SEA\LNG, an industry body that promotes the use of liquefied natural gas (LNG) and its partner the Society for Gas as a Marine Fuel (SGMF) commissioned what they called a well-to-wake study of the environmental impact of LNG as a marine fuel, claiming that the gas is “a pathway to 2050,” the maritime decarbonization target.
In the spring of 2018, the International Maritime Organization (IMO) voted to adopt ambitious greenhouse gas emissions targets to reduce carbon emissions from the maritime sector to 50 percent of 2008 levels. Achieving this aim is considered very challenging given that the global population is set to increase with a subsequent in demand for shipped goods, meaning an overall estimated decrease in emissions of 80 percent.
To achieve this kind of reduction there will need to be a new fuel and new technology that will radically alter the emissions from a ship’s main and auxiliary engines.
The SEA\LNG and SGMF study was conducted by thinkstep, a consultancy group specializing in sustainability. The Life Cycle Emission Study on the use of LNG as a marine fuel revealed that LNG reduces greenhouse gas emissions when compared to oil-based marine fuels by between 14 and 21 percent over the life cycle (that is, from well to wake) for two-stroke engines, and by 7 to 15 percent for four-stroke units.
More importantly for shipping, the study broke down the emissions from well to tank and from tank to wake and in this latter scenario the emissions reductions were higher, at 18 to 22 percent for two-stroke and 12 to 22 percent for four-stroke engines. Using LNG as a marine fuel reduces sulfur oxides to almost zero, while nitrogen oxide emissions decline 95 percent and particulates by up to 99 percent compared to conventional marine fuels.
The study revealed that methane slip, which results in unburned methane being emitted from the exhaust of a gas engine, a problem reported by many engine manufacturers to have been solved, was 1 percent in high-pressure two-stroke engines. However, methane slip remains a significant problem in low-pressure engines, ranging from 10 to 17 percent. Methane remains in the atmosphere for shorter periods than carbon dioxide but is considered to be more than 20 times more potent as a greenhouse gas than carbon dioxide.
The study used eight marine engine manufacturers’ data to measure and compare the emissions from marine main engines. According to thinkstep, “The study is based on steady-state test-bed data using standard test cycles.”
This was compared to the use of car manufacturers’ data on fuel consumption at a steady 53 mph. The data is indicative but not definitive, a point that thinkstep was happy to concede.
“Greenhouse gas emissions based on actual operational fuel consumption and measured emissions data will differ due to load cycles and duration and could be considered as further analysis,” said the report summary.
Nevertheless, Peter Keller, chairman of SEA\LNG, believes that the study is one that owners and investors “could lean on.” He added, “It shows a pathway to achieving the IMO’s 2050 carbon emission targets.”
Keller believes that the Energy Efficiency Design Index that is meant to see increased fuel efficiency through vessel design and the development of bio-LNG with synthetic gas could all substantially reduce carbon emissions from shipping to achieve the IMO 2050 goals.
“LNG is available now and it is a solution for now. The IMO changes are happening, they are not going away… LNG is not the be and end all, and how far LNG will go, we don’t know, but we do know that waiting is not a plan,” said Keller.