BTJ 5/2011 - Baltic Press

MaritimeLiquefied Natural Gas as a ship fuelIs LNG-mania healthy?The campaign for LNG-fuelled engines in many respects reminds of historical campaigns for other innovationsin shipping – for nuclear ships, gas turbine, air cushion vehicles or mechanical sails. In all cases lots ofwords were used with minor practical effect. And the whole mass of words has common features – some factsare left unsaid and others are underlined without compatibility, probably for propaganda purposes.In the article “Greener shipping in theBaltic – The best solution is LNG” (BTJ4/2011) we find information that the BSR“constitutes over 11% of the global shippingtrade volume.” Even if this figure weretrue it is not relevant to the subject of environmentalissues and misleads outsiders, whomight think that this number also representsthe Baltic’s share in global shipping emissions.If we were to look for the adequate proportionsin transport statistics, only one set ofdata seems to be proper – a transport work,because in order to cause emissions, the volumehas to be moved. And the BSR generatesonly 0.9% (9 per mile) of the global shippingtransport work! Consequently, the first questionis born: why is the whole world so interestedin such a small amount of emissions andenacts special laws for the Baltic Sea?through the engines unburned – from 32 to154 kg (!) per tonne of LNG (3.2-15.4%), dependingon the engine class, load factor, etc.It means that probably all Norwegian LNGfuelledships are less “green” than ships withinstalled selective catalytic reduction (SCR)on traditional Diesel engines.Looking at the GWP factor alone, theNOx mixture is much worse than CH 4, butthings change when we look at them from atime perspective – from 1750 till the end ofthe 20 th century the methane content in theatmosphere grew by 150% (from 700 to 1,750ppb) and NOx by 17% only (270-315 ppb).This means that the increase in CH 4duringthe industrial era was twice as bad for today’sclimate as the historical rise of NOx.Summing up, today LNG engines existthanks to a legal loophole, which ignoredtheir methane emissions. The emission factorfor methane slip should be established ona level close to one per cent (1% of unburnedCH 4balances the drop in CO 2emission intotal GWP of exhaust gas thanks to the useof methane), but according to MARINTEKmost modern gas engines have a methaneslip of around 2.5%. The question is: how safeand viable is an investment in gas engines ifa regime for methane emission will be establishedin the near future, say in 5-10 years?Question of methane slipsThree greenhouse gases are the worst forthe climate – carbon dioxide (CO 2) with aGlobal Warming Potential (GWP) factor ofone, methane (CH 4) with a GWP between 21-25 and a mixture of nitrogen oxides (NOx)with a GWP of about 300. Today regulationsonly limit the emissions of CO 2and NOx andare silent in the case of methane.In 2010 the Norwegian Marine TechnologyResearch Institute (MARINTEK) measuredexhaust gases from gas-driven vessels inNorwegian domestic shipping*. As it turnedout a significant amount of methane passedPhoto: DISC BV16 | Baltic Transport Journal | 5/2011