As we continue to seek cleaner alternatives to traditional fossil fuels, biofuels have emerged as a significant part of the solution. As biofuels enthusiasts, we at RINSTAR have noticed a growing debate in the biofuels industry while attending the many biofuels’ conferences that we attend yearly. Which is better – Renewable Diesel or Biodiesel?
What are Biodiesel and Renewable Diesel?
Both biodiesel and renewable diesel are categorized as biomass-based diesel fuels which means that they are produced from organic lipid feedstocks like vegetable oils, animal fats, or recycled grease. Where they differ is in their production methods.
Biodiesel: Often referred to as Fatty Acid Methyl Ester or FAME, biodiesel is produced through a process called transesterification. This involves reacting the feedstock with an alcohol, typically methanol or ethanol, in the presence of a catalyst. This process yields biodiesel and glycerin as a byproduct. Biodiesel contains oxygen in its chemical structure.
Renewable Diesel: Sometimes called hydrotreated vegetable oil (HVO) or green diesel, renewable diesel is chemically very similar to petroleum diesel. It is primarily produced through hydrotreating, a process that involves reacting the feedstock with hydrogen at high temperatures and pressures in the presence of a catalyst. This process removes oxygen from fats and oils, resulting in a hydrocarbon fuel.
The Differences
The different production processes detailed above lead to several notable distinctions between biodiesel and renewable diesel:
- Chemical Composition: Biodiesel contains oxygen while renewable diesel is a pure hydrocarbon making it more like petroleum diesel
- Fuel Properties: Biodiesel has a slightly lower energy content per gallon than both petroleum-based and renewable diesel, while renewable diesel’s energy density is much closer to petroleum diesel. In cold weather, biodiesel is more prone to gelling due to its higher cloud point, whereas renewable diesel can handle the cold better. Storage-wise, biodiesel is more susceptible to degradation, microbial growth, and corrosion, while renewable diesel remains more stable and is fully compatible with existing diesel infrastructure. Renewable diesel typically has a higher cetane number than biodiesel, resulting in improved ignition and combustion as well.
- Engine Compatibility: Biodiesel is typically blended with petroleum diesel, with common blends like B20 (20% biodiesel, 80% petroleum diesel) being widely used. Higher blends may require major engine modifications. Renewable diesel is a “drop-in” fuel, meaning that it can be used in existing diesel engines without any modifications or blending limitations. It can even be used in its pure form (R100).
- Emissions: Both fuels generally reduce greenhouse gas emissions compared to petroleum diesel. Biodiesel tends to reduce particulate matter, carbon monoxide, and hydrocarbon emissions but may slightly increase NOx emissions. Renewable diesel typically reduces hydrocarbons and NOx emissions.
With these differences in mind, the market’s consumption of renewable diesel has increased steadily, surpassing biodiesel in 2022. This growth is chalked up to its “drop-in” nature and compatibility with existing transportation fuel infrastructure.
While we at RINSTAR don’t pick sides in this debate and love all of our biofuels equally, we do find it interesting how technology and the market is evolving to progress past the blend wall issue.
As things continue to develop, RINSTAR will keep you updated through our newsletter.