Using LNG for bunkering is a way to reduce greenhouse gas (GHG) emissions from the marine sector, according to the gas industry. We disagree, some leading academics say. And it is because of methane leakage.
While it is true that burning LNG emits less CO2 than oil products, when the whole delivery chain is accounted for, then it is no different to existing oil products, University College London (UCL) energy transport lecturer Tristan Smith said.
Citing his own research and peer-reviewed papers, Smith concludes that using LNG is no better than burning fuel oil or marine gasoil in terms of GHG emissions.
The issue is methane slippage - from gas production at the well, to transport down pipelines, to the liquefaction process, to storage on the ship tanks - the tiny leaks would add up to discount any advantages from releasing less carbon during combustion.
"None of the fossil fuels scrutinised here - heavy fuel oil, marine gas oil, gas-to-liquid and LNG - would decrease the GHG emissions significantly from a life cycle perspective," a paper by the University of Technology in Sweden concluded.
But some of the papers do highlight that LNG-powered ships would decrease other pollutants on a local level.
"Natural gas in marine transportation applications will reduce important criteria air pollutants - such as SOx (sulphur dioxide) and PM10 (particulate matter) - substantially below all current and proposed emissions standards for traditionally fuelled marine diesel engines and does not increase NOx (nitrogen dioxide) emissions," researchers at the University of Delaware said.
But Smith argues that there are other ways to reduce these air pollutants and LNG is not the only solution. "There are at least four different ways to meet SOx/NOx regulations, and LNG is just one. Depending on your circumstances it may be the best value in which case this can make sense," he said.
Others agree that LNG would be more beneficial to the environment only if the methane issue was properly tackled.
"On the basis of the results from this study it would be preferable that shipowners would chose LNG as a marine fuel in the future, based on the environmental footprint. But there are areas that have still not been uncovered - such as methane slip along the supply chain, liquefaction emissions and energy use and bunkering emissions," a paper from the Norwegian University of Science and Technology concluded.
Smith points out that burning one tonne of LNG would still release three tonnes of CO2, which would make it impossible to decarbonise the shipping sector enough to meet the Paris agreement to restrict GHG emission and keep global warming to within 2°C this century.
"You cannot use LNG to substantially decarbonise shipping. It is an interim solution with a few niche applications," Smith said.
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