Renewable diesel fuel is produced from fats and oils, such as soybean oil or canola oil. It undergoes a chemical process to make it chemically identical to petroleum diesel. In the United States, it meets the ASTM D975 specification for petroleum, while in Europe it adheres to the EN 590 standard. One of the key advantages of renewable diesel is its versatility. It can be used as a direct replacement for diesel fuel or blended with any amount of petroleum diesel.
It is important to note that renewable diesel and biodiesel are not the same. Renewable diesel, previously known as green diesel, is primarily produced through hydrotreating, but it can also be produced via gasification, pyrolysis, and other biochemical and thermochemical methods. It complies with the ASTM D975 specification for petroleum diesel. On the other hand, biodiesel is a mono-alkyl ester produced through a process called transesterification. It meets the ASTM D6751 standard and is approved for blending with petroleum diesel.
How is Renewable Diesel Fuel Produced?
The production of renewable diesel fuel can be achieved through various technological methods. Currently, commercial production facilities predominantly employ the hydrotreating pathway, using fats, oils, and greases as the primary feedstocks. Let’s explore some of the technologies used in renewable diesel production:
1. Traditional hydrotreating
This way is commonly used in petroleum refineries and involves the reaction of lipids (feedstock) with hydrogen under high temperatures and pressures in the presence of a catalyst. Commercial plants presently utilize this technology.
2. Biological sugar upgrading
Similar to the process used for cellulosic ethanol production, this pathway employs biochemical deconstruction, with the addition of organisms that convert sugars into hydrocarbons.
3. Catalytic conversion of sugars
In this pathway, a series of catalytic reactions is employed to convert a stream of carbohydrates into hydrocarbon fuels.
Biomass is thermally converted to syngas in this process, which is then catalytically transformed into hydrocarbon fuels.
Organic materials undergo chemical decomposition at elevated temperatures without oxygen. This process yields a liquid pyrolysis oil that can be further processed into hydrocarbon fuels, either independently or as a feedstock for co-feeding with crude oil in standard petroleum refineries.
6. Hydrothermal processing
High-pressure and moderate-temperature conditions are employed in this process to initiate the chemical decomposition of biomass or wet waste materials, resulting in an oil that can be catalytically upgraded into hydrocarbon fuels.
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