LNG As A Marine Fuel: A Maturing Industry

The ship is being constructed at Fukuoka Shipbuilding’s Nagasaki Yard and is the first of its kind in Japan. It will be chartered to FJL upon completion.

The LNG dual-fuel engine significantly reduces CO2 emissions, making the ship compliant with the Energy Efficiency Design Index Phase 3 requirements before the regulation’s enforcement. ClassNK noted the use of LNG fuel helps decrease nitrogen oxide (NOx), sulphur oxide (SOx), and particulate matter (PM), as it complies with the NOx Tier III regulation and the SOx regulation. Environmental soundness at recycling is guaranteed, with proper plans that maintain an Inventory of Hazardous Materials, which is required by the Ship Recycling Convention.

But overall, LNG as a marine fuel in the tanker sector is almost entirely on the newbuilding side, despite the best efforts of companies like Newport Shipping. The group’s manager and managing director Oslo, Lianghui Xia, made the case for retrofitting LNG dual-fuel power on existing modern tankers at the Tanker Shipping & Trade Conference in Athens in 2022.

The available data on the benefits of LNG retrofits to an existing vessel is mainly from the gas carrier sector. LNG dual-fuel conversions have been applied to LNG carriers and resulted in around a 15–20% reduction in exhaust emissions, according to a paper by DNV and MAN ES titled Challenging road ahead for retrofitting to dual-fuel engines.

“Key retrofitting requirements for ships with two-stroke engines are electronically controlled engines, a bore size of at least 50 centimetres and a sea trial conducted after 1 January 2015,” stated the paper. It added that the cost of retrofitting ranges between US$5M to US$15M.

The advice to owners contemplating a retrofit conversion was “as a rule of thumb, this should not exceed 25% of the newbuild cost of a ship to be economically viable.”

Any newbuilding or retrofit installation of LNG as a marine fuel has to address the important issue of methane slip (gas migrating past the cylinder rings during the combustion process – adding methane to the atmosphere). Monitoring methane slip should be high on the agenda of any vessel using LNG as a marine fuel.

However, during a poll taken during the Riviera Maritime Media webinar, Measuring, monitoring and mitigating shipboard methane emissions, held 16 February 2023 and sponsored by Emsys Maritime, two-thirds of delegates felt that methane slip monitoring was not the norm for LNG carriers.

On the panel were Avenir LNG commercial director for LNG bunkering Jan Schubert, Emsys Maritime managing director Simon Brown and Queen Mary University of London senior lecturer in chemical engineering and renewable energy, Paul Balcombe.

Mr Brown said technology is available for monitoring emissions and gas releases in real time. To get a true indication of the slip of un-combusted methane passing through engines, operators must accurately measure each individual exhaust stream as parts per million or g/kWh, to determine generator and engine efficiency, then convert it to a CO2 equivalent for compliance reporting.

“Our reports allow us to identify emissions sources and determine where methane, CO2 and NOx, N2O and other gases are emitted,” said Mr Brown. Emsys is developing an application interface to other vessel performance software and automated off-vessel reporting​ functions

Queen Mary University of London is part of a multi-partner, three-year research project to study methane emissions from LNG carriers and other ship types. Its industry partners include Cheniere, Chevron, Sempra, Exxon, Williams, Pioneer, GTI, BAE Systems, Johnson Matthey, SIGTTO and SGMF.

One of the findings of the study was that methane releases through venting and fugitive emissions were extremely low, other than when there was a switch between diesel and LNG fuels, which requires venting through the pipes.