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Vegetable oil as Alternate Fuel
Vegetable oil, used as Straight Vegetable Oil (SVO) or converted to Biodiesel, serves as a renewable, biodegradable alternative to petroleum diesel, offering similar heat values but requiring engine modifications to address high viscosity. It significantly reduces greenhouse gas emissions, though it can increase NOx emissions, and offers a viable, eco-friendly fuel option for diesel engines. 
Key Aspects of Vegetable Oil Fuel
  • SVO/PPO (Straight/Pure Plant Oil): Used directly in modified diesel engines; requires heating systems to lower viscosity for proper combustion.
  • Biodiesel: Created via transesterification (treating oil with alcohol), resulting in a fuel that behaves similarly to petroleum diesel without engine modifications.
  • Engine Modifications: Essential for direct use to prevent carbon buildup, ring sticking, and injector fouling caused by high viscosity.
  • Sources: Both edible (soybean, peanut, cottonseed) and non-edible (jatropha, neem, karanj) oils are used, with waste vegetable oil being a sustainable option.
  • Performance: Vegetable oil blends provide good, consistent power output, comparable to diesel while lowering particulate matter emissions. 
Advantages
  • Renewable & Sustainable: Reduces dependence on fossil fuels.
  • Environmental Impact: Low sulfur content and net lower CO2 emissions.
  • Performance: Nearly equivalent energy density (heat values) compared to diesel. 
Disadvantages
  • High Viscosity: Causes fuel atomization issues, requiring preheating or conversion.
  • Engine Issues: Long-term use without proper conversion can lead to carbon deposits.
  • Cost: Biodiesel production involves chemical processing costs. 
Commonly Used Oils
  • Soybean and Rapeseed Oil: Common for biodiesel blends.
  • Non-Edible Oils: Jatropha, Mahua, and Karanja are heavily researched in India for energy security.
  • Waste Cooking Oil: Recycled oil is a cost-effective and environmentally friendly option. 
Common Methods to Improve Suitability
  • Blending: Mixing with diesel (e.g., B20 = 20% oil) reduces viscosity.
  • Preheating: Using a heat exchanger to reduce viscosity before injection.
  • Transesterification: Chemical process to create biodiesel.