Thinking outside the box with LPG

IOMSR said one innovation is to switch to the benefits of LPG, with the World LPG Association making it clear in early 2020 that the gas, which comes in the form of propane and butane, would play a major role in achieving the 50% reduction (as compared with GHG emissions in 2008).

For the last four years, it has been possible for vessels to be designed and built to the International Gas Carrier code (2016 IGC code) and permitted to run on LPG fuel under the new regulations from delivery.

Under the previous code (1983 IGC code as amended) this simply was not a permitted option – leaving shipping companies with a problem – the one experienced by BW LPG.

Discussions began in 2018 between with IOMSR, BW LPG, Wärtsilä Gas Solutions, MAN Energy Solutions and DNV GL to explore the feasibility of making LPG as marine fuel a possibility for its very large gas carriers (VLGCs) that fell under this category.

“The old code on which these ships were built only permitted the use of liquefied natural gas (LNG) as fuel so we looked at all the options and decided we needed to think outside the box,” says Bill Liddell, senior surveyor who led the project on behalf of IOMSR. “The benefits of LPG are improved safety over LNG – which is normally transported under cryogenic conditions – much cheaper materials are needed to accommodate the fuel characteristics, and there is a much wider availability of fuel gas, which can be supplied by road tankers at most ports, whereas LNG cannot.

“Gas is cleaner to burn than fuel oils and allows a large reduction in particulate emissions, helping to meet the ever-tightening restrictions placed upon the marine industry,” says Mr Liddell.

First flag state acceptance for modifying an VLGC to run on LPG

Each code provides regulation for variations to requirements by applying for a design equivalence for novel designs. After much discussion and research by interested parties, IOMSR put together the relevant paperwork and submitted an application to IMO. This design equivalence, granted in March 2020, allows the use of LPG as a fuel on the VLGC BW Gemini, setting a precedent in the industry enabling the IOMSR to issue the first flag acceptance of a modification to use LPG as fuel for older gas tankers.

“A full conversion of the ship, which has been in service for about 10 years, was not an option because it would have run into millions of pounds and taken much longer to carry out,” says Mr Liddell. “Instead, it was decided to carry out a modification of the engine and fuel supply system, which was much more commercially viable.”

Taking place in Q4 2020, the retrofitting work lasted just over two months, involving fitting the vessel with two extra LPG fuel deck tanks in the cargo area, a high-pressure liquid fuel system for the modified MAN Energy Solutions two-stroke engines, and significant upgrades to the associated safety and control systems.

The work was timed to be carried out during BW Gemini’s drydock period to ensure the vessel was not out of service any longer than necessary. In November, BW LPG announced the successful completion of sea and gas trials.

Initially, BW LPG plans to carry out retrofits of 12 of its VLGCs. Commenting on the programme, BW LPG executive vice president, technical and operations Pontus Berg said, “BW LPG has chosen to commit 12 of our VLGCs to be retrofitted with pioneering LPG propulsion technology. This is a significant upfront investment of over US$100M, and it represents our willingness to act on the ESG front.”

Continued Mr Berg, “Building new ships can provide the benefits of operating with LPG but comes at a heavy cost. Counting total emissions, a new ship represents about 70,000 tonnes of carbon dioxide in the materials and building process. Compared to 2,000 tonnes of carbon dioxide for retrofitting, the sustainability outcome is much better from retrofitting than from building new vessels. We thank the Isle of Man Ship Registry for its strong support and for embarking on this journey with BW LPG to take the lead and advance technology closer towards a zero-carbon future.”