"Well-to-Hull" Study Finds LNG Less Harmful than Diesel

The study looked at ocean-going ships as well as tug/tow vessels

A study of the "well-to-hull" emissions related to various marine fuels has found that natural gas is generally preferable to conventional petroleum-based low-sulfur fuel, but the results were somewhat mixed, environmental transportation site Green Car Congress reports.

The U.S. Department of Transportation's Maritime Administration (MARAD) released the results, which were based on the modeling of ocean-going vessels and inland tug/tow vessels on specific routes.

The analysis considered liquefied natural gas (LNG) and low- and high-sulfur fuel for all routes, and also looked at compressed natural gas (CNG) for inland routes, considering extraction, processing, distribution, and consumption for each fuel, and also looking at leakage rates for LNG.

Total energy needed for a voyage is higher for shipping using natural gas, and emissions of methane (CH4), nitrous oxide (N2O), and nitrogen oxides (NOx) are also higher.

However, diesel fuels produce more carbon dioxide (CO2), large particle matter (PM10), and sulfur oxides (SOx).

Natural gas resulted in less overall greenhouse gas emissions than diesel for coastal scenarios, but for inland river scenarios diesel produced less.

"Natural gas is considered by many to be a win-win-win marine fuel: i) economically attractive; ii) low-emitting for key air quality pollutants; and iii) lower GHGs (primarily lower CO2), the study's authors wrote.

"However, natural gas may achieve some goals better than others. … This study did find a small but positive GHG benefit along with economic and local/regional air quality benefits."

The European Environment Agency (EEA) said last year that reducing fuel use through efficiency measures is the best way to address both greenhouse gasses and air pollutants like sulfur oxides.