Lower-sulfur fuel key to upcoming 2007 marine emissions rule

Diesel Fuel News, Feb 17, 2003 by Jack Peckham

While U.S. EPA decided to delay more-aggressive diesel emissions/fuels rules in its now-final 2004 rule for the biggest "Category 3" ships (see Diesel Fuel News 2/03/03, p6), it's planning fuel sulfur reductions and tougher limits for upcoming 2007 marine rules.

Water-injection or diesel-water emulsions are high on EPA's list of 2007 marine emission control strategies, along with selective catalytic reduction (5CR), the EPA ruling says.

Lower-sulfur ship bunker fuel mandates also would be the "simplest way" to slash particulate matter (PM) emissions, EPA says.

EPA notes that the European Commission (EC) has proposed a 15,000-ppm sulfur limit on all ships in North Sea, English Channel and Baltic sea and all regular passenger vessels in Europe, to take effect by (at latest) 2007. Ocean ships also must switch to a 2,000-ppm sulfur marine gasoil while at berth in European ports. However: European Parliament's fuels rapporteur just unveiled a more radical "second-step" proposal for a 5,000-ppm bunker fuel limit (or stack scrubbing, or emissions trading offset) on ships in these same areas, by 2008, and then extend the 2,000-ppm sulfur limit for "at berth" to include outbound ships operating within EU territorial waters.

Meantime, International Maritime Organization (IMO) "Marpol Annex 6" rules would allow the U.S. to opt-into a "SOx emission control area" (SECA) scheme to slash bunker-fuel sulfur to 15,000 ppm, down from the current 45,000-ppm sulfur limit for bunker fuel. While the requisite 15 nations/50% of ship tonnage have yet to ratify "Annex 6," this could happen prior to 2007.

"We intend to investigate this [SECA] special designation for one or more areas in the United States," EPA says. "We will also reconsider this issue in our future rulemaking" for 2007, even if "Marpol 6" still lacks ratification.

Besides tougher "Tier 2" emissions standards on the big "Category 3" ship engines, EPA is also considering "whether we have the discretion under the Clean Air Act to apply any second tier of standards to engines on foreign vessels that enter U.S. ports," EPA says.

Because of treaty complications, imposing such limits on foreign-flag ships is complicated. So, EPA also will pursue tougher IMO standards. "These discussions [at IMO] are expected to begin in the next few years," EPA says. "The schedule for our future rulemaking will allow us to take into account progress in the international arena toward more stringent emission standards for marine diesel engines."

But even if EPA gets the 15,000-ppm sulfur "SECA" bunker fuel and decides to regulate foreign-flag ships, the agency still doesn't know whether such fuel is "clean enough" to pair with SCR or other technologies to hit tougher "Tier 2" emissions targets.

"By waiting a few years, we will be able to benefit from the manufacturers' experience as they continue to develop and apply these technologies on marine diesel engines," EPA says.

Meantime, EPA is also considering much lower sulfur fuels for the smaller (less than 30 liters/cylinder) "Category 1" and "Category 2" marine diesel engines, as part of EPA's upcoming non-road diesel rule. This rule could force refiners to desulfurize most non-road diesel fuel starting in 2008 or 2010, with a possible "two-step" scheme that would bring the current 3,000-ppm sulfur (average) non-road diesel to 500-ppm sulfur starting in 2007.

The non-road scheme would include 500-ppm sulfur limits on marine distillate and locomotive diesel, along with 15-ppm sulfur on all other non-road machines (see Diesel Fuel News 11/25/02, p1). Eventual conversion of marine/locomotive diesel fuel to 15-ppm limits isn't clear yet.

* Steeper Cuts Seen

Even the 2,000-ppm sulfur fuel that the EC aims to impose on ships in harbor might be "too much" sulfur for best nitrogen oxides (NOx) control, EPA notes.

What's more, a 15,000-ppm sulfur limit on bunker fuel still wouldn't resolve the problem of establishing a universally-accepted method for measuring PM from the biggest ship engines, in order to set tougher PM limits. "Currently established PM test methods show unacceptable variability when sulfur levels exceed 0.8%" (8,000-ppm sulfur), EPA notes. "Both distillate and residual marine fuels used in these [Category 3] engines commonly exceed that level."

Refiners could cut sulfur content in bunker fuel either by running more low-sulfur crude, or by blending resid with low-sulfur distillate, or by a "de-sulfonation step in the refinery process," EPA says.

Probably discouraging to refiners is the lack of any mention in the latest EPA marine diesel rule of possible "stack scrubbing" of the sulfur and soot emissions from high-sulfur bunker fuel combustion (see Diesel Fuel News 2/4/02, p6). Such technology could be far more cost-effective than bunker fuel desulfurization.

Meantime, here's EPA's analysis of two leading NOx emissions technologies:

# Water-based systems: Injecting water or steam into combustion chamber could cut NOx by 40-70%. Direct-water injection has been installed on over a dozen "Category 3" ships with four-stroke-engines -- in ferry and roll-on/roll-off freight services making short trips between European ports. So, water storage "is not a significant issue" on such short-haul service.