naturally odourless
• Ethyl Mercaptan / Ethanethiol is added to detect leaks (strong smell)

Liquefied Natural Gas (LNG)

🔹 What is LNG?

• Natural gas cooled to −120°C to −170°C
• Stored as a cryogenic liquid

✅ Advantage

• Occupies much less volume
• Allows longer travel range and fewer refuelling stops

❌ Disadvantages

• Very high cost of:
  • Cryogenic storage
  • Transportation
  • Distribution
• Not practical for most developing countries at present

Compressed Natural Gas (CNG)

🔹 What is CNG?

• Natural gas (mainly methane) compressed and stored in cylinders
• Drawn from gas wells or along with crude oil

🔹 Safety Feature

• Lighter than air
  • In case of leakage, it dissipates quickly
• Sulphur-based odorant added for leak detection

✅ Advantages of CNG

• Very clean burning fuel
• Produces much fewer GHGs than petrol or diesel
• Leaves little residue → lower engine maintenance
• Safer due to:
  • High auto-ignition temperature
• Cheaper than petrol and diesel
• High calorific value:
  • 50,000 kJ/kg, higher than petrol

❌ Disadvantages

• Large cylinders reduce boot space
• Shorter driving range
• Limited refuelling stations
• Older vehicles not designed for CNG

Calorific Value: Why It Matters

Calorific value indicates how much energy a fuel produces per kilogram.

Fuel	Calorific Value (MJ/kg)
Hydrogen	141
Methane (CH₄)	55
Ethane (C₂H₆)	52
Natural Gas / CNG	52
Liquefied Petroleum Gas (LPG)	50
Propane	50
Butane	49
Petrol / Gasoline	46.4
Kerosene	46.2
Diesel Fuel	45.5
Biodiesel (Methyl Ester)	37
Ethanol (CH₃–CH₂–OH)	29
Methanol (CH₃OH)	23
Coal (Anthracite → Peat)	17 – 32
Firewood (Dry)	16

🔹 Key Observations

• Hydrogen has the highest calorific value (141 MJ/kg)
• Among liquid fuels:
  • Petrol, diesel, and LPG are much higher than alcohols
• Methanol and ethanol are cleaner but have lower energy density
• Coal varies widely:
  • Anthracite (highest)
  • Peat (lowest)

👉 This explains:

• Why cleaner fuels may require larger volumes
• Why blending strategies are preferred over full replacement