The Climate Implications of Using LNG as a Marine Fuel

Liquefied natural gas (LNG) contains less carbon than conventional marine fuels. But according to a life-cycle analysis, it might not reduce greenhouse gas (GHG) emissions by much. The authors compare the life-cycle GHG emissions of LNG, marine gas oil (MGO), low-sulfur fuel oil, and heavy fuel oil in engines for international shipping, including cruise ships. The analysis includes upstream and combustion emissions, and unburned methane. The climate effects are evaluated using 100-year and 20-year global warming potentials (GWPs). Over 100 years, the maximum life-cycle GHG benefit of LNG is a 15% reduction compared with MGO, and only if ships use a high-pressure injection dual fuel (HPDF) engine while upstream methane emissions are well controlled. The latter might prove difficult as more LNG is produced from shale gas, with recent evidence that upstream methane leakage could be higher than expected. Also, only 90 of the more than 750 existing LNG-fueled ships use HPDF engines. With a 20-year GWP, which better reflects the urgency of reducing GHGs to meet the International Maritime Organization (IMO)’s climate goals, and factoring in higher upstream emissions for all systems and crankcase emissions for low-pressure systems, there is no climate benefit from using LNG. HPDF engines using LNG emitted 4% more life-cycle GHG emissions than if they used MGO. The most popular LNG engine technology is low-pressure dual fuel, four-stroke, medium-speed, which is used on at least 300 ships, especially in LNG-fueled cruise ships. Results show this technology emitted 70% more life-cycle GHGs when it used LNG instead of MGO and 82% more than using MGO in a comparable medium-speed diesel (MSD) engine. LNG does not deliver the emissions reductions required by the IMO’s GHG strategy, and it could actually worsen the environmental impacts of shipping. Further, continued investment in LNG infrastructure on ships and on shore might make the transition to low-carbon and zero-carbon fuels more difficult. Instead, energy-saving techniques, wind propulsion, and zero-emission fuels, batteries, and fuel cells would deliver improved air quality and climate benefits.

• Record URL:
  https://theicct.org/sites/default/files/publications/Climate_implications_LNG_marinefuel_01282020.pdf
• 
• Corporate Authors:

  International Council on Clean Transportation (ICCT)

  1500 K Street NW, Suite 650
  Washington, DC  United States  20005
• Authors:
  • Pavlenko, Nikita
  • Comer, Bryan
  • Zhou, Yuanrong
  • Clark, Nigel
  • Rutherford, Dan
• Publication Date: 2020-1

Language

• English

Media Info

• Media Type: Digital/other
• Edition: Working Paper
• Features: Appendices; Figures; References; Tables;
• Pagination: 40p

Subject/Index Terms

• TRT Terms: Climate change; Environmental impacts; Fuels; Life cycle analysis; Liquefied natural gas; Methane; Ships
• Subject Areas: Energy; Environment; Marine Transportation;

Filing Info

• Accession Number: 01743202
• Record Type: Publication
• Report/Paper Numbers: 2020-02
• Files: TRIS
• Created Date: Jun 19 2020 2:19PM