Implementation of lng as marine fuel in current vessels : Perspectives and improvements on their environmental efficiency

Abstract

Liquefied Natural Gas (LNG) as marine fuel currently appears to be an attractive, potential and technically feasible option for new building vessels to comply with air pollution regulations. Consequently, the implementation of LNG on board vessels has been conducted together with the development of LNG-fuelled engines, LNG fuel tanks, gas supply systems and LNG infrastructure. LNG-fuelled vessels are equipped principally with lean-burn gas engines or dual-fuel (DF) engines, vacuum insulated C-type tanks and compact fuel gas supply systems. Over the next decade, the number of LNG-fuelled vessels is forecasted to increase fast, even tough, certain LNG-fuelled vessel segments will experience a bigger expansion. Furthermore, potential for LNG-fuelled vessels depends on several features and car/passenger ferries seem to be the LNG-fuelled vessel segment with a higher potential. To date, air pollution regulations significantly reduce nitrous oxides (NOX) emissions and almost eliminate sulphur oxides (SOX) and particulate matter (PM) emissions, although, carbon dioxide (CO2) emissions are reduced only 20-30%. Owing to the foreseen rise of global seaborne trade, CO2 emissions are expected to grow even more emphasising the necessity to adopt highly restrictive measures. International legislative bodies have started to propose upcoming regulations and manufactures have developed technical improvements to improve energy efficiency of vessels and thereby decrease CO2 emissions. Nevertheless, these solutions merely provide small benefits on vessels’ environmental efficiency. As a result of the study, LNG-fuelled vessels present a bright future, as an alternative option to meet short-term air pollution regulations due to they do not sufficiently minimise CO2 emissions.