A: The EPA has now mandated that the sulfur content in diesel fuel
be lowered further for both on and off road uses. In 2006, EPA rules
lowers the sulfur content down to 15 ppm, a standard that is called Ultra
Low Sulfur diesel (ULSD) which is compared to current on-road diesel fuel
called Low Sulfur diesel, with a 300 to 500 ppm sulfur content. ULSD will
be required to be used nationwide in all on-road vehicles beginning June,
2006 and ULSD will appear "at-the-pump" at that time.
When sulfur is present in diesel fuel and then combusted by an engine, it
results in black smoke and high emission levels in the exhaust plume. The
sulfur level in petroleum-based diesel fuel that is used for on-road
purposes is limited to 0.05% by weight. This limit was mandated in 1993 by
the Environmental Protection Agency (EPA) as a method to decrease
particulate matter emitted from diesel powered vehicles.
Reduction in lubricity occurs due to the refinery process that removes
sulfur. Not only does this hydro-desulphurisation process lower the sulfur
content but it also removes trace amounts of certain polar impurities.
Both organo-sulfur compounds and these impurities are the ingredients that
give diesel fuel its needed natural lubricating qualities.
The oil companies will need to replace lubricity in diesel fuel when
sulfur levels are reduced in accordance with mandates starting in 2006.
Oil companies would not have to add a synthetic lubricity replacements if
they use biodiesel as a lubricity enhancer, easing the transition to Ultra
Low Sulfur diesel's availability nationwide. In short, expect this to have
a very positive effect on biodiesel production throughout the country.