A study conducted by the Transport Emission Control Team at VTT Technical Research Centre of Finland has documented how methane slip and other emissions from a dual-fuel LNG engine change under real-world operating conditions on a new cruise ship.

Methane has a higher hydrogen-to-carbon ratio than diesel, so LNG emits significantly less CO2 when combusted in a low-pressure dual-fuel engine. It also produces negligible amounts of particle emissions, NOx and sulphur – small enough to meet Tier III requirements. However, concerns have been raised regarding the slip of unburned methane which can offset some of the environmental benefits of LNG use.

A recently published study out of the Green Ray project, methane slip and other emissions from newbuild LNG engine under real-world operation of a state-of-the art cruise ship, documents emissions from a Wärtsilä 46DF, 14-cylinder, 600 rpm, 4-stroke low pressure dual-fuel engine with output of 16,030kW and shows how methane slip varied significantly according to engine load.