The discussion on diesel fuel doesn’t remain as monolithic as it may appear. Particularly, diesel has a connection with heavy machinery, trucks, and non-electric cars. And the discussion brings up “yellow diesel vs. green diesel.” Sounds pretty technical, right? Do not worry, as I am making things easier in this blog regarding diesel fuel.
First, diesel fuel is petroleum that we use for engines. Also, it works as a heating oil. The hydrocarbons (nitrogen and chlorine) cause the unique color of diesel. Now, this color varies from clear to yellow with a shade that indicates the sulfur content. If the fuel has a darker shade, it has more sulfur content. Similarly, lighter color indicates lower sulfur content.
Petroleum or fossil diesel is known as yellow diesel. It’s the traditional form of diesel fuel. Manufacturers derive diesel from crude oil – the oil found beneath the earth’s surface. Alternatively, we know green diesel as renewable diesel. It’s a relatively newer form of diesel fuel. It comes from renewable resources like vegetable oils, animal fats, and waste grease.
More technical things are ahead! Read the full blog to know more about these two types of diesel fuel.
Definition of Yellow Diesel
Remember I talked about clear diesel in the introduction section? Well, yellow diesel is a clear diesel fuel. It is also known as diesel fuel. This fuel contains branched-chain alkanes, cycloalkanes, aromatics, and mixed aromatic cycloalkanes (source).
Yellow diesel varies in color, from light brown to dark red, depending on its level of refinement (source). This color is naturally created for the sulfur content. And sulfur in the fuel causes oxidation (source). Diesel fuel is mainly used in diesel-powered vehicles and gear for off-road purposes (with a dye of red).
Hence, these engines operate without a spark but rely on compression for fuel ignition (source). Some examples can be construction equipment, heating oil, and agricultural machinery (source). The U.S. military also uses diesel fuel in tanks and trucks for its lower flammability and explosiveness than other fuels (source).
You may find that diesel fuels are classified into different classes. For example: 1D, 2D, and 4D. This marking depends on their viscosity and pour point (source).
An interesting thing about yellow diesel is that you can blend it with renewable diesel and biodiesel to create alternative fuels (source). However, the use and sale of yellow diesel fuel varies depending on the country.
Composition & Production of Yellow Diesel
The production of yellow diesel begins with the extraction of crude oil from the ground. The crude oil is then brought to refineries, where it undergoes a process known as fractional distillation (source). The crude oil is heated and causes it to vaporize.
Then, the vapors rise through a distillation column. They cool and condense into different components based on their boiling points. Diesel fuel is one of these components. Then, diesel fuel is treated to remove impurities like sulfur. Hence, impurities like sulfur can cause air pollution when the fuel is burnt. And this treated fuel is what we commonly call “Yellow Diesel”.
Performance & Efficiency
The performance of yellow diesel is typically characterized by its energy content, cetane number, and cold flow properties. The energy content of diesel fuel measures the amount of energy it can produce when burnt.
Yellow diesel has a high energy content. It means it can provide a significant amount of power. It is one of the reasons why diesel engines are often used in heavy-duty vehicles and machinery.
Then, the cetane rating of diesel fuel indicates its combustion speed and compression required for ignition. It is also a distinguishing factor (source). Usually, 1D and 2D diesel fuel have this cetane value of 45-55. If the rating is higher, the fuel will ignite easier. If you have high-compression engines, you will need higher-rated diesel fuel.
Cold flow properties mean the ability of the fuel to flow at low temperatures. Yellow diesel has issues with gelling or waxing at low temperatures. It can affect its performance.
Cost-effectiveness
Yellow diesel or diesel fuel is popular for heavy-duty vehicles and machinery for its high energy content and cost-effectiveness. But, this cost may fluctuate based on location, time of year, and political climate.
On average, diesel fuel prices tend to be higher than regular gasoline prices (source). But diesel engines are more fuel-efficient, which can offset the higher per-gallon price. Again, the initial cost of diesel-powered vehicles is typically higher than their gasoline counterparts. You should consider it when you think about overall cost-effectiveness.
