New report alleges underestimated methane emissions from LNG ships

A new report from the International Council on Clean Transportation (ICCT) has found that the most popular Liquefied Natural Gas (LNG) ship engine, particularly for cruise ships, emits between 70% and 82% more life-cycle greenhouse gas (GHG) emissions over the short-term compared to clean distillate fuels. The new report comes as the shipping sector grapples with its enormous climate footprint, and more ship operators are turning to LNG as a purported climate solution. 

The ICCT report examines the lifecycle GHG emissions from marine fuels, including a previously poorly understood source of climate emissions from LNG-powered ships — the unintentional releases of the climate super-pollutant methane from ship engines, known as methane slip. The authors found that using LNG could actually worsen the shipping industry’s climate impacts compared to marine gas oil (MGO) when considering the amount of heat these emissions will trap over a 20-year period. 

LNG is being hailed as a climate solution by many in the shipping industry — a sector that is responsible for more global GHG emissions than major climate polluting nations, including Germany, Iran, South Korea, and Canada. If left unchecked in a business-as-usual scenario, international shipping GHG emissions could rise from its current 3% share of emissions to a staggering 17% of global GHG emissions by 2050. If ships were to continue to uptake LNG as a marine fuel, emissions could be even worse. 

“The report shows the need for adopting policies that can reduce the broader GHG emissions of shipping instead of CO2 only, including the well-to-tank emissions of ship fuels. If we fail to include all GHGs and focus only on CO2, we might end up with a large number of ships fulfilling all efficiency requirements, but where the GHG savings are on paper only,” said Dr. Elizabeth Lindstad, Chief Scientist at SINTEF Ocean, Maritime Transport.

The Intergovernmental Panel on Climate Change has warned that global GHG emissions must be nearly halved from 2017 levels by 2030 to avert the worst impacts of climate change, and methane emissions from all sources must be cut by at least 35% from 2010 levels by 2050. 

Given this short timeframe to drastically reduce climate-disrupting pollution, the report authors evaluated the climate impacts of marine fuels using 20-year and 100-year global warming potentials. Methane emissions are particularly problematic because methane traps 86 times more heat than the same amount of carbon over a 20-year period. 

Of the 756 LNG ships currently in use or on order, the most popular engine type, by far, is also the worst offender with the highest rate of methane slip. This engine is especially popular with cruise ships, and the cruise industry promotes these LNG ships as having significant climate benefits. 

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