Understanding Renewable Diesel and Biodiesel

by | Mar 11, 2025

As the world transitions toward sustainable energy solutions, renewable diesel and biodiesel have emerged as key alternatives to conventional fossil diesel.

While often confused, these two fuels differ significantly in their production processes, chemical compositions, and applications. This article provides an authoritative breakdown of their characteristics, best uses, and compatibility with each other and conventional diesel.

Defining Renewable Diesel and Biodiesel

Biodiesel

Biodiesel is a renewable fuel produced through transesterification, a chemical process where triglycerides from fats and oils react with an alcohol, typically methanol, in the presence of a catalyst. This reaction yields fatty acid methyl esters (FAME), which serve as the primary component of biodiesel, with glycerol as a byproduct.
Common feedstocks for biodiesel include:
  • Vegetable oils (soybean, rapeseed, palm oil)
  • Animal fats
  • Used cooking oils
  • Algae-derived oils
  • Agricultural waste and biomass

Renewable Diesel

Renewable diesel, sometimes referred to as green diesel, is produced through hydro processing, a technology that employs hydrogen to remove oxygen from triglycerides in a catalytic reaction. This results in a hydrocarbon fuel that is chemically identical to petroleum diesel.

Typical feedstocks for renewable diesel include:
  • Vegetable oils
  • Animal fats
  • Waste oils
  • Agricultural waste and biomass

By utilising agricultural waste and biomass, both biodiesel and renewable diesel contribute to a circular economy, reducing waste and creating additional revenue streams for the agricultural sector.

Key Characteristics of Biodiesel and Renewable Diesel

Biodiesel Characteristics

  • Contains oxygen and has a slightly different chemical structure than fossil diesel.
  • Has a high boiling point, low vapor pressure, and a flash point exceeding 130°C.
  • Density of approximately 0.88 g/cm³, slightly higher than petroleum diesel.
  • Calorific value of around 37.27 MJ/kg, roughly 9% lower than conventional diesel.
  • Excellent lubricating properties, which enhance engine longevity.
  • High cetane number, leading to efficient ignition and combustion.

Renewable Diesel Characteristics

  • Chemically identical to petroleum diesel, making it a “drop-in” fuel.
  • Contains no oxygen, sulphur, or aromatics, reducing emissions and improving air quality.
  • Compatible with existing diesel infrastructure and engines without modifications.
  • Higher energy content compared to biodiesel, making it more efficient.
  • High cetane number, ensuring superior combustion performance.

Best Uses and Applications

Biodiesel Applications

Biodiesel can be used as a pure fuel (B100) or blended with petroleum diesel in various proportions. Blends such as B20 (20% biodiesel, 80% conventional diesel) are commonly used in:
  • Public transportation
  • Commercial trucking
  • Agricultural machinery
  • Marine vessels
Higher biodiesel blends or pure B100 require engine modifications, particularly in colder climates, due to biodiesel’s higher viscosity and tendency to gel at lower temperatures.

Renewable Diesel Applications

Renewable diesel, being chemically identical to petroleum diesel, can be used as a direct replacement in all diesel engines without modification. Its widespread applications include:
  • Heavy-duty transportation
  • Aviation (as a component of sustainable aviation fuel)
  • Power generation
  • Military and emergency response vehicles

Compatibility and Blending with Conventional Diesel

Both biodiesel and renewable diesel can be blended with fossil diesel. Biodiesel blends are denoted by the ‘B’ factor, such as B20, which indicates the percentage of biodiesel in the mix. However, renewable diesel can be blended seamlessly at any ratio with conventional diesel due to its identical chemical composition. Furthermore, biodiesel and renewable diesel can be combined, offering a fully renewable fuel solution that balances the benefits of both fuels.

Understanding the differences between biodiesel and renewable diesel is essential for making informed decisions regarding sustainable fuel adoption. While both serve as viable alternatives to fossil diesel, their distinct production methods, chemical properties, and compatibility influence their optimal applications. By utilising agricultural waste and biomass as feedstocks, both fuels contribute to waste reduction, lower emissions, and a more sustainable future. Whether through blending strategies or standalone use, these fuels play a crucial role in reducing carbon emissions and promoting a greener future for transportation and energy sectors.

The post Understanding Renewable Diesel and Biodiesel first appeared on Haush.