Synthetic Fuel

Synthetic fuel refers to liquid or gaseous fuels produced artificially from sources other than crude oil, such as coal, natural gas, biomass, or even carbon dioxide and hydrogen. These fuels, often termed synfuels, are chemically similar to conventional petroleum products like petrol, diesel, or kerosene, but they are derived through chemical conversion processes rather than natural refining. Synthetic fuels offer an alternative to fossil fuels, with potential applications in transport, power generation, and industry, especially in the context of energy security and carbon reduction.

Concept and Definition

Synthetic fuels are hydrocarbons produced by converting raw materials such as coal, natural gas, biomass, or carbon dioxide into liquid or gaseous forms using chemical and thermal processes. The purpose of synthesising fuels is to create a substitute for petroleum-based fuels that can utilise existing infrastructure and engines.
The term generally encompasses several categories of artificially produced fuels:

• Coal-to-Liquid (CTL): Fuel derived from coal.
• Gas-to-Liquid (GTL): Fuel produced from natural gas.
• Biomass-to-Liquid (BTL): Fuel derived from biological material.
• Power-to-Liquid (PTL): Fuel made using hydrogen (from electrolysis) combined with captured CO₂.

Historical Background

The development of synthetic fuels began in the early 20th century, driven by shortages of crude oil and the need for domestic energy independence.

• In Germany during World War II, synthetic fuels were produced on a large scale from coal using the Fischer–Tropsch process and the Bergius hydrogenation process, supplying up to 50% of Germany’s fuel needs.
• In South Africa, during the apartheid era, international oil sanctions led to the establishment of Sasol (South African Synthetic Oil Limited), which pioneered commercial-scale CTL technology.
• Since the 1970s oil crises, many countries have renewed interest in synfuels to diversify energy sources and reduce dependence on imported oil.

Raw Materials for Synthetic Fuel Production

1. Coal:
   • Used in Coal-to-Liquid (CTL) technology.
   • Abundant and reliable, especially in countries with limited oil reserves.
2. Natural Gas:
   • Used in Gas-to-Liquid (GTL) technology.
   • Produces cleaner fuels with lower sulphur and aromatic content.
3. Biomass:
   • Organic materials such as wood, agricultural residues, and waste are used in Biomass-to-Liquid (BTL) processes.
   • Considered renewable and carbon-neutral when sustainably sourced.
4. Carbon Dioxide and Hydrogen:
   • Used in Power-to-Liquid (PTL) technology, which combines CO₂ with hydrogen produced via electrolysis of water using renewable electricity.

Major Production Processes

1. Fischer–Tropsch Process (FT Process):

• Converts synthesis gas (a mixture of carbon monoxide and hydrogen) into liquid hydrocarbons.
• Feedstock: coal, natural gas, or biomass.
• Temperature and pressure are controlled to produce desired fuel types such as diesel, kerosene, or naphtha.
• Used in large-scale plants in South Africa (Sasol) and Qatar (Pearl GTL).

2. Bergius Process:

• Directly hydrogenates coal at high pressure and temperature in the presence of a catalyst to produce liquid hydrocarbons.
• Developed in Germany in the 1920s.

3. Methanol-to-Gasoline (MTG) Process:

• Converts methanol (produced from synthesis gas) into high-octane gasoline using zeolite catalysts.
• Commercially used in New Zealand and China.

4. Gasification and Pyrolysis:

• Biomass or coal is heated in limited oxygen to produce synthesis gas, which can then be processed into liquid fuels.

5. Power-to-Liquid (PTL) / E-Fuels:

• Uses renewable electricity to produce hydrogen via electrolysis and then combines it with captured carbon dioxide to create synthetic hydrocarbons.
• Considered a sustainable route to carbon-neutral fuels.

Types of Synthetic Fuels

1. Synthetic Petrol and Diesel: Produced from coal, natural gas, or biomass.
2. Synthetic Natural Gas (SNG): Methane-rich gas made from coal or biomass gasification.
3. Synthetic Kerosene / Jet Fuel: Used in aviation; can be blended with conventional jet fuel.
4. Methanol and Dimethyl Ether (DME): Oxygenated fuels with clean combustion characteristics.
5. Synthetic Hydrogen: Though not a hydrocarbon, hydrogen produced from renewable sources is a clean synthetic energy carrier.

Advantages of Synthetic Fuels

• Energy Security: Enables nations with limited oil reserves but abundant coal, gas, or biomass to meet fuel demands domestically.
• Compatibility: Can be used in existing engines, pipelines, and refineries without modification.
• Cleaner Combustion: Low sulphur content reduces air pollution and improves engine efficiency.
• Utilisation of Waste Resources: Biomass and waste-to-fuel processes contribute to waste reduction.
• Carbon Neutral Potential: When produced using renewable energy and carbon capture, synthetic fuels can achieve net-zero emissions.

Disadvantages and Challenges

• High Production Cost: Synfuel production is expensive due to capital-intensive technology and energy requirements.
• Energy Intensive: Conversion processes consume large amounts of energy, reducing overall efficiency.
• Environmental Concerns: CTL and GTL processes release significant carbon dioxide unless carbon capture systems are employed.
• Water Usage: Large quantities of water are required in gasification and cooling stages.
• Economic Viability: Dependent on crude oil prices—synthetic fuels become competitive only when oil prices are high.

Applications

• Transport Sector: Used as drop-in fuels for vehicles, aircraft, and ships.
• Military and Defence: Countries like the United States and China explore synthetic jet fuels for strategic independence.
• Power Generation: Synthetic natural gas and methanol are used in turbines and fuel cells.
• Chemical Industry: Acts as feedstock for producing lubricants, waxes, and petrochemicals.

Global and Indian Scenario

Global Perspective: Countries such as South Africa, Germany, Qatar, China, and Japan have invested in synthetic fuel technologies. South Africa’s Sasol remains a global leader in CTL and GTL production. The Pearl GTL Plant in Qatar, operated by Shell, is the world’s largest gas-to-liquid facility.
India’s Context: India has vast coal reserves, making Coal-to-Liquid (CTL) a potential strategic avenue for reducing crude oil imports. Institutions such as the Indian Institute of Petroleum (IIP) and Indian Oil Corporation (IOC) have been researching CTL and Biomass-to-Liquid (BTL) technologies. Pilot projects in Jharkhand and Chhattisgarh have explored coal-based fuel synthesis. India’s push towards green hydrogen and carbon capture aligns with developing sustainable synthetic fuels in the long term.

Environmental Considerations

Synthetic fuel production’s environmental footprint depends largely on the energy source used. If powered by renewable electricity and coupled with carbon capture, it can lead to carbon-neutral or even carbon-negative fuel cycles. However, fossil-based synfuel without emission control contributes to greenhouse gas accumulation. Sustainable development of synthetic fuels requires a transition to renewable inputs and strict emission regulations.

Future Prospects

The future of synthetic fuels lies in combining renewable energy, green hydrogen, and carbon recycling technologies. As global efforts intensify to achieve net-zero emissions, synthetic fuels can play a transitional role in decarbonising sectors like aviation, shipping, and heavy transport, where direct electrification remains challenging.
Emerging trends include:

• Expansion of Power-to-Liquid and E-fuel projects in Europe and Asia.
• Integration of carbon capture and utilisation (CCU) systems.
• Development of bio-based synthetic fuels to achieve full sustainability.