Definition of Green Diesel
“Renewable energy” – perhaps this is the most discussed issue in the modern age. It’s the energy that we can renew, right? Now, green diesel is a renewable diesel or biodiesel. This biofuel has a molecular structure like petroleum diesel. But it has better chemical and physical properties (source). When you use green diesel, it will provide greater lubrication and leave fewer deposits in the engine (source).
To be precise, green diesel is an advanced biofuel. It is produced from cellulosic biomass like crop residue, forestry waste, or woody biomass (source). The engineers create it by hydrotreating triglycerides in vegetable oils and animal fats with hydrogen.
The color difference between green and yellow diesel is for adding different dyes. For instance, green diesel is often used for off-road purposes. You may need to pay the fines if you use this diesel in on-road vehicles (source).
Another exciting factor is that the color of diesel can indicate the quality of it. If you find the fuel as clear or slightly green, it means the diesel is fresh. On the other hand, older diesel may appear more yellow, light brown or darker (source).
Green diesel has high cetane numbers, good chemical-thermal stability, and low sulfur content. It meets the ASTM D975 specification for petroleum diesel (source). Moreover, this diesel is considered as a second-generation biofuel. It is different from biodiesel (source).
You can get more advantages of using green or renewable diesel over traditional ones. It has lower CO₂ emissions and reduced levels of pollutants (like NOx) and particulates than diesel. Also, it behaves the same to fossil diesel in terms of storage and logistics. But there is a difference: biodiesel is associated with stability and water separation issues, which is different from green diesel (source).
Composition & Production of Green Diesel
Green diesel is chemically composed of pure paraffin, linear and branched in different proportions. This composition makes the fuel an ideal biocomponent for blending into mineral diesel (source). Thus, it contains a saturated hydrocarbon chain with approximately 15-18 carbon atoms.
Renewable diesel or hydrotreated vegetable oil (HVO) is chemically the same as yellow diesel. It has hydrocarbons but a different source of origin. Manufacturers do not use crude oil to produce this fuel. Instead, they create it from different renewable resources I have already discussed.
Well, the production process for green diesel involves a technique known as hydrotreating. The triglycerides in the feedstock (vegetable oils, animal fats, etc.) are reacted with hydrogen under high pressure and temperature in a catalyst presence (source). During this process, oxygen is removed from the triglycerides. It causes the presence of hydrocarbons with the same properties found in yellow diesel.
Performance & Efficiency
Renewable or green diesel can match or even exceed the performance metrics of Yellow Diesel. It has a similar energy content and cetane number. But it has superior cold flow properties.
Hence, the high cetane number or rating of green diesel helps burn the fuel more cleanly and efficiently. It leads to improved engine performance and reduced maintenance costs.
Then, there remains the excellent cold flow properties. Unlike yellow, green diesel does not gel or wax at low temperatures. So, you can choose it for use in cold climates where yellow diesel has performance issues.
Cost-effectiveness
Factors that determine the cost of green or renewable diesel are the cost of the feedstock used in its production and the market incentives available for renewable fuels.
In some regions (like California), renewable fuels like Green Diesel are heavily incentivized (source). It can make them more cost-effective compared to traditional diesel. But there is a concern – the feedstock sources for green diesel. Other industries also use these sources. So, possibly, it can create competition and drive up prices.
Here is an example: soyabean oil. It is a common feedstock for renewable diesel. And many food productions use it as an ingredient or source. This competition can increase the cost of producing green diesel (source).
Conclusion – Factors to Remind in Yellow Diesel vs. Green Diesel
So, I am at the end of the conversation. Before things get more complex, I sort the whole thing again.
Yellow diesel is commonly used for on-road vehicles. Alternatively, green diesel is intended for off-road equipment and heavy machinery. But this one is more environmentally friendly as it is produced from renewable resources. However, if you misuse these two diesels, you may be fined soon due to violation of regulations.
I hope you have understood the concept. Thanks for spending time reading this blog.
