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Education: Diesel

High Sulfur Content Diesel (HSCD)

The sulfur content of diesel fuel is a topic which deservingly receives a tremendous amount of attention. Not only is HSCD significantly more pollutive than low sulfur content diesel (37), HSCD also prohibits the application of catalytic technologies which could otherwise be employed to reduce PM emissions (38).

Sulfur Concentration and Fuel Classification

From an emissions perspective, it is common for diesel fuel grades to be categorized by their sulfur concentrations, which are measured in PPM (“parts-per-million”). The guidelines regarding which sulfur concentrations define which diesel grades differ widely between various regulatory agencies, NGO’s, diesel producers and product manufactures. For example: some manufactures define ultra-low sulfur diesel as fuel which contains sulfur in concentrations ≤ 50-PPM, while others define it as fuel which contains sulfur concentrations ≤ 15-PPM. The United States Department of Energy, for example, uses benchmark sulfur concentrations of 3-PPM (sulfur-free), 30-PPM (low), 150-PPM (intermediate), and 350-PPM (high) when testing the efficiencies of various catalytic PM emissions filtration technologies. In many parts of the world, however, 350-PPM is be considered very low sulfur content fuel. Notwithstanding, the following categorization is an attempt to provide a set of general guidelines that the reader can use to make informed generalizations regarding diesel sulfur concentrations:

  • High Sulfur Diesel: sulfur concentration > 500-PPM
  • Low Sulfur Diesel: sulfur concentration ≤ 500-PPM and > 150-PPM.
  • Very-low Sulfur Diesel: sulfur concentrations ≤ 150-PPM and > 50 -.PM
  • Ultra -low Sulfur Diesel: sulfur concentrations ≤ 50-PPM

Note: the US EPA defines "Ultra Low Sulfur Diesel" as fuel containing ≤ 15 PPM.

It is difficult to overstate the negative affects of high sulfur concentrations, as increases in TPM appear to be linearly correlated to increases in the sulfur content of diesel Fuel (39). In light of this relationship, the National Resource Defense Counsel (NRDC) reports that “the health benefits of reducing sulfur levels to ultra-low levels are significant (40); and the United States Environmental Protection Agency (USEPA) estimates that “reducing PPM from 500-PPM to 15-PPM in the United States alone would eliminate 8,300 premature deaths, 23,100 cases of chronic or acute bronchitis in children, more than 360,000 asthma attacks and 386,000 cases of respiratory symptoms in asthmatic children, and it would save more than 1.5 million lost workdays each year” ( 41).

The grounds upon which the USEPA supports its projections are: 1) Ultra-low sulfur diesel produces significantly less PM emissions than fuels with higher sulfur concentrations (42), and 2) the sulfur in diesel fuel renders catalytic technologies ineffective, and therefore prohibits these technologies from being widely employed (43).

The University of Washington’s Extension Energy Program reports “Diesel Oxidation Catalysts can oxidize sulfur dioxide to form sulfate particulates (sulfuric acid (H22SO4)). Therefore, high sulfur fuels can increase total particulate emissions [via the production of sulfuric acid] which can offset soluble organic fraction [“Wet PM”] emissions reductions” (44).

According to the United States Department of Energy (USDOC), “fuel sulfur has significant effects on post-DPF total PM emissions”, and, as fuel sulfur levels increase, DPF’s reduction efficiencies decreases to the point where DPF’s actually become a source of PM emissions when using fuels with sulfur concentrations ≥ 150 PPM (45).

The real challenge of reducing world-wide emissions becomes extremely clear when considering a report recently released by the NRDC which states, unfortunately, “most of the world continues to use diesel fuel that has extremely high sulfur levels. For example, China's sulfur levels often exceed 5,000-PPM, and in New Delhi, the typical truck burns a diesel fuel with a sulfur level of 2,500-PPM. In South America, sulfur levels exceed 2,500-PPM in many nations, and reach 10,000-PPM in Brazil. There has been no effort to reduce sulfur levels in Africa” (46).

Due to the serious consequences of HSCD, many organizations such USEPA, the World Heath Organization, the United Nations Environment Program, leading universities, fuel producers and emissions technology manufactures have become extremely active in monitoring and supporting the reduction of fuel sulfur levels around the world.

The United Nation's Partnership for Clean Fuels and Vehicles reports the following data on its website depicting geographic fuel sulfur concentration levels: http://www.unep.org/pcfv/main/Main.htm


 


 



Other Sources reveal sulfur concentrations statistics that are even higher than the UNEP data. In a report issued in 2004, the International Fuel Quality Center presentsed the following data:


The National Resource Defense Counsel hosts the following on its website:

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