Since we last discussed Liquid Natural Gas (LNG) as a maritime fuel in our April 2014 blog on Methane Slip and the Marine Industry there has been much research and development in the LNG industry, particularly as it relates to ship powering, methane slip, and GHG emissions. Recently, articles and research point to LNG as the fuel of the future, and the cost-effective option for vessel owners to meet IMO regulations and goals; yet LNG may not be the answer.
Cons of LNG
Disturbingly few articles have been published providing counter-arguments to LNG. These articles, such as from the International Council on Clean Transportation and SINTEF Ocean, posit that the global warming potential (GWP) of LNG is greater than that of HFO or MGO, calculated for 20 or 100-year time horizons. Dr. Lindstad of SINTEF notes that un-combusted “Methane gives a GHG impact 28-34 times higher per gram emitted than CO2 in a one hundred-year perspective… the warming impact of methane is 85 time (sic) larger per gram than CO2” over a 20-year period. Both studies note that only high injection pressure, dual-fuel, 2-stroke engines have low enough methane slip emissions to be considered a viable engine option for LNG-powered ships, which can be seen in the figure below. This is particularly concerning with the fact that LNG-powered four-stroke engines are the LNG fueling systems of choice in the marine industry today.
As in 2014, when we discussed ethanol as a fuel source that was doomed from the start as a result of poor research and those who capitalized on the flaws in the research for their personal gain, we can see how LNG will potentially follow in these footsteps. Although the research contradicting the viability of LNG as a marine fuel source is still in its infancy, many LNG-producers and corporations with stakes in the LNG industry will inevitably perpetuate false claims for their own benefit.
Regardless of its GWP, it is time to recognize that LNG as a ship fuel is not necessarily a sustainability solution; it is just a sexier substitution for other hydrocarbon fuels and at best a temporary transition until we engineer truly reliable solutions.
Is Hydrogen the Future?
In the 2014 blog, and in many other blog posts, we have noted that hydrogen fuel cells or using hydrogen (H2) in internal combustion engines seems to be the most promising fuel option for the future of transport, with the U.S. Energy Department’s Sandia National Laboratories providing corroborating research. Companies like Damen are currently developing and constructing hydrogen-powered ships as well.
Combustion of hydrogen may not be attractive either, as a 2006 UK study noted that hydrogen is an indirect greenhouse gas. However, its GWP is only a factor of 5.8 over a 100-year period: approximately five times less potent over the same time period as LNG. The same study also concluded that even with current inefficiencies in the extraction and storage processes of H2, “If a global hydrogen economy replaced the current fossil fuel-based energy system and exhibited a leakage rate of 1% then it would produce a climate impact of 0.6% of the current fossil fuel based system.”
Hydrogen poses a problem because its presence in the atmosphere perturbs the global distribution of greenhouse gases and may influence the ozone levels in the troposphere. However, even if hydrogen leakage is upwards of the study’s estimate, it is fairly clear that converting from a fossil fuel-based energy economy to one based on hydrogen would have a significant positive environmental impact and reduction in GWP. Since hydrogen extraction and internal combustion of hydrogen will probably have similar slip problems as methane, it appears that hydrogen fuel cells are the answer at this stage.
Only after many years of screaming into the storm by engineers and scientists who were willing to take a principled stand did it become apparent to the public at large that ethanol is folly. As engineers and scientists, we have to fight to distinguish the good from the bad. The future of energy may be LNG (unlikely), hydrogen, or another carbon-neutral fuel. Yet, we must continue to ask questions and pose hypotheses until our data, research, and experiments can answer the most daunting questions in the marine industry.