Beginning in 2009 the California Air Resources Board (CARB) established restrictions for both NOX and particulate output from diesel engines used in harbor craft, including tugboats and towboats. By 12/31/2009 all vessels are supposed to have US EPA Tier 2 engines installed, with a few notable exceptions as explained below.

The US EPA Tier system is a way to measure the NOX and particulate output of engines.

As of February all vessel operators were to register their vessels with CARB by completing a form that identified how many diesel engines each vessel has, the age of the engines, and whether or not the engines were US EPA Tier 1 or greater. 

Essentially, if an operator’s vessel is equipped with tier 1 or better engines then they are given more time for compliance. Depending on how old the engine is full tier 2 compliance may be put off for several years.

Pre 1975 non-tier 1 (tier 0) engines are no longer eligible for the CARB engine grant program, known as the Carl Moyer Program. That program has been in effect for several years and has supplied many California vessels with modern, lower polluting diesel engines.

For vessels with relatively lower horsepower engines (less than 1500) repowering is probably the most cost effective way for compliance. However, repowering vessels equipped with larger, medium speed engines, can be quite expensive.

There remain other options for NOX and particulate reduction, other than repowering. There are several manufacturers producing selective catalytic reduction systems for diesel engines for NOX reduction, as well as exhaust filtration for particulate reduction. In using these systems base line outputs must be established prior to installation and then measurements conducted after in order to qualify the reductions to CARB.

Fairbanks Morse is reportedly w orking on a system involving electronic fuel injection for their opposed piston engines. However, they have not committed to a release time and it is unknown if this will help those tug operators that have these engines.

Although California appears to be ahead of the rest of the country on diesel pollution reduction, we expect that many other states will follow suit in the next few years. This will add to the burden of vessel operators, making efficiency and automation of compliance systems even more important.

The CARB regulations can be viewed at:

http://www.arb.ca.gov/regact/2007/chc07/rev93118.pdf