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Methane slip challenge invalid says LNG group

SEA\LNG has dismissed claims by Norwegian institute SINTEF that methane slip outweighs the greenhouse gas emission advantages of LNG as a marine fuel.

According to the consortium of LNG stakeholders, which commissioned a study by consultancy Thinkstep, data used by SINTEF to challenge the report are based on only lean-burn four-stroke engines on coastal vessels. SEA\LNG therefore cast doubt on the validity of assumptions made about the amount of unburned methane escaping from two-stroke engines.

“The research by SINTEF relates to Norwegian coastal shipping and does not include measurements for two-stroke engines used by most deep-sea ships,” said SEA\LNG board member and Wärtsilä Americas vice president marine solutions John Hatley. “We therefore question whether it is directly applicable to global deep-sea shipping.”

SEA\LNG chief operating officer Stephen Cadden noted that the Thinkstep report was the first lifecycle study of LNG fuel to use emissions figures from OEMs. It also goes beyond previous studies in examining methane slip upstream during the production and transport of LNG fuel.

Operating reality

Another part of SINTEF’s challenge claimed that the study used unburned methane readings taken at an inappropriate engine load, around 80%. SINTEF chief scientist Dr Elizabeth Lindstad claimed that this does not represent operating reality for most ships and that a lower load – and consequently higher unburned methane emissions – would be more in line with emissions during slow steaming.

Mr Cadden countered that slow steaming is only a temporary phenomenon affecting some sectors of the fleet. Further, the increasing demands of IMO’s Energy Efficiency Design Index mean that ship operators are installing gradually smaller engines and running them at higher loads.

SEA\LNG noted that LNG offers a better solution than either heavy fuel oil or low-sulphur fuel oil to local emissions – namely NOx and sulphur. This is disputed by Dr Lindstad, who argues that continued HFO use with a scrubber and NOx abatement is both the most cost-effective and the most GHG-friendly means of meeting IMO NOx and sulphur limits.

The LNG consortium contends that combustion technology is advancing, with dramatic improvements in fuel efficiency and methane slip anticipated. Bulk infrastructure is already in place to deliver LNG, with only last-mile bunkering facilities requiring development – making LNG the most accessible of alternative fuels today. The use of LNG is also claimed to represent a pathway to carbon-neutral synthetic fuels.

Thinkstep is expected to publish a separate response to SINTEF’s challenge.

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