When LNG was first seriously proposed as a mainstream alternative ship fuel, much was made of its environmental benefits. Compared with conventional fuels it produced negligible amounts of SOx and particulate matter, offered potential for a considerable reduction in NOx emissions, and was seen as producing lower greenhouse gas (GHG) emissions. Side benefits are that there are no waste disposal issues – such as with scrubber-equipped engines burning HFO – and risk of oil spill pollution is eliminated.

However, one of the major criticisms aimed at LNG dual-fuel engines is methane slip, the emission into the atmosphere of unburned methane fuel. Methane is a powerful greenhouse gas – believed to be some 30 times more potent than CO2 over a 100-year period.

The industry has gone to great lengths to dispel fears of LNG as fuel turning out to be less ‘green’ than expected; not least the maritime collective SEA-LNG which has commissioned various reports and published numerous papers about the subject. SEA-LNG quotes a GHG reduction in the order of 20% or more compared with fuel oils, even taking into account methane emissions.