Energy-specific greenhouse gas emissions measurements from 2-stroke marine diesel engine using liquefied natural gas

This study reports the energy specific air emissions from a diesel-cycle high pressure injection dual fuel engine for operation on liquefied natural gas and heavy fuel oil. An experiment at sea was performed onboard a bulk carrier during commercial voyages, to measure the efficiency of the engine and to measure air emissions relevant to air pollution and climate impact for operation on both fuels. The measurements showed that the energy conversion efficiency of the engine was higher for operation on liquefied natural gas because its lower NOx emissions permitted the use of a higher effective compression ratio whilst meeting the same NOx emissions level. The results showed that the climate impact for operation on heavy fuel oil was 2.1–2.3 times higher than for liquefied natural gas at 50% load, if considering only the emissions occurring at the engine. Analysis of the air emissions for their individual contributions to climate impacts suggested that black carbon had the strongest climate impact of all air emissions in the case of operation on heavy fuel oil. For operation on liquefied natural gas, CO2 had the strongest individual climate impact amongst the air emissions from the engine.