Feasibility study points to benefits of LNG use in ferries

An LNG-fuelled ferry would not only have significant environmental benefits, but economic ones as well, according to a recently completed feasibility study for Washington State Ferries.

Naval architectural and marine engineering firm The Glosten Associates, Seattle, Wash. recently completed the feasibility study for Washington State Ferries (WSF) on converting its 144-car ferry design to liquefied natural gas (LNG) propulsion. Glosten’s study concluded that the conversion is both technically feasible and cost effective, although technical and regulatory challenges remain. The study examined design, economic, regulatory, and environmental issues.

To support the study, Glosten developed a preliminary design for both dual fuel and singlefuel (LNG only) engines. The operational savings for a single vessel are estimated to be between $900,000 and $1.25 million per year, after an upfront capital cost premium of $8.5 million to $10 million. Switching to natural gas fuel will significantly reduce emissions of nitrous oxides (NOx), sulfur oxides (SOx), particulate matter, and carbon dioxide (CO2). These greenhouse gases have been identified by the U.S. Environmental Protection Agency (EPA) as significant factors in harming human health, including respiratory illnesses, as well as damaging to the environment.

One significant finding in the report was that methane slip from the engines counteracts its reduction in CO2 emissions, minimizing the global warming benefits of switching to the lower carbon fuel.

Glosten’s design was formally reviewed by the United States Coast Guard (USCG). USCG provided extensive feedback as well as a written response, showing their willingness to work with owners early in developing a case-by-case design basis until official rules are developed. The USCG response provides WSF with a regulatory basis from which to advance the project design. This is an important result, as the lack of USCG regulations is often cited as a primary risk to vessel owners interested in reaping the benefits of LNG fuel conversion.

WSF vessels are normally certified under 46CFR Subchapter H, and must also meet the applicable requirements in Subchapters F and J. As these do not address LNG fuelled propulsion, the USCG has accepted the supplemental use of IMO’s Interim Guidelines on Safety for Natural Gas-Fuelled Engine Installations in Ships for this project.

Much of IMO’s Interim Guidelines are based on those developed by classification society DNV, which has worked extensively with the Norwegian Maritime Directorate. DNV classed the first LNG-fuelled ferry, Glutra, in 2000.

WSF is investigating LNG conversion for other vessels, using similar design features as applied to the 144-car ferry. This recent study builds on Glosten’s 2010 study investigating the use of LNG fuel in WSF vessels.

Washington State Ferries is the largest ferry operator in the U.S., carrying more than 23 million passengers and 10 million vehicles annually.

Sean Caughlin, PE, The Glosten Associates, will discuss the feasibility study at Marine Log’s FERRIES 2011 Conference, which is scheduled for Nov. 7-8, 2011 at the Hyatt Regency Boston.

August 23, 2011