ECA Reduces Pollution But NOx Minimally Affected, Study Says

Published Dec 25, 2015 4:30 PM by The Maritime Executive

A study commissioned by a citizens advisory group in Prince William Sound found that the new 0.1 percent sulfur fuel required in the Emissions Control Area (ECA) almost eliminates tanker vessel SOx emissions. The ultra-low sulfur fuel also brings deep cuts in harmful exhaust particulate matter, reducing PM by 80 percent.

Cumulatively, the fifteen oil tankers regularly calling at the Sound now emit about 500 tons less air pollution per year than they would have with 2.7 percent sulfur HFO, environmental analysts Starcrest Consulting Group said. The fuel is expensive and the study helps towards justifying the significant cost increase for tanker operators.

Starcrest employed sophisticated modeling techniques to estimate tanker emissions. For each of the fifteen tankers regularly calling at the terminal, they created main and auxiliary engine load profiles based on AIS tracking for speed and distance traveled and time at dock or at idle. The values were broken down by operator for three fuel sulfur levels (2.7, 1.0, and 0.1 percent).

While SOx and PM were greatly improved, nitrogen oxides make up only a small part of the ECA emissions reductions picture, at least for now. ECA regulations do not target exhaust NOx from all generations of ships equally, and the use of ultra-low sulfur fuel has minimal effect. The study found that this emissions component was reduced by only six percent.

The analysts also predicted SOx, PM, and NOx emissions out to 2024 based on forecasts for oil shipment volume at Valdez, with incremental annual improvements for SOx and PM. NOx is predicted to peak in 2015, then decline to 100 tons per year below 2014 levels by 2024, largely due to shipment volume.

In the absence of local laws, the only requirement for the NOx emissions component is in the IMO Tier I/II/III NOx schedule, regulated in the U.S. by certification of each manufacturer's engine designs by model year. Older vessels with previous generations of engines are not affected by ECA NOx regulation and may continue earlier, less restricted levels of NOx emissions.

There may be reductions “when the ships equipped with IMO NOx Tier 0 and Tier 1 engines . . . are replaced with ships with IMO Tier 2 and Tier 3 engines,” Starcrest concludes. But the study's data implies that a predicted 40 percent decline in oil shipments (rather than IMO Tier 3 requirements) will be the primary driver of vessel NOx reduction in Prince William Sound within the 10-year forecast period.

The full study is available by clicking here.